Influence of implant positioning and configuration on kinematics and pressure distribution in the knee joint

在全膝关节内假体的植入中，由于关节磨损而破坏的关节表面被切除并由人工表面替换。尽管现代膝关节假体具有很好的疼痛缓解和高耐用性，但仍有约20%的患者对结果不满意。目前，在专业界有两种不同的假体部件对线方法：机械对线（MA）和运动对线（KA）。KA的目标是恢复胫股关节线的自然方向、自然腿轴和膝关节的自然稳定性。为了评估根据KA原则植入的假体可能的长期成功率，必须了解作用在假体上的机械载荷，并将其与MA植入进行比较。该项目的目的是比较根据KA和MA以及不同假体设计对生物力学的影响。因此，可能改善患者的功能应归因于力学参数，并应得出关于机械载荷可能长期成功的结论。在本项目范围内，将测试以下工作假设：（1）与机械定向假体相比，运动定向假体显示出更接近生理天然状态的生物力学参数（内侧和外侧接触力、髌骨后压力、髌骨运动学、股骨后滚）。(2)双交叉韧带保留型假体设计提供的生物力学值与生理状态相比，比仅有一条交叉韧带或根本没有交叉韧带的假体设计更具可比性（参数见1）。该项目分为实验和模拟两部分，这两部分密切相关。在这两个部分中，工作假设将得到检验。实验研究将在全面的体外试验装置中进行。最重要的膝关节伸肌和屈肌的肌肉特性将由液压系统控制，膝关节将由工业机器人引导和加载。借助体外试验获得的数据，对现有的膝关节数值模型进行了扩展。除其他外，将确定无法直接测量的韧带结构的应变。此外，还将进行植入参数的变化，以评估其对生物力学的影响。在进一步的方法中，膝关节模型将被集成到一个完整的下肢模型中。这将允许对来自正在进行的临床研究（n=120例（n=60 KA和n=60 MA）患者）的现有数据进行详细分析。使用这些数据结合扩展模型，可以显示生物力学如何受到不同假体对线的影响，不仅在理想化的测试台上，而且在真实的患者中。

In the implantation of total knee endoprostheses, joint surfaces destroyed by arthrotic wear are resected and replaced by artificial surfaces. Despite the very good pain relief and high durability of modern knee prostheses, about 20% of patients remain dissatisfied with the result. There are currently two different approaches to the alignment of prosthesis components in professional circles: Mechanical Alignment (MA) and Kinematic Alignment (KA). The goal of KA is to restore the natural orientation of the tibio-femoral joint line, the natural leg axis and the natural stability of the knee joint. In order to estimate the possible long-term success of prostheses implanted according to KA principles, it is essential to know the mechanical loads acting on the prostheses and to compare them with an MA implantation.The aim of the project is to compare the effect of the alignment of the prosthesis according to KA and MA as well as additionally different prosthesis designs on biomechanics. Thus, a possible improved function in patients should be attributed to mechanical parameters and a conclusion about the possible long-term success with regard to mechanical loading should be made.Within the scope of the project, the following working hypotheses are to be tested:(1) Kinematically oriented prostheses show biomechanical parameters more comparable to the physiological native state compared to mechanically oriented prostheses (medial and lateral contact forces, retropatellar pressure, patella kinematics, femoral rollback).(2) Double cruciate ligament retaining prosthesis designs provide more comparable biomechanical values to the physiological state than prosthesis designs with only one or no cruciate ligament at all (parameters see 1.).The project is divided into an experimental and a simulative part, which are closely interlinked. In both parts the working hypotheses will be tested. The experimental investigations will be performed in a comprehensive in-vitro test setup. The muscle traits of the most important knee extensors and flexors will be controlled by a hydraulic system and the knee will be guided and loaded by an industrial robot. With the help of the data obtained from the in-vitro tests, an existing numerical knee model is to be extended. Among other things, the strains of ligament structures, which cannot be directly measured, will be determined. In addition, a variation of implantation parameters will be carried out to estimate their influence on biomechanics.In a further approach the knee model will be integrated into a complete model of the lower extremity. This will allow existing data from an ongoing clinical study with n=120 (n=60 KA and n=60 MA) patients to be analyzed in detail. Using these data in conjunction with the extended model, it can be shown how biomechanics are influenced by different prosthesis alignment not only on the idealized test bench but also in the real patient.