全髋关节置换前后股骨应力变化的有限元分析

目的:研究Chamley Elite骨水泥型和Summit近端多孔非骨水泥型股骨假体置换后股骨总体应力以及假体周围骨质区应力分布的变化。方法:根据Charnley Elite骨水泥柄和Summit非骨水泥柄假体形态建立三维有限元模型，并加载关节合力以及相关肌肉的肌力负荷，分析假体植入前后股骨总体应力模式并对股骨近端假体周围区域骨质应力分布进行分区量化研究。结果:两种假体植入后没有改变股骨总体的应力模式，应力峰值区域均位于全长股骨的中下段，但股骨应力峰值有所下降。股骨近端假体周围骨质等效应力水平出现了显著下降，下降最严重的区域为近段内侧象限即股骨距区，应力遮挡率分别达90．8％和95．3％；向假体远端应力水平逐渐增大，直至假体远段和末段水平应力值逐渐恢复并接近生理水平。就该两种不同固定方式的假体比较而言，引起的应力遮挡区域分布基本一致，应力下降程度Summit近端多孔非骨水泥型假体要高于Charnley Elite骨水泥型假体。结论:两种假体植入后均在股骨近端形成显著的应力遮挡，假体周围骨质应力大小和分布的改变是引起术后骨量丢失和假体松动的原因之一，也是术后股骨骨折发生的类型以术后肢体疼痛发生的力学基础。两种固定方式的假体均需通过进一步改进以减少应力遮挡。

Finite element analysis of femoral stress changes after total hip arthroplasty

Objective To determine the biomechanical variation in full-length femoral stress pat-tern and periprosthetic femoral stress distribution after implantation either with Charnley Elite cemented prostlesis or Summit proximal porous cementless femoral prosthesis. Methods Three-dimensional finite element models of intact femur, Charnley Elite and Summit femoral prostheses were developed. The stress distributions on the femur and the implants were measured. Applied with hip joint loading and related muscles strength, the stress changes of an intact femur and those implanted with either Charnley Elite or Summit protheses, especially changes in proximal femur, were respectively quantitatively analysed. Results Com-pared with intact femur, there was no change of the full-length femur stress pattern in implantation of both implants, the areas of peak values were all presented at middle and lower regions of the femur, and femoral stress value levels were decreased with both implants. Both prostheses induced significant decrease of stress in the periprosthetic bone tissue, the most serious loss of stresses all appeared at femoral calcar, the stress-shielding rates of Elite and Summit prostheses were 90.8% and 95.3% respectively. The distributions of stress shielding of both prostheses were consistent each other, the Summit proximal porous cementless pros-thesis had more serious stress decrease than the Charnley Elite cemented prosthesis. Conclusion Implan-tation of both implants may cause significant stress shielding in the proximal femur. This may be related with periprosthetic bone loss and aseptic loosening of stems, and can be used to explain the mechanism of post-operative femoral fracture and thigh pain. Both implants designs need further improvement to reduce stress changes in proximal femur.