The effect of Fracture Inclination in Multiple Planes on Fracture Stability and Reoperation Risks in Femoral-Neck Fractures of Nongeriatric Patients

Abstract BackgroundFor nongeriatric patients with femoral neck fractures (FNFs), internal fixation treatment is still the primary choice. Preoperative evaluation of fracture inclination and underlying stability is essential for selecting appropriate fixation strategies, thus improving clinical prognoses. The purpose of this study was to comprehensively investigate the 3-D inclination angle in both vertical and oblique planes from CT images, and its association with fracture stability and reoperation risks.MethodsWe retrospectively reviewed the medical records of 755 FNFs patients with over two years follow-up. The 3-D inclination angle in vertical (α) and oblique plane (β) were measured based on CT images. The optimal threshold for unstable 3-D inclination were identified by seeking the highest Youden Index in predicting reoperation and validated in the biomechanical test. According to the cut-off value proposed in the diagnostic analysis, forty-two bone models were divided into seven groups, and were all fixed with traditional three parallel screws. Interfragmentary motion (IFM) was used for comparison among seven groups. The association between reoperation outcome and 3-D inclination was analysed with a multivariate model.ResultsThe overall reoperation rate was 13.2%. Unstable 3-D inclination angles with an optimally determined Youden index (0.39) included α>70°; 50°<α<70° and β>20°/ β<-20°. Biomechanical validation showed these fractures had significantly greater (p<0.05) interfragmentary motion (1.374-2.387mm vs. 0.330-0.681 mm). The reoperation rate in 3-D unstable group (32.7%) is significantly (p<0.001) higher than that in 3-D stable group (7.9%). Multivariate analysis demonstrated that 3-D inclination angle was significantly (OR=4.699, p<0.001) associated with reoperation. ConclusionsFNFs with α>70°; 50°<α<70° and β>20°/ β<-20° are real unstable types with significantly worse interfragmentary stability and higher reoperation risks. Fracture inclination in multiple planes is closely related to reoperation outcomes and may enhance the way FNFs are currently evaluated.