n Feature Article
Factors Influencing Functional Outcomes in
United Intertrochanteric Hip Fractures:
A Negative Effect of Lag Screw Sliding
Je-Hyun Yoo, MD, PhD; Tae-Young Kim, MD; Jun-Dong Chang, MD, PhD; Yoon-Hae Kwak, MD;
Yong-Shin Kwon, MD
abstract
Full article available online at Healio.com/Orthopedics
The purpose of this study was to investigate the factors influencing functional outcomes in elderly patients with united intertrochanteric fractures treated with hip
nails and to ascertain whether decreased femoral offset due to lag screw sliding
has a negative effect on functional outcomes in these patients. This retrospective
study included 65 patients older than 65 years with united intertrochanteric fractures
treated with hip nails. Functional outcomes were assessed using the Short Form-36
(SF-36) and a visual analog scale (VAS) 6 months postoperatively. Mean patient age
was 77.8 years (range, 65-90 years); mean follow-up was 20.7 months (range, 12-38
months). More lag screw sliding occurred as bone mineral density (BMD) decreased.
It was also greater in unstable fractures and acceptable reduction status. Less accurate reduction and greater lag screw sliding showed significant negative effects on
most subscales of the SF-36, especially Physical Functioning and Role Physical. A
significant positive correlation was observed between the extent of lag screw sliding
and VAS. Lag screw sliding affected by fracture type, reduction quality, and BMD
has a negative effect on functional outcomes in elderly patients with united intertrochanteric fractures. Therefore, the preservation of anatomical femoral offset as much
as possible is needed to obtain better functional outcome through the minimization of lag screw sliding by more accurate reduction, which is a controllable factor,
especially in osteoporotic unstable intertrochanteric fractures. [Orthopedics. 2014;
37(12):e1101-e1107.]
Figure: Anteroposterior radiograph showing an
unstable intertrochanteric fracture (A2.3) in a
74-year-old man.
The authors are from the Department of Orthopaedic Surgery (J-HY, T-YK, Y-HK, Y-SK), Hallym
University Sacred Heart Hospital, Hallym University School of Medicine, Anyang; and the Department
of Orthopaedic Surgery (J-DC), Dongtan Sacred Heart Hospital, Hallym University School of Medicine,
Hwasung, South Korea.
The authors have no relevant financial relationships to disclose.
Correspondence should be addressed to: Je-Hyun Yoo, MD, PhD, Department of Orthopaedic
Surgery, Hallym University Sacred Heart Hospital, Hallym University School of Medicine, 896 Pyeongchon-dong, Dongan-gu, Anyang 431-070, South Korea ([email protected]).
Received: December 12, 2013; Accepted: March 25, 2014; Posted: December 10, 2014.
doi: 10.3928/01477447-20141124-58
DECEMBER 2014 | Volume 37 • Number 12
e1101
n Feature Article
T
he incidence of hip fracture continues to rise as the elderly population increases as a result of the
extension of the average life span.1 Hip
fractures are associated with a 22% mortality rate at 1 year postoperatively and are
also associated with a profound impairment of independence and quality of life,
either temporary or permanent.2 Successful operative treatment of these fractures
is essential for returning these generally
debilitated elderly patients to maximum
functioning.3
However, up to 50% of these patients
lose the ability to function independently
and are unable to return to their preinjury ambulatory levels despite favorable
surgical outcomes.4-7 Also, compromised
muscle strength and power in the fractured limb, persisting even years postoperatively, has been reported to be as high
as 50%.8,9 Based on the results of these reports, postoperative functional outcomes
in elderly patients with intertrochanteric
hip fractures may be worse than expected
despite the continuous evolution of surgical techniques and implant design and
better surgical outcomes compared with
the past.10 These functional outcomes
show great differences among elderly patients with united intertrochanteric fractures.
