Biomechanical investigations on the meniscus under dynamic and shock loading conditions

半月板部分切除仍然是半月板最常见的外科手术。这会导致接触压力增加，导致软骨过早退化的风险更高。为了克服这个问题，已经进行了一些尝试来替换半月板。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，半月板种植体所承受的机械载荷还不完全清楚。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中，只有较低的拉伸载荷作用于半月板附着体。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负荷时要大得多，因为它们通常发生在例如体育运动中。这可能会对半月板置换植入物的要求和设计产生强烈的影响。为了研究这一点，应该开发一种新的动态膝关节模拟器，它能够在跳跃着陆或轴向或旋转冲击载荷下产生几乎生理的载荷条件。该模拟器将基于牛津实验室的设计，其中安装了膝关节样本。在考虑所有需要的自由度的情况下，由液压执行器驱动的垂直移动的十字头动态地移动膝关节。为了获得逼真的关节和地面反作用力，模拟了最重要的膝关节跨越肌群。这些肌肉力的大小及其在动态活动期间的瞬时特性是由分包商使用逆动力学计算的。在设计和制造之后，模拟器将在一个理想的膝关节模型上进行验证。随后，将对20个膝关节标本进行体外实验，以确定在动态载荷和冲击载荷下作用于半月板及其附着体的载荷。在所有实验过程中，持续记录半月板附着体和半月板周边的应变和胫股接触压力。最后，对分离的半月板附着体进行了拉伸试验，以从模拟器实验中测量的应变中推导出力。此外，新的膝关节模拟器将支持各种其他需要在半月板、韧带或膝关节置换术上进行动态或冲击加载条件的实验。

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.