动力髋螺钉和Gamma钉置入固定不稳定股骨转子间骨折的三维有限元分析

Dynamic hip screw and Gamma nail fixation repair unstable intertrochanteric fracture: a three-dimensional finite element analysis

背景:对于不稳定型股骨转子间骨折的修复有两种观点:髓外固定或髓内固定。理论上讲,髓内固定符合微创原则,更具力学和生物学优势。但是循证医学及相关研究表明髓内固定与髓外固定比较并没有体现出理论上应有的优势。目的:通过有限元法比较目前修复股骨转子间骨折常用的2种内固定系统动力髋螺钉和Gamma钉的生物力学性能,评价二者治疗不稳定型股骨转子间骨折的优劣。方法:分别建立人股骨不稳定股骨转子间骨折的三维有限元模型(31-A2;骨折AO分类)和动力髋螺钉、Gamma钉的三维有限元模型,按骨科手术要求予以固定,模拟体质量700 N成人步态周期中关节承载处于峰值时刻的参考负载,分析骨、骨-内固定模型和锁钉或螺钉的应力分布状态、骨和骨-内固定模型表面的应变、骨折位置的变形,沿着股骨的应力分布情形以及沿着内固定物的负载传递情形等。结果与结论:(1)动力髋螺钉和Gamma钉具有良好的滑动加压功能,使骨折断面持续性、动态地轴向加压。在载荷条件下,动力髋螺钉的位移值较大。(2)在不稳定型股骨转子间骨折的治疗中,Gamma钉比动力髋螺钉坚强。两种内固定均使近端股骨承担负荷减少。(3)在31-A2型不稳定型股骨转子间骨折的治疗中,若股骨矩粉碎不严重,缺损不多或者无缺损,术中能够立即重建股骨矩区的稳定性,宜选择动力髋螺钉固定;反之则宜选择更坚强的内固定即Gamma钉固定。

BACKGROUND： For unstable intertrochanteric fracture repair, there are two views： extramedullary fixation or intramedullary fixation. Theoretically, intramedullary fixation is in line with the principles of minimally invasive, more mechanical and biological advantages. However, evidence-based medicine and related studies have shown that compared with the extramedullary fixation, intramedullary fixation did not reflect the proper theoretical advantage. OBJECTIVE： To compare the biomechanical performance of two kinds of internal fixation systems： dynamic hip screw and Gamma nail which commonly used in repair of intertrochanteric fractures by finite element method, and to evaluate the advantages and disadvantages of dynamic hip screw and Gamma nail in treatment of unstable intertrochanteric fracture.METHODS： Three-dimensional finite element model of human femur unstable intertrochanteric fractures （31-A2; AO fracture classification）, and the three-dimensional finite element models of dynamic hip screw and Gamma nail were established respectively, and were fixed according to the requirement of orthopedic surgery. The reference load which the joint bearing was at the peak time in adult step state period with the body mass of 700 N was stimulated. The stress distribution of bone, bone-internal fixation model, nail or screw, the strain and deformation of fracture location on the surface of the bone and bone-internal fixation model, the stress distribution along the femur and the loading transfer condition along the internal fixator and the like were analyzed. RESULTS AND CONCLUSION： Dynamic hip screw and Gamma nail have good sliding compression features which could make the continuous and dynamically axial compression of the fractured section. Under the load conditions, the displacement value of dynamic hip screw was larger. In the treatment of unstable intertrochanteric fracture, Gamma nail was stronger than dynamic hip screw. Two kinds of internal fixations all make the bearing load of the proximal femur reduce. In the treatment of 31-A2 type unstable intertrochanteric fractures, we should choose dynamic hip screw for fixation if the femoral calcar was not seriously crushed, little defect or no defects and can immediately rebuild the stability of femoral calcar during operation, otherwise, stronger internal fixation, namely Gamma nail fixation should be chosen.