Functional impairment in elderly patients with united intertrochanteric fractures can be affected by several factors, including muscle strength and power deficit
due to injury burden, osteoporosis, and insufficient rehabilitation. However, altered
hip biomechanics during bony union may
be an important contributor, as described
in the hip arthroplasty literature.11,12 During weight bearing after intramedullary
(IM) nailing, collapse of fracture fragments occurs despite the controlled sliding of the lag screw by IM nailing,13-15
which decreases both the abductor lever
arm and medial femoral offset. Eventually, lag screw sliding can lead to functional
impairment due to compromised abductor strength by decreased medial femoral
e1102
Table 1
Data for 65 Patients With United Intertrochanteric Fractures
Parameter
No. of patients
Sex, No. of M:F
Mean age (range), y
No. (%) of slip and fall injuries
Mean BMD (range)
Mean BMI (range), kg/m2
Mean time to surgery after injury (range), d
Mean hospitalization period (range), d
Value
65
15:50
77.8 (65 to 90)
65 (100)
-2.4 (-4.2 to -1.0)
22.6 (17.8 to 31.2)
2.8 (1 to 7)
16.5 (14 to 28)
AO classification, No. (%)
Stable
33 (50.8)
31-A1.1
10
31-A1.2
9
31-A1.3
2
31-A2.1
12
Unstable
32 (49.2)
31-A2.2
16
31-A2.3
11
31-A3.1
3
31-A3.2
2
Reduction status, No. (%)
Good
51 (78.5)
Acceptable
14 (21.5)
IM nail used, No. (%)
PFNA
37 (56.9)
ITST
28 (43.1)
Mean lag screw sliding distance (range), mm
4.9 (0.2 to 12.5)
Abbreviations: BMD, bone mineral density; BMI, body mass index; F, female; IM,
intramedullary nail; ITST, Intertrochanteric/Subtrochanteric (Zimmer, Warsaw, Indiana); M,
male; PFNA, Proximal Femoral Nail Antirotation (Synthes, Davos, Switzerland).
offset and subsequent altered hip biomechanics, especially in elderly patients with
generalized muscle weakness due to the
aging process.
The purpose of this study was to investigate the factors influencing functional
outcomes in elderly patients with united
intertrochanteric fractures treated with hip
nails and to ascertain whether shortened
femoral offset due to lag screw sliding has
a negative effect on functional outcomes
in these patients.
Materials and Methods
The authors conducted a retrospective
study of a consecutive series of elderly patients older than 65 years presenting to the
authors’ hospital between November 2008
and February 2011. Consecutive patients
who sustained intertrochanteric fractures
during that period underwent IM nailing
with Proximal Femoral Nail Antirotation
(PFNA; Synthes, Davos, Switzerland)
or Intertrochanteric/Subtrochanteric nail
(ITST; Zimmer, Warsaw, Indiana). Intra-
ORTHOPEDICS | Healio.com/Orthopedics
n Feature Article
medullary nails were randomly selected in
these patients. A total of 133 patients were
identified.
Eligible patients met the following inclusion criteria: (1) no prior surgery on either hip, (2) American Society of Anesthesiologists (ASA) grade of III or less, (3)
independently ambulatory outdoors prior
to injury, (4) bony union obtained without fixation failure, and (5) completed the
Short Form-36 (SF-36) questionnaire16
and visual analog scale (VAS) 6 months
postoperatively. Thirty-five patients who
did not meet the inclusion criteria were
excluded. Nineteen patients met the criteria but refused to participate, and 14 patients abandoned participation in the study
due to other conditions during follow-up.
This resulted in a cohort of 65 patients at
all defined time points (Table 1).
All patients underwent closed reduction and internal fixation with IM nailing
using traction and manipulation on the
fracture table under image-intensifier control. The lag screw tip was placed within
the central to slightly inferior position
of the femoral head on both anteroposterior (AP) and lateral views. One distal
interlocking screw was used to achieve
rotational stability. All patients received
standard medical care postoperatively,
and postoperative rehabilitation was initiated 3 days postoperatively. At hospital
discharge, it was possible for patients to
independently ambulate with the aid of
a walker. Because the National Public
Health System and private health insurance companies covered most of the hospitalization cost, post-acute inpatient rehabilitation was performed consecutively
during the postoperative hospitalization
period.
