Orthopedics

Feature Article 

Analysis of Risk Factors for Femoral Head Necrosis After Internal Fixation in Femoral Neck Fractures

Tao Wang, MD; Jun-Ying Sun, MD; Guo-Chun Zha, MD; Tao Jiang, MD; Zhen-Jun You, MD; De-Jing Yuan, MD

Abstract

Femoral head necrosis is a rare but devastating complication following femoral neck fracture. The reported incidence of avascular necrosis after femoral neck fracture fixation varies widely, and there is no consensus regarding its risk factors. The aim of this study was to analyze the risk factors for femoral head necrosis after internal fixation in femoral neck fracture. This retrospective study included 166 patients with femoral neck fractures treated with surgical reduction and internal fixation at the authors’ institution from January 2004 to December 2008. Eight patients died for reasons unrelated to the surgery, and 12 patients were lost to follow-up. The remaining 146 patients (146 fractures) were followed until union or until conversion to total hip arthroplasty. The patients included 61 males and 85 females with an average age of 47.5 years (range, 18–68 years). The authors analyzed the following factors: age, sex, Garden classification, reduction quality, surgical methods, injury-to-surgery interval, preoperative traction, weight-bearing time, and implant removal. All patients were followed for a mean of 52 months (range, 6–90 months). The incidence of femoral head necrosis was 14.4% (21/146). Garden classification (P=.012), reduction quality (P=.008), implant removal (P=.020), and preoperative traction (P=.003) were significantly associated with femoral head necrosis. Patient age (P=.990), sex (P=.287), injury-to-surgery interval (P=.360), weight-bearing time (P=.868), and surgical methods (P=.987) were not significantly associated with femoral head necrosis. In multivariate logistic regression analysis, implant removal was not a significant risk factor for femoral head necrosis development (P=.498). Garden classification, reduction quality, and preoperative traction had a significant effect on femoral head necrosis development. [Orthopedics. 2014; 37(12):e1117–e1123.]

The authors are from the Department of Orthopaedics, The First Affiliated Hospital of Soochow University, Jiiangsu, China.

The authors have no relevant financial relationships to disclose.

Correspondence should be addressed to: Jun-Ying Sun, MD, Department of Orthopaedics, The First Affiliated Hospital of Soochow University, 188 Shizi St, Suzhou, Jiangsu 215006, China ( wtfamily@163.com).

Received: November 13, 2013
Accepted: March 25, 2014

Abstract

Femoral head necrosis is a rare but devastating complication following femoral neck fracture. The reported incidence of avascular necrosis after femoral neck fracture fixation varies widely, and there is no consensus regarding its risk factors. The aim of this study was to analyze the risk factors for femoral head necrosis after internal fixation in femoral neck fracture. This retrospective study included 166 patients with femoral neck fractures treated with surgical reduction and internal fixation at the authors’ institution from January 2004 to December 2008. Eight patients died for reasons unrelated to the surgery, and 12 patients were lost to follow-up. The remaining 146 patients (146 fractures) were followed until union or until conversion to total hip arthroplasty. The patients included 61 males and 85 females with an average age of 47.5 years (range, 18–68 years). The authors analyzed the following factors: age, sex, Garden classification, reduction quality, surgical methods, injury-to-surgery interval, preoperative traction, weight-bearing time, and implant removal. All patients were followed for a mean of 52 months (range, 6–90 months). The incidence of femoral head necrosis was 14.4% (21/146). Garden classification (P=.012), reduction quality (P=.008), implant removal (P=.020), and preoperative traction (P=.003) were significantly associated with femoral head necrosis. Patient age (P=.990), sex (P=.287), injury-to-surgery interval (P=.360), weight-bearing time (P=.868), and surgical methods (P=.987) were not significantly associated with femoral head necrosis. In multivariate logistic regression analysis, implant removal was not a significant risk factor for femoral head necrosis development (P=.498). Garden classification, reduction quality, and preoperative traction had a significant effect on femoral head necrosis development. [Orthopedics. 2014; 37(12):e1117–e1123.]

