“Outcomes for the morbidly obese after total knee arthroplasty.”
By:
Brandy Ann Benton
Doctoral Candidate
University of New Mexico School of Medicine
Division of Physical Therapy
Class of 2014
Advisor:
Assistant Professor. Dr. Fred Carey, PT, PhD
Printed Name of Advisor: ______________________
Signature:________________________ Date:______________
Approved by the Division of Physical Therapy, School of Medicine, University of
New Mexico in partial fulfillment of the requirements for the degree of Doctor of
Physical Therapy.
Abstract
Background/Purpose: According to the Journal of Bone and Joint Surgery, there are more than
half a million total knee arthroplasty (TKA) surgeries performed each year in the United States (Iorio,
Robb, Healy, et al, 2008) in an attempt to ease the pain of osteoarthritis of the tibiofemoral joint. The
rising number of the obese population in America is a contributing factor to knee joint degeneration
(Schulte, Wagner, Ostry, et al, 2007), thereby causing an increased elective surgery for total joint
replacement. Some of these surgeries are performed on patients during a simultaneous bilateral (both
knees, BTKA) surgery, while other patients are electing to have unilateral (one knee only, UTKA) or
staged TKA (one knee at a time, STKA) surgery. While there is ample research to support that both
BTKA and UTKA procedures are safe (Sculco, 2012), patients have a difficult time deciding which
surgery to have, depending on what their individual level of health is at the time of their surgery, and in
order to have the best physical outcomes postoperatively. The purpose of this case study is to offer
the most recent research available to morbidly obese patients so they may make informed decisions
and balance the pros and cons of BTKA v. UTKA while keeping in mind their individual physical needs
in order to yield the best outcomes postoperatively. Furthermore, the research presented
demonstrates which particular identifiers of functional strength and range of motion are required in
order to have the best outcomes postoperatively.
Case Description: A 53-year-old, female patient with a BMI of 50 was admitted into the
medical/surgery floor hospital 21 October 2013 on post-op day zero (POD#0) after undergoing bilateral
total knee arthroplasty (BKA). Pre-operative diagnosis was osteoarthritis (OA) of bilateral tibiofemoral
joints.
Outcomes: Over the course of three days, the patient was seen by physical therapy six times.
At each visit, vitals were screened for safe ambulation, and pain levels were assessed. Unfortunately
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at each visit, the patient was unable to meet the minimal goals of bed mobility, sit to stand, ambulation
or stand to sit to chair/back to bed required for discharge to home health care (HHC), and was
therefore discharged by ambulance to a skilled nursing facility (SNF) on POD #3.
Discussion: It is well known that excess weight and pressure on the joints are a major
contributing factor to the degeneration of cartilage at the tibiofemoral joints (knees). Because of the
recent obesity epidemic in our country, we as physical therapists in the acute care setting will see an
increase in the number of obese patients electing to cure their OA pain by having BTKA or UTKA
surgery. Understanding the risk factors associated with each type of surgery may aid this population of
patients to make informed decisions as to whether they want to have BTKA v. UTKA based on their
particular physical status and expected standard outcomes and goals. Early identification, as well as
establishing ongoing screening procedures allows for appropriate referrals to medical professionals,
thus improving patient safety and optimizing outcomes following either TKA the patient has chosen.
SECTION 1: Background and Purpose
A severely obese, 53-year-old, female patient was admitted into the hospital on post-op day zero
after undergoing bilateral total knee arthroplasty. Pre-operative diagnosis was osteoarthritis of bilateral
tibiofemoral joints. During the “Pre-hab Joint Replacement Class” taught by the lead physical therapist,
this patient had difficulty deciding which elective surgery to choose in order to have the best outcome.
Therefore the research question being expounded for this case study is: “Do morbidly obese patients
in the acute care setting with bilateral osteoarthritis of the knees undergoing bilateral total knee
replacement surgery have better ambulation, discharge disposition and less peri/post-op complications
after receiving inpatient physical therapy care than patients that have unilateral/staged total knee
replacement surgery?”
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As stated in the American Journal of Public Health, osteoarthritis has long been researched and
linked to obesity as a risk factor (Schulte, et al., 2007). Bilateral osteoarthritis was found to occur more
than unilateral osteoarthritis and is twice as likely to occur for women than men (Davis, et al., 1989). A
review of studies pertaining to TKA surgery and osteoarthritis shows that many patients are choosing
elective surgery of bilateral total knee replacement/arthroplasty because pain with motion has become
too severe to manage due to the degeneration of cartilage between the tibia and femur at the knee joint
(Gurunathan, 2013). When patients were asked in the “Pre-hab” joint clinics onsite at our hospital why
they chose BTKA over UTKA they gave one of two answers: they were afraid that if the first surgery
was too painful, they would not elect to have the second; or they did not believe they would be able to
stand on the non-surgical leg while trying to rehabilitate the prosthetic knee joint.
In an Acute Care Perspectives literature review, Orest (2004) claimed that the inpatient acute care
setting at the hospital generally involves a three-day stay and the predominant outcome is that the
patient is able to perform supervised bed mobility, sit to stand-transfer, and ambulation of fifty or more
feet. Discharge to return home with home health care (HHC) within this allotted time frame is then
possible (Orest, 2004). Unfortunately, many obese patients have poor outcomes and are sent to
skilled nursing facilities (SNF) instead of HHC (Bozic, et al., 2006). Some return to the hospital with
complications such as infections at the surgical site (Minnema, et al., 2004).
A wide variety of research is available to both support and refute the use of bilateral total knee
arthroplasty as a solution to the diagnosis of bilateral osteoarthritis in this obese population. This
summary of research will enable caregivers to provide the most recent evidence available so that the
patient can make an informed decision regarding the best surgery for their individual needs.
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SECTION 2: Case Description:
This case study patient is a 53-year-old female who has undergone bilateral total knee arthroplasty
and was admitted to the acute care section of the medical/surgery level of the hospital physical therapy
rehabilitation department with a diagnosis of bilateral knee surgery to alleviate osteoarthritis pain at
both knee joints. The patient described having had arthroscopic surgeries over the past twelve years in
an effort to address a variety of knee joint pains. Because these surgeries did not alleviate the pain
and because the joints continued to degenerate, the patient elected to have bilateral total knee
replacements.
Chief Complaint (CC): The patient has a history of chronic osteoarthritis of bilateral knee joints
and presents with acute onset pain following bilateral total knee arthroplasty and a history of
arthroscopic surgeries to bilateral knees over the course of the last twelve years. The patient's chief
complaints were pain (9/10 for right leg, and 8/10 for left leg), stiffness, decreased strength, and
decreased functional ability. At the time of the initial postoperative visit, the patient stated that she felt
she was at about 40% of her normal functional level.
History of present illness: This patient is a 53-year-old Caucasian female status post bilateral
TKA. Prior to the surgery the patient was diagnosed with severe osteoarthritis (OA) of bilateral knees;
the patient noted that the symptoms in her right knee were much worse than those in her left. Before
resorting to TKAs she had two series of steroid injections in bilateral knees. She did not receive any
other conservative care such as physical therapy. The patient underwent a bilateral TKA in which her
right knee was operated on first using an anterior approach with dissection of soft tissue of the medial
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capsule, removal of medial and lateral osteophytes, soft tissue release to correct varus angle, sparing
of the posterior cruciate ligament (PCl), insertion of a 13mm spacer with cement, removal of part of the
patella and placement of button with cement, pulse lavage cleaned, placement of a deep drain, and
closure of her right knee, as per the procedure initiated by Scott and Thornhill in1986. The same
procedure was then done on her left knee.
Past medical history (PMH): The patient's relevant medical history includes: osteoarthritis of
bilateral tibiofemoral joints; depression; diabetes Type II, hypertension (controlled by medications);
severe obesity (BMI 50).
Medications: Zoloft 50 mg daily, ibuprofen 600 mg a few times per week, Vicodin a few times per
week and Lisinopril 10mg two times daily. Currently receiving Ropivacaine and Hydromorphine
Patient-Controlled Analgesic, Oxycodone, Oxycontin, and Coumadin.
Allergies: None.
Social history: The patient lives with her husband and three small dogs in a two-story
family house with three short steps about four inches high and about ten inches wide at the entrance.
She has worked as a medical receptionist for 25 years as well as a cosmetics distributor. She denies
tobacco or illicit drug use and rarely drinks a glass of wine.
Family history: Patient’s mother had migraines and died at the age of 70 after a heart attack. Her
maternal grandfather had a stroke at age 69. There is no other family history of stroke or vascular disease,
but she has no information about her father’s side of the family.
Systems Review: She states that she had an upper respiratory infection with rhinorrhea, congestion,
sore throat, and cough about six weeks ago. She denies fever, chills, malaise, weight loss, neck stiffness,
chest pain, dyspnea but confirms abdominal pain, diarrhea, constipation, urinary symptoms, joint pain, and
back pain upon waking after her surgery.
Upon observation, the patient on POD#0 from her BTKA had the following lines, tubes, and positioning
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devices: Epidural catheter, femoral nerve catheter, PCA pump for pain medication administration, Foley
catheter, nasal cannula for oxygen therapy, cryocuff over the knee joint for cryotherapy, venodyne
(compression) boots for DVT prophylaxis, telemetry/cardiac, continuous oxygen saturation monitors, knee
immobilizer to maintain the knees in extension, especially at night, when the patient is in bed, towel roll
under the ankles while in bed to maintain knee extension, hemovac and JP Drain to extract excess fluid
from the operated knee joint.
General physical examination: The patient is severely obese with pallor and diaphoresis.
Temperature is 37.6, blood pressure is 148/85, and pulse is 85. There is tenderness at the surgical site but
no sensation at bilateral quadriceps likely due to a “pain ball” attachment block for bilateral femoral nerve
called Ropivacaine. Cardiac record shows a regular rate and no murmur. The patient has general
weakness overall and especially at the tibiofemoral joints. The reflexes were not tested at the knee and the
upper extremity was difficult to assess due to adiposity. Light touch, pinprick, position sense, and vibration
sense are intact in fingers and toes. Rapid alternating movements and fine finger movements are intact.
There was no dysmetria on finger-to-nose while heel-knee-shin was not tested at this time. There were no
abnormal or extraneous movements. Balance was unsteady and patient stooped against the front wheel
walker. The bilateral upper extremities tremble after just a moment in the stance position and patient states
she was unable to hold or lift herself upward in the walker at post op day zero through three. Gait could not
be assessed because patient was unable to perform any ambulation activities with physical therapy.
In summary, this 53-year-old woman with longstanding OA had an acute onset of pain and weakness
associated with a bilateral total knee arthroplasty surgery. Because this surgery entails severing a minor
cutaneous nerve, the patient complains of lack of sensation at lateral aspect of the knee. The OA should
be alleviated since the surfaces in question were surgically replaced with a prosthesis material designed to
improve motion in all functional knee joint planes.
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EVALUATION: The patient was evaluated on POD#0. With any standard evaluation for knee
replacement surgery, there are four main questions to ask about their home environment. These detail
their ability to have assistance from family, the number of stairs needed to traverse in order to be a
household ambulator with front wheeled walker, and their strength and range of motion (ROM) in order to
mobilize themselves around in their bed and inside their home. She answered these clearly and she was
able to orient X3. Her ROM and strength were globally low and weak respectively. It was not clear if this
was due to lack of exercise routine implementation, the existence of adiposity impeding the movements or
the presence of pain or all of the above.
Diagnosis: The patient’s diagnosis was “osteoarthritis of bilateral tibiofemoral joints.” Based on the
Guide to Physical Therapist Practice this patient following BTKA is classified into the practice pattern 4H:
Impaired Joint Mobility, Motor Function, Muscle Performance, and Range of Motion Associated With Joint
Arthroplasty with ICD-9 Codes: 715 (osteoarthrosis and allied disorders), 718 (articular cartilage disorder,
derangement of joint), 719 (effusion of joint), 729 (disorders of soft tissue), 733 (disorders of bone and
cartilage), 836 (dislocation of knee), 958 (certain early complications of trauma) (APTA, 2001). These
practice patterns and codes include this patient’s particular diagnosis of osteoarthritis (OA) as well as many
other existing conditions.
Narrative Assessment: The 53-year-old female patient in this practice pattern was demonstrating the
following impairments: decreased range of motion, decreased muscle performance (including strength,
power, and endurance), decreased motor control, decreased balance, decreased gait, compromised tissue
integrity, and presence of excruciating pain. Particularly in the patient’s first few post-operative days, these
impairments resulted in decreased independence with bed mobility, transfers, ambulation, functional
activities, basic/instrumental activities of daily living (B/IADL), and quality of life. Re-evaluations and
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reassessments were done daily. It was consistently difficult to discern whether pain from surgery or
severely obese limbs was the cause of her general weakness. Her inability to get full range was also
difficult to discern at time of evaluation and during the recovery period of her stay in the hospital.
Re-evaluation / Assessment: The patient’s length of stay following her BTKA was three days. The
patient was re-evaluated on a daily basis with respect to her range of motion, quality of movement, muscle
contraction, pain intensity, gait quality, and functional independence. A formal re-evaluation was not
performed at the established seven to ten day period because the patient was discharged to a skilled
nursing facility.
Discharge Planning: Ideally, patients are discharged home after several days in the medical/surgery
department. Commonly expected outcomes for discharge home are the ability to perform bed mobility and
functional transfers independently, safely ambulate distances of 50-100 feet on even and uneven surfaces
with an assistive device, and increased knee ROM and strength, as previously identified in the goals
outlined above. This hospital uses a contemporary prospective study aimed at the community-based
population this patient may be associated with to assess normal return home time frame. The research
states that more than half of the patients were discharged home with home health care services following
their respective TKA, and all patients returned to the community within six months post-operatively (Jones,
2003). Those who were discharged directly home tended to be younger than those who were transferred
to another facility (Jones, 2003). During the acute care stay, TKA patients are typically seen once or twice
daily and are usually discharged home with HHC. Since the patient in question was on the “younger”
spectrum of patients seen for this particular type of BTKA, the expectation was that she would return home
after her allotted three days of recovery in the acute care wing of the medical/surgery department of this
hospital.
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Unfortunately this patient was discharged to a skilled nursing facility because she had several factors
causing unexpected poor progress as well as impractical home environment, and lack of assistance and
support from family and caregivers.
Inter-professional correspondence: Upon POD#1, collaboration with the patient’s hospitalist,
pharmacologist and student, charge nurse, physical therapist, occupational therapist and caseworker was
achieved during rounds. Rounds are held in a conference room with all departments of care providers
concerning this patient’s particular needs, in order to provide the best course of care for intervention while
she was staying in the hospital as well as for discharge planning at the time of initial evaluation. The round
discussion was documented in the initial physical therapy evaluation note. This assisted in facilitation of
appropriate discharge destination of skilled nursing facility with services, and an ambulance transfer to the
extended care facility.
Patient and Family Education: Because this patient ‘s husband was present at bedside on POD#1,
we educated him and his wife on the correct positioning of the bilateral operative tibiofemoral joints, the
benefits and use of the continuous passive motion (CPM) machines, the importance of initiating early
mobility, safety, weight bearing awareness with the Ropivacaine medication, details of our physical therapy
intervention plan including her expected independent exercises, and the anticipated discharge goals and
outcomes. Because her orthopedic surgeon referred her, the patient and her husband attended our “Prehab” joint education class for patients that plan to undergo BTKA. This hospital utilizes recent research of a
meta-analysis to support pre-operative education for orthopedic patients because it appears to reduce
anxiety levels and increase their knowledge (Johansson, et al, 2005).
Problem/Intervention: 1. The patient is experiencing decreased ROM from adiposity at UE and LE
joints causing decreased independence with bed mobility, transfers, and ambulation. The patient received
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attempted AROM/AAROM/PROM activities for therapeutic exercise approach. 2. Decreased strength from
deconditioning at UE and LE joints and decreased strength from TKA surgery to bilateral tibiofemoral joints.
The patient was given a series of bed exercises to build bed mobility and strength. The patient was
informed of risks and benefits of this procedure and was scheduled to perform ankle pumps and quad sets
every four hours. 3. Depression. The patient denied current symptoms and will continue Zoloft at current
dose. 4. Severe Obesity. The patient requested referral to a dietician.
Physical therapy plan and interventions: The plan of care treatment during the patient’s stay in
inpatient acute care was focused on increasing knee joint ROM, muscle control, and functional
independence with bed mobility, sit to stand transfers as well as ambulation with the assistive device of a
fitted front-wheeled walker. In order to maximize this patient’s functional outcomes, outpatient therapy is
enlisted in the plan and this arena will focus on ROM, strength, gait, balance, and controlling inflammatory
responses while treatment is progressed as appropriate for this individual’s response to care throughout the
physical therapy received over the course of her recovery.
Beginning POD#1, the patient was asked to try to actively flex and extend the knee joints and an
estimated range of zero motion was recorded; when actively assisted with these motions, the pain was too
great to make an objective assessment; passive range of motion of bilateral knees at each visit was also
difficult to assess due to the excruciating pain the patient described at the attempt of any motion.
Therapeutic exercises such as strength training with focus on isometric and functional quadriceps control,
hamstrings, as well as hip abductors and adductors were assessed and the patient was not able to
perform unless moving in and out of the CPM machines, and even then she needed maximum assistance
with two care providers. The patient was given exercises beginning POD#1 for respiratory and circulatory
systems to include deep breathing by utilizing an inspirometer, as well as a request for coughing. Closed
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chain exercises while pushing against the foot of the bed, such as ankle pumps, were also taught once she
demonstrated good pain control, muscle strength, and balance. We did not use resistive exercises for the
quadriceps and hamstrings because we expect they will be employed at the two months post-op time frame
(Scott, 2006).
We were not able to initiate the patient for gait training on the hospital floors, nor were we able to assess
the patient on stairs using the FWW due to her high level of pain and refusal to try and move from her bed
or bedside commode.
Ice therapy (cryotherapy) was utilized and recommended for 72 hours post-op because it has been
shown to reduce or maintain the current inflammatory response from the surgical procedures as well as
control some of the surface pain by slowing the metabolic processes and nerve conduction velocity of the
nerve signals (Cameron, 2003).
Assistive Device Protocol: Because this particular patient needed a special fit front-wheeled walker
(FWW), coordination with the caseworker was achieved in rounds and the patient received her walker on
POD#1. Physical therapy worked with the patient and husband and demonstrated the fitting and sizing of
the walker. The patient was measured, fitted, and trained with this FWW assistive device to increase safety
and independence during ambulation and transfers. We also educated the patient and family member that
the patient should be progressed to a less restrictive assistive device as safety allows and upon the
reassessment and recommendation of whichever professional caregiver and physical therapist they are
working with upon discharge from this institution. Occupational therapy recommended other durable
medical equipment (DME) to facilitate safe and independent transfers. These included a bedside
commode, raised toilet seat, as well as a tub/shower seat.
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Prognosis: Due to the nature of the patient’s pre-existing conditions, the prognosis was poor. The
patient had severe obesity as well as weak upper body strength and was unable to support her own weight
in the walker. A lift was not utilized at this hospital because neither the hospital nor the patient owned one
and therefore it would not have been useful to train the patient with a tool she would not have at home.