Demographic data collected included
patient age at injury, sex, body mass index (BMI), bone mineral density (BMD),
hospitalization period, time to surgery
after injury, fracture type, reduction quality, tip-apex distance (TAD), extent of lag
screw sliding, and functional outcomes
measured by the SF-36 and VAS score
DECEMBER 2014 | Volume 37 • Number 12
A
B
C
6 months postoperatively. Institutional
review board approval was obtained for
the chart review. Bone mineral density
was measured in the contralateral femoral
neck using dual-energy x-ray absorptiometry (DEXA). Fracture type and reduction quality were determined on pre- and
postoperative AP and lateral views, respectively. Fracture type was classified
according to AO/OTA classification. Reduction quality was assessed by a slight
modification in the criteria of Baumgaertner et al.10,17 Radiographic measurements
were standardized. All radiographs were
calibrated with the diameter of the IM nail
used in each case on an electronic picture
archiving and communication system
(STARPACS; Infinitt Healthcare, Seoul,
South Korea). The TAD was measured on
postoperative AP and lateral views, and
the extent of lag screw sliding was measured according to the method proposed
Figure 1: Anteroposterior radiographs showing
an unstable intertrochanteric fracture (A2.3) in a
74-year-old man (A), hip nailing using the Proximal
Femoral Nail Antirotation (Synthes, Davos, Switzerland) with good reduction status and a 12.3-mm
distance from the lateral prominence of the blade
to the lateral edge of the nail (B), and bony union
with the preservation of medial femoral offset
(47.2 mm in operated hip vs 49.5 mm in contralateral normal hip) at 6 months postoperatively (C).
The final amount of lag screw sliding was 2.2 mm,
the difference between 14.5 and 12.3 mm.
by Paul et al18 on an AP view taken postoperatively and at final follow-up (Figure
1). The TAD and the extent of lag screw
sliding were evaluated independently by 2
orthopedic surgeons (T.Y.K., Y.S.K.) with
significant measurement experience. Each
surgeon measured each case twice, with
an interval of 2 weeks between measurements. The average of the values measured by the 2 surgeons was used. Radiographic assessment was completed before
evaluation of functional outcome to prevent bias. The interobserver reliability of
the TAD and lag screw sliding measurements were assessed using the intraclass
correlation coefficient (ICC), which quantifies what proportion of the difference is
e1103
n Feature Article
duction quality) and the other continuous
variables were examined using Student’s t
tests. The effects of categorical variables
on the SF-36 subscales were also analyzed
using Student’s t tests. Multiple regression
analysis was used to investigate the effects
of continuous variables on the SF-36 subscales. Significance was determined as a P
value less than .05 in all analyses.
Results
A
B
C
due to measurement variability. The ICC
can assume any value from 0 to 1, where
a value greater than 0.75 represents good
agreement and less than 0.40 represents
poor agreement. The interobserver reliability of the TAD and lag screw sliding
were 0.84 and 0.81, respectively; these
values indicated good reliability.
To evaluate the functional outcome,
the authors used the SF-36 because this
self-administered questionnaire has demonstrated good construct validity, high
internal consistency, and high test-retest
reliability.19 All patients completed the
SF-36 questionnaire 6 months postoperatively during a personal interview,
and VAS score was used to evaluate the
extent of pain remaining in the operated
hip (0=none; 1-3=mild; 4-6=moderate;
7-10=severe).
SPSS statistical software version 16.0
(SPSS, Inc, Chicago, Illinois) was used
for statistical analysis. Spearman’s cor-
e1104
Figure 2: Anteroposterior radiographs showing
an unstable intertrochanteric fracture (A2.3) in a
77-year-old woman (A), hip nailing using the Intertrochanteric/Subtrochanteric nail (Zimmer, Warsaw, Indiana) with acceptable reduction status and
a 15.9-mm distance from the lateral prominence of
the blade to the lateral edge of the nail (B), and severe loss of medial femoral offset (29.7 mm in operated hip vs 37.7 mm in contralateral normal hip)
and excessive lag screw sliding of 10.9 mm despite
bony union (C). The patient had a poor functional
outcome with hip pain and limping during walking,
although she independently ambulated with a cane.
relation coefficient was used to assess
the association of continuous variables
(age, BMI, BMD, hospitalization period,
time to surgery after injury, and VAS
score) with the extent of lag screw sliding. According to the method of Landis
and Koch,20 correlation coefficients of 0
to 0.20 represent slight agreement, 0.21
to 0.40 represent fair agreement, 0.41 to
0.60 represent moderate agreement, 0.61
to 0.80 represent substantial agreement,
and less than 0.80 represent almost perfect agreement. A 2-tailed P value less
than .05 was considered significant. The
association between 2 independent categorical variables (fracture type and re-
Mean age of the study group was 77.8
years (range, 65 to 90 years). There were
15 men and 50 women in the study cohort.