The authors are from the Department of Orthopaedics, The First Affiliated Hospital of Soochow University, Jiiangsu, China.

The authors have no relevant financial relationships to disclose.

Correspondence should be addressed to: Jun-Ying Sun, MD, Department of Orthopaedics, The First Affiliated Hospital of Soochow University, 188 Shizi St, Suzhou, Jiangsu 215006, China ( wtfamily@163.com).

Received: November 13, 2013
Accepted: March 25, 2014

Internal fixation of femoral neck fractures has been shown to be a safe and effective treatment method. However, because of the special morphological anatomy and blood supply of the femoral head, the overall incidence of femoral head necrosis after femoral neck fracture is 10% to 30%.1,2 This condition significantly impairs quality of life. Many variables, including age, sex, initial fracture displacement, reduction quality, postoperative weight-bearing time, time to surgery, and fixation methods, have been hypothesized to be related to femoral head necrosis. No solid evidence exists on which factor poses a high risk for femoral head necrosis. Most previously reported influencing factors used univariate analysis; thus, the results may be imprecise. The current study assessed the clinical data of 146 patients with surgical reduction and internal fixation of femoral neck fractures from January 2004 to December 2008 at the authors’ institution. The study also analyzed the factors that affect femoral head necrosis incidence by using multivariate logistic regression analysis.

Materials and Methods

Patients

This retrospective study was approved by the ethics committee of the First Affiliated Hospital of Soochow University. The authors retrospectively reviewed the records of 166 patients with femoral neck fractures treated with internal fixation at the authors’ institution from January 2004 to December 2008. Eight patients died for reasons unrelated to the surgery, and 12 patients were not followed up. Therefore, 146 patients were available for complete analysis. The patients included 61 males and 85 females with an average age of 47.5 years (range, 18–68 years). Fractures were in the left hips of 86 patients. Patients were divided into 4 groups according to age: 8 patients were 20 years or younger, 32 patients were between 21 and 40 years, 98 patients were between 41 and 60 years, and 16 patients were older than 60 years. The fractures were classified according to Garden3 (Figure 1): 10 were Garden I, 46 were Garden II, 62 were Garden III, and 28 were Garden IV.

Illustration showing a Garden I incomplete fracture (A), Garden II complete fracture without displacement (B), Garden III complete fracture with partial displacement (C), and Garden IV complete fracture with full displacement (D).

Figure 1:

Illustration showing a Garden I incomplete fracture (A), Garden II complete fracture without displacement (B), Garden III complete fracture with partial displacement (C), and Garden IV complete fracture with full displacement (D).

Considering the limitation of the authors’ country’s medical technology and transportation, few patients underwent surgery within 24 to 48 hours of injury. Average time between injury and surgery was 2.4 days (range, 2–14 days). A total of 62 fractures were treated within 72 hours after injury, and 84 fractures were treated after 72 hours because of late presentation or the need to treat other life-threatening injuries. Among these cases, 90 patients were placed under skeletal traction preoperatively, and 56 patients were not placed under traction.

Postoperatively, 69 implants were removed due to patient preference. The remaining 77 patients maintained their implants. Clinical and radiographic evaluations were performed at 3 and 6 months and 1 year postoperatively and then annually thereafter. Serial radiographs were analyzed by an independent observer (G.-C.Z).

Patients with undisplaced fractures were stabilized in situ. Patients with displaced fractures to be treated with internal fixation were placed on the fracture table. Closed reduction was initially attempted with the hip in extension by using minimal traction combined with internal rotation. Among the 146 patients, 28 fractures underwent open reduction and internal fixation (ORIF) using a lateral approach after the authors attempted closed reduction and internal fixation (CRIF). All internal fixations were achieved with 2 or 3 cannulated cancellous screws.

