Evaluation of full thread screw and different fixation configurations in Pauwels type III femoral neck fracture

OBJECTIVES: The purpose of this study is to evaluate the value of full thread screw and different fixation configurations in Pauwels type III femoral neck fracture. METHODS: A total of 40 artificial femoral model specimens were chosen, and Pauwels type III femoral neck fracture was simulated upon osteotomy at 80°. According to random number table, models were divided into four groups (10 cases in each group): Group A received the paralleled fixation with three partial thread screws (PTSs), group B received the crossed fixation with three PTSs, group C received the paralleled fixation with two full thread screws (FTSs) and one PTS, and group D received the crossed fixation with two FTSs and one PTS. Changes including the model rigidity, axial displacement in fatigue test and limit loads for Pauwels type III femoral neck fracture models were analyzed through MTS 858 Mini Bionix Ⅱ test system. RESULTS: Among four groups, the model rigidity, axial displacement in fatigue test and limit loads were the highest in group D, and they were the lowest in group A. However, the model rigidity, axial displacement in fatigue test and limit loads between group B and group C showed no statistically significant difference (P＞0.05). Eventually, all the specimens were displaced along the fracture lines while the femoral head was split at varying degrees. After splits, the removal rate of fixation screws in group A (60.0 %) and group C (40.0 %) was significantly higher than that of group B (10.0 %) and group D (0 %) (P＜0.05), but it showed no statistically significant difference between group A and group C, and between group B and group D (P＞0.05). CONCLUSIONS: The crossed fixation configuration with two FTSs and one PTS in group D is proven to be more effective, which can go against the shear stress, tension and introversion in Pauwels type III femoral neck fracture models.