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

在全膝关节内假体植入过程中，由于关节磨损而破坏的关节面被切除并用人工表面代替。尽管现代膝关节假体具有很好的止痛效果和高耐用性，但仍有大约20%的患者对其结果不满意。目前在专业领域有两种不同的假体部件对齐方法：机械对齐（MA）和运动学对齐（KA）。KA的目的是恢复胫骨-股关节线的自然方向，腿的自然轴和膝关节的自然稳定性。为了估计根据KA原理植入的假体可能的长期成功，有必要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的假体对齐以及其他不同的假体设计对生物力学的影响。因此，患者可能的功能改善应归功于机械参数，并应得出关于机械负荷可能的长期成功的结论。在项目范围内，需要测试以下工作假设：(1)与机械导向假体相比，运动学导向假体的生物力学参数更接近生理原生状态（内侧和外侧接触力、髌骨后压力、髌骨运动学、股骨回滚）。(2)双十字韧带保留假体设计比只有一个或根本没有十字韧带的假体设计提供更具有可比性的生理状态的生物力学值（参数见1）。项目分为实验部分和模拟部分，这两个部分紧密相连。在这两个部分中，工作假设将得到检验。实验调查将在一个全面的体外测试设置中进行。最重要的膝关节伸肌和屈肌的肌肉特征将由液压系统控制，膝关节将由工业机器人引导和加载。在体外试验数据的帮助下，对已有的膝关节数值模型进行了扩展。在其他方面，韧带结构的应变，不能直接测量，将被确定。此外，植入参数的变化将进行评估其对生物力学的影响。在进一步的方法中，膝关节模型将被整合到一个完整的下肢模型中。这将允许对n=120例（n=60 KA和n=60 MA）患者正在进行的临床研究的现有数据进行详细分析。将这些数据与扩展模型相结合，可以显示不同的假体对齐方式对生物力学的影响，不仅在理想的测试台上，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.