Short Term Goals: Time frame for achievement of short-term goals in acute care hospital setting is
three days. Patient will perform all bed mobility and transfers with the least amount of assistance and
devices; Patient will ambulate household distances (50-100 feet) and transfer on stairs (step-to pattern,
non-reciprocal) with the least amount of assistance and using front wheeled walker device; patient will
demonstrate a fair to good isometric quad contraction for five seconds at three repetitions, will have ability
to perform straight leg raise (SLR), and manual muscle testing (MMT) of greater than or equal to (>=)3-/5
so that she will be able to increase independence with her bed mobility, transfers, and ambulation; Patient
will gain >=90 degrees of flexion and full extension knee ROM to allow for proper biomechanics during gait
cycle and stair climbing. Long-Term Goals: Patient will ambulate without assistive devices within two to four weeks of the
surgery. Bilateral knee ROM will reach 0-115 degrees and quadriceps strength >=4+/5 MMT within three
months following BTKA. The latest research studies state that the average knee flexion ROM after TKA
may range from 105 - 113 degrees (Miner, 2003). The overall long-term goal for the patient is to at least
return to her pre-operative level of function with less pain. The patient's goals for physical therapy included
returning to normal ambulation (defined by the patient as without an assistive device, without pain, and with
a normal-looking gait pattern), ambulation of stairs because she has a two-story home, driving for her job
and errands, normal level of function with activities of daily living (ADLs), and getting to and from her place
of business as well as ability to visit clients in their various homes to deliver her orders.
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Outcomes: Patient was discharged on POD#3 by ambulance to a skilled nursing facility. The patient
was transported in this manner due to the inability to move from the bed and transfer to a wheelchair with
the assistance of four of the care providers. A daily attempt to assist this patient with bed mobility and
transfers was made but to no avail. Due to the unexpected lack of progress, the patient was discharged
from inpatient acute care hospital PT to a SNF on POD# 3. Had the most recent research been provided to
this patient, perhaps she could have made a more informed decision regarding whether to have a unilateral
or bilateral knee replacement surgery and thereby prevented a poor outcome. At the writing of these
reports, it was discovered that she was readmitted to hospital with an infection at the incision site.
Citations:
Bozic K, MD, MBA, Wagie A, Naessens JM, MPH, Berry DJ, MD, Rubash HE, MD. Predictors of Discharge
to an Inpatient Extended Care Facility After Total Hip or Knee Arthroplasty.The Journal of Arthroplasty.
Volume 21, Issue 6, Supplement, September 2006, Pages 151–156
Cameron MH. Physical Agents in Rehabilitation: From Research to Practice. Saunders and Elsevier, 2003,
2nd Edition.
Davis MA, Ettinger WH, Neuhaus JM, Cho SA, Hauck W. The association of knee injury and obesity with
unilateral and bilateral osteoarthritis of the knee. Am J Epidemiol. 1989 Aug;130(2):278-88.
Guide to Physical Therapist Practice; 2nd Edition, APTA. Phys Ther 2001; 81: 9-744.
Interactive Guide to Physical Therapist Practiceby American Physical Therapy Association.2003. DOI :
10.2522/ptguide.978-1-931369-64-0.
Gurunathan U. Perioperative considerations of bilateral total knee replacement: a review. J Clin Anesth.
2013 May;25(3):232-9. doi: 10.1016/j.jclinane.2013.01.001. Epub 2013 Apr 2.
Iorio R, Robb WJ, Healy WL, Berry DJ, Hozack WJ, Kyle RF, Lewallen DG, Trousdale RT, Jiranek WA,
Stamos VP, Parsley BS. Orthopaedic surgeon workforce and volume assessment for total hip and knee
replacement in the United States: preparing for an epidemic. J Bone Joint Surg Am. 2008;90:1598–1605.
Johansson K, Nuutila L, Virtanen H et al. Preoperative education for orthopaedic patients: systematic
review. Journal of Advanced Nursing 2005; 50(2): 212-223.
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Jones CA, Voaklander C, Suarez-Almazor ME. Determinants of function after total knee arthroplasty. Phys
Ther. 2003; 83: 696 –706.
Miner AL, Lingard EA, Wright EA et al. Knee range of motion after total knee
arthroplasty: how important is this as an outcome measure? J Arthroplasty 2003; 18: 286-294.
Minnema B, Vearncombe M, Augustin A, Gollish J, Simor AE. Risk factors for surgical-site infection
following primary total knee arthroplasty. Infection Control and Hospital Epidemiology. 2004;25(6):477- 480
Orest MR. Total Joint Replacement Literature Review. Acute Care Perspectives 2004;
Spring: 8-10
Schulte, P., PhD, Wagner, G., PhD, Ostry, A., MD, et al. Work, Obesity, and Occupational Safety and
Health. Am J Public Health. 2007 March; 97(3): 428–436.
Scott RD. Total Knee Arthroplasty. Saunders and Elsevier, 2006.
Scott RD, Thornhill TS. Press-fit condylar total knee replacement. Tech Orthop 1986; 1(4): 41-58.
Sculco TP, Sculco PK. Simultaneous-bilateral TKA: double trouble - opposes. J Bone Joint Surg Br. 2012
Nov; 94(11 Suppl A):93-4.
SECTION 3: Evidence Based Analysis
Methodologies of Search:
“Do morbidly obese patients in the acute care setting who have had Simultaneous-BTKA surgery have
better outcomes in regards to: complications, ambulation, hospital stay days, and D/C disposition after
receiving inpatient PT care than patients that have Staged-UTKA surgery?”
Summaries:
Amin AK, Clayton RAE, Patton JT, Gaston M, Cook RE, Brenkel IJ. Total knee replacement
in morbidly obese patients. J. Bone Joint Surg. Br. 2006; 88: 1321–6.
Level of evidence: 1b
Purpose: To assess the influence of morbid obesity on the outcome after total knee arthroplasties, in a
consecutive series of morbidly obese patients (BMI > 40 kg/m2), with a matched group of non-obese
patients (BMI < 30 kg/m2).
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Methods: Forty-one primary total knee arthroplastys were done on thirty-eight morbidly obese patients.
Matched control groups consisted of thirty-eight non-obese participants. Match criteria consisted of age,
gender, diagnosis, and type of prosthesis, laterality, as well as pre- op Knee Society Score. A Knee
Society Score joint specific outcome scoring system was used to determine the ability of patients to walk
and to take the stairs. Seven consultant orthopedic surgeons took part in surveying the study, overall.
Several outcome measures were used to calculate results. Radiographs and Knee Society Score were
consulted. Survivorship analysis was based upon the Kaplan-Meir methods.
Results: Results of forty-one total knee arthroplasty surgeries done on patients with a BMI of 40kg/m2
were compared with a matched population of forty-one similar procedures done on non-obese patient sets.
Follow up was done on all for a mean time of 38.5 months. Results of fifty primary total knee arthroplastys
were tabulated in morbidly obese patients and compared with 1768 parallel procedures done on patients
who were not obese. Outcome scores showed inferior numbers in the study population with regard to rates
of revision and in peri-operative complications.
Mean post-op knee scores and function were lower in the morbidly obese set of patients. One morbidly
obese patient died 3 years later due to deep infection revision. Five-year survivorship was at 74.2% in the
morbidly obese set and 2 people reported pain, one in each group.
Critique/Bottom Line: Results are similar in patients with a BMI between 30 and 40 and with the nonobese patients. However, overall results do show as inferior when compared to the patients who were not
obese. Patients with a BMI of 40 or above should be warned of the possibility of an inferior outcome with
total knee arthroplasty or be counseled about the importance of losing a substantial amount of weight
before undergoing such a surgery. There exists a need for much further testing in this area where the
morbidly obese patients are concerned.
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Fabi D, Mohan V, Goldstein WM, Dunn JH, Murphy BP. Unilateral vs. bilateral total knee
arthroplasty: risk factors increasing morbidity. The Journal of Arthroplasty. 2011, Aug: 26(5): 66873.
Level of evidence: 2b
Purpose: Identifying which patients are at risk for complications are a concern because more surgeons
are performing bilateral total knee arthroplasty.
Methods: Retrospective studies were considered in the analysis of one hundred fifty patients with
unilateral total knee arthroplasty vs. one hundred fifty patients who underwent simultaneous bilateral total
knee arthroplasty. Patients undergoing unilateral total knee arthroplasty were included in the control group
while the patients with bilateral total knee arthroplasty were identified in the study group. Five people in the
control group and twenty-two people in the bilateral study group had existing pulmonary disorders at the
times of their surgeries. Patients had either general anesthesia or spinal or epidural anesthesia. Knee
immobilizer was placed in the OR and was not used by post-op day two. Physical therapy was
administered during post-op day one. All participating patients were then sent to an extended care facility,
ongoing physical therapy, rehabilitation or home. Complications that were noted were wound
complications, gastrointestinal disturbances, hyperglycemia, neurovascular insult, fractures, and renal or
pulmonary complications.
Results: The bilateral group showed a 2.1 times greater mean complication rate and an increased
transfusion rate. Significantly higher complications rates surfaced in patients older than 70 years of age
such as increased risks for cardiovascular problems, pulmonary and neurological complications. The pros
of bilateral total knee arthroplasty have the potential for reducing costs for surgery and would appear to
promote a shorter length of recovery time and only one anesthetic event. Performing only one knee at a
time guarantees that the patient would need to endure twice the surgeries, twice the recovery time and
double the lost wages as a result of that choice. It was determined that a patient’s age must be considered
when determining the outcome and success rate mostly because of the physiological stressors in older
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patients enduring the bilateral procedures. In patients older than 75 and undergoing unilateral total knee
arthroplasty, higher mortality rates have been noted. One important option that could help reduce the risk
for complications during surgery is to appeal to the patient the importance of losing weight before
undergoing these procedures. In obese patients, the complications were significant because the rates
were more than double.
Critique/Bottom Line: The data was collected and compiled from both clinic and hospital records which
could have been under-reported and were based on one single surgeon’s experience and may not fully
represent other orthopedic surgeons work or single experience within the same field. Patients should be
consulted about the pros and cons of both unilateral and bilateral procedures and compare for costs and
recovery time as well as for age and obesity related potential complications before undergoing either
procedure.
Foran JRH, Mont MA, Etienne G, Jones LC, Hungerford DS. The outcome of total knee arthroplasty
in obese patients. J. Bone Joint Surg. Am. 2004; 86: 1609–15.
Level of evidence: 2b
Purpose: High body weight could be the cause of increased stress across the components in the knees
and tends to place a larger load on the bone surrounding it. Extra body weight could also be the cause of
some degenerative joint disease. This study compared both clinical and radiographic end results of total
knee arthroplasty surgeries in obese patients with those in non-obese patients.
Methods: Both clinical and radiographic data concerning seventy-eight total knee arthroplasty in sixtyeight obese patients were compared to a separate group of non-obese patients. Data included Knee
Society criteria and scoring, symptoms for patellofemoral issues, the activity levels and various
complications. Separate statistical data gathered that compared the obese and non-obese groups showed
no major difference and authors were blinded to the outcomes at that time. Follow-up data was gathered
18
by way of a blinded, retrospective review of database charts, radiographs and by interviews conducted by
telephone.
Results: Eighty eight percent of the obese group resulted in a low count by the Knee Society Score. This
score was lower than the non-obese group’s rate. The morbidly obese group ended up with a high revision
rate when compared with the non-obese group (p=0.02).
Critique/Bottom Line: This study seemed to be a bit more in-depth than the others because the study
was conducted over a longer period of post-operative time than some of the other studies. However, some
findings in this study could be seen as limiting because there were such a small number of patients to
consider. The obese patients did show a lower pre-op Knee Society objective and functional scoring, which
could account for the lower satisfaction levels reported. The consensus for obese patients remains similar
to what other studies have proven in the past. Obesity has a negative effect on the outcomes of total knee
arthroplasty surgeries and even more so if the patient is morbidly obese. Revision rates are expected to
have negative effects in the obese and the morbidly obese populations considering total knee arthroplasty.
Recovery times are expected to be longer and infection rates were higher in this group, as well.
Fu D, Li G, Chen K, Zeng H, Zhang X, Cai Z. Comparison of clinical outcomes between
simultaneous-bilateral and staged-bilateral total knee arthroplasty: a systematic review of
retrospective studies. The Journal of Arthroplasty. 2013, Aug; 28(7): 1141-7.
Level of evidence: 2a
Purpose: The purpose of this study was to perform a systematic review to find the clinical outcomes
comparing simultaneous bilateral and staged bilateral total knee arthroplasty. A total of eighteen
retrospective comparative studies were considered. Gathered results showed that thirty days post-op, the
propensity for pulmonary embolisms and blood transfusion rates were higher in the simultaneous total knee
arthroplasty patients while a lower rate of deep infection and revision were needed in the group. In the
staged bilateral total knee arthroplasty group, simultaneous bilateral total knee arthroplasty was associated
19
with higher rates of mortality, pulmonary embolism and blood transfusions but a decreased risk of infection
and revision rate were concluded. The purpose of this meta-analysis was to evaluate the occurrence of
mortality rates, to study the complications that arise and the cost effectiveness between the two surgeries.
Methods: To avoid selection bias, criteria were used including clinically significant cases of osteoarthritis,
rheumatoid arthritis in both of the knees of participants and reports of severe pain that has been of no relief
through traditional therapies. The most important outcomes focused on details of the incidence of any
complications, mortality rates within thirty days of the procedure, blood loss and transfusions, the length of
the patient’s post op hospital stays and finally, the rate of necessary revision arthroplasties, if any.
Results: Eighteen retrospective cohort studies were included and 107,318 patients considered, of which
28,760 had simultaneous bilateral total knee arthroplasty and 78,558 had staged bilateral total knee
arthroplasty and were chosen to be included in the study, as well. Cardiac complications occurred in both
patient populations. Hypertension was the common comorbidity in both groups and was noted in at least
50% of the entire set of participants. There was no increased risk of neurological complications observed.
Hospital stays were observed as an average of 2 days.
Critique/Bottom Line: All included studies were reviewed in methodological quality and the information
was not consistent in the meta-analysis studies. Future trials are necessary in results of simultaneous
bilateral total knee arthroplasty. Actions in pre-op prevention steps need to be taken to avoid complications
to be sure that every preventative measure has been taken. Simultaneous bilateral total knee arthroplasty
remains an acceptable option to alleviate chronic knee pain but only in a very select population.
20
Kerkhoffs GMM, Servien E, Dunn W, Dahn D, Bramer JAM, Haverkamp D. The influence of obesity
on the complication rate and outcomes of total knee arthroplasty: a meta-analysis and systematic
literature review. J Bone Joint Surg. Am. 2012, Oct; 94(20): 1839-44.
Level of evidence: 2a
Purpose: Many people in the United States are carrying around extra body weight and obesity has
become an epidemic. It is well documented that obesity is a risk factor for the development of
osteoarthritis. The aim of this study was to find out if obesity had a negative influence for the outcome in
primary total knee arthroplasty. The primary research question was to determine whether or not the
outcomes of primary total knee arthroplasty would be influenced by BMI.
Methods: A search of available literature was done and studies were compared in the outcomes of total
knee arthroplasty, including different weight groups. The studies were scored using the Cochrane
guidelines. Both weighted mean difference and weighted odds ratios were calculated. The use of the I2
statistics calculated heterogeneity. Studies including various different types of cemented and non-cemented
total knee prosthesis designs were consulted. The aim of the systematic review was to indicate whether
obesity lead to a worse outcome after total knee arthroplasty. Higher risks were associated with both the
short and the long-term. It was determined that patients should be advised to make every effort to lose
weight before their surgery because of this factor. Twenty studies were consulted in data analysis after a
consensus was reached.
Results: Obese groups of patients suffer more comorbidities than the non-obese patients and this is the
reason they have more complications during surgery. Obese patients were more prone to developing
infection than non-obese patients were, post-operative. Of fourteen studies including 15,276 patients,
infection developed in the obese patients. Deep infection occurred more in the obese population and the
odds ratio was 2.38 and included 5,061 patients. Revision of total knee arthroplasty occurred in 12,101
21
patients. The revisions happened more in the obese patients and the odds ratio was 1.30. Obesity was a
factor and did have a negative influence after total knee arthroplasty.
Critique/Bottom Line: Concerning Level-I evidence of the result of morbid obesity in the outcomes of total
knee arthroplasty was difficult to assess. The highest of quality type study cannot be observed because
blinding was not completely possible. Gathering of the methodology results showed that the studies
involved in this entire review were similar and pooling them was justified. Revisions of the total knee
arthroplasty (exchange or removal of the components for any reason) were found to have occurred in at
least eleven studies that included 12,101 patients.
Powell RS, Pulido P, Tuason MS, Colwell Jr CW, Ezzet KA. Bilateral vs. unilateral total knee
replacement: a patient based comparison of pain levels and recovery of ambulation skills. The
Journal of Arthroplasty. 2006, Aug; 21(5): 642-9.
Level of evidence: 2b
Purpose: The intention of this research was to explore the differences between pain levels and recovery
time and then compare the differences between unilateral total knee arthroplasty and bilateral total knee
arthroplasty. Orthopedic surgeons attempted to answer the questions that patients have when trying to
decide whether to have one knee surgery at a time and if they would experience more pain having both
knees done at the same time or if one knee at a time would constitute less pain, overall.
Methods: The study consulted records and charts on fifty-nine matched pairs of patients undergoing total
knee arthroplasty in a retrospective appraisal. All patients had identical techniques done by one of the four
surgeons on staff and received identical postoperative protocols. No revisions were included in the study
and upon completion of their surgery; patients were mobilized with physical therapy in the morning the day
after their surgery occurred. Patients were treated with enoxaparin for prophylaxis to guard against deep
vein thrombosis. Narcotics use in postoperative patients was studied and compared between the two
22
groups. Patients receiving spinal narcotics, epidural narcotics, intra-articular infusion pumps or peripheral
nerve blocks were excluded from this study. Analog pain scores were calculated every four hours and the
bilateral group’s data on their day of discharge were further calculated and placed into three basic
categories: max ambulatory ability of 0 to 49, 50 to 99, or 100 feet and greater. Discharged patients were
either sent home or placed into a skilled nursing facility. Any complications were then collected, recorded
and compared.
Results: Both men and women participated in the study with a mean age of 67.71 years. In the unilateral
group, there were twenty-five right total knee arthroplastys and thirty-four left knee total knee arthroplastys.
Fifty-eight patients had a diagnosis of osteoarthritis as well as rheumatoid arthritis and superimposed
degenerative joint disease (in one patient). Fifty-nine patients received the diagnosis of osteoarthritis. The
need for analgesics was greater in the bilateral group, although, narcotics use was necessary in both
groups. The analog pain scale data showed a major difference between the unilateral and the bilateral
groups, the reported pain being less in the unilateral group. By the third day, the pain was indistinguishable
within either group. Both groups progressed rapidly in the ambulatory category but the unilateral group
ambulated further.
