[Pressure side and tension side comminution of femoral neck cortex are independent risk factors for aseptic necrosis after femoral neck fracture surgery].

OBJECTIVE: To investigate the related factors of aseptic necrosis of femoral head after closed reduction and internal fixation of femoral neck fracture. METHODS: From January 2009 to January 2016, 236 patients with femoral neck fracture were treated with closed reduction and internal fixation with 3 hollow lag screws, including 111 males and 125 females, aged from 19 to 89 (50.17±12.88) years. According to the follow-up results, the correlation of aseptic necrosis of femoral head was analyzed. Univariate analysis of age, gender, injured side, body weight, injury mechanism, preoperative waiting time, Garden classification and whether there was comminution of femoral neck cortex was conducted to obtain the independent variables with significant difference. Then binary logistic regression analysis was conducted to explore the independent risk factors of avascular necrosis of femoral head. RESULTS: The average follow-up period of 236 cases was 4.58 years. There were significant differences in the range of injury (24.69% vs. 5.16%, χ2=19.405, P=0.000), operation waiting time>48 hours (20.00% vs. 6.38%, χ2=10.065, P=0.002), Garden type Ⅲ/Ⅳ (18.52% vs. 2.97%, χ2=13.357, P=0.000), femoral neck cortex comminution (66.67% vs. 4.88%, χ2=39.968, P=0.000). Multivariate logistic regression analysis showed that:injury mechanism [high energy injury, Exp (B)=4.397, 95%CI=(1.672-11.562), P=0.003], preoperative waiting time >48 h [Exp (B)= 3.060, 95%CI=(1.176-7.966), P=0.022], comminution of femoral neck cortex [comminution of femoral neck pressure side cortex, Exp (B)=3.944, 95%CI=(1.245-12.494), P=0.020;comminution of femoral neck pressure side and tension side cortex, Exp(B)= 23.761, 95%CI=(3.805-148.374), P=0.001) were independent risk factors for avascular necrosis after internal fixation of femoral neck fracture. Garden type Ⅲ/Ⅳ was not an independent risk factor in this study [Exp (B) = 1.985, 95%CI=(0.436-9.032), P=0.375]. CONCLUSION: High energy injury, preoperative waiting time (>48 h) and comminution of femoral neck cortex were independent risk factors for aseptic necrosis of femoral head. In addition, cortical comminution on the pressure side and tension side of the femoral neck is a strong prognostic risk factor for aseptic necrosis of the femoral head, because it indicates a more serious and complex injury mechanism.