Of these, PFNAs were used in 37 patients
and ITST nails in 28.
Mean follow-up duration was 20.7
months (range, 12 to 38 months). Mean
BMI was 22.6 kg/m2 (range, 17.8 to 31.2
kg/m2), and mean BMD T-score was -2.4
(range, -4.2 to -1.0). Mean hospitalization period was 16.5 days (range, 14 to
28 days), and mean time to surgery after
injury was 2.8 days (range, 1 to 7 days)
(Table 1).
According to AO/OTA classification,
fractures were classified as the following types: A1.1 (n=10), A1.2 (n=9), A1.3
(n=2), A2.1 (n=12), A2.2 (n=16), A2.3
(n=11), A3.1 (n=3), and A3.2 (n=2); there
were 33 stable and 32 unstable fractures.
The criteria for good reduction were met
in 51 (78.5%) of the 65 patients, and the
remaining 14 patients had an acceptable
reduction (Figure 2). The TAD was less
than 20 mm in all patients. Mean lag
screw sliding distance was 4.9 mm overall (range, 0.2 to 12.5 mm), 5.3 mm in
the PFNA group, and 4.6 mm in the ITST
group. There was no significant difference
in the extent of lag screw sliding between
the 2 groups.
Mean VAS score was 3.6 (range, 1 to
6) 6 months postoperatively. Moderate
pain was reported by 47% of the patients,
whereas 53% had mild pain.
On correlation analysis between the
continuous variables and the extent of
lag screw sliding, only BMD had a significant association with the extent of lag
ORTHOPEDICS | Healio.com/Orthopedics
n Feature Article
screw sliding, and the correlation coefficient was -0.41, representing a negative
moderate correlation between BMD and
the extent of lag screw sliding (P=.023).
The extent of lag screw sliding and BMD
according to fracture type showed significant differences. There was greater sliding of the lag screw in unstable fractures
(mean, 6.06±3.64 mm) than in stable fractures (mean, 2.54±1.90 mm) (P=.003),
and BMD T-score was significantly lower
in unstable fractures (mean, -2.63±0.86)
than in stable fractures (mean, -1.92±0.76)
(P=.031). Greater sliding of the lag screw
occurred in the acceptable reduction
group (mean, 6.67±1.92 mm) than in the
good reduction group (mean, 4.40±3.24
mm) (P=.012); however, there was no
significant difference in BMD T-score between the 2 groups.
The reduction quality of intertrochanteric fractures showed significant differences on most subscales of the SF-36. The
good reduction group had significantly
higher scores in 5 subscales: Physical
Functioning, Role Physical, Bodily Pain,
Social Functioning, and Role Emotional
(Table 2). There were no significant differences found in all SF-36 subscales according to patient sex, fracture type, and
IM nail type.
Table 2
Results of SF-36 Subscales According to Reduction Quality
Mean Score
Acceptable Reduction
(n=14)
Good Reduction
(n=51)
P
Physical Functioning
25.5±9.12
32.7±11.5
.041
Role Physical
29.1±12.2
40.3±12.1
.015
Bodily Pain
34.9±11.3
43.0±11.8
.048
General Health
33.9±8.8
37.9±10.6
NS
Vitality
40.6±9.9
45.3±11.4
NS
Social Functioning
33.2±15.1
44.4±10.4
.012
Role Emotional
22.2±12.8
38.9±16.3
.002
Mental Health
37.6±15.0
43.8±12.2
NS
SF-36 Subscale
Abbreviations: NS, not significant; SF-36, Short Form-36.