Critique/Bottom Line: Narcotic use is difficult to predict ahead of time. Each patient’s pain tolerance can
be diverse. Discharge decisions must be based upon different variables, such as whether or not they have
an adequate support system at home or if a skilled nursing home facility might be the better choice. The
patient may use this valuable information to make the decision for unilateral vs. bilateral.
23
Samson A, Mercer G, Campbell D. Total knee replacement in the morbidly obese: a literature review.
ANZ J Surg. 2010 Sep; 80(9): 595-9.
Level of evidence: 2b
Purpose: The intention of this research was to specifically evaluate outcomes of total knee replacement in
patients with morbid obesity because obesity is becoming a global epidemic. Problems stemming from
morbid obesity are concurrent with much comorbidity such as: type II Diabetes, Cardiovascular Disease,
Obstructive sleep Apnea, Malignancy and Musco-Skeletal Disorders. There is strong evidence that obesity
is an independent cause of knee osteoarthritis, therefore, a need for discussion regarding total knee
replacement in obese patients is tantamount.
Methods: A systematic review of PubMed, Medline, Cochrane Library, and Science Direct during January
1990 to September 2009 commenced. The researchers used keywords such as: knee, arthroplasty, morbid
obesity, body mass index, KSS, clinical outcome and complications. Articles in this review were assessed
for the level of evidence based on guidelines provided their National Health and Medical Research Council
of Australia and New Zealand. The final analysis yielded ten prospective; case-control, reviews and
retrospective comparative studies with levels of evidence from A to C III-3 were included an studies were
omitted if the level of evidence was less than C IV.
Results: The morbidly obese had a higher prevalence of complications in all studies.
Total knee replacement in morbidly obese carried significantly higher complications of wound healing,
superficial infection, deep-vein thrombosis and deep prosthetic infection. Not only did morbidly obese
populations have a significantly higher incidence of wound complications, they notably did not result in
weight loss for the morbidly obese patients.
Critique/Bottom Line: The aim of total knee replacement is to alleviate pain, restore alignment, and
enhance function as well as improve quality of life for patients. This article reviewed the literature and
discussed implications and outcomes for this population of patients. Functional Knee Society Score (KSS)
24
Knee function after total knee replacement was assessed with the functional component of the outcome
measure. KSS examines walking distance and ability to walk up and down stairs and subtracts points for
use of walking aides. Studies demonstrated a significantly lower post-op functional score in the morbidly
obese patients. The morbidly obese have higher stress across the total knee replacement but this may be
compensated by the nature of the patient’s reduced activity. Morbidly obese patients had a significantly
higher prevalence of deep prosthetic infections and treatment of those infections had considerable financial
and psychological costs. Morbidly obese patients suffered wound complications, poor oxygenation of
adipose tissue, increased wound tension and underlying endocrine disorders. Patients with a wound
complication subsequently developed a deep joint infection. In light of these results, morbidly obese
patients could be encouraged to lose weight before undergoing these surgical procedures.
Winiarsky R, Barth P, Lotke P. Total knee arthroplasty in morbidly obese patients. J Bone Joint
Surg [Am] 1998;80-A:1770–4.
Level of evidence: 2b
Purpose: The clinical outcomes for 50 (40 patients, 50 knees) total knee arthroplasty surgeries that were
performed with cement were reviewed and included morbidly obese patients. Surgeries performed in the
same time span and by the same surgeon were compared involving 1,768 patients who were not morbidly
obese. By the time five years had passed, there were remarkable differences between the groups with
regard for knee functional scores. Rates of perioperative complications were notably higher in the morbidly
obese patients. Wound complications, infection and avulsion of the medial collateral ligament became
problems in the morbidly obese patients and the authors of this study found that changes needed to be
made in the operative techniques during the soft-tissue closure and more protection of the medial collateral
ligament could possibly decrease the complications occurring post-operatively in these patients in future
surgeries.
25
Methods: Patients were evaluated pre and postoperatively using the Knee Society rating system and
during this 15-year span of the study, the total condylar, posterior stabilized, press-fit condylar designs
were implemented. The same pharmaceuticals were utilized for infection and pain prevention and obese
patients were treated no differently concerning prevention against thromboembolism. The Fisher exact
two-tailed test analyzed the differences in the obese patients as well as the control group and ages for all
patients were considered. Quetelex indexes were consulted regarding the best measure to define BMI.
Rate of infections, wound complications and knee functions as well as radiographic scores were tabulated.
Lesser P values were acknowledged as important in the study.
Results: The mean age of obese patients was 64.6 years of age. Thirty-six women and four men were
considered in this study. Some potential problems causing pre-op concern were osteoarthritis in 38
patients, rheumatoid arthritis in two patients and Paget disease in one. No significant differences in either
group were found regarding range of motion or the overall radiographic score (p=0.77). Problems in areas
of primary wound healing seemed common in the obese group. Two out of five infections occurred, one
being Staphylococcus aureus and the other being Staphylococcus epidermis. Treatments of these
infections were successful. One of the prosthesis failed and a second failed because of aseptic loosening
and multiple revisions.
Critique/Bottom Line: Morbidly obese patients tend to have a lower level of activity than their
counterparts in the control group and that issue needs to be addressed if infection and post-op
complications are to be avoided. Patients undergoing total knee arthroplasty also need to be coached and
informed extensively in future surgeries about the importance of wound care after their procedure to steer
clear of further infection and complications.
26
Discussion of all studies:
A compilation of the studies by Amin, Foran, Kerkhoffs, Samson and Winiarsky addressed the
research question section regarding the issue of the morbidly obese patient who had undergone total knee
arthroplasty of either staged unilateral, unilateral or simultaneous bilateral procedures.
The Amin study was designed to assess the influence of morbid obesity on the outcome after TKR, in a
consecutive series of morbidly obese patients (BMI > 40 kg/m2), with a matched group of non-obese
patients (BMI < 30 kg/m2). These found that at less than four years after operation, the results were worse
in the morbidly obese group compared with the non-obese, as demonstrated by inferior Knee Society
Scores (mean knee score 85.7 and 90.5 respectively, p = 0.08; mean function score 75.6 and 83.4, p =
0.01), a higher incidence of radiolucent lines on post-operative radiographs (29% and 7%, respectively, p =
0.02), a higher rate of complications (32% and 0%, respectively, p = 0.001) and inferior survivorship using
revision and pain as end-points (72.3% and 97.6%, respectively, p = 0.02) (Amin, 2006). The Foran
research compared the clinical and radiographic results of TKA performed in obese patients with those of
arthroplastys performed with the same prosthesis in non-obese patients and there was no significant
difference in the need for revision surgery at 5 years between the obese and non-obese group of patients.
However, at seven years after surgery, the obese group had a significantly higher “implant failure” rate
(12.3%) as defined by re-operation, clinical failure (Knee Society objective score < 80 points), or
radiographic implant failure, as compared to the non-obese group (1.3%) and there was no statistically
significant difference in the perioperative complication rates in their relatively small study population, and
DVT occurred only in the obese group (Foran, 2004). The Kerkhoffs article determined that obesity had a
negative influence on outcome after primary total knee arthroplasty with more short-term complications and
poorer long-term outcome compared with non-obese patients (Kerkhoffs, 2012) while the Samson study
evaluated outcomes of TKR in patients with morbid obesity (MO; BMI >40) and found clinical and functional
27
Knee Society Scores (KSS) improve after TKR for patients with MO while the post-operative functional KSS
was less than in controls (Samson, 2010). All studies in the Samson review noted a greater prevalence of
complications in MO patients (10–30%) and of concern was the significantly higher infection rate (3–9-times
that of controls) as well as the MO group also had a significantly higher incidence of wound complications
(Samson, 2010). Unfortunately, TKR did not result in weight loss for MO patients, and did not have and
bearing on weight-related medical conditions (Samson, 2010). The Winiarsky research studied the clinical
outcomes of fifty primary TKAs performed with cement in fifty MO patients and compared results with 1768
similar procedures, performed during the same time-period by the same surgeon, in 1539 patients who
were not morbidly obese (controls) and at a mean of approximately five years postop, and found there was
a significant difference between the MO patients and the control group RE: knee and functional scores (84
and 53 points compared with 92 and 67 points; p < 0.00005 for both scores) (Winiarsky, 1998). However,
there was no significant difference with the numbers re: range of motion or the radiographic score (p =
0.77) but the rate of perioperative complications was significantly higher in the morbidly obese patients (p <
0.00005) and of the fifty knees in MO patients, eleven (22 percent) had a wound complication, five (10
percent) had an infection, and four (8 percent) had an avulsion of the medial collateral ligament (Winiarsky,
1998). The overall findings of these studies indicate the increased risks for lower functioning and higher
peri and postoperative rates of complications and infections in the obese and morbidly obese groups.
The studies by Fabi, Fu and Powell addressed the research question section regarding the issue of
the different types of total knee arthroplasty of either staged unilateral, unilateral or simultaneous bilateral
procedures and whether one or the other had better outcomes as well as assessing BMI as an indicator.
The Fabi study identified which patients may be at increased risk when undergoing unilateral or
bilateral total knee arthroplasty and found the BTKA group had a higher transfusion rate of 0.47 as
compared with 0.12 for the control group, with a significant P value of .0019, almost a 4x higher rate of
28
transfusion than those patients undergoing UTKA while the complication rate for BTKA patients (0.95) was
slightly more than double that of the control group (0.45), with a P value of .012, which was significant
(Fabi, 2011). Patients with a BMI > 30, had 62 patients in the control group and 74 in the bilateral group
and a significant difference in complication rates between the control (0.44) and bilateral (0.96) groups, with
a P value of .0126, was found while there was a significant difference between means when comparing the
length of stay between the control and bilateral groups and the mean values for the control and bilateral
groups were 3.3 and 4.9 days, respectively, with a P value of less than .0001 (Fabi, 2011).
Fu’s systematic review assessing the clinical outcome associated with simultaneous-bilateral (SmBTKA) and staged-bilateral TKA (Sg-TKA) assessed rate of mortality within 30 days after surgery,
pulmonary embolism, and blood transfusion associated with Sm-TKAs and found they were higher
compared to Sg-TKAs (Fu, 2013). Sm-BTKA may be concurrent with a lower rate of infection, revision,
lower costs, shorter anesthetic time and lower total recovery time without increasing the incidence of neuro,
DVT, and cardiac complications and use of TKA on select criteria may lower perioperative complications
(Fu, 2013). The Powell article answered questions regarding pain and ambulation outcome differences
using a cohort of BTKA patients compared with a matched cohort of UTKA patients and the BTKA group
had significantly higher pain perception at POD#1 and there were no statistically significant differences
narcotic use while a significant difference occurred in ambulation skills where UTKA performed much
higher than BTKA in acute care and a higher percentage of BTKA are discharged to a skilled nursing facility
than UTKA, however, complications were identical in both groups (Powell, 2006).
The overall findings of these studies indicate the increased complication rates, pain, length of stay
and being discharged to a skilled nursing facility as well as a decreased ambulation skill for those patients
that were obese and having had the simultaneous bilateral procedure done. The costs seemed to be less
and when the data looked at select populations, meaning little or no comorbidities, the simultaneous
bilateral procedure looked promising. All these studies applied to the patient because she was in the
29
morbidly obese category as well as having undergone a bilateral total knee arthroplasty and was recovering
in the acute care section of the medical surgery department for physical therapy at Lovelace Women’s
Hospital.
Conclusion/Bottom Line:
This compilation of research presents all the recent information available regarding the issues
surrounding the outcomes of simultaneous bilateral total knee arthroplasty for the morbidly obese patients.
The research supports the notion that there are higher perioperative and postoperative risks associated
with choosing this simultaneous bilateral surgery in the obese or morbidly obese population. There are
also low functional outcomes associated with this procedure and population as well as an unfavorable
discharge disposition because many of this patient population do not get to return home and have to go to
a skilled nursing facility, which may, in turn, cost more money than the patient thought they would save by
having both knees done at once. It was noted that some of the reviews that state that the simultaneous
procedures may be less risky and lower cost are doubling the data of the unilateral outcomes when they
may not have actually followed that patient and really taken the exact numbers from each hospital
procedure and stay and compared them with that of the simultaneous bilateral data. Overall, the
information is clear and there is statistical data to support the idea that bilateral simultaneous total knee
arthroplasty carries with it higher risk, pain, longer hospital stays, unfavorable discharge disposition, and
less functional ambulation outcomes (especially for those with comorbidities such as morbid obesity) than
having the staged or unilateral procedures.
30
References
Amin AK, Clayton RAE, Patton JT, Gaston M, Cook RE, Brenkel IJ. Total knee replacement in
morbidly obese patients. J. Bone Joint Surg. Br. 2006; 88: 1321–6.
Fabi D, Mohan V, Goldstein WM, Dunn JH, Murphy BP. Unilateral vs. bilateral total knee
arthroplasty: risk factors increasing morbidity. The Journal of Arthroplasty. 2011, Aug: 26(5): 66873.
Foran JRH, Mont MA, Etienne G, Jones LC, Hungerford DS. The outcome of total knee arthroplasty
in obese patients. J. Bone Joint Surg. Am. 2004; 86: 1609–15.
Fu D, Li G, Chen K, Zeng H, Zhang X, Cai Z. Comparison of clinical outcomes between
simultaneous-bilateral and staged-bilateral total knee arthroplasty: a systematic review of
retrospective studies. The Journal of Arthroplasty. 2013, Aug; 28(7): 1141-7.
Kerkhoffs GMM, Servien E, Dunn W, Dahn D, Bramer JAM, Haverkamp D. The influence of obesity
on the complication rate and outcomes of total knee arthroplasty: a meta-analysis and systematic
literature review. J Bone Joint Surg. Am. 2012, Oct; 94(20): 1839-44.
Powell RS, Pulido P, Tuason MS, Colwell Jr CW, Ezzet KA. Bilateral vs. unilateral total knee
replacement: a patient based comparison of pain levels and recovery of ambulation skills. The
Journal of Arthroplasty. 2006, Aug; 21(5): 642-9.
Samson A, Mercer G, Campbell D. Total knee replacement in the morbidly obese: a literature review.
ANZ J Surg. 2010 Sep; 80(9): 595-9.
Winiarsky R, Barth P, Lotke P. Total knee arthroplasty in morbidly obese patients. J Bone Joint
Surg [Am] 1998;80-A:1770–4.
31
Table 1. Part I Inclusion / Exclusion Criteria
#
Study
Inclusion Criteria
41 consecutive TKAs of MO
1 Amin AK, et al.
(2006).
(>40BMI) matched to 41 TKAs of
non-obese and groups matched for
age gender, Dx, prosthesis,
laterality (UTKA or BTKA) and preop Knee Society Score
150 consecutive Sm-BTKA
2 Fabi D, et al.
(2011).
between April 2000 and December
2001. 150 UTKA were randomly
chosen from all patients who
underwent UTKA by the senior
surgeon between January 1999
and December 2001.
78 knees in 68 patients who were
3 Foran JRH, et al.
(2004).
obese (defined as a body mass
index of =30) at the time of the
surgery and who had been
followed for a minimum of five
years
4 Fu D, et al. (2013). 18 retrospective comparative
studies RE: BTKA & UTKA
between 1965 and 2012 that
evaluated the outcome of patients
and clinically significant OA or RA
in both knees and severe pain
unrelieved by conventional
therapy.
5 Kerkhoffs GMM, et Studies comparing the outcome of
al. (2012).
TKA in different weight groups
were included & databases of
PubMed/MEDLINE, the Cochrane
Database of Systematic Reviews,
and Embase from 1970 to 2009
were searched for publications on
obesity and total knee arthroplasty.
The search terms “arthroplasty,”
Exclusion Criteria
Patients not closely matched to MO patients for age gender, Dx,
prosthesis, laterality (UTKA or BTKA) and pre-op Knee Society Score as
well as those medical co-morbidity or disease in the adjacent hip or knee.
After the random selection of 150 patients, no patients were excluded
4 died and 4 had been lost to follow-up and hence were excluded from
the study
Patients who had a primary trauma, knee infection, TKA or revision
Review articles, expert opinions, surgical techniques, and abstracts from
scientific meetings
6
Powell RS, et al.
(2006).
7
Samson A, et al.
(2010).
8
Winiarsky R, et al.
(1998).
“knee,” “weight,” “BMI,” and
“obesity” were used.
Database at the authors'
institution, showing 59 pts for
BTKA matched to pts w/
demographic factors w/ UTKA
during the same time b/w 1994
and 2002. Hospital and clinic
charts for these 59 matched pairs
of patients available for
retrospective review. Patients w/
“matched pair” were matched with
respect to sex, age, date of
surgery, surgeon, and Dx.
Standard length anterior incisions,
medial capsulotomies, routine use
of patellar eversion to aid
exposure, intramedullary suction of
marrow contents, intramedullary
align femur and tibia, routine
resurfacing of patella, and
cemented fixation of all
components were included.
Articles in this review were
assessed for the level of evidence
based on guidelines provided by
the National Health and Medical
Research Council of Australia and
New Zealand.10 Prospective,
case-control, reviews and
retrospective comparative studies
with levels of evidence from A to C
III-3 were included
MO pts (BMI >40) from a database
w/info on TKA performed by the
senior author (P. L.) be/w January
1980 and September 1994 and
Revisions or complex primaries that required stems, augmentations, or
bone grafts and patients receiving spinal narcotics, epidural narcotics,
intra-articular infusion pumps, or peripheral nerve blocks.
Studies were excluded if the level of evidence was less than C IV. Four
articles were excluded from this review because: of insufficient sample
size (n = 12), and >30% loss to follow-up; uni-compartmental knee
replacement and TKR grouped together in study; patients with an
American Society of Anaesthesiologists score of III or the
immunosuppressed were placed in the MO group; statistical analysis was
not carried out on the results.
It does not appear that any patients were excluded from the time frame of
the cohort of patient under the care of the senior author and surgeon.
33
had been followed for a min of 2
years consisting of 40 pts (50
knees). 5 MO pts w/BTKA staged
at intervals ranging from 3 months
to 3 years. The control group
consisted of the remaining 1539
patients (1768 knees) who had
had the same procedure,
performed by the same surgeon in
the same time-period, with the
same minimum duration of followup.
34
Figure 1. Part I Methods: Articles Included and Excluded for Analysis
2034
MeSH Database
Different keyword
combinations & 0
limits
145
1319
171
Keyword Search
Different keyword
combinations & 0
limits
Some keywords:
Simultaneous, TKA,
BTKA, BTKR, BMI,
morbid/obesity,
outcomes, PT
704
Keyword Search
One keyword
combination
Keyword Search
Different key word
combinations
15
13
202
Selected based on
appropriateness/
relevance of title
in relation to
PICO question
300 Excluded:
Topic not closely
related, Non-similar
population, >20
years old, Low level
of evidence
375
Total Articles (Relevant to Topic)
15
TKA and revision
rates among obese
TKA/TKR in Morbidly
Obese Pts
3
32
Morbid obesity &
obesity of OA/TKA
outcomes
3
BTKA & Obesity 310 year outcomes
Function/Outcome with
UTKA v BTKA
2
15
UTKA vs BTKA RE:
morbidity and
mortality rates
Obesity & Morbid
Obesity Outcomes of
TKA
2
10
Pt characteristics and
outcomes for BTKA
BTKA v UTKA
Ambulation
1
67 Excluded:
Low numbers, poor study
design, study’s purpose not
closely related to P.I.C.O.
question
8 Total Studies
-Reviewed
-Analyzed
-Compared to PICO
35
Table 2. Part I Results / Article Summaries
#
Study
&
Origin
Amin
AK, et
al.