Clinical Evaluation

Reduction quality was graded A, B, or C according to Garden4 and Dong et al5 (Table 1). The diagnosis of femoral head necrosis was based on plan radiographs and magnetic resonance imaging (MRI).6,7 Femoral head necrosis was defined on radiographs by the presence of density discrepancy, calcification bands, spotty calcification, radiotransparent cystic changes of the femoral head, early-stage necrotic and repairing bone around the sclerotic bone, or late-stage circumscribed subchondral fracture and femoral head collapse. Magnetic resonance imaging signal changes included subchondral band-like lesions with low signal intensity on T1-weighted images and a typical double-line sign on T2-weighted images in the early stage of femoral head necrosis or in later phases of femoral head collapse.

Reduction Quality According to Garden4 and Dong et al5

Table 1:

Reduction Quality According to Garden4 and Dong et al5

Statistical Analysis

Data were analyzed with SPSS version 19.0 statistical software (SPSS, Inc, Chicago, Illinois). Statistical methods included descriptive analysis (mean, proportion), chi-square test, Fisher’s exact test, and multivariate logistic regression analysis. The presence or absence of femoral head necrosis was considered the dependent variable, whereas age, sex, Garden classification, reduction quality, reduction methods, injury-to-surgery interval, preoperative traction, weight-bearing time, and implant removal were considered independent variables. Chi-square test or Fisher’s exact test was applied to determine the significant differences between risk factors, which were then tested with logistic regression analysis. A P value less than .05 was considered significant.

Results

Mean follow-up was 52 months (range, 9–84 months). A total of 21 (14.4%) patients had avascular necrosis (Figures 23). Mean elapsed time until postoperative diagnosis of femoral head necrosis was 18 months (range, 12–56 months). The patients were classified into the CRIF and ORIF groups according to reduction quality: for CRIF, 5 patients were in group A, 8 patients were in group B, and 4 patients were in group C; for ORIF, 1 patient was in group A, 1 patient was in group B, and 2 patients were in group C. Reduction quality in both the CRIF and ORIF groups was not statistically significant (P=.391). At final follow-up, 15 patients were treated with total hip arthroplasty due to the development of femoral head necrosis. The statistical outcome is presented in Table 2.

Preoperative anteroposterior radiograph of a right femoral neck fracture (Garden III) in a 38-year-old man (A). Anteroposterior radiograph at 1-year follow-up showing excellent healing and no evidence of femoral head necrosis (B). Anteroposterior radiograph at 4 years postoperatively showing the development of femoral head necrosis (C).

Figure 2:

Preoperative anteroposterior radiograph of a right femoral neck fracture (Garden III) in a 38-year-old man (A). Anteroposterior radiograph at 1-year follow-up showing excellent healing and no evidence of femoral head necrosis (B). Anteroposterior radiograph at 4 years postoperatively showing the development of femoral head necrosis (C).

Preoperative anteroposterior radiograph of a left femoral neck fracture (Garden III) in a 53-year-old man (A). Anteroposterior radiograph at 1 year postoperatively showing a good result (B). Anteroposterior radiograph at 1 year after implant removal showing femoral head necrosis (C).

Figure 3:

Preoperative anteroposterior radiograph of a left femoral neck fracture (Garden III) in a 53-year-old man (A). Anteroposterior radiograph at 1 year postoperatively showing a good result (B). Anteroposterior radiograph at 1 year after implant removal showing femoral head necrosis (C).

Univariate Analysis of Incidence of Femoral Head Necrosis

Table 2:

Univariate Analysis of Incidence of Femoral Head Necrosis

Univariate Analysis

Whereas age (P=.990), sex (P=.287), injury-to-surgery interval (P=.360), surgical method (P=.987), and weight-bearing time (P=.868) were not statistically significant risk factors for the development of femoral head necrosis, Garden classification (P=.012), reduction quality (P=.008), preoperative traction (P=.003), and implant removal (P=.020) were statistically significant risk factors (Table 2).

Multivariate Logistic Regression Analysis

Multivariate logistic regression analysis indicated that Garden classification (P=.011), reduction quality (P=.026), and preoperative traction (P=.000) were statistically significant risk factors for the development of femoral head necrosis, but implant removal (P=.498) was not a statistically significant risk factor (Table 3).