Using multiple regression analysis to
measure the effects of continuous variables such as age, BMI, BMD, hospitalization period, time to surgery after injury,
and extent of lag screw sliding on each
subscale of the SF-36, the extent of lag
screw sliding showed significant negative
effects on 4 subscales: Physical Functioning, Role Physical, Social Functioning,
and Role Emotional. Regarding the other
variables, only age had a significant negative effect on Role Physical (Table 3). On
multiple regression power analysis, a total sample size of 65 patients provided a
statistical power of 85% to detect an R2
of 0.20 (range, 0.17 to 0.31) attributed to
1 independent variable (lag screw sliding
distances) using an F-test with a significance level (ß) of 0.05. The variable tested
was adjusted for the other 5 independent
variables with an R2 of 0.10 (range, 0.09
to 0.14). Meanwhile, the correlation between the extent of lag screw sliding and
VAS was moderate, with an absolute val-
Table 3
Effects of Variables on SF-36 Subscales Using Multiple Regression Analysis
Regression Beta Coefficient (P)
Age
BMI
BMD
Hospitalization
Period
Time to Surgery
From Injury
Lag Screw Sliding
Distance
R2, %
PF
0.188 (.333)
-0.103 (.583)
-0.114 (.577)
0.147 (.428)
-0.024 (.900)
-0.454 (.005)
36.6
RP
-0.336 (.039)
-0.083 (.591)
-0.275 (.107)
0.282 (.070)
-0.028 (.862)
-0.589 (.001)
37.5
BP
-0.083 (.649)
-0.195 (.281)
-0.117 (.548)
0.291 (.106)
0.099 (.596)
-0.320 (.112)
15.0
GH
0.162 (.374)
0.119 (.504)
0.158 (.413)
0.174 (.321)
-0.081 (.658)
-0.229 (.243)
17.1
VT
-0.053 (.772)
0.112 (.513)
0.029 (.593)
0.186 (.402)
-0.071 (.646)
-0.289 (.151)
14.5
SF
-0.172 (.287)
0.193 (.223)
-0.197 (.250)
0.300 (.058)
-0.153 (.348)
-0.472 (.009)
35.5
RE
-0.301 (.057)
-0.271 (.077)
-0.307 (.066)
0.219 (.144)
-0.016 (.918)
-0.644 (.000)
40.7
MH
0.163 (.389)
0.022 (.906)
0.101 (.617)
0.245 (.182)
0.097 (.613)
-0.247 (.230)
13.0
SF-36 Subscale
Abbreviations: BMD, bone mineral density; BMI, body mass index; BP, Bodily Pain; GH, General Health; MH, Mental Health; PF, Physical
Functioning; RE, Role Emotional; RP, Role Physical; SF, Social Functioning; VT, Vitality.
DECEMBER 2014 | Volume 37 • Number 12
e1105
n Feature Article
ue of 0.47 (P=.014) on correlation analysis, which also showed the adverse effect
of lag screw sliding on hip pain in united
intertrochanteric fractures.
Discussion
Intertrochanteric hip fractures are the
most serious consequence of osteoporosis
in elderly people and are often associated
with deterioration in quality of life, together with an increased risk of death.21-23
Therefore, the aim of treatment in these
fragile patients with intertrochanteric hip
fractures is to obtain bony union with no
complications with 1 operation and to restore preinjury functional level as much
as possible. As patient care and surgical
techniques have improved in recent years,
better clinical outcomes with fewer surgical complications have been reported
in elderly patients with intertrochanteric
fractures.3,5,6,10 However, treatment of
intertrochanteric fractures in elderly patients may result in worse functional outcomes than expected despite bony union
without surgical complications.23-27 This
result most likely relates to altered hip
biomechanics such as decreased medial
femoral offset due to lag screw sliding
during the bony union process, aside from
muscle strength and power deficit, osteoporosis, and insufficient rehabilitation.
To date, several studies have evaluated
functional outcomes after hip fracture
surgery in elderly patients.18,21,23-25,27-29
However, few studies have evaluated
functional outcomes in elderly patients
with united intertrochanteric fractures
treated with only IM nails. Therefore,
the current study was designed to investigate the factors influencing functional
outcomes in elderly patients with united
intertrochanteric fractures treated with hip
nails and to ascertain whether decreased
femoral offset due to lag screw sliding has
a negative effect on functional outcomes.
Several studies have found that most
functional recovery following hip fracture
surgery occurs within 6 months postoperatively.24-27 Accordingly, the current au-
e1106
thors used the SF-36 and VAS 6 months
postoperatively as an assessment measure
of functional outcomes, and they believe
that 6-month postoperative functional outcomes are significant and represent maximal functional recovery.