(2006).
Pedro
Score
Purpose of
Study
Outcome
Measures
Results
1b
7/10
Knee Society Scores
Complication rate
Radiolucent lines
Survivorship-revision
& pain
At less than four years after operation, the
results were worse in the morbidly obese
group compared with the non-obese, as
demonstrated by inferior Knee Society
Scores (mean knee score 85.7 and 90.5
respectively, p = 0.08; mean function score
75.6 and 83.4, p = 0.01), a higher
incidence of radiolucent lines on postoperative radiographs (29% and 7%,
respectively, p = 0.02), a higher rate of
complications (32% and 0%, respectively, p
= 0.001) and inferior survivorship using
revision and pain as end-points (72.3% and
97.6%, respectively, p = 0.02).
Yes
2b
5/10
To assess the
influence of
morbid obesity
on the outcome
after TKR, in a
consecutive
series of
morbidly obese
patients (BMI >
40 kg/m2), with
a matched
group of nonobese patients
(BMI < 30
kg/m2).
To identify
which patients
may be at
increased risk
when
undergoing
unilateral or
bilateral total
knee
arthroplasty.
Transfusion rate
Total number of early
and late
complications
Pulmonary disorders
Length of hospital
stay
The BTKA group had a transfusion rate of
0.47 as compared with 0.12 for the control
group, with a significant P value of .0019,
almost a 4x higher rate of transfusion than
those patients undergoing UTKA. The
complication rate for BTKA patients (0.95)
was slightly more than double that of the
control group (0.45), with a P value of .012,
which was significant. For all patients with
a BMI greater than 30, there were 62
patients in the control group and 74 in the
bilateral group. A significant difference in
complication rates b/w the control (0.44)
and bilateral (0.96) groups, with a P value
of .0126, was found.
There was a
significant difference b/w means when
Yes
1
GB
Fabi D,
et al.
(2011).
2
US
Accept
Results to
Answer
Clinical
Question
Oxford
Level of
Evidence
36
comparing the length of stay b/w the
control and bilateral knee arthroplasty
groups. The mean values for the control
and bilateral groups were 3.3 and 4.9 days,
respectively, with a P value of less than
.0001.
3
Foran
JRH, et
al.
(2004).
2b
N/A
Compare the
clinical and
radiographic
results of TKA
performed in
obese patients
with those of
arthroplastys
performed with
the same
prosthesis in
non-obese
patients.
Knee Society
Objective Rating
Scale
No significant difference in the need for
revision surgery at 5 years between the
obese and non-obese group of patients. @
7 years after surgery the obese group had
a significantly higher “implant failure” rate
(12.3%) as defined by re-operation, clinical
failure (Knee Society objective score < 80
points), or radiographic implant failure, as
compared to the non-obese group (1.3%).
No statistically significant difference in the
perioperative complication rates in their
relatively small study population, and DVT
occurred only in the obese group.
Yes
2a
5/10
A systematic
review
assessing the
clinical outcome
associated with
simultaneousbilateral and
staged-bilateral
TKA.
Mortality
Revision
Complications
Recovery time
Yes
2a
6/10
Determine
whether obesity
has a negative
Infection (deep,
superficial, any)
Revision for infection,
Rate of mortality within 30 days after
surgery, PE and blood transfusion
associated with Sm-TKA are higher
compared to Sg-TKA. Mortality from PE
seems controllable with anticoage
techniques and updated policies have
lowered use of blood transfusion. SmBTKA may be concurrent w/lower rate of
infection, revision, lower costs, shorter
anesthetic time and lower total recovery
time w/out increasing the incidence of
neuro, DVT, and cardiac complications.
Use of TKA on select criteria may lower
perioperative complications.
Obesity had a negative influence on the
outcome of patients treated with total knee
arthroplasty, with more short-term
US
Fu D, et
al.
(2013).
4
China
Kerkhoff
s GMM,
et al.
Yes
37
5
(2012).
influence on
outcome after
primary total
knee
arthroplasty.
US
6
Powell
RS, et
al.
(2006).
2b
5/10
2b
4/10
US
Samson
A, et al.
(2010).
7
Australia
Answer
questions
regarding pain
and ambulation
outcome
differences
using a
retrospective
review of a
cohort of BTKA
patients
compared with a
matched cohort
of UTKA
patients.
Evaluate
outcomes of
TKR in patients
with morbid
obesity (MO;
BMI >40).
aseptic loosening,
hematoma, venous
thromboembolism,
perioperative
fracture, nerve
damage, tendon or
ligament rupture
Knee Society Score,
Knee Society
function sub-score,
and range of knee
motion.
Analog pain scores
and narcotic use
Ambulatory distances
Length of stay
Discharge disposition
Complications
complications and poorer long-term
outcome compared with non-obese
patients.
The BTKA group had significantly higher
pain perception at POD#1 and there were
no statistically significant differences
narcotic use. A significant difference
occurred in ambulation skills where UTKA
performed much higher than BTKA in acute
care. A higher % of BTKA are D/C’d to SNF
than UTKA. Complications were identical in
both groups.
Yes
Knee Society Scores
Complications
Infection rate
Clinical and functional Knee Society
Scores (KSS) improve after TKR for
patients with MO. The post-operative
functional KSS was less than in controls.
Radiographic analysis was inconclusive. All
studies noted a greater prevalence of
complications in MO patients (10–30%). Of
concern was the significantly higher
infection rate (3–9-times that of controls).
The MO also had a significantly higher
Yes
38
8
Winiarsk
y R, et
al.
(1998).
US
2b
4/10
Review clinical
outcomes of 50
primary TKAs
performed w/
cement in 50
MO patients and
compared
results w/ 1768
similar
procedures,
performed
during the same
time-period by
the same
surgeon, in
1539 patients
who were not
morbidly obese
(controls).
Knee & functional
scores
ROM or radiographic
Periop complications
Wound complications
Avulsed MCL
incidence of wound complications. TKR did
not result in weight loss for MO patients,
and therefore has no benefit on weightrelated medical conditions.
At a mean of ~ five years postop, there was
a significant difference between the
morbidly obese patients and the control
group RE: knee and functional scores (84
and 53 points compared with 92 and 67
points; p < 0.00005 for both scores). No
significant difference was detected, with
the numbers available, RE: range of motion
or the radiographic score (p = 0.77). The
rate of perioperative complications was
significantly higher in the morbidly obese
patients (p < 0.00005). Of the fifty knees in
MO patients, eleven (22 percent) had a
wound complication, five (10 percent) had
an infection, and four (8 percent) had an
avulsion of the medial collateral ligament.
Yes
39
APPENDIX
Article Analysis Worksheets for each article:
Prognostic Study 1 – Evidence Appraisal Worksheet
Citation:
Amin AK, Clayton RAE, Patton JT, Gaston M, Cook RE, Brenkel IJ. Total knee replacement in morbidly
obese patients. J. Bone Joint Surg. Br. 2006; 88: 1321–6.
Level of Evidence (Oxford scale): 1b
Is the purpose and background information sufficient? Yes the purpose is to assess the influence of
morbid obesity on the outcome after TKR. The background discusses the rising number of morbidly obese
patients with osteoarthritis of the knees and that there was not enough conclusive evidence available to
track the outcome of morbid obesity on TKA and therefore the study was prompted.
Study Purpose Stated clearly? Yes.
Consider how the study can be applied to PT and/or your own situation. This study is relevant to the
section of PT performed in the acute care hospital in that more detailed reviews of research can be made
available to the morbidly obese patient when they are examining the need for TKA and to help them decide
whether their outcome will be to their satisfaction depending on whether they choose the BTKA or the
UTKA.
What is the purpose of this study? This study was designed to assess the influence of morbid obesity on
the outcome after TKR, in a consecutive series of morbidly obese patients (BMI > 40 kg/m2), with a
matched group of non-obese patients (BMI < 30 kg/m2).
Literature/Relevant background presented? Yes.
Describe the justification of the need for this study. With the recent rise in morbid obesity in the US
and Europe, there will also be an increase in TKA surgeries and a clear evaluation of the possible higher
risks also needs to be assessed.
Does the research design have strong sampling techniques? Yes, there were 41 consecutive total
knee replacements performed on morbidly obese patients with a body mass index > 40 kg/m2, and these
were compared with a matched group of 41 comparable procedures carried out in a control group of nonobese patients (body mass index < 30 kg/m2). The groups were matched for age, gender, diagnosis, type
of prosthesis, laterality and pre-operative Knee Society Score.
Did the investigators provide sufficient information to describe the sample in their study? Yes, see
above.
Does the study clearly define the group of patients; is there a clear inclusion and exclusion
criterion? Yes, the patients included are listed above and the patients excluded are those not closely
matched to morbidly obese (MO) patients for age gender, diagnosis (Dx), prosthesis, laterality (UTKA or
BTKA) and pre-op Knee Society Score as well as those with medical co-morbidity or disease in the
adjacent hip or knee.
Is there a clear description of the stage and timing of the problem (illness) studied? Yes, between
1995 and 2004, 41 primary TKRs were performed in 38 morbidly obese patients. These were individually
matched with a control group of 41 primary TKRs performed in 38 non-obese patients. The two groups
were matched for age, gender, diagnosis (rheumatoid or osteoarthritis), type of prosthesis (Press fit
condylar (PFC) or PFC Sigma; both Depuy International, Leeds, United Kingdom), laterality (unilateral or
bilateral) and the pre-operative knee and function score components of the Knee Society Score (KSS).
Are the subjects representative of the population from which they were drawn? Yes, they were in a
category of BMI > 40 or control for < 30 BMI and then matched according to other demographics listed
above.
41
Did they capture all eligible subjects? Yes, however there is discussion that the morbidly obese
population are making up only a marginal percent of their overall patients undergoing TKA in that time
frame and therefore more data is needed from other institutions to complete the picture.
Are the results of this prognostic study valid? Yes. An analysis of results in the subgroup of obese
patients who are MO, has consistently demonstrated worse results in the morbidly obese patients when
compared with non-morbidly obese and non-obese patients. While the post-operative function score
element of the KSS was significantly lower in the morbidly obese group, the difference in the post-operative
knee score component was not. This suggests that while MO patients may attain similar pain relief, ROM
and stability, they are likely to remain more functionally impaired following TKR, with limitation of walking
distance, ability to climb stairs and greater dependence on walking aids.
1.
Were the subjects assembled at a common (usually early) point in the course of their
disorder? Yes between 1995 and 2004 an independent, prospective follow-up for all appropriate patients
was undertaken.
2.
Was the study time frame long enough to capture the outcome(s) of interest? Was patient
follow-up sufficiently long and complete? Yes, all patients were followed up at 6, 18, 36 and 60 months
following knee replacement.
3.
Did all subjects originally enrolled complete the study? Yes
a.
If not, how many subjects were lost. No peri-operative deaths occurred.
b.
What if anything did the authors do about this attrition? They detailed the deaths of two of the
members of the population by stating that “ there were two deaths from unrelated causes – one patient in
the morbidly obese group died three years after revision for deep infection, and one patient in the nonobese group died four years after a primary TKR which was not causing any problems when last reviewed
at 37 months.”
42
c.
What are the implications of this attrition and the way it was handled with respect to the
study’s findings? I don’t like that they stated that the MO patient’s death was unrelated when it clearly
was caused by a revision of the TKA. I understand that it wasn’t the immediate factor or outcome they
were reporting, however, they aren’t taking responsibility by saying that it was unrelated because if the
patient had never elected for that TKR surgery they wouldn’t have died from an infection.
4.
Were objective outcome criteria applied to the subjects in a masked or blinded fashion?
Yes, a “dedicated audit team” undertook independent, prospective follow-up for all patients led by an
arthroplasty nurse practitioner and a physiotherapist who were not directly involved in the study and were
not aware of the aims at the time of data collection. The matching of patients was undertaken using preoperative data in isolation and without knowing the individual outcomes.
5.
If subgroups with different prognoses are identified, was there adjustment for important
prognostic or risk factors? Yes, however, “it was not always possible to identify a non-obese patient with
exactly the same pre-operative knee and function score as a morbidly obese patient. In this instance, the
control with the next ‘worse’ score was identified. If no other control with a ‘worse’ score could be identified,
the control with the next ‘better’ score was used. This protocol was maintained for matching all the patients
so that the control group would have either a similar, or worse, pre-operative knee and functional status
compared with the morbidly obese patients.”
6.
Was there an independent set of patients to validate the study? There was a study group of
MO and a control of matched non-obese patients. There was no third group of untreated patients.
Are the valid results of this prognostic study important? Yes because they help patients and
caregivers provide more information regarding the higher risks present in the morbidly obese populations
and their outcomes of interest after TKA surgeries.
7.
What were the statistical findings of this study? “The level of significance was set at p < 0.05.
There were no significant differences between the morbidly obese and non-obese groups for the pre43
operative matched variables. The mean follow-up in the morbidly obese group was for 38.5 months (6 to
66) and in the non-obese group for 44 months (6 to 67). The difference was not statistically significant (p =
0.3). In both groups, the mean post-operative knee and function score components of the KSS were
significantly better compared with the pre-operative scores (paired sample t-test, p < 0.001). The mean
post-operative knee and function scores were lower in the MO, although the difference in the knee
score component only approached statistical significance. There was a significantly higher rate of
radiolucent lines around the implants in the MO patients compared with the non-obese group (29% and 7%,
respectively, p = 0.02), with approximately half being progressive. All radiolucent lines were present around
the tibial component. In one patient, a progressive radiolucent line was noted around both the femoral and
tibial components. There was no difference in the overall alignment of the components. The overall rate of
complications following TKR was significantly higher in the morbidly obese group compared with the nonobese group (32% and 0%, respectively, p = 0.001). Of the seven superficial wound infections in the MO
group, organisms were cultured from five, and no growth was obtained in the remaining two. Organisms
were cultured from both the knees with deep infection in the MO group. No peri-operative deaths occurred
in either group but there were two deaths from unrelated causes – one patient in the MO group died three
years after revision for deep infection, and one patient in the non-obese group died four years after a
primary TKR which was not causing any problems when last reviewed at 37 months. The last available
data after the primary procedure for both patients is included in the analysis. There were no intra-operative
avulsions of the medial collateral ligament in the MO group, a complication that has been previously
reported during TKR in such patients. Using revision as an end-point, the five-year survivorship was 74.2%
(95% confidence interval (CI) 53.8 to 94.6) in the MO group, compared with 100% (95% CI 100 to 100) in
the non-obese group (log-rank test, p = 0.01). Using revision and pain as the end-point, the five-year
survivorship was 72.3% (95% CI 52.1 to 92.5) in the MO group and 97.6% (95% CI 92.9 to 100) in the nonobese group (log-rank test, p = 0.02). As there were no patients lost to follow-up, the ‘worst-case’
44
survivorship would be the same as the five-year survivor-ship based on revision and pain as an end-point.
There are summaries that detail the TKRs considered as failures for the survivorship analysis. Two had
unexplained pain; one in each group. Both patients complained of severe pain in the knee immediately after
the surgery, and required referral to the pain management service. They both remained symptomatic at the
latest review despite the lack of any obvious clinical or radiological abnormality.”
8.
What is the meaning of these statistical findings for your patient/client’s case? What does
this mean to your practice? The meaning of these statistical findings is that patients will have better
research available to help them determine the risks and outcomes associated with TKA surgical procedures
and the complications that may accompany them. The practice of physical therapy will also have better
outcomes for its patients when the patients are able to see how important pre-hab is to their surgical and
physical healing outcomes.
Can you apply this valid, important evidence about this prognostic study in caring for your
patient/client? What is the external validity? This is a strong study in that it can be given to patients in
their pre-hab experience in the hospital before their surgery so they can make informed decisions and learn
how important it is to enter an elective surgical procedure in the best possible health they can attain. The
research is externally valid because it can be generalized to any population in the hospitals enrolling in the
pre-hab classes or as a resource from their doctor’s office.
9.
How likely are these outcomes over time? These outcomes are of interest because they
address the function of the knee(s) (Knee Society Scores), complication rate, radiolucent lines,
survivorship-revision and pain. These issues are always on the forefront of any patient’s mind when
entering into a surgical procedure.
10.
Are the study subjects similar to your patient/ client? Yes because my patient was a MO
patient that elected to have BTKA performed and one of the patients in the study matched her profile.
45
11.
Would sharing this information help your patient/client given their expressed values and
preferences? I believe it would help patients make a more informed decision.
What is the bottom line? There is truly a need for delineation of MO and any associated risks that it poses
when undergoing TKA of either laterality. This study was helpful in presenting the associated risks that are
emerging due to the increase in this patient population.
Prognostic Study 2 – Evidence Appraisal Worksheet
Citation:
Fabi D, Mohan V, Goldstein WM, Dunn JH, Murphy BP. Unilateral vs bilateral total knee arthroplasty: risk
factors increasing morbidity. The Journal of Arthroplasty. 2011, Aug: 26(5): 668-73.
Level of Evidence (Oxford scale): 2b
Is the purpose and background information sufficient? Yes, “Because surgeons are electing to perform
simultaneous bilateral total knee arthroplasty (TKA), it is important to identify which patients are at
increased risk.”
Study Purpose Stated clearly? See above.
What is the purpose of this study? To identify which patients may be at increased risk when undergoing
unilateral or simultaneous bilateral total knee arthroplasty.
Literature/Relevant background presented? Describe the justification of the need for this study Yes,
a complete discussion is available regarding the need for TKA and its increasing use to cure osteoarthritis.
The latest trends are indicating that both knees are equally involved with OA and therefore the need to
assess the risks of bilateral surgery is ever apparent.
46
Does the research design have strong sampling techniques? Yes, a retrospective review of 150 charts
of patients who had UTKA as compared with 150 patients who had simultaneous (Sm-BTKA) was
performed.
Did the investigators provide sufficient information to describe the sample in their study? Yes, The
control group's age range was 51 to 87 years old, with a mean age of 71 years. The ages in the bilateral
group varied from 51 to 90 years, with a mean age of 70 years.
Does the study clearly define the group of patients; is there a clear inclusion and exclusion
criterion? Is there a clear description of the stage and timing of the problem (illness) studied? Yes,
150 patients who underwent UTKA were randomly chosen from all patients who underwent UTKA by the
senior surgeon between January 1999 and December 2001. After the random selection of 150 patients, no
patients were excluded.
Are the subjects representative of the population from which they were drawn? Yes of the 150
patients in each group, there were 62 in the control group and 74 in the study group whose BMI was 30 or
greater.
Did they capture all eligible subjects? Yes
Are the results of this prognostic study valid? Yes
1.
Were the subjects assembled at a common (usually early) point in the course of their
disorder? Yes a consecutive cohort of 150 patients who had Sm-BTKA between April 2000 and December
2001 was included in the study group and 150 who had UTKA were randomly chosen from all patients who
underwent UTKA by the senior surgeon between January 1999 and December 2001.
