Association between spatial displacements of femoral neck fracture and avascular necrosis of femoral head after internal fixation

Abstract

Objective To explore the association between the spatial displacements in the three-dimensional reconstruction of femoral neck fracture and avascular necrosis of femoral head after internal fixation. Methods One hundred and sixty-three patients with femoral neck fracture were included in this study who had been treated at our institute between January 2010 and January 2013. They were 61 males and 102 females, with an average age of 55.7 years. By Garden classification, 20 cases were type Ⅰ, 30 type Ⅱ, 57 type Ⅲ and 56 type Ⅳ. All their preoperative and postoperative primitive CT data were imported to Mimics 10.01 software for three-dimensional reconstruction of femoral neck fractures in which the spatial displacement parameters (the lowest displacement at the dimple, central displacement, and spatial displacement angle) were measured. The patients were divided into 2 groups according to presence or absence of postoperative avascular necrosis of femoral head. The 2 groups were compared in terms of demographic data, preoperative and postoperative spatial displacement parameters. Multivariate logistic regression analysis was performed to explore the risk factors of avascular necrosis of femoral head. Results The average duration of follow-up was 3.1 years (range, from 2.5 to 5.4 years) . Avascular necrosis of femoral head was found in 33 cases (20.2%) . There were significant differences between the necrosis and necrosis-free groups in preoperative Garden classifications, all the preoperative and postoperative spatial displacement parameters (the lowest displacement at the dimple, central displacement, and spatial displacement angle) (P<0.05) . Multivariate logistic regression analysis showed that preoperative spatial displacement parameters of the femoral head, preoperative Garden classification of the fracture, and postoperative spatial displacement parameters of the femoral head were associated with avascular necrosis of femoral head (P<0.05). Conclusions Three-dimensional reconstruction of femoral neck fracture can accurately assess preoperative displacements and postoperative reduction. Preoperative displacement of the femoral head, fracture classification and postoperative reduction are the major risk factors for incidence of femoral head necrosis. Key words: Femoral neck fractures; Imaging, three-dimensional; Photogrammetry; Femur head necrosis