股骨颈骨折2枚空心螺钉内固定的力学稳定性研究

目的:分析2枚和3枚空心螺钉固定不同骨折线方向的股骨颈骨折的力学稳定性,为2枚空心螺钉临床应用及其适应证的选择提供理论依据。方法:采集15具国人股骨尸体标本,构建3种Pauwels角(30°、50°和70°)的股骨颈骨折模型,分别行3枚及2枚空心螺钉内固定,采用生物力学检测仪分别测定抗张位移、竖向位移、剪切位移、综合位移、缝隙距、扭矩和刚度值,评价2枚和3枚空心螺钉内固定的力学稳定性。结果:Pauwels角为30°和50°时,2枚空心螺钉内固定的抗张位移、竖向位移、剪切位移、综合位移、缝隙距、扭矩和刚度值与3枚空心螺钉内固定相比较,差异无统计学意义(P0.05);当Pauwels角为70°时,采用3枚空心螺钉内固定后,其力学稳定性优于2枚螺钉内固定,差异有统计学意义(P0.05),同时发现Pauwels角为70°时,即使采用3枚空心螺钉内固定,其力学稳定性明显较Pauwels角为30°和50°时差。结论:Pauwels角为30°和50°时,2枚空心螺钉内固定与3枚空心螺钉内固定的力学稳定性相同,2枚空心螺钉内固定已能较好地维持股骨颈骨折的稳定。而当Pauwels角为70°时,3枚空心螺钉内固定力学稳定性则优于2枚空心螺钉内固定,但其力学稳定性较Pauwels角为30°和50°时弱,手术时需采用角稳定系统或者加用抗滑螺钉以增强骨折内固定的稳定性。

Study on biomechanical stability in simulated femoral neck fracture fixation by two cannulated screws

Objective: To investigate the stability of internal fixation for femoral neck fracture(FNF) using two or three cannulated screws directed to different fracture lines,and to provide a theoretical basis for the clinical decision making.Methods: Fifteen fresh frozen human femur samples were selected and the FNF model was established with Pauwels angle of 30°,50° and 70° respectively. The models were fixed with three or two cannulated screws,and their differences at tensile strength,subsidence,shear strength and composite displacement,gap distance,torsional angle and stiffness values of four types of femur were evaluated to identify their biomechanical stability.Results: With Pauwels angle of 30° and 50°,no statistical differences at the referenced outcomes were observed between two and three cannulated screw fixation for FNF(P>0.05). With the Pauwels angle of 70°,three cannulated screws fixation were significantly superior to two cannulated screws fixation for FNF(P<0.05). Nevertheless,when Pauwels angle was 70°,three cannulated screws fixation turned out to be relative instable compared with Pauwels angle of 30° and 50°.Conclusion: With Pauwels angle of 30° and 50°,two cannulated screws fixation was similarly stable as using three cannulated screws for FNF. Three cannulated screws fixation were obviously superior to two cannulated screws fixation when Pauwels angle was 70°,but the application of three cannulated screws could still be insufficiently stable when only such routine fixations were utilized. Therefore,Angle Stabilizing System or anti-sliding screws were needed to enhance the stability of FNF fixation.