2.
Was the study time frame long enough to capture the outcome(s) of interest? Was patient
follow-up sufficiently long and complete? The study does not detail patient follow up or exact points in
time that the data was reviewed and only provided a range of time with which the data was extracted.
47
a.
If not, what are the potential consequences of the follow-up time for the study’s results? Not
listing the follow up times doesn’t present the reader of the research with a clear category for healing rates.
If they are different, then the outcomes could be invalidated. They did, however, track postoperative data to
examine the complication rates associated with bilateral knee arthroplasties vs single knee arthroplasties
and included the following: transfusion rate, length of hospital stay, and total number of early and late
complications.
3.
Did all subjects originally enrolled complete the study? Yes
a.
If not, how many subjects were lost? No deaths were reported.
b.
What if anything did the authors do about this attrition? They discussed the rate of survival
and compared them to the study and control groups and found that after ten years there were actually more
mortalities in the UTKA than the BTKA but they did not speculate as to why.
c.
What are the implications of this attrition and the way it was handled with respect to the
study’s findings? From these results, the researchers state that “one can capitulate that in the early
postoperative period, there is a definite increased risk of mortality that returns to baseline after time.”
4.
Were objective outcome criteria applied to the subjects in a masked or blinded fashion? If
they performed this, they did not discuss the procedure in the research.
a.
If not, what are the potential consequences for this study’s results? The surgeon/author that
performed these procedures and compiled this data could have had a bias to choose and categorize his
patients in a better light so that they could make the procedure to appear safer than it was.
5.
If subgroups with different prognoses are identified, was there adjustment for important
prognostic or risk factors? Yes there were several sub categories with which subjects were placed. The
preoperative conditions that were collected were placed in categories for comparison between the control
and study groups. The first category was age that was subdivided by decade into 50s, 60s, 70s, and older
than 80 years. The second category was body mass index (BMI). The final category was the presence of a
48
preoperative pulmonary or airway disorder, which can potentially increase perioperative risk. Of the patients
with pulmonary disorders, there were 5 in the control and 22 in the bilateral study group. The disorders
seen in patients were the following: asthma, chronic obstructive pulmonary disease, lung cancer, laryngeal
cancer, and history of pneumonia.
6.
Was there an independent set of patients to validate the study? There was a study group of
150 BTKA. There was a control group of 150 UTKA. There was no third group of untreated patients.
Are the valid results of this prognostic study important? Yes because it presents the various risks
associated with having a BTKA procedure over having a UTKA.
7.
What were the statistical findings of this study? A P value of less than .05 was considered to
represent a significant difference. In patients aged 70 to 79 years, the complication rate was 1.1356 in the
bilateral group vs 0.3279 in the unilateral group, and the difference was significant (P = .0007). In patients
older than 80 years, the complication rate was 1.4 in the bilateral group and 0.4667 in the unilateral group
(P = .0366). The bilateral knee group had a transfusion rate of 0.47 as compared with 0.12 for the control
group, with a significant P value of .0019, almost a 4 times higher rate of transfusion than those patients
undergoing unilateral TKA. For all patients with a BMI greater than 30, there were 62 patients in the control
group and 74 in the bilateral group. A significant difference in complication rates between the control (0.44)
and bilateral (0.96) groups, with a P value of .0126, was found. There was a significant difference between
means when comparing the length of stay between the control and bilateral knee arthroplasty groups. The
mean values for the control and bilateral groups were 3.3 and 4.9 days, respectively, with a P value of less
than .0001. The complication rate in patients with pulmonary disorders from both groups was compared.
The control group had a mean complication rate of 0.20, and the bilateral group had a mean of 1.63, with a
P value of .0097. To note, there were only 5 patients in the control group with pulmonary disorders, as
compared with 22 in the bilateral study group. To compare the effect of having a bilateral TKA performed
with or without a preexisting pulmonary disorder, the investigators compared the complication rates of
49
those 2 subgroups undergoing bilateral knee arthroplasty. The mean complication rate for patients without
preexisting pulmonary disease (n = 128) was 0.78 as compared with 1.64 for those with preexisting
pulmonary disease (n = 22). The P value was significant at .045, with a relative risk of 1.45 times higher in
those with pulmonary disease undergoing a bilateral TKA. The mean overall complication rate for patients
in the bilateral group (0.95) was slightly more than double that of the control group (0.45), with a P value of
.012, which was significant.
8.
What is the meaning of these statistical findings for your patient/client’s case? It means that
patients electing to have BTKA are at higher risk in many categories than those electing to have UTKA
based on their age, BMI and pre-operative conditions.
What does this mean to your practice? Can you apply this valid, important evidence about this
prognostic study in caring for your patient/client? In the acute care setting, the patients coming out of
a BTKA procedure are looking at increased LOS and higher complication rate and may be more medically
fragile than UTKA patients. Those that are in the higher age bracket or BMI category may also be facing
more health risks and may have poorer outcomes during the time that they are in the hospital. This
information is helpful when setting goals for these patients and deciding what their discharge status may be
as well. What is the external validity? The data were collected from a single high-volume arthroplasty
surgeon's experience and may not be applicable to all orthopedic surgeons.
9. How likely are these outcomes over time? There was no clear delineation of which outcomes and
how long they were taken apart from the actual surgical procedures so this question is difficult to answer.
10. Are the study subjects similar to your patient/ client? Yes because my patient was morbidly obese
and decided to have BTKA.
11. Would sharing this information help your patient/client given their expressed values and
preferences? Had this patient had this research I think she would have elected to have only one done at a
50
time (UTKA) if at all.
What is the bottom line? Patients must be made aware of the inherent level of risk associated with the
various procedures available out there involving total knee arthroplasty surgeries. This research stratified
subjects and clearly delineated age and BMI and pre-op co-morbid conditions so there could be a clear
picture as to whether or not they would choose UTKA over BTKA.
Prognostic Study 3 – Evidence Appraisal Worksheet
Citation:
Foran JRH, Mont MA, Etienne G, Jones LC, Hungerford DS. The outcome of total knee arthroplasty in
obese patients. J. Bone Joint Surg. Am. 2004; 86: 1609–15.
Level of Evidence (Oxford scale): 2b
Is the purpose and background information sufficient? Yes, there is discussion of research associated
with increased body weight and OA of the knee and the high prevalence of obesity indicating a need to
define the outcome of TKA in obese patients. The purpose was clear as well and stated as a comparison of
clinical and radiographic results of TKA performed in obese patients with those of TKA performed in nonobese patients.
What is the purpose of this study?
Compare the clinical and radiographic results of TKA performed in obese patients with those of
arthroplasties performed with the same prosthesis in non-obese patients.
51
Literature/Relevant background presented? Yes there is extensive summarizing of all preexisting data
on the subject in order to provide the reader with adequate information about the current need for this
study.
Describe the justification of the need for this study: The study indicates that, there is strong evidence
linking excessive body weight to degenerative joint disease of the knee and references such research.
Subsequently, the research also demonstrates “a large proportion of patients who undergo total knee
arthroplasty are obese or morbidly obese,” and marks concerns that “authors believe that a high body
weight will lead to a less-than-optimal outcome of total knee arthroplasty as a result of increased stress
across the components and increased load on the surrounding bone.” These several studies have
“implicated excessive weight as a negative predictor of success of total knee arthroplasty, whereas others
have indicated that obesity is not a negative predictor of knee arthroplasty outcomes.” This study helps
clarify the risk for each group.
Does the research design have strong sampling techniques? Did the investigators provide
sufficient information to describe the sample in their study? Yes, they studied seventy-eight knees in
sixty-eight patients who were obese (defined as a body mass index of =30) at the time of the surgery and
who had been followed for a minimum of five years. Subjects were identified from a database of all
patients and matched with the first non-obese, control patient (with a body mass index of <30), handselected from a computerized database, who was appropriately matched with respect to the preoperative
diagnosis, age at surgery (within ten years), duration of follow-up (within two years), and whether he or she
had had a unilateral or bilateral arthroplasty.
Does the study clearly define the group of patients; is there a clear inclusion and exclusion
criterion? Is there a clear description of the stage and timing of the problem (illness) studied? Yes,
between September 1, 1991, and December 31, 1996, 772 total knee arthroplasties were performed and
52
78 in 68 patients who were obese (defined as a body mass index of =30) at the time of the surgery and
who had been followed for a minimum of five years were identified from that database of all patients.
Are the subjects representative of the population from which they were drawn? Yes
Did they capture all eligible subjects? Yes
Are the results of this prognostic study valid? Yes
1. Were the subjects assembled at a common (usually early) point in the course of their disorder?
Yes this is a retrospective cohort chosen from September 1, 1991, and December 31, 1996 and followed
for a minimum of five years.
2. Was the study time frame long enough to capture the outcome(s) of interest? Was patient followup sufficiently long and complete? Yes
3. Did all subjects originally enrolled complete the study? No.
a. If not, how many subjects were lost? 8
b. What if anything did the authors do about this attrition? They gave full disclosure regarding the loss
by stating, “An additional eight knees in eight obese patients were identified, but four of those patients had
died and four had been lost to follow-up and hence were excluded from the study.”
c. What are the implications of this attrition and the way it was handled with respect to the study’s
findings? “All of those eight knees were functioning well at the time of the latest follow-up (mean duration,
four years; range, two to five years),” so this apparently did not affect the study or its outcomes.
4. Were objective outcome criteria applied to the subjects in a masked or blinded fashion? Yes, the
data was chosen in a manner that “the authors were blinded to the outcomes at the time of the match. All
patients had been followed for a minimum of five years. Seventy-eight knees in sixty-eight non-obese
patients were included in the study. Demographic data for each group are summarized [in the research
table 1]. Follow-up data were obtained by means of a blinded, retrospective review of the computerized
database, charts, and radiographs as well as with telephone conversations. The mean duration of follow-up
53
was eighty months (range, sixty to 123 months) for the obese group and eighty-three months (range, sixty
to 123 months) for the non-obese group.”
5. If subgroups with different prognoses are identified, was there adjustment for important
prognostic or risk factors? Yes there were sub groups for morbidly obese, BTKA, and men from women
(because their were so many more obese women than men) and the appropriate adjustments were made
with respect to stratifying the statistical models to meet the sub-groups of the morbidly obese and obese
differences. There was discussion that patients could not be matched for gender due to a “disproportionate
amount of women in the obese group.”
6. Was there an independent set of patients to validate the study? There were only the obese and nonobese groups undergoing TKA.
a. If not, what are the potential consequences for this study’s results? Involving the data from an
independent group could obfuscate the data.
Are the valid results of this prognostic study important? Yes.
7. What were the statistical findings of this study? “A p value of <0.05 was considered significant and
69 (88%) of the 78 knees in the obese group were considered to have a successful outcome at the time of
the latest follow-up. 4 knees in 4 obese patients required revision and thus were considered failures, and 5
knees in 5 obese patients were considered failures because of a fair/poor Knee Society objective score. In
comparison, 77 (99%) of the 78 knee replacements in the non-obese group were successful, and there
were no revisions in that group. At the time of the latest follow-up, there was a significant difference in the
success rates between the knees in the obese group and those in the non-obese group (p = 0.02). KaplanMeier survivorship analysis revealed similar rates of prosthetic survival between the obese and non-obese
groups until between 60 and 80 months, when the decreased survival rate in the obese group became
apparent. At 80 months, the obese group had an 87.7% ± 5.4% (standard error) chance of prosthetic
survival (95% confidence interval, 72.1% to 95.1%), with a reoperation, clinical failure, and radiographic
54
failure as the end points, and the non-obese group had a 98.7% ± 1.9% chance of prosthetic survival (95%
confidence interval, 87.9% to 99.9%). The curves were not continued beyond 80 months because the
confidence intervals became quite large at that point. Stratification of knees in the obese group into
morbidly and non-morbidly obese subgroups revealed a lower success rate when those subgroups were
compared with the non-obese group. 10 of the 12 knee replacements in the morbidly obese subgroup were
successful at the time of the latest follow-up, whereas 59 (89%) of the 66 knees in the non-morbidly obese
subgroup and 77 (99%) of the 78 knees in the non-obese group were successful. The rate of success in the
non-obese patients was significantly higher than the rate in the non-morbidly obese patients (p = 0.02).
The survivorship curves revealed that, at 80 months, there was a 91.7% ± 11.8% (standard error) chance
of prosthetic survival (95% confidence interval, 47.9% to 99.2%) in the morbidly obese subgroup (Fig. 2),
an 83.6% ± 8.7% chance (95% confidence interval, 58.7% to 94.8%) in the non-morbidly obese group, and
a 98.7% ± 1.9% chance (95% confidence interval, 87.9% to 99.9%) in the non-obese group. There were
no significant differences in the mean preoperative Knee Society objective scores among the groups, but
the mean preoperative functional scores differed significantly between the morbidly obese and non-obese
groups (p < 0.02). There was a significant difference in the mean postoperative Knee Society objective
scores between the obese and non-obese groups
(p < 0.05). There was also a significant difference in the mean changes in the objective Knee Society score
(postoperative minus preoperative score) between those groups (p < 0.05), although this may be slightly
skewed as the obese group started with a 2-point higher mean objective score. The difference in the mean
postoperative Knee Society scores between the morbidly obese and non-obese groups was significant as
well (p = 0.04). There were no differences in revision and infection rates between the non-obese and obese
groups. However, the difference in revision rates became significant when the obese group was stratified
into morbidly and non-morbidly obese subgroups and the morbidly obese group was compared with the
non-obese group (p = 0.02).
55
The clinical function of the patellofemoral articulation at the time of the latest follow-up in the obese group
was grade 0 in forty-five knees (58%), grade I in twenty-three knees (29%), and grade II in ten knees
(13%). In the non-obese group, forty knees (51%) had grade-0 function; twenty-eight knees (36%), grade-I;
and ten knees (13%), grade-II. Statistical analysis revealed no difference in patellofemoral scores among
the subgroups, with the numbers available. The rates of patellar complications were also similar among the
groups. One morbidly obese patient required a patellar revision at 103 months postoperatively, and one
non-obese patient required repair of a traumatic rupture of a patellar ligament. There was no difference in
activity levels or the rate of perioperative complications between the obese and non-obese groups. No
patient was bedridden (activity level of 0), and only two patients (one obese and one non-obese patient)
had an activity level of 5. The obese and non-obese patients had similar rates of hypertension, clinically
relevant coronary artery disease, and cancer. The obese group had a higher prevalence of diabetes
mellitus (eight of sixty-eight patients compared with zero of sixty-eight patients in the non-obese group) (p =
0.02). The radiographic results are presented in the Appendix. No knee that had a good or excellent clinical
outcome in either group had impending radiographic failure. There were similar rates of non-progressive
radiolucencies in the three groups, and no knee in any group showed progressive radiolucencies. The
postoperative knee-alignment measures were virtually identical among the groups.”
8. What is the meaning of these statistical findings for your patient/client’s case? What does this
mean to your practice? This study highlights the increasing rise of obese patients undergoing TKA
surgeries and then raises awareness of the risks involved as well as demonstrates the functional outcomes
and differences between patients that have TKA and are obese and those that are not. This is valuable
information for patients trying to make decisions about whether or not they should undergo TKA and gives
them a better picture of what their outcomes might look like.
Can you apply this valid, important evidence about this prognostic study in caring for your
patient/client? What is the external validity? The information is valid and the statistical difference was
56
significant in many of the categories tested. This demonstrates that outcomes, in general were poorer for
those patients that met the criteria of the study group in that they were obese or morbidly obese. This can
be generalized to that population of obese patients who also have that type of implant.
9. How likely are these outcomes over time? In light of the research stating, “at a mean of
approximately seven years postoperatively, the obese group had a significantly lower rate of success than
did the non-obese group. Stratification of the obese group into non-morbidly obese and morbidly obese
subgroups revealed significant differences in revision rates and postoperative objective and functional
scores when those subgroups were compared with the non-obese group. Kaplan-Meier survivorship
analysis revealed similar rates of prosthetic survival between the two cohorts until between sixty and eighty
months, at which time the decrease in the survivorship in the obese group became apparent. The survival
analysis of the morbidly and non-morbidly obese groups showed a similar pattern of failure, “ it appears that
the outcomes are very likely.
10. Are the study subjects similar to your patient/ client? Yes, because the case study I observed had
morbid obesity and underwent TKA. Although they did not detail or stratify the BTKA from the UTKA, they
did provide general information regarding the TKA surgical procedure, which was just as informative as the
BTKA research available.
11. Would sharing this information help your patient/client given their expressed values and
preferences? Yes, I think this information would provide the patient with valuable clinical outcomes and
help them make informed decisions regarding the choices about the elective surgical procedures and
assess their various expected outcomes.
What is the bottom line? This research provides a wealth of information regarding the outcomes of the
Knee Society Objective Rating Scale. It provides a clear time frame and outcome of the patients in the
obese and non-obese groups and also stratified the morbidly obese group from the obese and measured
57
these outcomes as well. This study allows patients to assess their current level of health and age and
make decisions based on these outcomes.
Systematic Review Study 4 – Evidence Appraisal Worksheet
Citation:
Fu D, Li G, Chen K, Zeng H, Zhang X, Cai Z. Comparison of clinical outcomes between simultaneousbilateral and staged-bilateral total knee arthroplasty: a systematic review of retrospective studies. The
Journal of Arthroplasty. 2013, Aug; 28(7): 1141-7.
Level of Evidence (Oxford scale): 2b
Does the design follow the Cochrane method? Yes
Step 1 – formulating the question
Do the authors identify the focus of the review? This study was designed as a systematic review for
clinical outcomes associated with two different surgical procedures regarding total knee arthroplasty. The
first is simultaneous bilateral knee replacement (Sm-BTKA) and the second is staged unilateral total knee
replacement (Sg-UTKA).
Step 2 – locating studies: Did they include multiple databases? Was the search strategy defined
and includes: Bibliographic databases used as well as hand searching Terms (key words and index
terms) Citation searching: reference lists, Contact with ‘experts’ to identify ‘grey’ literature (body of
materials that cannot be found easily through conventional channels such as publishers), Sources
for ‘grey literature? Yes, they “carried out a literature search using Medline, Embase, Ovid and Cochrane
databases to identify all articles published between 1965 and 2012 that evaluated the outcome of patients
undertaking either simultaneous bilateral TKA or staged bilateral TKA. No other restrictions were placed
58
except that the language of the publications was limited in English. Reports relating to both simultaneous
TKA and staged TKA were included regardless of whether unilateral TKA was involved in the comparison.
The following Medical Subject Headings (MeSH) and terms were used in searching: “bilateral total knee
arthroplasty”, “staged total knee arthroplasty”, and “total knee arthroplasty”. The reference list of each
comparative study and previous reviews were manually examined to find additional relevant studies. Each
author of the included studies was also contacted by email to identify more details of the clinical outcome
and further studies on the same topic.
