Biomechanical investigations on the meniscus under dynamic and shock loading conditions

半月板部分切除术仍然是最常见的半月板手术。它会导致接触压力增加，导致过早软骨退化的风险更高。为了克服这个问题，已经进行了一些尝试来替换弯月面。然而，由于所用材料的机械性能不足，这些方法尚未成功。到目前为止，还没有完全了解，哪些机械负荷的种植体暴露。生物力学研究显示，在准静态载荷条件下和缓慢的膝关节屈伸运动期间，只有低拉伸载荷作用于关节附件。这与这些韧带的高强度相矛盾。因此，假设这些力在动态运动和冲击载荷期间相当高，因为它们通常发生在例如体育运动中。这可能对人工关节置换植入物的要求和设计有很大的影响。为了研究这一点，应该开发一种新的动态膝关节模拟器，它能够创建几乎生理负载条件，因为它们发生在例如跳跃着陆期间或轴向或旋转冲击负载下。模拟器将基于Oxford-Rig设计，其中安装了膝关节样本。由液压致动器驱动的垂直移动十字头在考虑所有所需自由度的情况下动态地移动膝关节。为了实现逼真的关节和地面反作用力，模拟了最重要的跨膝肌肉群。这些肌肉力量的大小和动态活动期间的瞬态特性由分包商使用逆动力学计算。在设计和制造后，将使用理想化的膝关节模型对模拟器进行验证。随后，将对20个膝关节标本进行体外实验，以确定在动态和冲击载荷下作用于胫骨平台及其附件的载荷。在所有实验过程中，持续记录在股骨附件和股骨外周中发生的应变以及胫股接触压力。最后，对孤立的牙列附着体进行拉伸试验，以从模拟器实验期间测量的应变中推导出力。此外，新的膝关节模拟器将使各种其他实验需要动态或冲击载荷条件下，如半月板，韧带或膝关节成形术。

Partial meniscal resection is still the most frequent surgical procedure performed on the meniscus. It results in an increased contact pressure leading to a higher risk of premature cartilage degeneration. To overcome this problem some attempts have been conducted to replace the meniscus. However, due to the insufficient mechanical properties of the used materials these approaches have not yet been successful. By now, it is not completely understood, which mechanical loads meniscal implants are exposed to. Biomechanical investigations revealed only low tensile loads acting in the meniscal attachments during quasistatic loading conditions and during slow knee flexion-extension movements. This contradicts to the high strength of these ligaments. It is therefore hypothesized that these forces are considerably higher during dynamic movements and shock loads, as they typically occur e.g. in sports. This might have strong implications for the requirements and the design of meniscal replacement implants. To investigate this, a new dynamic knee joint simulator should be developed, which enables the creation of almost physiological loading conditions, as they occur e.g. during jump landing or under axial or rotational shock loads. The simulator will be based on an Oxford-Rig design, in which the knee joint specimen is mounted. A vertically moving cross head driven by a hydraulic actuator dynamically moves the knee joint under consideration of all required degrees of freedom. To achieve realistic joint and ground reaction forces the most important knee spanning muscle groups are simulated. The magnitude of these muscles forces and their transient characteristics during dynamic activities are calculated using inverse dynamics by a subcontractor. After designing and manufacturing the simulator will be validated with an idealized knee joint model. Subsequently, in vitro experiments on 20 knee joint specimens will be carried out to determine the loads acting on the menisci and their attachments under dynamic and shock loads. During all experiments the strain occurring in the meniscal attachments and in the meniscal periphery and the tibiofemoral contact pressure are continuously registered. Finally, tensile tests on isolated meniscal attachments are carried out to deduce the forces from the strains, which were measured during the simulator experiments. Furthermore, the new knee joint simulator will enable for a variety of other experiments requiring dynamic or shock loading conditions on e.g. meniscus, ligaments or knee joint arthroplasty.