Hardware-in-the-Loop Simulation for Dynamic Analysis of the Shoulder after Total Joint Replacement

近年来，肩关节人工置换术已被确立为一种标准化的治疗方法，并且数量不断增加。然而，高度不同的并发症发生率和功能失效证明，全肩关节置换术后仍有许多问题未解决。在这方面，对导致不稳定、脱位、肌肉功能障碍或关节僵硬的潜在失效机制的深刻理解并不存在。尤其适用于潜在影响因素的识别和量化。为此，需要进行生物力学研究，以便在并发症和失败的体内条件下深入了解事件的过程。由于固有的缺点，目前的测试或模拟技术无法满足这种需求。此外，由于伦理原因，对仪器患者的测量受到强烈限制。本项目的目的是基于硬件在环（HiL）方法，深入分析活体条件下全肩关节置换术后复杂的关节动力学。因此，肌肉骨骼多体模型与移动和装载植入部件的工业机器人相互作用。在多体模型中，所有负责生理手部和手臂运动的相关肌肉结构都被实现。一个主要的优先事项是HiL环境中肌肉和关节力的预测，这是通过使用逆动力学技术解决的。为了建立HiL测试系统，需要在先前为测试全髋关节和膝关节置换术而开发的HiL环境中进行进一步的改进，并对物理设置进行修改。一个关键的方面是对整个HiL测试系统的验证，以对照来自有器械肩部植入物患者的实验数据。我们的项目侧重于系统评估与功能缺陷、关节不稳定和植入物失败相关的生理运动和负荷的潜在连锁效应。第一项研究将针对不同肌肉功能障碍对盂肱关节的影响进行，以解决开放性临床问题。此外，通过主动路径规划算法将模型拓扑中的运动冗余转化为备选联合轨迹。通过这种方法可以复制受并发症影响的可重复性和生理性手臂运动。因此，在考虑真实接触条件和肩带及上肢所有相关肌肉结构的情况下，首次模拟全关节置换术后肩关节的生理运动和负荷。

In recent years the artificial replacement of shoulder joints has been established as standardised treatment with rising numbers. Highly varying complication rates along with functional failures, however, prove that many problems remain unresolved after total shoulder arthroplasty. In this regard, a profound understanding of underlying failure mechanisms leading to instability, dislocation, muscle dysfunction or joint stiffness does not exist. Especially this applies for the identification and quantification of potential influencing factors. For this biomechanical investigations would be required which provide insights into the course of events under in-vivo conditions during complications and failures. Due to inherent shortcomings this demand cannot be met by current testing or simulation techniques. Furthermore, measurements on instrumented patients are strongly limited for ethical reasons.The objective of this project is to conduct in-depth analyses of the complex joint dynamics after total shoulder arthroplasty under in-vivo-like conditions based on a hardware-in-the-loop (HiL) approach. Hereby a musculoskeletal multibody model and an industrial robot that moves and loads the implant components are in mutual interaction. Into the multibody model all relevant muscle structures that are responsible for physiological hand and arm movements are implemented. A major priority is the prediction of muscle and joint forces in the HiL environment which is addressed by using inverse dynamics techniques. To establish the HiL test system further advancements within the HiL environment that was previously developed for testing total hip and knee replacements are required along with modifications of the physical setup. A key aspect is the validation of the overall HiL test system against experimental data derived from patients with instrumented shoulder implant. Our project focuses on the systematic assessment of potential chain of effects for physiological movements and loads which are connected to functional deficiencies, joint instability, and implant failure. First studies will be conducted with respect to effects of different muscular dysfunctions on the glenohumeral joint addressing open clinical questions. In addition, kinematic redundancies in the model topology are transcribed into alternative joint trajectories by means of an active path planning algorithm. This way reproducible and physiological arm movements affected by complications can be replicated. As a result physiological movements and loads of the shoulder after total joint replacement will be simulated for the first time under consideration of the real contact conditions and all relevant muscular structures of the shoulder girdle and upper extremity.