Impact of Overload and Overuse Following Subscapularis Tears: Mechanisms of Shoulder Joint Damage

在美国，肩袖撕裂每年影响数百万人，影响 老兵和平民都一样。泪水戏剧性地改变了关节力学，导致显著 肩关节软骨和邻近的(完整的)肌腱受损。这一损害 导致功能丧失、疼痛、撕裂进展，甚至修复后肌腱再次撕裂。 因此，确定肌腱撕裂后关节损伤的机制是一个活跃的领域。 研究。我们之前已经发现了如何在冈上肌和棘上肌后发生关节损伤 用活体大鼠肩袖撕裂模型研究冈下肌撕裂。这些结果改变了临床 通过清楚地证明前后力偶的丧失会导致 肩关节的永久性有害变化。而肩袖下肌腱撕裂是 曾经被认为是不常见的，关节镜检查的增加和成像的改进导致了 肩胛骨下撕裂的诊断率显著增加，尤其是在接受 肩袖修复。此外，有人建议，未被识别的肩胛骨下撕裂 可能是慢性功能障碍和疼痛的根源。然而，还没有研究检查过 肩胛下肌腱撕裂如何影响肩关节的关键问题，因此， 对于这种常见的、使人衰弱的疾病，目前还没有明确的最佳临床治疗方法。 因此，这项工作的临床目标是具体确定范围和 肩袖致肩关节损伤、功能改变和疼痛的机制 撕裂累及肩胛下肌。我们假设前后力偶的丧失 在肩胛下撕裂导致有害的关节损伤，功能丧失和疼痛之后， 由于肩胛下肌的关键作用，这些影响在以下情况下显著增加 而不是单单的冈上肌撕裂。此外，我们假设这些有害的 肌腱脱离后关节过度使用会加剧变化。 我们的特性良好、体内受控的临床前模型系统是被定位者的理想选择 问题。假说将通过一系列肌腱分离进行评估，然后是 机械性能测量、组织成分的综合组合 测量，并纵向活体关节运动学功能评估，肩关节范围 受影响肢体的运动和握力，定义在体内的变化如何在EX中反映 活体测量。实验将重复，增加跑步机过度使用 损伤后识别肌腱撕裂后过度使用的复合影响的协议。这个 拟议中的研究将确定肩胛骨下撕裂如何影响关节健康和功能， 未诊断的撕裂的后果，以及肩部过度使用在肩袖下撕裂后的作用 在强化这些问题的同时，也为慢性肩痛提供了重要的见解 和功能丧失。这些研究的结果将被用于适当地设计有针对性的 随机对照试验。随后，一项或多项前瞻性临床试验的结果 将对临床护理产生明显和直接的影响。这项临床前研究的结果将 提供关键信息，最终指导肩袖下撕裂的治疗策略 以减轻疼痛，改善功能，保持长期的肩关节健康。

Rotator cuff tears affect millions of individuals each year in the United States, impacting veterans and civilians alike. Tears dramatically alter joint mechanics leading to significant damage to articular cartilage and adjacent (intact) tendons within the shoulder. This damage leads to loss of function, pain, tear progression, and even tendon re-tear following repair. Therefore, identifying mechanisms of joint damage after tendon tear is an active area of research. We have previously discovered how joint damage occurs following supraspinatus and infraspinatus tears using an in vivo rat rotator cuff tear model. These results altered clinical practice by clearly demonstrating that loss of the anterior-posterior force couple leads to permanent detrimental changes to the shoulder joint. While subscapularis tendon tears were once thought to be uncommon, increased use of arthroscopy and improved imaging have led to a dramatic increase in subscapularis tear diagnosis, specifically in ~ 50% of patients undergoing rotator cuff repair. Furthermore, it has been suggested that unrecognized subscapularis tears may be a source of chronic dysfunction and pain. However, no studies have examined the critical question of how subscapularis tendon tears affect the shoulder joint, and as a result, a clear best clinical approach has not been identified for this common and debilitating condition. Therefore, the clinical objective of this work is to specifically determine the extent and mechanisms of shoulder joint damage, functional alteration, and pain that result from rotator cuff tears involving the subscapularis. We hypothesize that loss of the anterior-posterior force couple after subscapularis tear leads to detrimental joint damage, loss of function, and pain, and that, due to the critical role of the subscapularis, these effects are significantly increased when compared to a supraspinatus tear alone. Additionally, we hypothesize that these detrimental changes are exacerbated by joint overuse after tendon detachment. Our well-characterized, controlled in vivo pre-clinical model system is ideal for the posed questions. The hypotheses will be evaluated with a series of tendon detachments followed by comprehensive combination of mechanical property measurements, tissue composition measures, and longitudinal in vivo functional evaluation of joint kinematics, shoulder range of motion, and grip strength of the affected limb, defining how in vivo changes are reflected in ex vivo measurements. Experiments will be repeated with the addition of a treadmill overuse protocol post-injury to identify the compounding effects of overuse after a tendon tear. The proposed research will identify how subscapularis tears affect joint health and function, the consequences of an undiagnosed tear, and the role of shoulder overuse after subscapularis tear in intensifying these issues, while also providing important insights into chronic shoulder pain and loss of function. Results from these studies will be used to appropriately design targeted randomized controlled trials. Subsequently, results from one or more prospective clinical trials will have a clear and direct impact on clinical care. Results from this pre-clinical study will provide critical information that will ultimately guide treatment strategies for subscapularis tears in order to reduce pain, improve function, and preserve long-term shoulder joint health.