Part 3:Critical Appraisal/Criteria for Inclusion: Were criteria for selection specified? Did more than
one author assess the relevance of each report? Were decisions concerning relevance described;
completed by non-experts, or both? Yes, “To minimize any possible selection bias, the following criteria
were established. Strict inclusion criteria included clinically significant osteoarthritis or rheumatoid arthritis
in both knees and severe pain unrelieved by conventional therapy. Patients who had a primary trauma,
knee infection, total knee arthroplasty or revision were excluded. Two reviewers (D. F and Gd. L)
independently assessed each of the studies for eligibility for inclusion. Firstly the title or the abstract was
judged by either reviewer and then if it was potentially eligible, the full article would be examined. All
disagreements were resolved by consensus.”
Relevant background presented? The background was presented clearly and outlines the previous gaps
in research regarding the concerns facing patients undergoing BTKA and their outcomes thereby
underlining the need for this current study.
Does the research design have strong sampling techniques? Did the investigators provide
sufficient information to describe the sample in their study? Yes, the researchers looked at the
outcome of patients either choosing the Sm-BTKA procedure or the Sg-BTKA procedure over the course of
1965-2012. The population and description of the participants in their study are labeled as those
“undertaking either simultaneous bilateral TKA or staged bilateral TKA.”
59
Does the study clearly define the group of patients; is there a clear inclusion and exclusion
criterion? Is there a clear description of the stage and timing of the problem (illness) studied? Yes,
they clearly define the databases as “Medline, Embase, Ovid and Cochrane databases to identify all
articles published between 1965 and 2012 that evaluated the outcome of patients undertaking either
simultaneous bilateral TKA or staged bilateral TKA” and state that “No other restrictions were placed except
that the language of the publications was limited in English.” Their inclusion criteria were any “reports
relating to both simultaneous TKA and staged TKA were included regardless of whether unilateral TKA was
involved in the comparison.” Search terms were delineated as “Medical Subject Headings (MeSH) and
terms were used in searching: “bilateral total knee arthroplasty”, “staged total knee arthroplasty”, and “total
knee arthroplasty.” Furthermore, “to minimize any possible selection bias, the following criteria were
established. Strict inclusion criteria included clinically significant osteoarthritis or rheumatoid arthritis in both
knees and severe pain unrelieved by conventional therapy. Patients who had a primary trauma, knee
infection, total knee arthroplasty or revision were excluded. Two reviewers (D. F and Gd. L) independently
assessed each of the studies for eligibility for inclusion. Firstly either reviewer judged the title or the abstract
and then if it were potentially eligible, the full article would be examined. All disagreements were resolved
by consensus.”
Are the subjects representative of the population from which they were drawn? Yes they all
represent the correct population of those receiving total knee arthroplasty.
Did they capture all eligible subjects? Yes the research states that “all pertinent information regarding
participant and clinical outcome [was] recorded.”
Did the people assessing the relevance of studies know the names of the authors, institutions,
journal of publication and results when they apply the inclusion criteria? Or is it blind? The
researchers only looked at the article title, not the authors. See above.
Part 3 – Critically appraise for bias:
60
Selection – Were the groups in the study selected differently? Random? Concealed?
Two authors extracted data independently subsequently after all the eligible studies were recruited. All
pertinent information regarding participant and clinical outcome were recorded. Participant data included
the number of patients, age, gender (the rate of males in all participants). The principal outcomes of interest
included details of the incidence of complications (pulmonary embolism, deep-vein thrombosis, cardiac
complications, neurological complications, deep infection and superficial infection) and mortality (within
30 days after surgery) as well as blood loss and transfusion, length of hospital stay, and the rate of revision
arthroplasty.
Performance- did the groups in the study receive different treatment? Yes in the compilation of
studies “a flow chart [was] recruited in [the] review and 18 retrospective cohort studies with 107,318
patients of which 28,760 were simultaneous bilateral TKA and 78,558 were staged bilateral TKA were
selected for inclusion in the meta analysis. Details on all of the studies were shown in [tables]. Preoperative
patient characteristics did not show any significant differences between groups with the exception of a
greater percentage of female in the staged group. The result of each comparison was shown in [a final
table].”
Was there blinding? Based on the Cochrane Bone, Joint and Muscle Trauma Group assessment of the
methodological quality of each included study was made by the 2 reviewers (D.F and Gd. L) who were
blinded with respect to the journal, the authors and the source institution. Any controversy was
crosschecked and resolved by a third author (K.C) to reach a final consensus.
Attrition – Were the groups similar at the end of the study? Account for dropouts? Because this
meta-analysis is reviewing a compilation of many studies, it does not detail each and every attrition,
however, it does give a percentage of deaths stating “The predominant cause of death (77.8%) was a
disease of the circulatory system” and then delineates that there was a significantly higher number of
61
deaths in the simultaneous group than the unilateral staged. One study was reported as deleted and that
was the Ritter study because it was too “heterogeneous.”
Detection – Did the study selectively report the results? Is there missing data? Detailed reports
about outcome percentages were included and list studies that were excluded. Studies could be eliminated
if they did not help prove the outcome of interest. This was taken into consideration and an attempt to
document findings in an unbiased fashion is noted in the research.
Part 4 – Collection of the data
Was a collection data form used and is it included? If it was used, it is not included.
Are the studies coded and is the data coding easy to follow? Yes. There is a table outlining each
study and each outcome of interest.
Were studies identified that were excluded & did they give reasons why (i.e., which criteria they
failed)? Yes.
Are the results of this SR valid? Yes.
1.
Is this a SR of randomized trials? Did they limit this to high quality studies at the top of the
hierarchies?
a. If not, what types of studies were included?
b. What are the potential
consequences of including these studies for this review’s results? This study discusses the limitations
and states, “it is difficult to carry out a truly controlled randomized trial of patients with bilateral total knee
replacement as patients with more comorbidities are often suggested to be inappropriate candidates for
simultaneous total knee arthroplasty knee arthritis because of ethical issues. It would have been expected
that the sequential group would have fewer overall complications. All included studies were retrospectively
reviewed with a poor methodological quality. In addition, because of the inability in extracting the related
information about whether single or two team surgeons operated on the patients in the simultaneous group.
Some experts have argued that only when the procedure on both knees is truly carried out simultaneously,
62
the safety of bilateral total knee arthroplasty should be a concern. Third, the information was not
consistently reported in all studies included in this meta-analysis. Some comparisons between
simultaneous and staged bilateral TKA were limited with the present data. Although this current Meta
analysis is the one with the most studies and largest population, further well-designed and large-scale
clinical trials and Systemic review are required to confirm these findings.”
2.
Did this study follow the Cochrane methods selection process and did it identify all relevant
trials? Yes
3.
Do the methods describe the processes and tools used to assess the quality of individual
studies? Yes. They stated, “Data were extracted independently by two authors subsequently after all the
eligible studies were recruited. All pertinent information regarding participant and clinical outcome were
recorded. Participant data included the number of patients, age, gender (the rate of males in all
participants). The principal outcomes of interest included details of the incidence of complications
(pulmonary embolism, deep-vein thrombosis, cardiac complications, neurological complications, deep
infection and superficial infection) and mortality (within 30 days after surgery) as well as blood loss and
transfusion, length of hospital stay, and the rate of revision arthroplasty.”
4.
Describe the quality of the individual studies that were included. Were the results
consistent from study to study? Did the investigators provide details about the research validity or
quality of the studies included in review? The table below outlines the findings of the 18 studies.
63
Outcome Measures In The Meta-Analysis of Comparisons Between Simultaneous And Staged Bilateral
TKA.
Outcome
Odds Ratio (95%
P
Heterogene
CI)
I
Number of
Number of
2
Patients
Studies
%
Mortality⁎
2.25 (1.87–2.72)
< 0.0001
0.009
7 104,120
7
3
⁎
Pulmonary embolism⁎
1.39 (1.11–1.76)
0.005⁎
0.9
0 39,135
9
Deep-vein thrombosis
1.07 (0.86–1.33)
0.57
0.86
0 36,507
5
Cardiac complications
0.52 (0.27, 1.03)
0.06
0.05
4 36,820
10
6
Neurological
1.01 (0.71–1.44)
0.96
0.65
0 39,015
9
0.52 (0.42–0.64)
< 0.0000
0.9
0 38,743
7
complications
Deep infection⁎
1⁎
Superficial infection
0.92 (0.62–1.38)
0.69
0.85
0 38,085
5
Other minor
1.65 (0.92–2.96)
0.10
0.01
5 38,321
9
complications
Revision Rate⁎
9
0.48 (0.37–0.62)
< 0.0001
0.64
0 36,198
4
0.009
8 586
3
⁎
Blood transfusion rate⁎
11.52 (2.59–
51.28)
0.001⁎
6
⁎ Significantly different between simultaneous and staged bilateral TKA
64
5.
Did the investigators address publication bias?
Yes, they have a conflict of interest
statement outlining any possible bias and give full disclosure of all interested parties.
Are the valid results of this SR important? It appears the collected data is valid and correctly pertains to
the PICO question.
6.
Were the results homogenous from study to study? Yes and any that were too heterogeneous
were eliminated.
7.
If the paper is a meta-analysis did they report the statistical results? Yes Did they include a
forest plat? Yes What other statistics do they include? See above table. Are there CIs? Yes these are
included in the table above.
8.
From the findings, is it apparent what the cumulative weight of the evidence is? Can you
apply this valid, important evidence from this SR in caring for your patient/client? What is the
external validity? These outcomes are important to present to patients so that they are aware of the
higher risks when making the decision to have simultaneous procedures done. This study can be
generalized to the population of people choosing these types of knee surgery.
9.
Is your patient different from those in this SR? No the patient underwent BTKA and was
morbidly obese. How likely are these outcomes over time?
The discussion section states,
“Approximately 20% of patients with OA have severe symptoms from the other knee at the time of primary
TKA and10% of patients have the other knee operated on within 1 year. In patients with symmetrically
severe disease in both knees, a decision must be made whether to operate at 2 different settings or a
single setting. Multiple studies have shown the procedure of simultaneous bilateral TKA to be safe in
selected patient populations [because] the sum of the risks associated with the two operations of a staged
procedure may equal or exceed the risk of simultaneous total knee replacement.”
65
10.
Are the study subjects similar to your patient/ client? Yes, the patient I am researching for had
simultaneous bilateral total knee procedure with poor acute care outcomes with higher than average
complication rates.
11.
Would sharing this information help your patient/client given their expressed values and
preferences? I believe that this patient would have reconsidered her choice of simultaneous BTKA had
she been presented with these studies.
What is the bottom line? This study was performed to compile and compare the outcomes of SmBTKA and Sg-UTKA. It states “Simultaneous bilateral TKA is associated with potential benefit of lower
rate of infection and revision, reduced costs, shorter anesthetic time and decreased total recovery time
without increasing the incidence of neurological complications, DVP, cardiac complications. When active
prevention measurements of perioperative complications are strictly applied, it remains an appropriate
option in selected patients.” As long as the reader understands that the outcomes of simultaneous bilateral
total knee replacement are being compared to staged, unilateral studies whose outcomes have been
DOUBLED in many of the categories, then this information can be assessed properly. The take home
message is that complications rates were less in bilateral than unilateral because they double the outcomes
of the unilateral and many times that made the bilateral procedure appear safer.
66
Systematic Review Study 5 – Evidence Appraisal Worksheet
Citation:
Kerkhoffs GMM, Servien E, Dunn W, Dahn D, Bramer JAM, Haverkamp D. The influence of obesity on the
complication rate and outcomes of total knee arthroplasty: a meta-analysis and systematic literature review.
J Bone Joint Surg. Am. 2012, Oct; 94(20): 1839-44.
Level of Evidence (Oxford scale): 2a
Literature
Relevant background presented? Yes, this study is relevant because it notes the rising number of obese
patients with severe osteoarthritis and their subsequent need to have a TKA procedure.
Does the design follow the Cochrane method? Yes.
Step 1 – formulating the question. Do the authors identify the focus of the review? Is the purpose
and background information sufficient? What is the purpose of this study? To “determine whether
obesity has a negative influence on outcome after primary total knee arthroplasty.”
Does the research design have strong sampling techniques? Yes, data was extracted by two
reviewers for specific outcomes of interest and applied to a list of criteria.
Did the investigators provide sufficient information to describe the sample in their study? Yes,
there is a detailed procedure listing the steps they used to collect data.
Does the study clearly define the group of patients; is there a clear inclusion and exclusion
criterion? Yes, the research states, “A study was included if it represented a comparative trial in which the
outcome of primary total knee arthroplasty was reported according to BMI. Studies involving all types of
cemented and non-cemented total knee prosthesis designs were included. Review articles, expert opinions,
surgical techniques, and abstracts from scientific meetings were excluded. Only articles written in English
were included.”
67
Is there a clear description of the stage and timing of the problem (illness) studied.
Are the subjects representative of the population from which they were drawn?
Did they capture all eligible subjects? The databases of PubMed/MEDLINE, the Cochrane Database of
Systematic Reviews, and Embase from 1970 to 2009 were searched for publications on obesity and total
knee arthroplasty. The search terms “arthroplasty,” “knee,” “weight,” “BMI,” and “obesity” were used.
Furthermore, the reference lists of retrieved publications were checked manually for additional studies that
potentially met the inclusion criteria but had not been found by the electronic search.
Step 2 – locating studies. Did they include multiple databases? Was the search strategy defined
and includes: Bibliographic databases used as well as hand searching? Terms (key words and
index terms)? Citation searching: reference lists? Contact with ‘experts’ to identify ‘grey’ literature
(body of materials that cannot be found easily through conventional channels such as publishers)?
Sources for ‘grey literature? Yes, they stated, “Our search strategy followed the recommendations of the
Cochrane collaboration. The databases of PubMed/MEDLINE, the Cochrane Database of Systematic
Reviews, and Embase from 1970 to 2009 were searched for publications on obesity and total knee
arthroplasty. The search terms “arthroplasty,” “knee,” “weight,” “BMI,” and “obesity” were used.
Furthermore, the reference lists of retrieved publications were checked manually for additional studies that
potentially met the inclusion criteria but had not been found by the electronic search.”
Part 3:Critical Appraisal/Criteria for Inclusion
Were criteria for selection specified? Did more than one author assess the relevance of each
report? Were decisions concerning relevance described; completed by non-experts, or both? Did
the people assessing the relevance of studies know the names of the authors, institutions, journal
of publication and results when they apply the inclusion criteria? Or is it blind? Yes the study stated,
68
“Two investigators (G.M.M.J.K. and D.H.) independently reviewed the literature to identify relevant articles
for full-text review. The reviewers independently applied the criteria described above and below to the full
text of these articles to select articles for inclusion in this review. The reviewers are orthopedic surgeons
who are familiar with total knee arthroplasty surgery and are also trained and experienced in performing
meta-analyses. Disagreement regarding the search was resolved by consensus, with arbitration by a third
author (J.A.M.B.) if differences remained. A study was included if it represented a comparative trial in which
the outcome of primary total knee arthroplasty was reported according to BMI. Studies involving all types of
cemented and non-cemented total knee prosthesis designs were included. Review articles, expert opinions,
surgical techniques, and abstracts from scientific meetings were excluded. Only articles written in English
were included. Author, affiliation, or source did not blind studies. Our primary research question was to
determine whether the outcome of primary total knee arthroplasty was influenced by BMI. Outcomes of
interest were infection (deep, superficial, or any), revision for infection, aseptic loosening, hematoma,
venous thromboembolism, perioperative fracture, nerve damage, tendon or ligament rupture, Knee Society
Score, Knee Society function sub-score, and range of knee motion. The methodology of the randomized
clinical trials and controlled clinical trials was independently assessed by two reviewers (E.S. and D.D.).
First, the methodology was assessed with use of the list of criteria recommended by the Cochrane
Collaboration Back Review Group, with adaptation of the bias criteria for observational studies. Second, the
criteria listed on The Journal of Bone and Joint Surgery web site, which are an adaptation of the criteria
developed by the Centre for Evidence-Based Medicine (Oxford, United Kingdom), were used to define the
level of evidence. Disagreement was resolved by group assessment.”
Part 3 – Critically appraise for bias: Selection – Were the groups in the study selected differently?
Random? Concealed? A search of the literature was performed, and studies comparing the outcome of
total knee arthroplasty in different weight groups were included. The methodology of the included studies
69
was scored according to the Cochrane guidelines. Data extraction and pooling were performed. The
weighted mean difference for continuous data and the weighted odds ratio for dichotomous variables were
calculated. Heterogeneity was calculated with use of the I2 statistic.
Were the subjects assembled at a common (usually early) point in the course of their disorder? The
research is looking at outcomes after TKA for obese or non-obese patients. There is no mention of specific
time points of assemblage of the patient population. The inclusion criteria are only geared to look at
whether BMI influences the outcomes and there is no time frame reported for the outcomes.
a.
If not, what are the implications of multiple starting points for this study’s results? It could
create a bias issue if some of the population of patient’s outcomes are recorded at different points in time
because it may appear that one group has better outcome over a longer course of time.
Was the study time frame long enough to capture the outcome(s) of interest? Was patient follow-up
sufficiently long and complete? The only report of time frame is regarding the 1970-2009 periods
through which they are collecting the research data.
a.
If not, what are the potential consequences of the follow-up time for the study’s results?
When the studies don’t individually list the follow-up time it can cause bias in outcomes because the
outcomes can appear to be better in one of the study groups over the control.
Were objective outcome criteria applied to the subjects in a masked or blinded fashion? No blinding
of the study procedures was performed.
a.
If not, what are the potential consequences for this study’s results? It may cause bias in that
the researchers could pull only the studies they wanted in order to support their hypothesis that BMI has a
negative influence on TKA outcomes.
If subgroups with different prognoses are identified, was there adjustment for important prognostic
or risk factors? They looked at two groups: BMI < 30 or >30.
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a.
If not, what should have been included? What are the potential consequences for the lack of
this adjustment? There is a strict criterion that was applied per a Cochrane advisement for collecting this
type of data. There should have been more detail, however, regarding the differences in levels of obesity
because it appears that the higher a BMI there are associated risks accompanying the higher BMI –
perhaps a level for morbidly obese.
Performance- Did the groups in the study receive different treatment? No they are all receiving TKA
and then looking at the outcomes related to whether obesity has a negative influence on those outcomes.
Was there blinding? Author, affiliation, or source did not blind studies.
Attrition – Were the groups similar at the end of the study? Account for drop outs? Did all subjects
originally enrolled complete the study? There is no list of attrition.
a.
If not, how many subjects were lost? There is no list of attrition.
b.
What if anything did the authors do about this attrition? They did not report this element.
c.
What are the implications of this attrition and the way it was handled with respect to the
study’s findings? It could skew the findings of this research because it does not clearly delineate what
happened to the population and if there were patients that dropped out, died, or failed to report for follow
up, then it may make the procedure outcomes appear better than they really were.
Detection – Did the study selectively report the results? Is there missing data? There are detailed
procedural steps regarding the pooling of studies and these steps are listed above in the answer to the
question regarding inclusion and exclusion efforts as well as listed below in the data collection tools. It
does not appear that any data is missing.
Was there an independent set of patients to validate the study? They looked at those with BMI of < 30
and > 30. Are the valid results of this prognostic study important? Yes, because they give a better
picture of the risks associated with undergoing this procedure when the patient is also obese.
