The reported incidence of avascular necrosis after femoral neck fracture
fixation varies widely, and there is no consensus regarding its risk factors.
We evaluated the incidence of avascular necrosis of the femoral head with the
use of contemporary techniques for femoral neck fracture fixation. We then
sought to determine what potential risk factors influenced the development of
Between 1990 and 2005, one hundred sixty-three intracapsular femoral
neck fractures in 163 patients were treated with internal fixation at our
level-I trauma center. All patients were monitored until conversion to total
hip arthroplasty (THA) or for a minimum of 2 years postoperatively. Ten
patients (10 hips) died and 7 patients (7 hips) were lost to follow-up. The
remaining 146 patients (146 hips) had a mean 5.2 years of follow-up (range, 3
months to 17 years). The incidence of avascular necrosis was 25.3% (37 hips).
The average time to diagnosis of avascular necrosis was 18.8 months (range,
3-47 months). Patient sex, age, interval from injury to surgery, and mechanism
of injury were statistically not associated with the development of avascular
necrosis. The quality of fracture reduction, adequacy of fixation, degree of
displacement, and comminution of the posterior cortex were significantly
associated. After we controlled for patient and radiographic characteristics,
multivariate analyses indicated that the important predictors for avascular
necrosis are poor reduction (odds ratio=13.889) and initial displacement of the
fracture (odds ratio=4.693).
Internal fixation is the treatment of choice for femoral neck fracture
in young adults.1 However, it has a relatively high rate of failure
from loss of fixation, nonunion, and avascular necrosis of the femoral
head.1,2 Avascular necrosis causes a repaired femoral neck fracture
to fail and may make additional surgery necessary.3-5 However, the
reported incidence of avascular necrosis after femoral neck fracture fixation
varies between 7% and 80%,1,6-10 and no consensus exists regarding
the risk factors of avascular necrosis of the femoral head after internal
fixation of femoral neck fracture.
This study evaluates the incidence of avascular
necrosis with the use of contemporary techniques for femoral neck fracture
fixation and investigates the potential risk factors influencing the
development of avascular necrosis.
Materials and Methods
We operatively treated 554 intracapsular femoral neck
fractures in 522 consecutive patients between 1990 and 2005. Of the 522
patients, we excluded those treated by arthroplasty (324 hips [58.5%]) and
those with pathologic fracture due to neoplasm (22 hips [4.0%]), an associated
femoral shaft fracture (33 hips [6.0%]), preexisting hip disease (6 hips
[1.1%]), heavy alcohol abuse (4 hips [0.7%]), and prednisolone use within the
preceding 3 years (2 hips [0.3%]). A treatment protocol was adopted whereby
patients younger than 70 years were treated with internal fixation. This left
163 patients (29.4%) with 163 intracapsular femoral neck fractures included in
The patients were monitored prospectively by means of scheduled visits
to determine whether avascular necrosis had developed, as defined by the
criteria of Ficat.11 Diagnosis of avascular necrosis was done by
radiographs. All patients gave informed consent for participation, and our
Institutional Review Board approved the protocol. All patients were monitored
until conversion to total hip arthroplasty (THA) or for a minimum of 2 years.
Ten patients (10 hips) died from causes unrelated to surgery, and 7 patients (7
hips) were lost to follow-up before the end of the minimum 2-year follow-up
period; this left 146 patients (146 hips) in the study. None of the 17 patients
(10.4%) who died or were lost to follow-up showed avascular necrosis by the
time of their final evaluation (8-23 months after initial surgery). The study
group comprised 83 men and 63 women with a mean age of 45.7 years (range, 17-70
years). Mean duration of follow-up was 5.2 years (range, 3 months to 7 years)
because 7 patients required conversion to THA after <2 years of follow-up.
Therefore, 139 patients were monitored clinically and radiographically for a
minimum of 2 years (mean, 5.6 years; range, 2-7 years).
