A Comprehensive Testing Program for Shoulder Implant Assessment

肩关节植入物的失效对于解剖设计和反向设计都是一个日益关注的问题-这是“球窝”反向以增加肌肉力矩臂并减少关节载荷的地方。虽然存在许多潜在失效模式，但由于蠕变和磨损导致的聚乙烯内衬组件结构完整性丧失是最紧迫的问题。这可能是由于关节面上发生的过度载荷所致。 随着婴儿潮一代人口的老龄化，对这些植入物的需求显着增加。此外，随着负荷和活动范围的增加，这一群体对运动和锻炼等活动需求的增加也是对这些植入物的潜在挑战。然而，这些结构的当前生物力学评价很可能不是活动的准确表示，这是由于在实验室和计算中对围绕植入物和骨建模的负载和其他因素进行了大量简化。 该计划的长期目标是阐明植入物重建肩关节的生物力学，并对其进行全面评价，特别关注武装生物力学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。 本次Discovery项目资助的首要主题是“深入研究”并确定植入物系统的负载和最终响应。在这项工作的5年任期内，具体的短期目标是：（1）确定作用于肩关节的载荷包络，以及（2）量化植入物系统（特别关注聚乙烯组件）在承受此类载荷时的反应。 该方法包括实验研究，以模拟活动的尸体手臂，通过开发协议的一个专门的模拟器，重点是高速（即动态）运动。此外，还将开发一种加载装置，用于向手臂施加外部载荷，就像锻炼时发生的那样。然后将这些测得的载荷用于待开发的“试验台”，以评估植入物的机械响应。 预计本文提出的工作将彻底改变通过这些肩关节植入物的载荷传递的理解，并推进我们对该结构的基于工程的治疗，超越迄今为止的简化实验和计算建模方法。这些发展也将导致最先进的测试程序的发展，这将允许对肩关节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.