Hafez Ahmed H, El-Rich Marwan, Liu Tao, Jomha Nadr, Schiffer Andreas
Department of Mechanical Engineering, Khalifa University, Abu Dhabi, United Arab Emirates.
Healthcare Engineering Innovation Center (HEIC), Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates.
Front Bioeng Biotechnol. 2023 Aug 24;11:1228809. doi: 10.3389/fbioe.2023.1228809. eCollection 2023.
Total talus replacement is a promising alternative treatment for talus fractures complicated by avascular necrosis and collapse. This surgical option replaces the human talus bone with a customized talus implant and can maintain ankle joint functionality compared to traditional treatment (e.g., ankle fusion). However, the customized implant is costly and time-consuming due to its customized nature. To circumvent these drawbacks, universal talus implants were proposed. While they showed clinically satisfactory results, existing talus implants are heavier than biological talus bones as they are solid inside. This can lead to unequal weight between the implant and biological talus bone, and therefore leading to other complications. The reduction of the implants' weight without compromising its performance and congruency with surrounding bones is a potential solution. Therefore, this study aims to design a lightweight universal talus implant using topology optimization. This is done through establishing the loading and boundary conditions for three common foot postures: neutral, dorsi- and plantar-flexion. The optimized implant performance in terms of mass, contact characteristics with surrounding joint cartilage and stress distributions is studied using a 3D Finite Element (FE) model of the ankle joint. The mass of the optimized implant is reduced by approximately 66.6% and its maximum stresses do not exceed 70 MPa, resulting in a safety factor of 15.7. Moreover, the optimized and solid implants show similar contact characteristics. Both implants produced peak contact pressures that were approximately 19.0%-196% higher than those produced by the biological talus. While further mechanical testing under loading conditions is required to determine clinical feasibility, preliminarily, the use of a lightweight universal implant is expected to provide the patient with a more natural feel, and a reduced waiting period until surgery.
距骨全置换术是治疗并发缺血性坏死和塌陷的距骨骨折的一种有前景的替代治疗方法。这种手术选择用定制的距骨植入物替代人体距骨，与传统治疗方法（如踝关节融合术）相比，可以维持踝关节功能。然而，定制植入物因其定制性质而成本高昂且耗时。为了规避这些缺点，人们提出了通用距骨植入物。虽然它们在临床上显示出令人满意的结果，但现有的距骨植入物比生物距骨重，因为它们内部是实心的。这可能导致植入物和生物距骨之间的重量不均，从而引发其他并发症。在不影响其性能和与周围骨骼的贴合度的情况下减轻植入物的重量是一个潜在的解决方案。因此，本研究旨在使用拓扑优化设计一种轻质通用距骨植入物。这是通过为三种常见足部姿势（中立位、背屈和跖屈）建立加载和边界条件来实现的。使用踝关节的三维有限元（FE）模型研究优化后的植入物在质量、与周围关节软骨的接触特性和应力分布方面的性能。优化后的植入物质量减少了约66.6%，其最大应力不超过70MPa，安全系数为15.7。此外，优化后的植入物和实心植入物显示出相似的接触特性。两种植入物产生的峰值接触压力比生物距骨产生的压力高出约19.0% - 196%。虽然需要在加载条件下进行进一步的力学测试以确定临床可行性，但初步来看，使用轻质通用植入物有望为患者提供更自然的感觉，并缩短手术等待时间。
