Tang Fan, Zhou Yong, Zhang Wenli, Min Li, Shi Rui, Luo Yi, Duan Hong, Tu Chongqi
Department of Orthopedics, West China Hospital, Sichuan University, Guoxue Xiang #37, Chengdu, 610041, Sichuan, People's Republic of China.
J Orthop Surg Res. 2017 Apr 4;12(1):57. doi: 10.1186/s13018-017-0555-6.
Whether all-polyethylene tibial (APT) components are beneficial to patients who received distal femur limb-salvage surgery lacks high-quality clinical follow-up and mechanical evidence. This study aimed to investigate the biomechanics of the distal femur reconstructed with APT tumor knee prostheses using finite element (FE) analysis based on our previous, promising clinical outcome.
Three-dimensional FE models that use APT and metal-backed tibial (MBT) prostheses to reconstruct distal femoral bone defects were developed and input into the Abaqus FEA software version 6.10.1. Mesh refinement tests and gait simulation with a single foot both in the upright and 15°-flexion positions with mechanical loading were conducted. Stress distribution analysis was compared between APT and MBT at the two static positions.
For both prosthesis types, the stress was concentrated on the junction of the stem and shaft, and the maximum stress in the femoral axis base was more than 100 Mpa. The stress on the tibial surface was relatively distributed, which was 1-19 MPa. The stress on the tibial bone-cement layer of the APT prosthesis was approximately 20 times higher than that on the MBT prosthesis in the same region. The stress on the proximal tibial cancellous bone and cortical bone of the APT prosthesis was 3-5 times greater than that of the MBT prosthesis, and it was more distributed.
Although the stress of bone-cement around the APT component is relatively high, the stress was better distributed at the polyethylene-cement-bone interface in APT than in MBT prosthesis, which effectively protects the proximal tibia in distal femur tumor knee prosthesis replacement. These results should be considered when selecting the appropriate tibial component for a patient, especially under the foreseeable conditions of osteoporosis.
全聚乙烯胫骨（APT）组件对接受股骨远端保肢手术的患者是否有益，缺乏高质量的临床随访和力学证据。本研究旨在基于我们之前良好的临床结果，通过有限元（FE）分析来研究使用APT肿瘤膝关节假体重建股骨远端的生物力学。
开发了使用APT和金属背衬胫骨（MBT）假体重建股骨远端骨缺损的三维有限元模型，并输入到Abaqus FEA 6.10.1软件版本中。进行了网格细化测试以及在直立和15°屈曲位置单脚负重的步态模拟。比较了两种静态位置下APT和MBT之间的应力分布分析。
对于两种假体类型，应力都集中在柄部和杆部的交界处，股骨轴基部的最大应力超过100兆帕。胫骨表面的应力分布相对均匀，为1 - 19兆帕。在相同区域，APT假体胫骨骨水泥层上的应力比MBT假体高约20倍。APT假体近端胫骨松质骨和皮质骨上的应力比MBT假体大3 - 5倍，且分布更广泛。
尽管APT组件周围骨水泥的应力相对较高，但APT中聚乙烯 - 骨水泥 - 骨界面处的应力分布比MBT假体更好，这在股骨远端肿瘤膝关节假体置换中有效保护了近端胫骨。在为患者选择合适的胫骨组件时，应考虑这些结果，尤其是在可预见的骨质疏松情况下。