In patients with polytrauma, life-threatening injuries were treated
first and then femoral neck fractures were treated urgently. The average time
elapsed between injury and surgical treatment was 3.4 days (range, 4 hours to
23 days). Fifty-one fractures (34.9%) were treated within 12 hours of injury
(mean, 8.2 hours; range, 4-12 hours), and 95 fractures (65.1%) were treated
>12 hours after injury (mean, 4.9 days; range, 15 hours to 23 days) because
of late presentation or the need to treat other life-threatening injuries or
diseases. Fifty-five fractures (38%) were nondisplaced and 91 (62%) were
All operations were performed by 1 surgeon (B.W.M.). Patients with
undisplaced fractures were stabilized in situ. Patients with displaced
fractures to be treated with internal fixation were placed on the fracture
table, and closed reduction was attempted initially with the hip in extension,
using minimal traction combined with internal rotation, as suggested by
Garden.12 A capsulotomy was not performed when a closed reduction
was possible. There were 9 open reductions with capsulotomies. All fractures
were fixed with either a sliding hip screw (57 hips) or cannulated screws (89
hips). Screw fixation was achieved with three or four 6.5-mm cannulated,
partially threaded, cancellous screws. All patients were allowed progressive
partial weight bearing as tolerated on postoperative day 3.
Because there is no generally accepted method of grading the quality of
reduction and fixation, we graded reduction and fixation based on the degree of
residual gap and angulation.4,12-14 Reduction was considered
satisfactory if the Garden alignment index was 160° to 180° as measured
on anteroposterior radiograph and 180° on lateral radiograph, with a gap of
<5 mm. In hips with a sliding screw, satisfactory fixation was defined as
center-to-center or inferior-to-posterior positioning of the lag screw; in hips
with cannulated screws, it was defined as parallel positioning of screws, no
penetration into the joint of the screw, and screw insertion in a triangular
pattern. Nonunion was defined as fixation failure, loss of reduction, or
persistent visible fracture line at a minimum of 12 months after the index
procedure.15 At final follow-up, each patient was evaluated by the
treating surgeon for pain, walking ability, and the need for walking aids.
Radiographs of all patients were analyzed by 1 reader who was blinded to the
patients’ clinical and radiographic histories.
Statistical analysis to identify factors predisposing to avascular
necrosis was performed with SAS software version 9.13 (SAS Institute, Cary,
North Carolina). Independent samples test was used for comparisons of mean age,
and chi-square test was used for analyses of sex, time interval from injury to
surgery, mechanism of injury, fixation method, displacement, osteoporosis,
comminution, quality of reduction, and fixation status. We defined osteoporosis
as a Singh index of <3.16 The level of significance was
set at P<.05. Potential predictive variables, including radiographic
and clinical factors, were also analyzed in a multivariate logistic regression
analysis to determine if they influenced the development of avascular necrosis.
With conversion to THA as the endpoint, survival statistics were calculated and
plotted according to the Kaplan-Meier method.
The incidence of avascular necrosis was 25.3% (37/146). Avascular
necrosis was classified as stage II in 7 hips, stage III in 17, and stage IV in
13. Five fractures were associated with the development of both avascular
necrosis and nonunion. Other complications included nonunion in 4 hips (2.7%).
The average elapsed time until diagnosis of avascular necrosis after surgery
was 18.8 months (range, 3-47 months). At last follow-up, 23 of the 146
fractures (16%) had been treated with THA because of the development of
avascular necrosis. The average elapsed time from index surgery to conversion
to THA was 3.3 years (range, 3 months to 8.3 years). With conversion to THA as
the endpoint, the cumulative survival rates for the native femoral head were
84.4% (95% confidence interval [CI], 75.8%-90.1%) at 5 years and 73.0% (95% CI,
59.7%-82.5%) at 10 years (Figure). A total of 9 patients (6%) required
procedures in addition to THA.
|Figure: Kaplan-Meier survivorship curve
demonstrating survival of the femoral head without conversion to THA. Error
bars show 95% confidence intervals.
Patient sex, age, time interval from injury to surgery, the method of
reduction, and mechanism of injury were statistically not associated with the
development of avascular necrosis. There was no difference between the types of
fixation methods (dynamic hip screw vs multiple screws; P=.829). Singh
indices were also not different between groups. Other radiographic parameters,
including quality of fracture reduction, adequacy of fixation, degree of
displacement, and comminution of the posterior cortex, were significantly
different (Table 1). The rate of avascular necrosis was different between
displaced and undisplaced fracture groups. Only 4 of 55 patients (7.3%) with
displaced fractures were found to have avascular necrosis at follow-up
(P=.000). After we controlled for patient and radiographic
characteristics, multivariate analyses indicated that the significant
predictors of avascular necrosis were poor reduction (odds ratio=13.889; 95%
CI, 1.972-100.000) and initial displacement of the fracture (odds ratio=4.693;
95% CI, 1.362-16.178).
