颈短缩对股骨头颈生物力学的影响

The biomechanical effects of femoral neck shortening on femoral head and neck

目的运用有限元分析法研究股骨颈短缩以后股骨头颈的生物力学变化，探讨股骨颈短缩病例中股骨头坏死概率明显高于颈正常组的力学机制。 方法利用MIMICS软件分别建立Pauwells角为70°的颈正常、颈短缩2.5 mm和颈短缩5.0 mm的股骨颈骨折模型，将3种模型分别与3枚空心钉进行装配，导入有限元分析软件ABAQUS，进行相应的加载和约束，分析比较股骨头颈的应力变化。 结果颈正常、颈短缩2.5 mm和颈短缩5 mm 3种情况下，股骨颈上方空心钉最大拉伸应力值分别为15.7、14.1、12.4 mPa；股骨颈下方骨质最大压缩应力值分别为20.2、19.1、17.8 mPa；同时，股骨头高应力分布区由其外上象限转移到其正上方，非主要负重区的最大应力分别为10.6、12.8、17.2 mPa。 结论股骨颈短缩使股骨近端偏心距减小，不影响内固定和骨折断端的稳定性，但使股骨头负重区发生转移，同时非主要负重区出现高应力区。

Objective Using finite element analysis to study how the biomechanics of femoral head and neck changes after neck shortening, and discuss the mechanism of obvious higher osteonecrosis of the femoral head （ ONFH ） rate in femoral neck shortening cases. Methods MIMICS was used to build three femoral neck fracture models with Pauwells angle of 70 degrees. The neck lengths of the three models respectively were normal, 2. 5 mm shortened and 5.0 mm shortened. Every model was assembled with 3 hollow screws, and imported into the finite element analysis software ABAQUS. The stress change of femo- ral head and neck was analyzed by loading and restraint. Results When the femoral neck length was nor- mal, 2. 5 mm shortened and 5.0 mm shortened, the maximal tensile stress of hollow screws in upper part of the femoral neck was 15.7, 14. 1 and 12.4 mPa, and the compressive stress of lower part of femoral neck was 20. 2, 19. 1 and 17. 8 mPa, respectively. Meanwhile, the high stress bearing district was transfered to right above the femoral head from its superior lateral quadrant, and the maximum stress of non - main stress bearing district was 10. 6, 12.8 and 17.2 mPa respectively. Conclusion The femoral neck shortening re- duces the proximal femoral eccentricity. It doesn＇ t affect the stabilities of internal fixation and fracture ends, but it transfers the stress bearing district of femoral head and causes the forming of high stress bearing district in non -main stress bearing district.