股骨小转子在转子间骨折内固定术中作用的有限元研究

目的建立Evans-Jensen’s I、IIb型股骨转子间骨折的滑动髋螺钉（DHS）、股骨近端防旋髓内钊‘（PFNA）内固定有限元模型，通过4种模型有限元分析、对比研究股骨小转子在该类骨折中的维稳作用和模型中内固定的安全性。方法采集健康成年男性左侧股骨CT图像和DHS、PFNA系统三维数据，建立左侧上段股骨DHS、PFNA内固定模型，设定边界条件以及负荷加载方式，进行有限元运算，研究500N至2000N及其间分级载荷下模型的有限元应力、位移。结果建立了左侧上段股骨Evans．Jensen’SI、IIb型股骨转子间骨折在DHS、PFNA内固定下4种工况的有限元模型，上段股骨模型（长196．777mm，40373节点，216255个单元）以及DHS（7761节点，33699单元）、PFNA（4312节点，18146单元）。4种内固定模型在递增载荷下，模型III内固定器压应力增加幅度较大，2000N下最大压应力为727．256＋34．66，为模型I的1．98倍，超出钛合金钢板强度范围。存分级载荷下模型III的z向位移增加幅度、曲率都明显高于模型I、II、Iv。结论在有限元角度，股骨小转子在股骨转子间骨折内固定手术中具有稳定支持作用，在Evans．Jensen’SIIb型骨折中应用DHS系统进行内固定是不安全的，PFNA是比较理想的内固定器械。

Finite element analysis of femoral small rotor's role in the maintenance of stability in intertrochanteric fracture fixation

Objective To Build four finite element models of Evans-Jensen＇s I, II b intertrochanteric fracture fixed by DHS or PFNA, and to study femoral small rotor＇s role in the maintenance of stability and safety of intemal fixation. Methods Left femur CT images and the systems ofDHS, PFNA 3D data from health adult male were collected, and left femur DHS fixation model was established, and then boundary conditions and load loading method was set to do fi- nite element computation for studying the model＇s finite element stress and displacement when it was under the load of 500 N to 2000 N with the grade of 500 N. Results Four finite element models used by DHS and PFNA internal fixation for the left femur ofEvans-Jensen＇s I and II b intertrochanteric fracture was established as follows： the upside femoral model （196.777 mm long, 40373 nodes, 216 255 units）, the DHS system model （7 761 node, 33 699 units）, and the PFNA system model （4312 node, 18146units）. The stress distributions under the grading load the of four internal fixation models showed： when it was under increasing load, the stress increasing amplitude of internal fixator in model IIIwas larger. The stress was 727.25649-a：34.66 under 2000 N, which was 1.98 times larger than that of model I and beyond the scope of tit- anium alloy steel. The displacement under the grading load of the model displayed： the increasing amplitude and curva- ture of the Z axis displacement in model III were higher than those of the other models obviously. Conclusions Ac- cording to the finite element, femoral small rotor has good stability effect in intertrochanteric fracture fixation, but it is not safe to use DHS internal fuxation in Evans-Jensen＇s IIb intertrochanteric fracture. PFNA is better for internal fixation.