Multivariate Logistic Regression Analysis of Risk Factors for Femoral Head Necrosis

Table 3:

Multivariate Logistic Regression Analysis of Risk Factors for Femoral Head Necrosis

Discussion

Given the increase in the geriatric population, the prevalence of femoral neck fractures is steadily increasing. With developments in surgical techniques and implant technology, the healing rate of femoral neck fractures has considerably improved. However, incidental femoral head necrosis has not declined accordingly.2,8,9 Therefore, neck fractures of the femur are described as unsolved fractures10 and have presented challenges to orthopedic surgeons. A widely varying rate of femoral head necrosis after reduction and internal fixation has been reported (Table 4).1,2 In the current study, the incidence of femoral head necrosis was 14.4% (21 of 146), which was similar to previously reported rates.1

Literature Review of Femoral Head Necrosis After Internal Fixation

Table 4:

Literature Review of Femoral Head Necrosis After Internal Fixation

Possible Causes of Femoral Head Necrosis

After femoral neck fractures, the main cause of femoral head necrosis is the impairment of blood flow to the femoral head.11,12 The retinacular arteries from the medial femoral circumflex artery are considered the most important blood vessel to the femoral head. These arteries are always impaired at the time of femoral neck fracture, thus interrupting the arterial flow to the femoral head. The trauma at the moment of fracture can cause major damage to vessels and impair the blood circulation in the femoral head. Consequently, the blood supply to the femoral head is decreased and femoral head necrosis occurrence is increased.

The tamponade effect may be another cause of femoral head necrosis.13,14 The increased joint fluid caused by hemarthrosis after the intracapsular fracture of the femoral neck causes increasing intraarticular pressures that lead to the occlusion of the vascular supply to the femoral head.13 The extension and internal rotation of the hip joint and the traction position produce higher intracapsular pressure, thus increasing the intracapsular pressure by greater than 80 mm Hg. This is greater than the diastolic blood pressure, significantly diminishes the femoral head perfusion, and poses a high risk of femoral head necrosis.

Some scholars considered decreasing the intramedullary oxygen tension in the femoral head and neck, thus playing a central role in the development of posttraumatic femoral head necrosis.15,16 For femoral neck fractures, vessel lesions and increased outflow resistance may decrease the blood flow perfusion of the femoral head and intraosseous oxygenation. The tamponade effect decreases the subchondral perfusion and oxygen pressure. Finally, this condition might result in bone cells with hypoxic ischemic; death will occur if osteocyte hypoxic ischemic lasts for 2 to 3 hours.

Scholars have begun to emphasize the biomechanical factors in the development of femoral head necrosis. Femoral neck fractures change the anteversion and destroy Wolff’s law, which indicates the balance between bone structure and function.17 Abundant hip muscle contraction makes the fracture extremity produce considerable shear force and increases the instability of the extremity. Malreduction makes the anteversion shift and transforms the relationship between the femoral head and acetabulum, thus concentrating the stress on the surface of the femoral head and rearranging the internal ultrastructure of the trabecular bone. If the rearranged trabecular bone cannot accommodate the stress of the acetabulum demand, the trabecular bone degenerates, absorbs, collapses, and causes femoral head necrosis.18

Relationship Between Risk Factors and Femoral Head Necrosis

Garden Classification and Reduction Quality. Garden classification is considered an important factor in the development of femoral head necrosis after femoral neck fracture.19,20 Clinical results have demonstrated that the rate of femoral head necrosis for displaced fractures (20% to 40%) was higher than that for nondis-placed fractures (5% to 20%).21,22 Lu-Yao et al23 demonstrated a strong correlation between femoral head necrosis development and fragment displacement. The current study showed a femoral head necrosis rate of 20% for displaced fractures and 5.35% for nondisplaced fractures. Thus, fracture displacement is considered an important factor in femoral head necrosis.