Three patients experienced intraoperative complications. In 2 patients,
penetration of an intra-articular screw necessitated a return to the operating
room for screw exchange, and in 1 patient, a broken guide wire was left in
place. At last follow-up, 123 patients with a preserved femoral head had
excellent clinical function: 119 patients (97%) had no or slight pain
(associated with no activity restriction and no use of analgesics), and 4 had
moderate pain (associated with slight activity restriction and regular use of
non-narcotic analgesics). Most of the patients did not use walking aids; only 3
used a cane occasionally. Among the 14 patients with avascular necrosis who had
not undergone conversion to THA, 10 patients had slight pain and 4 patients had
moderate pain with intermittent cane use.
The reported incidence of avascular necrosis after femoral neck fracture
fixation varies widely, and no consensus exists regarding the factors
predicting avascular necrosis, although considerable evidence relates risk
factors (eg, the time interval from initial injury to surgery, accuracy of
reduction, fixation status, and posterior cortical comminution) to development
of avascular necrosis in internally fixed femoral neck fractures. We therefore
wanted to determine whether a number of radiographic and clinical risk factors
influenced the development of avascular necrosis and, if so, for how long after
the occurrence of avascular necrosis and initial fixation of femoral neck
Our study has several limitations. The number of patients involved was
small and the period was long. A prospective clinical trial involving multiple
centers would be a more practical way to garner adequate numbers of patients to
detect the causes of avascular necrosis after femoral neck fracture, although
the feasibility of such a trial is doubtful because other factors such as
operating room availability would not necessarily be predictable or
controllable. Diagnosis of avascular necrosis on radiographs, especially when
hardware is in situ, can be challenging, although magnetic resonance imaging
has also a limited role in evaluation of avascular necrosis with hardware in
situ. Reliance on radiographs to diagnose avascular necrosis implies the
possibility that no patients with Ficat stage I avascular necrosis were
detected. That the diagnosis of avascular necrosis was not confirmed by another
observer is an important factor in this study. This increased the risk of
systemic bias, although it eliminated interobserver variation.
Femoral neck fractures are relatively rare fractures, and those in our
study were treated over a long enough time period that surgical techniques and
internal fixation devices evolved. We used screws or dynamic hip screws for
fixation with no guiding principle, although there was no difference in the
incidence of avascular necrosis between implants. We excluded patients with
heavy alcohol abuse and those with prednisolone use within the 3 years
preceding our study because these substances have been implicated in the
development of avascular necrosis. The strengths of our study include the
treatment of a large number of consecutive patients at a single institution and
high rates of follow-up, which allowed us to accurately determine rates of
avascular necrosis and femoral head survival for a relatively long
The overall rate of avascular necrosis in our patients was 25.3%, which
is consistent with rates reported for previous studies (Table
2).5,13,17-21 Our study demonstrates that the use of contemporary
fixation techniques for the treatment of femoral neck fractures is associated
with a low nonunion rate (2.7%; 4/146). When 5 fractures associated with the
development of both avascular necrosis and nonunion were considered, the
nonunion rate was 6.2% (9/146). However, the use of contemporary methods for
the treatment of femoral neck fracture in our study did not significantly
decrease the development of avascular necrosis. Fortunately, a substantial
number of our patients who had avascular necrosis did not require THA (62%;
23/37). Among the 14 patients with avascular necrosis who did not undergo
conversion to THA, the femoral head was preserved in 5 patients with secondary
procedures such as transtrochanteric rotational osteotomy (2 hips) and core
decompression (3 hips). The remaining 9 patients reported slight pain and no
The mean interval between internal fixation and diagnosis of avascular
necrosis in this study was 18.8 months (range, 3-47 months). Although avascular
necrosis usually develops within 3 years after fixation, it can occur after 3
years.17 Therefore, the incidence of avascular necrosis may be
higher if all patients were monitored for a longer period. However, we
monitored patients for a minimum of 2 years (mean, 5.2 years). We monitored 92
of 130 patients (71%) for >3 years; 16 patients developed avascular necrosis
within <3 years of monitoring. In our study, all avascular necrosis after
femoral neck fracture fixation was diagnosed within 4 years.
