扭转力传递的非骨水泥髋关节假体设计、制作及实验分析

Design, manufacture and experimental analysis of cementless hip prosthesis in torsional force transmission

背景:人体股骨髓腔具有扭转的解剖结构,如果股骨髓腔的扭转结构被复制到假体的柄体上,当假体插入髓腔并在假体上加载力时,假体将加载的力转换成股骨髓腔对柄体的扭转力并将该力传递到股骨近端。目的:优化股骨近端的力传递,避免假体近端应力遮挡。方法:利用人股骨标本的CT图片重建股骨髓腔的3D模型,将该3D模型作为柄体的设计模型。将定制式柄体模型与标准假体的近端模型拼合,形成定制式假体。采用机器人磨削技术制作定制式假体,并将定制式假体与标本股骨髓腔匹配。利用有限元仿真和实验方法分析假体上加载的力与假体近端扭转微动的关系。结果与结论:仿真和实验结果表明,股骨髓腔与柄体匹配的扭转结构,可有效地将假体上加载力以扭转力的形式传递到股骨近端,假体近端的扭转微动与柄体的微动相关,而柄体的微动可通过改变柄体与髓腔的匹配区大小得到控制。

BACKGROUND： Human femur medullary cavity has torsional anatomic structure. If the femur medullary cavity＇s torsional structure is copied to the stem of the prosthesis, the prosthesis will transform the force loaded to torque between femur medullary cavity and prosthesis stem, and the torque is transmitted to the proximal femur when the prosthesis is inserted in the medullary cavity and load force on the prosthesis. OBJECTIVE： To optimize the force transmission of the proximal femur, and to avoid the stress shielding at the proximal end of the prosthesis. METHODS： We reconstructed a three-dimensional（3D） model of the femoral canal with the CT images of specimen femur and took the 3D model as the design model for prosthesis stem. The customized stem model and the proximal model of standard prosthesis could be put together to form customized prosthesis. We took advantage of robot grinding technology to manufacture the customized prosthesis, and matched it with specimen femur canal. Finite element analysis simulation and experimental methods were used to analyze the relationship between the loading force on the prosthesis and the micromotion of proximal end of the prosthesis. RESULTS AND CONCLUSION： The simulation and experimental results showed that the torsional structure matching by femoral canal and stem could effectively transmit the force on the prosthesis to the proximal end of the prosthesis in the form of torque. The torsional fretting of the proximal end of the prosthesis was related to the movement of the handle body. However, stem micromotion can be controlled by varying the matching size between stem and medullary cavity.