Tradeoffs Between Avoiding Complications and Restricting Access to Total Joint Arthroplasty:
The Implications of BMI Cutoffs
Nicholas J. Giori1,2, Shalini Gupta1, Thomas Bowe1, Derek F. Amanatullah2, Alex H.S. Harris1,2
1
VA Palo Alto Health Care System, Palo Alto, CA, 2Stanford University, Stanford, CA
Disclosures: Nicholas J. Giori (3C-NuRep; 4-Cytonics), Shalini Gupta (N), Thomas Bowe (N), Derek F. Amanatullah (3B-Bluejay Mobile Health,
Exactech, Omni, Sanofi; 5-Acumed, Bluejay Mobile Health, Stryker; 7-WebMD), Alex H.S. Harris (N)
INTRODUCTION: Patients with severe osteoarthritis of the hip or knee can experience reduced pain and improved function following successful total joint
arthroplasty. This is true even in people with morbid obesity. However, morbid obesity is a risk factor for complications following total joint arthroplasty,
causing some surgeons to enforce a BMI cut-off above which total joint arthroplasty is delayed or denied. Before implementing BMI cutoffs, it is important
for surgeons and patients to quantitatively understand the tradeoffs of enforcing a BMI cut-off - avoiding complications on the one hand but restricting
access to people who would not have experienced a complication on the other.
METHODS: A retrospective review of national data in the Veterans Health Administration (VHA) Corporate Data Warehouse (CDW) and the Veterans
Affairs Surgical Quality Improvement Program (VASQIP) databases was conducted. Patients undergoing primary total knee or total hip arthroplasty
between October 1, 2011 and September 30, 2014 were included in this study. Patients were stratified based on preoperative BMI. VASQIP data were used
to determine the occurrence of major complications (readmission, reoperation, MI, CVA, peripheral nerve injury, pneumonia, DVT, PE, reintubation, wound
dehiscence, deep infection, sepsis, renal failure, and death). We then evaluated what would have happened to these patients if a BMI cut-off had been
enforced at the time of their surgery. We determined how many complications would have been avoided, and how many patients would have been denied
surgery who would not have experienced complications.
RESULTS: 27,671 total hip or knee arthroplasty surgeries were done in this 3-year period. As the cut-off for acceptable BMI becomes more stringent (goes
down), major complications are reduced, but greater numbers of patients who would not have had a complication are denied surgery (Table 1). Using a BMI
cut-off of 40 kg/m2, a surgeon can expect that 90.8% of all patients will proceed with surgery and not have a complication (True Negative), 4.75% of all
patients will proceed with surgery but end up with a complication (False Negative), 4.15% of all patients would be blocked from having surgery who would
not have had a complication (False Positive), and 0.3% of patients would be blocked from having surgery and would have had a complication (True
Positive). In statistical terms, the sensitivity of using a BMI of 40 kg/m 2 as test for major complications is 5.4%, and the positive predictive value is 6.7%.
The implications of other BMI cut off values are shown in Table 1.
DISCUSSION: There is a trade-off between reducing complications and providing access to an operation that can improve quality of life and reduce pain.
Looking at the patients in this study who were deemed to be well enough for surgery at their respective VA medical centers, enforcing a BMI cut-off of 40
kg/m2 would have successfully screened out 83 of 27,671 patients who would have had a complication, but would have blocked access to surgery for 1,148
patients who would not have had a complication. This quantitative assessment of risk and benefit when applying a strict BMI cut-off should be considered
when evaluating a patient with morbid obesity who is otherwise acceptable for surgery.
SIGNIFICANCE: It is important for orthopedic surgeons to quantitatively understand the trade-off between risk reduction and access to care for patients
with severe osteoarthritis and morbid obesity. This paper provides data that will help to inform critical decisions made at the point of care.
ACKNOWLEDGEMENTS: This work was supported by the Department of Veterans Affairs HSR&D IIR 13-051-3
Table 1: Expected outcome when setting various BMI cut-off values
BMI Cut-off
(kg/m2)
30
35
40
45
50
Surgery
without a
Complication
Denied
without a
Complication
Surgery
with a
Complication
Denied
with a
Complication
42.60%
52.35%
2.01%
2.95%
75.70%
19.25%
3.88%
1.17%
90.80%
4.15%
4.75%
0.30%
94.12%
0.83%
4.96%
0.09%
94.80%
0.16%
5.01%
0.04%
ORS 2017 Annual Meeting Paper No.0016