Several studies have attempted to identify factors predictive of
avascular necrosis.1,4,20,22 With the numbers available, we found no
association between the development of avascular necrosis and patient age, sex,
type of fixation, interval from injury to surgery, or mechanism of injury. In
some studies,23 age is been considered a modulating factor, although
reported data are contradictory.1,24 There is a tendency for
avascular necrosis to be reported more often in women than in
men.1,25 We did not find the presence of osteoporosis to be a
significant prognostic factor. We agree with other researchers26
that the Singh index has wide intraobserver variation and poor
Although the effect of delaying surgery is debatable and the data are
inconclusive, most studies have proposed early surgery.27,28 Using
the logistic regression model to evaluate the effect of factors, 1 group of
researchers found that only time elapsed until fracture reduction significantly
affected the development of avascular necrosis.20 However, 2 large
clinical trials reported no correlation between the time interval to surgery
and the development of avascular necrosis.1,7 In our study, the
average time elapsed between injury and surgical treatment was 3.4 days because
of associated medical problems; the rates of avascular necrosis among patients
who underwent fixation within the first 12 hours of trauma did not differ from
those of patients who underwent fixation later.
Fracture displacement is considered to be a main factor for the
development of avascular necrosis. In a review of 23 series reported between
1930 and 1970, the average avascular necrosis rate was 8.5% for undisplaced
fractures and 29.3% for displaced fractures.3 Other researchers have
demonstrated a strong correlation between the development of avascular necrosis
and fragment displacement.29 Our study showed an avascular necrosis
rate of 7.3% for undisplaced fractures and 33.9% for displaced fractures. Our
findings support the premise that the quality of reduction has an impact on the
development of avascular necrosis. The incidence of avascular necrosis was 20%
in patients with satisfactory reduction and 75% in patients with unsatisfactory
reduction, which was statistically significant (P=.000).
Even with the use of contemporary techniques for the treatment of femur
neck fractures, we did not see a significant decrease the development of
avascular necrosis. Our study findings confirm that most important predictors
are initial displacement of the fracture and poor reduction. To reduce the
incidence of avascular necrosis after femoral neck fracture, anatomic reduction
- Barnes R, Brown JT, Garden RS, Nicoll EA. Subcapital fractures of
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- Brown TD, Way ME, Ferguson AB Jr. Mechanical characteristics of bone
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- Nikolopoulos KE, Papadakis SA, Kateros KT, et al. Long-term outcome
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- Asnis SE, Wanek-Sgaglione L. Intracapsular fractures of the femoral
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- Kyle RF, Cabanela ME, Russell TA, et al. Fractures of the proximal
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- Parker MJ, Raghavan R, Gurusamy K. Incidence of fracture-healing
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- Cho MR, Lee SW, Shin DK, et al. A predictive method for subsequent
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- Gerber C, Strehle J, Ganz R. The treatment of fractures of the
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- Haidukewych GJ, Rothwell WS, Jacofsky DJ, Torchia ME, Berry DJ.
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- Graham J. Early or delayed weight-bearing after internal fixation of
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- Strömqvist B, Hansson LI, Nilsson LT, Thorngren KG. Hook-pin
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- Smith MD, Cody DD, Goldstein SA, Cooperman AM, Matthews LS, Flynn MJ.
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- Parker MJ, Pryor GA, Myles JW. The value of a special surgical team
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Dr Min is from the Department of Orthopedic Surgery, and Dr Kim is from
the Department of Emergency Medicine, School of Medicine, Keimyung University,
Drs Min and Kim have no relevant financial relationships to
Correspondence should be addressed to: Byung-Woo Min, MD, Department of
Orthopedic Surgery, Keimyung University Dongsan Medical Center, 194
Dongsan-dong, Joong-gu, Daegu 700-712, Korea (firstname.lastname@example.org).