The accurate apposition of the fragment is conducive to union and determines the fate of the femoral head. Beris et al19 reported that reduction quality was an important factor that affected the treatment of femoral neck fractures. Accurate reduction can restore stability and create beneficial conditions for the healing of femoral neck fractures. The mechanical stability of the fracture after reduction and fixation prevents early displacement. Min and Kim24 reported that the incidence of femoral head necrosis was 20% (26 of 130 hips) in patients with satisfactory reduction and 68.8% (11 of 16 hips) in patients with unsatisfactory reduction. Garden4 believed that malreduction would increase the rate of femoral head necrosis after femoral neck fractures. In the current study, the incidence of femoral head necrosis was 7.9%, 7.3%, and 37.5% in groups A, B, and C, respectively, which is statistically significant (P=.008). The results showed that Garden classification and reduction quality had a significant effect on femoral head necrosis development after femoral neck fracture fixation.

Preoperative Traction and Implant Removal. Previous research showed that preoperative traction provided effective stabilization and protection from potential displacement.1 This approach can restore the blood supply to the femoral head and neck segment and avoid the femoral head necrosis caused by a displaced fragment. However, some authors believe traction could increase the occurrence of femoral head necrosis.20,25 In the current study, logistic regression analysis showed that preoperative traction was significantly associated with femoral head necrosis (P=.000). The authors assumed that pre-operative traction could not effectively prevent the rotation of the injured limb. With the extension and internal rotation of the injured limb, the capsule became tense and the intraarticular volume decreased, thus leading to high intracapsular pressure or the so-called tamponade effect. Traction also impairs blood perfusion to the femoral head, blood flow in the retinacular arteries decreases, and the venous drainage becomes impeded.25 Thus, traction may be a major cause of femoral head necrosis after a femoral neck fracture.

Sun et al26 suggested that screw removal might be a primary inducing factor in the development of femoral head necrosis. They reported that all compressive, tensile, and shear stresses were concentrated on the fracture site after screw removal, thus changing the biological stress. This condition could lead to the adjustment of the trabecular bone and might increase the femoral head and neck ischemia, which ultimately lead to femoral head necrosis. In the current study, univariate analysis showed that the existence of the screw had a significant effect on the development of femoral head necrosis (P=.020). The intraosseous pressure of the femoral head might increase because of the presence of the screw and then increase the femoral head ischemia.27 On the contrary, in multivariate logistic regression analysis, screw removal had an insignificant effect on femoral head necrosis (P=.498). However, few studies have focused on the correlation between the removal or the presence of screws and femoral head necrosis in both domestic and foreign cases. Further research on this topic is needed in the future.

Time to Surgery. The time from injury to surgery is a controversial topic, and data are inconclusive. Some studies have suggested that early surgery could decrease the risk of femoral head necrosis.28,29 Szita et al28 reported that the rate of avascular necrosis was significantly lower (10.5%) in patients who underwent surgery within 6 hours of injury than in patients treated 6 hours after trauma (20%). They believed that the aim of surgical treatment was to protect arteries by early reduction, thus relieving the blood vessel compression to the femoral head and restoring the blood supply. On the contrary, Holmberg et al30 reported 2418 cases of femoral neck fracture and reported that no evidence suggested that a surgery delay of up to 7 days adversely affected the fate of the femoral head. In the current study, the authors considered 72 hours as the cutoff point in 2 groups: within 72 hours and after 72 hours. The rates of femoral head necrosis in these 2 groups were 11.3% and 16.7%, respectively (P=.360), thus showing that the injury-to-surgery interval did not significantly affect the development of femoral head necrosis. This observation was also in agreement with a previous meta-analysis.31

Other Risk Factors

Gender. The results of the current study show that sex does not have a significant effect on the development of femoral head necrosis. Bachiller et al32 reported that the femoral head necrosis rate after femoral neck fractures in males with good bone quality was higher than that in osteoporotic females. Nevertheless, the relationship between bone quality and femoral head necrosis is still unclear and demands further research.

Age. The traditional view of a higher incidence of femoral head necrosis among young adults than the elderly is related to good bone stock, high-energy trauma, displacement fracture, and severe blood vessel damage. By contrast, poor bone quality, low-energy trauma, and mild disruption of the blood supply in osteoporotic elderly patients contribute to lower rates of femoral head necrosis. The authors’ literature review found no correlation between femoral head necrosis and age.