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Part 4 – Collection of the data
Was a collection data form used and is it included? The data from the included studies were extracted
by two reviewers (G.M.M.J.K., D.H.), with use of a data extraction tool tested in a pilot study and were
verified by a third reviewer (W.D.). The available data from the selected studies were then pooled with use
of the review manager software from the Cochrane collaboration.
Are the studies coded and is the data coding easy to follow? Yes, there are flow charts and tables
outlining the different studies and their outcomes.
Were studies identified that were excluded & did they give reasons why (i.e., which criteria they
failed). Yes these are listed above.
Are the results of this SR valid? Yes.
1. Is this a SR of randomized trials? Did they limit this to high quality studies at the top of the
hierarchies? No, “the methodology of the randomized clinical trials and controlled clinical trials was
independently assessed by two reviewers (E.S. and D.D.). First, the methodology was assessed with use
of the list of criteria recommended by the Cochrane Collaboration Back Review Group, with adaptation of
the bias criteria for observational studies. Second, the criteria listed on The Journal of Bone and Joint
Surgery web site, which are an adaptation of the criteria developed by the Centre for Evidence-Based
Medicine (Oxford, United Kingdom), were used to define the level of evidence. Disagreement was resolved
by group assessment. The data from the included studies were extracted by two reviewers (G.M.M.J.K.,
D.H.), with use of a data extraction tool tested in a pilot study and were verified by a third reviewer (W.D.).
The available data from the selected studies were then pooled with use of the review manager software
from the Cochrane collaboration.
a. If not, what types of studies were included? They also had clinical control trials.
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b. What are the potential consequences of including these studies for this review’s results? It can
change the study to appear statistically heterogeneous.
2. Did this study follow the Cochrane methods selection process and did it identify all relevant
trials? Yes
3. Do the methods describe the processes and tools used to assess the quality of individual
studies? Yes, “The data from the included studies were extracted by two reviewers (G.M.M.J.K., D.H.),
with use of a data extraction tool tested in a pilot study and were verified by a third reviewer (W.D.).”
4. What was the quality of the individual studies included? Were the results consistent from study
to study? Did the investigators provide details about the research validity or quality of the studies
included in review? Yes they discuss the studies in their charts and tables as well as stating, “Obtaining
Level-I evidence for the impact of morbid obesity on the outcome of total knee arthroplasty is difficult; a
highest-quality study cannot be performed since blinding is only partially possible. We chose to include all
comparative studies in this systematic review since that represented the best evidence available at present.
Differentiation between retrospective and prospective trials can be difficult because many authors present a
study with prospective data collection and retrospective analysis of the data as being prospective in design.
Scoring of the methodology, however, showed that the studies included in this review were comparable and
that pooling them was therefore justifiable.”
5. Did the investigators address publication bias? Yes, they stated which studies may have introduced
bias and why in the following statement. “The study by Bordini et al.8 may have introduced a bias in our
meta-analysis of infection. This study could have influenced the outcome because the study population was
large (8892 patients) and the infection rate was dramatically low, with four superficial infections and fiftyeight revisions for infection. The superficial infection rate was only 0.04%, and the rate of any infection
(calculating revision for infection as representing deep infection) was 0.6%. We performed an additional
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analysis in which this study was omitted from the calculation of the infection rate in the studies with shortterm outcome. This did alter the results of the meta-analysis, with the obese group scoring worse for
infection risk, with an odds ratio of 3.57 (95% CI, 2.17 to 5.88). Heterogeneity remained low, with an I2 of
0%.”
Are the valid results of this SR important? Yes
6. Were the results homogenous from study to study? Heterogeneity remained low, with an I2 of 0%.
7. If the paper is a meta-analysis did they report the statistical results? Yes Did they include a
forest plat? Yes What other statistics do they include? Are there CIs? Yes, they are stated as “A flow
diagram showing the selection of the studies is shown. After consensus was reached, twenty studies were
included for data analysis. The baseline characteristics and methodology of the included trials are
summarized. Data regarding the presence of any infection were extracted from the studies in which this
outcome was reported; in addition, deep and superficial infections were analyzed separately in studies that
distinguished between them. The presence of any infection was reported in fourteen studies including
15,276 patients; these studies had a low heterogeneity, with an I2 of 26%. Overall, infection occurred more
often in obese patients, with an odds ratio of 1.90 (95% CI, 1.46 to 2.47). Superficial infection was reported
separately in nine studies including 4905 patients; the heterogeneity among these studies was low, with an
I2 of 6%. Superficial infection occurred more often in obese patients, with an odds ratio of 2.17 (95% CI,
1.47 to 3.13). Deep infection requiring surgical debridement was reported separately in nine studies
including 5061 patients; no heterogeneity was found among these studies (I2, 0%). Deep infection occurred
more often in obese patients, with an odds ratio of 2.38 (95% CI, 1.28 to 4.55). Overall infection rate after
total knee arthroplasty according to body mass index (BMI, in kg/m2). M-H = Mantel-Haenszel, CI =
confidence interval, and df = degrees of freedom. Revision of the total knee arthroplasty, defined as
exchange or removal of the components for any reason, was documented in eleven studies including
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12,101 patients. Heterogeneity among these studies was low, with an I2 of 25%. Revision for any reason
occurred more often in obese patients, with an odds ratio of 1.30 (95% CI, 1.02 to 1.67). With the numbers
available, the revision rate did not differ significantly between obese and non-obese patients when revision
surgery for infection and revision for aseptic loosening were analyzed separately. The complications that
occurred during the surgical procedure were mentioned in only four studies. The low heterogeneity among
these studies allowed pooling of the results and, on the basis of the numbers, no significant differences
were found in the occurrence of intraoperative fracture, nerve injury, or tendon or ligament rupture. This
lack of difference may be the result of the small number of events in these studies. The main postoperative
complication not related to the implant was the occurrence of a clinically manifest deep venous
thromboembolism and/or pulmonary embolism. Nine studies with a total of 13,459 patients reported on this
complication, and the results were pooled since no heterogeneity among the studies was found (I2, 0%).
This complication rate did not differ significantly between obese and non-obese patients (odds ratio, 1.19;
95% CI, 0.78 to 1.82). The most commonly reported functional outcomes in the studies were the Knee
Society Score and Knee Society function sub-score. Nine studies including 670 patients reported the Knee
Society Score for obese and non-obese patients. After pooling of the studies, which had an I2 of 0%, this
score showed a difference of 3.23 points (95% CI, 1.57 to 4.90 points) in favor of the non-obese patients;
however, the clinical significance of such a small difference on a scale of 0 to 100 can be questioned. The
Knee Society function sub-score was reported for a greater number of patients, but it could not be pooled
because of the high heterogeneity (I2, 84%). Subgroup analyses of certain outcomes were performed for
short or long-term follow-up. The overall infection rate was analyzed for studies that reported the short-term
outcome, since infection may be better documented in such studies. The eight studies including 13,133
patients that reported short-term results indicated a twofold greater infection rate in the obese patients
(odds ratio, 2.06; 95% CI, 1.46 to 2.91); the heterogeneity was moderate (I2, 46%) . In addition, revision for
any reason was analyzed for studies with more than five years of follow-up, since the number of revisions
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was expected to increase with elapsed time. The nine studies including 2284 patients that fulfilled this
criterion indicated the revision rate to be twice as high in the obese patients in the long term (odds ratio,
1.79; 95% CI, 1.15 to 2.78) (I2, 0%).” The overall results were reported, “After consensus was reached,
twenty studies were included in the data analysis. The presence of any infection was reported in fourteen
studies including 15,276 patients (I2, 26%). Overall, infection occurred more often in obese patients, with
an odds ratio of 1.90 (95% confidence interval [CI], 1.46 to 2.47). Deep infection requiring surgical
debridement was reported in nine studies including 5061 patients (I2, 0%). Deep infection occurred more
often in obese patients, with an odds ratio of 2.38 (95% CI, 1.28 to 4.55). Revision of the total knee
arthroplasty, defined as exchange or removal of the components for any reason, was documented in
eleven studies including 12,101 patients (I2, 25%). Revision for any reason occurred more often in obese
patients, with an odds ratio of 1.30 (95% CI, 1.02 to 1.67).”
8. From the findings, is it apparent what the cumulative weight of the evidence is? Yes. Can you
apply this valid, important evidence from this SR in caring for your patient/client? What is the
external validity? Yes, it shows that there is emerging research to support the idea that obesity carries
with it an increased risk factor for poor outcomes when these patients choose to undergo a TKA procedure.
Yes, these findings can be generalized to the population of obese patients so that they are aware of their
inherent risks.
9. Is your patient different from those in this SR? Only in that these focused on primary TKA and my
patient underwent BTKA. The patient I studied had a BMI of > 40.
10. Is the treatment feasible in your setting? Do you have the facilities, skill set, time, 3rd party
coverage to provide this treatment? This information would be helpful to the patient’s decision-making
process.
11. Does the intervention fit within your patient/client’s stated values or expectations? Yes, the
research discusses the outcomes and states, “the aim of our systematic review of the literature was to
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show whether obesity leads to a worse outcome following total knee arthroplasty. Our results showed that
patients with a BMI of ≥30 kg/m2 had more infections and a higher revision rate compared with patients
with a BMI of <30 kg/m2. Total knee arthroplasty in obese patients was therefore associated with higher
risks in both the short and the long term. We believe that obese patients should be informed of the abovementioned risks and should be advised to lose weight. Many patients will fail to achieve this goal without
professional help, so we refer obese patients with osteoarthritis to a multidisciplinary obesity outpatient
clinic. If this approach fails to result in weight loss, the patient at least benefits from a thorough analysis of
existing comorbidity and optimization of his or her medical condition. We do not withhold a total knee
arthroplasty from these patients, but we inform them extensively regarding the risk that their obesity poses
with regard to this procedure.”
What is the bottom line? This study had many limitations because it did not present a detail of information
and had many threats to its internal validity. It did, however, list these threats at full disclosure so that the
valid data could be assessed and extrapolated. Overall, this research is still valid in light of the many
limitations.
Prognostic Study 6 – Evidence Appraisal Worksheet
Citation:
Powell RS, Pulido P, Tuason MS, Colwell Jr CW, Ezzet KA. Bilateral vs unilateral total knee replacement:
a patient based comparison of pain levels and recovery of ambulation skills. The Journal of Arthroplasty.
2006, Aug; 21(5): 642-9.
Level of Evidence (Oxford scale): 2b
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Is the purpose and background information sufficient? Study Purpose Stated clearly? What is the
purpose of this study? Yes, this study answers questions regarding pain and ambulation outcome
differences using a retrospective review of a cohort of BTKA patients compared with a matched cohort of
UTKA patients.
Literature/Relevant background presented? Describe the justification of the need for this study.
Yes, this study outlines the answers to the questions whether BTKA is more painful and whether it also
creates more difficult recovery than a UTKA.
Does the research design have strong sampling techniques? Yes, they matched BTKA to UTKA
patients and recorded data for the outcomes of interest.
Did the investigators provide sufficient information to describe the sample in their study? Is there a
clear description of the stage and timing of the problem (illness) studied. Are the subjects
representative of the population from which they were drawn? Did they capture all eligible
subjects? Yes they state, “From the computerized database at the authors' institution, 59 patients who
underwent bilateral TKA could be matched to suitable patients with appropriate demographic factors
undergoing unilateral TKA during the same general time frame. All cases were carried out between 1994
and 2002. Hospital and clinic charts for these 59 matched pairs of patients were available for retrospective
review. Patients forming a “matched pair” were matched with respect to sex, age, date of surgery, surgeon,
and diagnosis. Institutional review board approval was obtained before review of the charts.”
Does the study clearly define the group of patients; is there a clear inclusion and exclusion
criterion? Yes, they are listed as inclusion of “Patients w/ “matched pair” were matched with respect to
sex, age, date of surgery, surgeon, and Dx. Standard length anterior incisions, medial capsulotomies,
routine use of patellar eversion to aid exposure, intramedullary suction of marrow contents, intramedullary
align femur and tibia, routine resurfacing of patella, and cemented fixation of all components were
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included.” And exclusion as “Revisions or complex primaries that required stems, augmentations, or bone
grafts and excluded patients receiving spinal narcotics, epidural narcotics, intra-articular infusion pumps, or
peripheral nerve blocks.” Furthermore the patients are described in detail as “The bilateral TKA cohort [that]
consisted of 29 female and 30 male patients with a mean age of 67.83 years in comparison with 29 female
and 30 male patients in the unilateral group with a mean age of 67.71 years. The unilateral group had 25
right TKAs and 34 left TKAs. The diagnosis was osteoarthritis in 58 patients and rheumatoid arthritis with
superimposed degenerative joint disease in one patient for the bilateral cohort, whereas all 59 patients in
the unilateral group carried the diagnosis of osteoarthritis.”
Are the results of this prognostic study valid? Yes
1. Were the subjects assembled at a common (usually early) point in the course of their disorder?
Yes they were matched to same general time frame.
2. Was the study time frame long enough to capture the outcome(s) of interest? Was patient followup sufficiently long and complete? Yes there is detailed listing of data collection points and the time
frames each were collected for the patients in the study.
3. Did all subjects originally enrolled complete the study? There were some patients that were
discharged earlier than others and when this occurred the researchers detailed the outcome and how they
matched for discrepancies.
a. If not, how many subjects were lost? In regards to the outcome for pain scale, “Data for narcotic use
during the final 24-hour interval were not used for tabulation if the patient was discharged from the hospital
before completion of the entire 24-hour interval. Five patients in the bilateral group and 14 in the unilateral
group were therefore eliminated from the 48-hour to 72-hour time interval comparison.” In regards to the
outcome for ambulatory skill, “The ambulatory ability of all 59 patients in each group was compared for
postoperative days 1 and 2. For postoperative day 3, 56 patients in the bilateral group and 55 patients in
the unilateral group had data for comparison. Data were not available for some patients in this interval
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because of discharge before day 3 or because of early discharge on day 3. On the day of discharge,
regardless of which postoperative day, 54 of the bilateral patients and 57 of the unilateral patients had data
for comparison. The bilateral group's data for the day of discharge were further stratified into one of three
categories: maximum ambulatory ability of 0 to 49, 50 to 99, and 100 ft or greater. Stratification was done to
determine if age had any bearing on patients' ability to ambulate after bilateral TKA. Length of stay,
discharge disposition of home vs a skilled nursing facility, and complications were also collected and
compared between groups.”
b. What if anything did the authors do about this attrition? They detailed their methods. See above.
c. What are the implications of this attrition and the way it was handled with respect to the study’s
findings? They are giving full disclosure with regards to each outcomes case for attrition.
4. Were objective outcome criteria applied to the subjects in a masked or blinded fashion? No,
instead a strict criterion was adhered to regarding the nature of their data collecting methods for which they
assess these studies retrospectively.
a. If not, what are the potential consequences for this study’s results? The outcomes could be biased
if they did not follow the outcome criteria.
5. If subgroups with different prognoses are identified, was there adjustment for important
prognostic or risk factors? There were no sub-groups.
6. Was there an independent set of patients to validate the study? There was a control group and a
study group compared.
Are the valid results of this prognostic study important? Yes, because they help answers regarding
ambulation and pain outcomes in the two different surgical procedures.
7. What were the statistical findings of this study? The types of statistics used in the study were, “done
with 2-tailed Student t test with statistical significance set at a P value of .05. Analysis of variance was used
to analyze three sets of data with a P value of .05 signifying statistical significance. χ2 analysis was done to
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compare sets of categorical data. Standard deviations of the mean were also calculated for evaluation.”
The outcomes of analysis for the pain scale were, “Narcotic requirements were slightly greater for the
bilateral group for each of the intervals studied although none of the differences were statistically significant
(Table 2). Narcotic use was equivalent in both groups by 48 to 72 hours after surgery. Narcotics required
intraoperatively were uniform with 2.01 (±1.67) DE in the unilateral group and 2.06 (±1.47) DE in the
bilateral group. During the first 24 hours after surgery, the unilateral group used an average of 6.08 DE
compared with 7.14 DE in the bilateral group. This 15% difference in narcotic use was not statistically
significant (P = .16). From 24 to 48 hours after surgery, the unilateral group used less pain medication than
the bilateral group (3.40 vs 4.44 DE, respectively), a 23% difference (P = .17). In both groups, narcotic use
steadily declined over the 72-hour period studied. By the 48-hour to 72-hour time interval, the two groups
were using virtually identical quantities of pain medication (bilateral group 1.69 DE vs unilateral group 1.67
DE) (P = .86). Combining the narcotic use for the first 72 hours after surgery, no statistically significant or
clinically significant difference was noted in narcotic use. Analysis of the analog pain scale data
demonstrated a significant difference in perceived pain between the unilateral and bilateral group in the
early postoperative period; however, after the first postoperative day, no significant difference was noted.
The unilateral group reported a lower average pain score on the day of surgery than the bilateral group
(4.53 vs 5.83, respectively) (P = .03). This finding of lower pain carried on into postoperative day 1, with the
unilateral group reporting a mean score of 4.26 vs 5.49 for the bilateral group (P = .001) (Table 3). By
postoperative day 2, the groups were comparable, with the bilateral group reporting less pain than the
unilateral group, although the difference was not statistically significant. By day 3, the pain level in both
groups was indistinguishable.” And for ambulation outcomes,” When comparing the two groups, both
groups progressed rapidly, but the unilateral group ambulated further in each interval studied and all
intervals reached statistical significance (P < .05). The bilateral group lagged behind the unilateral group by
roughly 1.5 days in terms of reaching ambulatory milestones. The mean ambulatory distances for the
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bilateral cohort were 4.9, 18.2, 56.9, and 78.3 ft for postoperative days 1, 2, and 3 and the day of
discharge, respectively. In contrast, the unilateral group walked on average 28.8, 114.5, 162.6, and 169.1 ft
for postoperative days 1, 2, and 3 and the day of discharge, respectively (Table 4). After stratifying the data
for the bilateral group on the day of discharge, 18 patients (7 men and 11 women) with a mean age of
67.05 years ambulated 0 to 49 ft, 14 patients (7 men and 7 women) with a mean age of 67.71 years
ambulated 50 to 99 ft, and 22 patients (12 men and 10 women) with a mean age of 66.82 years ambulated
greater than 100 ft. No statistical difference in age was found among these three groups based on analysis
of variance calculation (P = .93). The authors are of the opinion that a patient needs to walk at least 50 ft to
be safely discharged home. Using these criteria, unilateral patients, on average, reach this milestone
between postoperative day 1 and postoperative day 2. Bilateral patients, on average, did not reach this
milestone until postoperative day 3. This difference is statistically significant.” The outcomes for length of
stay were, “for the two groups less than 1 day and appears to correspond to the 36-hour lag in achieving
ambulation milestones between the two groups. The mean length of stay for the bilateral group was 4.00
days (SD = 0.45) in comparison with the unilateral group who stayed a mean of 3.15 days (SD = 1.11) (P <
.001). Twenty-two (37%) of the 59 bilateral patients were discharged to home whereas 36 (61%) of 59 were
discharged to a skilled nursing facility. The discharge disposition for one patient in this group was unclear in
the chart and therefore was not included in the analysis. Thirty-seven (63%) of 59 unilateral patients were
discharged home from the hospital whereas 22 (37%) of 59 were discharged to a skilled nursing facility.
