肿瘤型膝关节置换后股骨-假体-胫骨复合体生物力学响应

目的研究肿瘤型铰链式膝关节置换术后股骨-假体-胫骨复合体正常站立状态下的生物力学响应,探讨病人术后发生股骨穿孔的原因,为肿瘤型铰链式人工膝关节假体的优化设计与制造提供理论基础。方法兼顾CT及三维光学扫描数据建立股骨远端骨肉瘤瘤段切除肿瘤膝关节置换后的病人股骨-假体-胫骨有限元模型,并进行相关有效性验证,从而进一步分析人体站立状态下股骨-假体-胫骨复合体的应力分布及应力遮挡现象。结果 (1)在站立加载状态下,相对胫骨,股骨的应力明显更大且集中分布趋势显著,股骨前1/3区域应力较大,呈现应力遮挡效应。(2)由于模型基于临床病人几何及骨质特征建立,股骨应力集中位置与临床中病人股骨穿孔位置接近,表明在施加自身重力状态下可能发生与病人病症一致的股骨损伤行为。结论肿瘤型铰链式膝关节假体植入后,由于假体髓针深入骨髓腔,正常站立状态下亦对骨髓腔产生一定的压力;由此产生的应力遮挡效应以及假体髓针与特定骨髓腔的匹配情况均可能引起股骨应力集中,从而将可能引起股骨开裂,甚至穿破,影响手术质量。建议术前优化假体设计以减轻或避免此类现象,从而减少术后患者的并发症发生率。

Biomechanical responses of the femur-prosthesis-tibia complex after tumor-type total artificial knee replacement

Objective By studying biomechanical responses of the femur-prosthesis-tibia complex under normal standing condition after tumor-type hinged knee arthroplasty, to investigate the cause of femoral perforation in patients after knee arthroplasty, so as to provide a theoretical basis for optimal design and manufacturing of tumor-type hinged artificial knee prosthesis. Methods By coupling CT and 3D optical scanning, the finite element model of the subject-specific femur-prosthesis-tibia complex was established and was validated regarding its availability, so as to analyze stress distribution and stress shielding phenomenon of the complex in standing position. Results (1) Under the loading state of standing, the stress on the femur was significantly larger than that on the tibia, and presented an evident concentration phenomenon. The proximal 1/3 of femoral shaft presented a larger stress, with a stress shielding effect. (2) As the model was based on geometry and bone characteristics of the patient in clinic, the location of femur stress concentration was close to that of femur perforation in the patient, which indicated that femur injury behavior might occur when its own gravity was applied such as the patient condition. Conclusions After implantation of the tumor-type hinged artificial knee prosthesis, the prosthesis marrow needle goes deep into marrow cavities, which brings certain pressure to the marrow cavities even under normal standing condition. The produced stress shielding effect and the match of the prosthesis marrow needle to the marrow cavity are all likely to cause stress concentration on the femur, even make femur crack or perforation, and eventually affect the surgery quality. Thus, the prosthesis design should be carefully optimized before surgery in order to reduce or avoid such phenomenon that is related to the postoperative complication rate.