聚醚醚酮髋股骨头假体置换术后股骨近段载荷传递的力学性能

背景:人工关节无菌性松动的力学因素是传统金属假体的弹性模量远远超过骨的弹性模量,组合后产生应力遮挡,引起骨吸收、骨萎缩.目的:体外测试自制的碳纤维增强聚醚醚酮(CF/PEEK)假体置换后股骨的应变,并与国产AML假体进行比较,探讨复合材料在全髋股骨头假体中的应用前景.设计、时间及地点:对比分析实验,于2002-09/2004-03在苏州大学第一附属医院骨科实验室和上海大学生物力学工程研究所完成.材料:CF/PEEK假体为自行设计,内层采用长CF/PEEK复合材料,模量为100 GPa;外层采用短CF/PEEK复合材料,模量为 20 GPa;在应力集中区,适当加强铺层密度;几何形态与相关尺寸同国产仿AML型钴合金假体.AML假体为北京华杰豪公司生产.标本为5对新鲜成人尸体股骨10具.方法:5 对人体新鲜尸体股骨平均分成左右两组,一组行钴铬钼合金股骨头假体置换术,另一组行CF/PEEK假体置换术.在假体和近端股骨表面粘贴应变片,模拟单肢站立施加载荷.主要观察指标:①正常股骨表面和两种假体置换后的股骨表面的应变分布.②两种假体置换后股骨-假体界面剪切应变分布. 结果:股骨应变在假体植入后,从近端到远端逐渐增加,变化形式与完整股骨的应变形式相似,并且在假体远端最大.两种假体植入后,股骨内外侧表面的应变皆减少;但CF/PEEK假体组产生的应变形式和大小比钴铬钼合金假体组更接近正常股骨. 结论:CF/PEEK复合材料假体的力学性能与骨组织相近,加载时两者的应变量一致,因此能提供术后即刻稳定性和良好的近端载荷传递.

Mechanical performance of proximal human femur after poly-ether-ether-ketone femoral prosthesis implantation

BACKGROUND: Greatly higher elastic modulus of traditional metal prosthesis than bone elastic modulus is mechanical factor for aseptic loosening of artificial joint, resulting in stress shielding, bone resorption and bone atrophy.OBJECTIVE: To measure femoral stress after prosthetic replacement made of carbon fiber reinforced poly-ether-ether-ketone (CF/PEEK), and compare with domestic AML prosthesis, so as to explore the application prospect of compound material in total hip femoral head prosthesis. DESIGN, TIME AND SETTING: Comparative analysis was performed at Orthopedics Laboratory, First Hospital of Soochow University and Institute of Biomechanical Engineering of Shanghai University from September 2002 to March 2004.MATERIALS: CF/PEEK prosthesis was designed by the authors, composed of long CF/PEEK compound material as inner layer, 100 Gpa and short CF/PEEK compound material as outer layer, 20 Gpa; the layer intensity at stress center was strengthened, and the appearance and size of the CF/PEEK prosthesis simulated domestic AML cobalt alloy prosthesis (Beijing Huajiehao Company). Five pairs (10 femurs) of femurs were from fresh adult cadavers. METHODS: Five pairs of human cadaveric femora were divided equally into left and right groups: one group received a cobalt-chrome molybdenum alloy (CoCrMo) implant and the other received CF/PEEK implant. Strain-gauge rosettes were attached to external surface of each implant and proximal femora. The loading condition simulated single-limb stance. MAIN OUTCOME MEASURES: strains distribution on the normal femur and femoral surface after replacement with two kinds of prostheses; shearing strain at femur-prosthesis interface of two groups.RESULTS: Following prosthesis implantation, the strains exhibited a progressive proximal-to-distal increase, which was similar to that in the intact femur, and the strain was maximum near the distal prosthesis. The strains on the medial and lateral surface of the femur were reduced after implantation of both types of implants. The pattern and magnitude of the strains, however, were closer to those in the intact femur after insertion of CF/PEEK prosthesis than in the CoCrMo one. CONCLUSION: Mechanical performance of CF/PEEK compound prosthesis is similar to bone tissue, and can provide similar strain under loading condition. Therefore, it can provide immediate postoperative stability and proximal loading transfer.