Among patients discharged to home, the mean ambulatory distance on the day of discharge averaged 127
ft for the bilateral group and 193 ft for the unilateral group. Among patients discharged to a skilled nursing
facility, the mean ambulatory distance on the day of discharge averaged 49.8 and 131.6 ft for the bilateral
and unilateral groups, respectively.”
8. What is the meaning of these statistical findings for your patient/client’s case? What does this
mean to your practice? Can you apply this valid, important evidence about this prognostic study in
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caring for your patient/client? What is the external validity? It means that the patients in this study
don’t necessarily have a significant difference with perception of pain from UTKA to BTKA but do seem to
have a lag time in ambulation skills and have higher overall complication rate than the UTKA.
9. How likely are these outcomes over time? There were no statistical models built to measure
likelihood ratios.
10. Are the study subjects similar to your patient/ client? Yes, because the patient underwent BTKA
and had very poor outcomes in ambulation skills.
11. Would sharing this information help your patient/client given their expressed values and
preferences? Yes, it definitely would.
What is the bottom line? “Patients considering TKA must be counseled as to the risks and benefits of the
procedure. Because TKA remains an elective procedure, the ultimate decision whether to proceed with
surgical intervention lies with the patient. Similarly, patients with bilateral disease who wish to undergo
surgery must decide whether they wish to have both knees replaced at one setting or during separate
hospitalizations. Patients who are candidates for bilateral knee arthroplasty often have reservations about
having both knees replaced at the same time and request advice from the orthopedic surgeon. Most
patients question the relative increase in pain and fear twice as much pain if proceeding with bilateral knee
arthroplasty. Patients also have concerns that they will not be able to walk for a prolonged period after
surgery if both knees are replaced simultaneously. The results of the present study help to answer these
patient concerns.”
Systematic Review Study 7– Evidence Appraisal Worksheet
Citation:
Samson A, Mercer G, Campbell D. Total knee replacement in the morbidly obese: a literature review. ANZ
J Surg. 2010 Sep; 80(9): 595-9.
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Level of Evidence (Oxford scale): 2b
Does the design follow the Cochrane method? That is not stated in the research, however, the list of
databases was provided.
Step 1 – formulating the question: Do the authors identify the focus of the review? Is the purpose
and background information sufficient? Study Purpose
Stated clearly? What is the purpose of this study? This study was designed to evaluate outcomes of
TKR in patients with morbid obesity (MO; BMI >40).
Literature/Relevant background presented? Does the research design have strong sampling
techniques? Yes, because there has been a consistent increase in the number of patients emerging with
a diagnosis of osteoarthritis that also have a BMI greater than 40 and therefore there is also an increase in
TKR surgeries. Concurrent with these events, there has also been an increase in inconclusive results in
the past research that begs for a more recent review of the literature. The sampling is strong and was
described as using a review of medical databases.
Did the investigators provide sufficient information to describe the sample in their study? Yes there
is detailed information regarding the procedure for data collecting.
Step 2 – locating studies: Did they include multiple databases? Was the search strategy defined
and include: Bibliographic databases used as well as hand searching, Terms (key words and index
terms), Citation searching: reference lists? Contact with ‘experts’ to identify ‘grey’ literature (body
of materials that cannot be found easily through conventional channels such as publishers),
Sources for ‘grey literature?
Their methods were defined as “A systematic review of medical databases
(PubMed, Medline, Cochrane Library, ScienceDirect) from January 1990 to September 2009 was
undertaken. The keywords used were: knee, arthroplasty, morbid obesity, body mass index, KSS, clinical
outcome and complications. Articles in this review were assessed for the level of evidence based on
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guidelines provided by the National Health and Medical Research Council of Australia and New Zealand.10
Prospective, case-control, reviews and retrospective comparative studies with levels of evidence from A to
C III-3 were included. Studies were excluded if the level of evidence was less than C IV. Australia Key
words bariatric surgery, complication, Knee Society Score, morbid obesity, total knee replacement.
Abbreviations BMI, body mass index; KSS, Knee Society Scores; MO, morbid obesity; ORI, odds ratio of
deep prosthetic infection; SF12, 12-item Short-Form Health Survey; TKR, total knee replacement; WHO,
World Health Organization; WOMAC, Western Ontario and McMaster Osteoarthritic Index”
Part 3:Critical Appraisal/Criteria for Inclusion: Were criteria for selection specified? Yes, these were
delineated in their methods section.
Did more than one author assess the relevance of each report? The number of data assessors is not
discussed. Were decisions concerning relevance described; completed by non-experts, or both?
This information was not provided.
Did the people assessing the relevance of studies know the names of the authors, institutions,
journal of publication and results when they apply the inclusion criteria? Or is it blind? This was not
discussed.
Part 3 – Critically appraise for bias: Selection – Were the groups in the study selected differently?
Random? Concealed? The only information provided regarding the types of studies that were
included/excluded were, “10 Prospective, case-control, reviews and retrospective comparative studies with
levels of evidence from A to C III-3 were included. Studies were excluded if the level of evidence was less
than C IV.”
Performance- Did the groups in the study receive different treatment? Was there blinding? There is
no discussion of blinding.
Attrition – Were the groups similar at the end of the study? Account for drop outs?
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The only mention of attrition exists in a list of studies that were excluded because they had >30% lost to
follow up.
Detection – Did the study selectively report the results? Is there missing data?
They clearly list their data detection methods.
Part 4 – Collection of the data: Was a collection data form used and is it included?
Are the studies coded and is the data coding easy to follow? They clearly list their data collecting
methods.
Were studies identified that were excluded & did they give reasons why (i.e., which criteria they
failed)? Yes, they stated that 10 Prospective, case-control, reviews and retrospective comparative studies
with levels of evidence from A to C III-3 were included. Studies were excluded if the level of evidence was
less than C IV.
Are the results of this SR valid?
1. Is this a SR of randomized trials? Did they limit this to high quality studies at the top of the
hierarchies? Yes, again they stated that 10 Prospective, case-control, reviews and retrospective
comparative studies with levels of evidence from A to C III-3 were included. Studies were excluded if the
level of evidence was less than C IV.
a. If not, what types of studies were included? Listed in above answer
b. What are the potential consequences of including these studies for this review’s results? They
could skew the outcomes or bias them
2. Did this study follow the Cochrane methods selection process and did it identify all relevant
trials? They followed a criteria for the countries of Australia and New Zealand.
a. If not, what are the consequences for this review’s results? It may seem that the outcomes could
only be generalized to that population.
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3. Do the methods describe the processes and tools used to assess the quality of individual
studies? No.
a. If not, what are the consequences for this review’s results? It may be difficult to reproduce their
research methods.
4. What was the quality of the individual studies included? Were the results consistent from study
to study? Did the investigators provide details about the research validity or quality of the studies
included in review? Again they listed them as 10 Prospective, case-control, reviews and retrospective
comparative studies with levels of evidence from A to C III-3 were included. Studies were excluded if the
level of evidence was less than C IV.
5. Did the investigators address publication bias? No. Are the valid results of this SR important?
Although the outcomes are from another country, they are still pertinent to the population of patients in the
PICO question.
6. Were the results homogenous from study to study? There is no discussion of homogeneity.
a. If not, what are the consequences for this review’s results? It could skew the results.
7. If the paper is a meta-analysis did they report the statistical results? Did they include a forest
plat? What other statistics do they include? Are there CIs? Yes they are listed as, “All studies
reviewing the clinical KSS reported an improvement post-TKR for controls and patients with MO. Only one
study reported a significantly higher post-operative clinical KSS in the control group: 92 versus 84 (P <
0.001). The change score (the difference between the preoperative and post-operative KSS) was higher for
patients with MO: 53 versus 22. This highlights the fact that, on average, the patients with MO in that study
had a considerably lower preoperative clinical KSS. Of the six articles that evaluated functional scores, one
article utilized the Western Ontario and McMaster Osteoarthritic Index (WOMAC), the remainder used the
functional component of the KSS. All studies reported an increase in post-operative functional score for
controls and patients with MO. The control group in four studies had a significantly higher post-operative
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score. Only one of these studies reported a significantly higher change score for controls compared with
MO, 26 versus 13, respectively (P < 0.001). From the three remaining studies, one did not comment on
change scores; another noted a change score of 22 and 13 for controls and MO, respectively, but did not
comment on significance; and the third demonstrated no difference. Radiolucent lines were investigated in
five studies by using the Knee Society Roentgenographic Evaluation and Scoring System. The mean
duration of radiographic follow-up was 38.5–90 months. Only one study demonstrated a significant
increase in radiolucent lines for MO at 38.5 months: 29% versus 7% (P < 0.001). Three studies showed an
increase in radiolucent lines in MO patients versus controls (5.1% versus 0%15; 6.8% versus 1.2%17; and
32% versus 28%14) and these were not significant. Conversely, Mont et al. reported a higher prevalence of
radiolucent lines in controls, 6% versus 4%, but this difference was not significant. The morbidly obese had
a higher prevalence of complications in all studies, and this difference was significant in five studies. Two
studies reported only deep prosthetic infection. The odds ratio of deep prosthetic infection in MO patients
was significantly higher in both studies (3.3 and 8.9) in comparison with the BMI values of controls (<40 and
<30, respectively) (P < 0.01, Table 1). The remaining three articles noted significantly higher complications
of: wound healing, superficial infection, deep-vein thrombosis and deep prosthetic infection in MO patients.
Winiarsky et al. reported four medial col- lateral ligament avulsions in patients with MO. One surgeon
carried out the surgery and no other study reported this complication. The remaining two articles reported
an increase in complications for patients with MO, 26% versus 15 %, and 12% versus 2%, but neither
reached significance. Amin et al. reported inferior survival of prostheses after TKR in patients with MO
using revision as an endpoint at 5 years, 74.2% versus 100% (P < 0.01).
8. From the findings, is it apparent what the cumulative weight of the evidence is? Can you apply
this valid, important evidence from this SR in caring for your patient/client? What is the external
validity? Yes, this evidence can be generalized to the population in question.
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9. Is your patient different from those in this SR? No, the patient in question was morbidly obese and
that factor was included in the study group.
10. Is the treatment feasible in your setting? Do you have the facilities, skill set, time, 3rd party
coverage to provide this treatment? Yes, we have the ability to intervene and provide valuable
information regarding the outcomes to patients so they can make the best-informed decision regarding their
outcomes.
11. Does the intervention fit within your patient/client’s stated values or expectations? Yes, the
patient can use this research information to make informed decisions regarding their particular level of risk
associated with this type of procedure as well as assess their possible outcomes.
What is the bottom line? Overall, the research states, “the literature reviewed, patients with MO can
expect an improvement in the clinical KSS after TKR. Similarly, the functional KSS is likely to improve albeit
by a lesser magnitude than non-MO. Post-operative weight is unlikely to change, so a reduction in weightrelated medical conditions is unlikely. Of concern is the significant increase in deep prosthetic infection and
potential reduced survival of prostheses. Morbidly obese patients are exposed to a risk of earlier revision
and its association with long-term morbidity and costs. MO patients should therefore be encouraged to lose
weight before TKR. There is currently limited evidence to support surgical intervention for weight reduction
in patients requiring TKR. Future studies assessing the outcomes of bariatric surgery prior to TKR in
patients with end-stage osteoarthritis are required.”
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Prognostic Study 8 – Evidence Appraisal Worksheet
Citation:
Winiarsky R, Barth P, Lotke P. Total knee arthroplasty in morbidly obese patients. J Bone Joint Surg [Am]
1998;80-A:1770–4.
Level of Evidence (Oxford scale): 2b
Is the purpose and background information sufficient? Study Purpose Stated clearly? What is the
purpose of this study?
To review clinical outcomes of 50 primary TKAs performed w/ cement in 50 MO patients and compared
results w/ 1768 similar procedures, performed during the same time-period by the same surgeon, in 1539
patients who were not morbidly obese (controls).
Literature/Relevant background presented? Yes, the researchers discuss the need for studies that
discuss the outcomes of TKA for the morbidly obese.
Does the research design have strong sampling techniques? Yes, they are looking at the database of
their own hospital records and assessing their own patient’s records.
Did the investigators provide sufficient information to describe the sample in their study? Yes they
clearly list all demographics pertaining to the sample.
Does the study clearly define the group of patients; is there a clear inclusion and exclusion
criterion? Is there a clear description of the stage and timing of the problem (illness) studied? Are
the subjects representative of the population from which they were drawn? Did they capture all
eligible subjects? Yes they state “Morbidly obese patients (those having a Quetelet index of more than
forty) were identified from a database containing information on all patients who had had a total knee
arthroplasty performed by the senior one of us (P. L.) between January 1980 and September 1994 and had
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been followed for a minimum of two years. The study group consisted of forty patients (fifty knees). Five
morbidly obese patients had had a bilateral total knee arthroplasty, with the procedure staged at intervals
ranging from three months to three years. The control group consisted of the remaining 1539 patients
(1768 knees) who had had the same procedure, performed by the same surgeon in the same time-period,
with the same minimum duration of follow-up.” It does not appear that any patients were excluded from the
time frame of the cohort of patient under the care of the senior author and surgeon.
Are the results of this prognostic study valid? Yes
1. Were the subjects assembled at a common (usually early) point in the course of their disorder?
Yes they were retrospectively selected from the hospital records from the same time period.
2. Was the study time frame long enough to capture the outcome(s) of interest? Was patient followup sufficiently long and complete? Yes, they followed the subjects for 5 years.
3. Did all subjects originally enrolled complete the study? Yes, they provide information for all subjects.
What are the implications of this attrition and the way it was handled with respect to the study’s
findings? They clearly list all the outcomes for each of the subjects in this study whether it was a positive
or negative outcome.
4. Were objective outcome criteria applied to the subjects in a masked or blinded fashion? If there
were, they were not listed.
a. If not, what are the potential consequences for this study’s results? The outcomes could have been
biased.
5. If subgroups with different prognoses are identified, was there adjustment for important
prognostic or risk factors? Yes, these are clearly listed.
6. Was there an independent set of patients to validate the study? Yes, there is a clear listing of control
and study participants.
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Are the valid results of this prognostic study important? Yes, these findings are pertinent to the patient
population undergoing TKA procedures.
7. What were the statistical findings of this study? “The mean age of the forty morbidly obese patients
at the time of the operation was 64.6 years (range, 45.6 to 76.5 years). There were thirty-six women and
four men. The preoperative diagnosis was osteoarthrosis in thirty-eight patients (95 percent), rheumatoid
arthritis in two (5 percent), and Paget disease in one (3 percent). (One patient had both osteoarthrosis and
Paget disease.) The mean Quetelet index was 44.0 (range, 40.3 to 56.2), with the men averaging 1.7
meters (range, 1.5 to 1.9 meters) in height and 113.3 kilograms (range, 97.2 to 158.9 kilograms) in weight
and the women averaging 1.6 meters (range, 1.3 to 1.7 meters) in height and 112.3 kilograms (range, 78.5
to 136.1 kilograms) in weight. These patients were followed for a mean of 4.8 years (range, two to thirteen
years). The mean age of the 1539 patients in the control group at the time of the operation was 67.7 years
(range, 13.4 to 94.2 years). There were 1016 female patients and 523 male patients. The preoperative
diagnosis was osteoarthrosis for 1432 knees (81 percent) and rheumatoid arthritis for 195 (11 percent); the
remaining 141 knees (8 percent) had other diagnoses. The mean Quetelet index was 28.0 (range, 10.9 to
39.7), with the male patients averaging 1.8 meters (range, 1.5 to 2.0 meters) in height and 88.0 kilograms
(range, 54.4 to 136.0 kilograms) in weight and the female patients averaging 1.6 meters (range, 1.4 to 1.9
meters) in height and 75.0 kilograms (range, 21.3 to 136.0 kilograms) in weight. Preoperatively, the
morbidly obese patients had a mean knee score of 31 points (range, 0 to 66 points) and a mean functional
score of 40 points (range, 0 to 70 points). Postoperatively, the mean knee score increased to 84 points
(range, 0 to 100 points) and the mean functional score, to 53 points (range, 0 to 90 points). Postoperatively,
the mean range of motion was 106 degrees (range, 45 to 125 degrees) and the mean radiographic score
was 98 points (range, 70 to 100 points). Preoperatively, the patients in the control group had a mean knee
score of 65 points (range, 0 to 100 points) and a mean functional score of 45 points (range, 0 to 100
points). Postoperatively, the mean knee score increased to 92 points (range, 38 to 100 points) and the
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mean functional score, to 67 points (range, 20 to 100 points). Both of these postoperative scores were
significantly higher than those in the morbidly obese group (p < 0.00005). Postoperatively, the mean range
of motion was 109 degrees (range, 15 to 130 degrees) and the mean radiographic score was 98 points
(range, 60 to 100 points). With the numbers available, no significant difference between the groups could
be detected with regard to either the range of motion or the radiographic score (p = 0.77). Problems with
primary wound healing (hereafter referred to as wound complications) and other perioperative problems
were significantly more common in the morbidly obese patients. Of the fifty knees in those patients, thirteen
(26 percent) had a perioperative complication compared with thirty-two (2 percent) of the 1768 knees in the
control group (p < 0.00005). Eleven (22 percent) of the fifty knees had a wound complication and five (10
percent) had a deep joint infection, whereas in the control group a total of thirty-five (2 percent) of the 1768
knees had a wound complication and a total of eleven (less than 1 percent) had a deep joint infection. All
five infections in the morbidly obese patients developed within twenty weeks after the operation, and three
were associated with a wound complication. The differences in the rates of infection and wound
complications between the two groups were highly significant (p < 0.0001 and p < 0.00005, respectively).”
8. What is the meaning of these statistical findings for your patient/client’s case? What does this
mean to your practice? Can you apply this valid, important evidence about this prognostic study in
caring for your patient/client? What is the external validity? Yes, these findings are relevant and show
that undergoing any TKA procedures while being morbidly obese carry with it statistically significant risks
for poor outcomes in many realms. These findings may be generalized to the population with which they
are interested in as their study group.
9. How likely are these outcomes over time? The outcomes were not studied with respect to confidence
intervals so there is no statistical measure of their likelihood over time.
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10. Are the study subjects similar to your patient/ client? Yes, this patient population described in the
study group was morbidly obese and many of the patients underwent BTKA procedures and these are
primary identifiers for my patient.
11. Would sharing this information help your patient/client given their expressed values and
preferences? Yes, sharing this information could assist this patient in making informed decisions regarding
risk and poor functional outcomes.
What is the bottom line? In summary, the effect of morbid obesity on the outcome of total knee
arthroplasty is of great concern to the orthopedic surgeon. Proper operative technique, experience, and
meticulous attention to wound healing are important and are related to the overall success of the procedure
in this population. The authors recommend that morbidly obese patients be made aware of their greater risk
of complications following total knee arthroplasty and that the surgeon attempt to decrease this risk by
exercising increased vigilance in the care of the wound during the perioperative period.
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