In general, it has been perceived that
lag screw sliding induces more stable
configuration through compression on the
fracture site and enhances fracture healing
in intertrochanteric fractures.2,30 However,
lag screw sliding adversely decreases the
abductor moment lever arm in an operated hip, and decreased moment lever
arm increases the abductor force that is
required for walking as well as the joint
reactive force.2,31 Paul et al18 reported that
a greater difference in the abductor lever
arm due to greater sliding of the lag screw
and unstable fracture type predicted poor
functional recovery. This implies that the
shortening of anatomical femoral offset
due to lag screw sliding in united intertrochanteric fractures can have a negative
effect on functional outcomes. However,
to date, the adverse effect of a decreased
femoral offset due to lag screw sliding
has been largely unrecognized in the orthopedic trauma literature. The current
study is the first to report a negative effect of decreased femoral offset by fracture collapse due to lag screw sliding on
functional outcomes in elderly patients
with united intertrochanteric fractures
treated with IM nails. The authors believe that their results are caused by the
shortening of anatomical femoral offset
and subsequent abductor weakness due
to lag screw sliding18 and that limited lag
screw sliding with no significant effect
on abductor weakness should be allowed
for better functional outcomes. However,
the acceptable limit of decreased femoral
offset due to lag screw sliding that does
not cause significant abductor weakness
and inferior functional outcomes is not
revealed in this study, although it is best
to preserve anatomical femoral offset as
much as possible. Therefore, this study
should be regarded as preliminary until
confirmed by larger prospective studies
and biomechanical studies verifying the
acceptable limit of lag screw sliding and
decreased femoral offset.
In this study, fracture type, BMD, and
reduction quality directly or indirectly affected the extent of lag screw sliding in
united intertrochanteric fractures. Namely,
lag screw sliding was greater in unstable
fractures, severe osteoporosis, and inaccurate reduction status. However, fracture
type and BMD are determined preoperatively and uncontrollable perioperatively.
Therefore, it is important to reduce more
accurately and obtain consequent stable
fixation, especially in osteoporotic unstable intertrochanteric fractures. Factors
directly influencing functional outcomes
were the quality of reduction and the extent of lag screw sliding. These 2 factors
showed significant effects on most subscales of the SF-36, especially Physical
Functioning and Role Physical, which
reflect physical activities of daily living.
There is a significant positive correlation
between the extent of lag screw sliding
and VAS, and there are negative correlations between the extent of lag screw sliding and the most important 2 physical subscales of the SF-36 (Physical Functioning
and Role Physical) as well as 2 mental
subscales (Social Functioning and Role
Emotional). This means that the shortening of anatomical femoral offset due to
lag screw sliding induces the alteration of
normal hip biomechanics and can cause
pain on the operated hip and the impairment of practical daily activities in elderly
patients. Accordingly, surgeons should be
cautious in maintaining anatomical femoral offset as much as possible through
more accurate reduction and the minimization of lag screw sliding when treating
intertrochanteric fractures. The authors
suggest that poor functional outcomes
due to decreased femoral offset caused by
excessive lag screw sliding in united intertrochanteric fractures be regarded as a
so-called functional failure, different from
a conventional failure (fixation failure).
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n Feature Article
This study is limited by its retrospective nature and, to some extent, by the
small cohort size. Also, it did not consider
the adverse effects of comorbid conditions
such as cognitive impairment and osteoporotic vertebral fractures, nutrition, and
social support on functional outcomes,
and there are no objective data verifying
abductor weakness due to the decreased
femoral offset caused by lag screw sliding. However, the study is strengthened
by a comprehensive search for eligible
patients with united intertrochanteric fractures treated by 1 surgeon (J.H.Y.) at a
single center. Other strengths of the study
are the consideration of patients’ preinjury general condition and physical status, which could have affected functional
outcomes postoperatively; the selection of
appropriate and thorough inclusion criteria that excluded variables bearing no
direct relationship to the index surgery;
and the use of an objective, reliable, and
highly validated physical functional outcome measurement.
Conclusion
This study shows that lag screw sliding,
affected mainly by fracture type, BMD,
and reduction quality, has a negative effect on the functional outcomes of elderly
patients with united intertrochanteric fractures. Therefore, efforts should be made
to preserve anatomical femoral offset as
much as possible through the minimization of lag screw sliding by more accurate
reduction for better functional outcomes,
especially in osteoporotic unstable intertrochanteric fractures.
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