Surgical Method. This study found no difference between the incidence of femoral head necrosis in patients who underwent ORIF compared with patients treated with CRIF. This observation was consistent with the research outcome of Upadhyay et al.33

Limitations

First, this study is a retrospective study with inherent and well-known limitations and biases. Second, the study is a single-center study, and the number of patients was limited the authors’ ability to obtain definitive conclusions. Third, the authors did not consider the number and location of cannulated screws, which might influence the development of femoral head necrosis. Fourth, patients were treated by multiple surgeons. Surgeon level of experience and type of implant used might have some influence on healing complications.

Conclusion

This study found that Garden classification, reduction quality, and preoperative traction were the most important risk factors influencing the development of femoral head necrosis. Displaced fracture, reduction quality C, and preoperative traction also increased the occurrence of femoral head necrosis.

References

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  33. Upadhyay A, Jain P, Mishra P, et al. Delayed internal fixation of fractures of the neck of the femur in young adults. J Bone Joint Surg Br. 2004; 86(7):1035–1040. doi:10.1302/0301-620X.86B7.15047 [CrossRef]

Reduction Quality According to Garden4 and Dong et al5

Classification Angle of Deviationa Neck-Shaft Angle
A <15° 125°–140°
B 15°–30° 120°–125° or 140°–150°
C >30° <120° or >150°

Univariate Analysis of Incidence of Femoral Head Necrosis

Variable No. (%)
P
Patients With FHN (n=21) Patients Without FHN (n=125)
Age, y .990
  ≤20 1 (12.5) 7 (87.5)
  21–40 5 (15.6) 27 (84.4)
  41–60 13 (14.4) 77 (85.6)
  >60 2 (12.5) 14 (87.5)
Sex .287
  Male 11 (18) 50 (82)
  Female 10 (11.7) 75 (88.3)
Reduction method .987
  Open 4 (14.3) 24 (85.7)
  Closed 17 (14.4) 101 (85.6)
Preoperative traction .003
  Yes 18 (20) 72 (80)
  No 3 (5.4) 53 (94.6)
Weight-bearing time, min .868
  <3 7 (14.3) 48 (85.7)
  3–6 11 (14.8) 63 (85.2)
  >6 3 (22.2) 14 (77.8)
Implant removal .020
  Yes 5 (7.2) 64 (92.8)
  No 16 (20.8) 61 (79.2)
Garden classification .012
  I 1 (10) 9 (90)
  II 2 (4.3) 44 (95.7)
  III 9 (14.5) 53 (85.5)
  IV 9 (32.1) 19 (67.9)
Injury-to-surgery interval, h .360
  ≤ 72 7 (11.3) 55 (88.7)
  >72 14 (16.7) 70 (83.3)
Reduction quality .008
  A 6 (7.9) 70 (92.1)
  B 9 (17.3) 45 (82.7)
  C 6 (37.5) 10 (62.5)

Multivariate Logistic Regression Analysis of Risk Factors for Femoral Head Necrosis

Risk Factor ß Wald Value P OR 95% CI
Garden classification 3.054 2.54 .011 21.19 2.010–223.443
Preoperative traction 4.674 4.68 .000 107.1 15.146–757.798
Implant removal −0.547 −0.68 .498 0.578 0.118–2.818
Reduction quality 1.695 2.22 .026 5.445 1.220–24.287

Literature Review of Femoral Head Necrosis After Internal Fixation

Study No. of Hips Mean Follow-up, y No. (%) of Hips With Femoral Head Necrosis
Gerber et al1 44 1.3 5 (11)
Nikolopoulos et al2 84 4.7 24 (29)
Min and Kim24 146 5.2 37 (25.7)
Jain et al29 38 2.5 6 (16)
Upadhyay et al33 92 2.0 15 (16.3)
Current study 146 4.6 21 (14.4)

10.3928/01477447-20141124-60

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