A Comprehensive Testing Program for Shoulder Implant Assessment

肩部植入物的失败是解剖学和反向设计中越来越令人担忧的问题--这是为了增加肌肉力矩臂和减少关节负荷而颠倒的“球和窝”。虽然有许多潜在的失效模式，但由于蠕变和磨损而导致的聚乙烯衬里组件的结构完整性损失是最紧迫的问题。这很可能是由于关节表面的负荷过大造成的。 随着婴儿潮一代人口的老龄化，对这些植入物的需求正在显著增加。此外，随着负荷和活动范围的增加，这一群体对包括运动和锻炼在内的活动需求的增加也是对这些植入物的潜在挑战。然而，目前对这些结构的生物力学评估在很大程度上并不能准确地表示活性，这是因为在实验室和计算上，已经进行了一些与载荷和围绕种植体和骨模型的其他因素相关的简化。 该计划的长期目标是阐明植入物重建肩的生物力学，并提出一种全面的评估方法，特别是让生物机械师获得与这些结构的力学行为相关的新知识。这些进展将为评估这些植入物的测试方法和标准奠定基础。 这项发现计划拨款的主要主题是“深入研究”，并确定植入系统的负荷和结果反应。在这项工作的5年时间里，具体的短期目标是(1)确定作用于肩关节的载荷的包络，以及(2)量化植入系统(特别关注聚乙烯组件)在承受这种载荷时的反应。 该方法包括通过开发专注于高速(即动态)运动的专门模拟器的协议来模拟身体手臂中的活动的实验研究。此外，还将开发一种加载装置，以向手臂施加外部载荷，就像锻炼时一样。然后，这些测量的载荷将被用在将要开发的评估植入物的机械响应的“试验台”中。 预计本文提出的工作将彻底改变对通过这些肩部植入物转移负荷的理解，并推动我们对这种结构的基于工程的治疗，而不是迄今为止简化的实验和计算建模方法。这些进展还将导致一项最先进的测试计划的发展，这将允许对肩部植入物进行广泛的高级研究。

Failure of shoulder implants is a growing concern for both the anatomic and reverse designs – this is where the “ball and socket” is reversed to increase muscle moment arms and reduce joint loads. While there are a number of potential failure modes, loss of the structural integrity of the polyethylene liner component due to creep and wear is a most pressing problem. This is likely due to the excessive loads that occur on the articular surfaces. With the aging baby-boomer population, the demand for these implants is increasing significantly. Moreover, the elevated activity demands including sport and exercise of this group are also a potential challenge to these implants, as the loads and range of motion are increasing. However, the current biomechanical evaluation of these constructs is, in all probability, not an accurate representation of activity, due to a number of simplifications that have been made related to loading and other factors surrounding the implant and bone modeling in the laboratory and computationally. The long-term objective of this program is to elucidate the biomechanics of the implant reconstructed shoulder and produce a comprehensive approach to its evaluation, with special interest in arming the biomechanist with new knowledge related to the mechanical behavior of these constructs. These advances will set the stage for testing methodologies and standards for the assessment of these implants. The overarching theme of this Discovery program grant is to “drill-down” and determine the loading and the resultant response of the implant system. Over the 5-year tenure of this work, the specific short-term objectives are to (1) determine the envelope of loads that act at the shoulder joint, and (2) to quantify the response of the implant systems (with special interest in the polyethylene component) when subjected to such loading. The methodology includes experimental studies to simulate activity in the cadaver arm via developing protocols for a specialized simulator with a focus on high velocity (i.e. dynamic) motions. In addition, a loading device will be developed to apply external loads to the arm as would occur with exercise. These measured loads will then be employed in a “test-bed” to be developed that evaluates the mechanical response of the implant. It is anticipated that the work proposed herein will revolutionize the understanding load transfer through these shoulder implants and advance our engineering-based treatment of this construct beyond the simplified experimental and computational modeling approaches to date. These developments will also result in the evolution of a state of the art testing program that will permit a wide range of advanced studies on shoulder implants.