BACKGROUND Superior translation of the humeral head is often identified in large and massive rotator cuff (RC) tears. However, the ability of the remaining RC muscles to compensate for the forces causing such superior translation in RC tears remains unclear. The purpose of this study was to investigate the impact of compensatory forces exerted by the remaining RC muscles on humeral head translation using a progressive RC tear model. METHODS Eight fresh-frozen cadaveric shoulders (mean donor age, 57 years) were tested using a custom shoulder testing system. In addition to an intact RC model, 3 RC tear models were created: a supraspinatus tear (Tear I); combined supraspinatus and infraspinatus tears (Tear II); and combined tears of the supraspinatus, infraspinatus, and superior one-third of the subscapularis (Tear III). Compensatory conditions were simulated by increasing the loading of the remaining RC muscles in each RC tear model. Humeral head translation was measured at different abduction and neutral rotation angles in each condition with normal and high deltoid muscle loading. RESULTS Significant superior translation of the humeral head was observed in Tears II and III (but not Tear I), compared with the intact state, under high loading of the deltoid during abduction and during rotation. In Tear II, compensatory conditions involving increased loading of the teres minor and subscapularis muscles effectively reduced superior translation, so that no significant differences were observed compared with the intact state, even under high deltoid muscle loading. However, in Tear III, significant superior translation was still observed, regardless of the compensatory conditions. CONCLUSIONS ompensation by the remaining RC muscles, particularly the teres minor and subscapularis, effectively reduced superior translation of the humeral head in the posterosuperior RC tear model, whereas this compensatory strategy was insufficient if tears also involved the superior one-third of the subscapularis. CLINICAL RELEVANCE Patients with posterosuperior RC tears may find conservative treatment focusing on strengthening the remaining RC muscles, especially the subscapularis and teres minor, to be beneficial. Conversely, patients with repairable massive RC tears also involving the subscapularis tendon may benefit from surgical interventions aimed at primarily repairing the subscapularis tendon to restore the transverse force couple. Massive tears deemed not to be repairable should be evaluated for arthroplasty or other procedures.

中文翻译：

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在肩袖撕裂中维持盂肱关节稳定的肌肉补偿策略：一项尸体研究。


背景 肱骨头的上移通常见于大块和大块的肩袖 （RC） 撕裂。然而，剩余 RC 肌肉补偿导致 RC 撕裂如此优越平移的力量的能力仍不清楚。本研究的目的是使用进行性 RC 撕裂模型研究剩余 RC 肌肉施加的代偿力对肱骨头平移的影响。方法 使用定制的肩部检测系统对 8 例新鲜冷冻的尸体肩部 （供体平均年龄 57 岁） 进行了检测。除了完整的 RC 模型外，还创建了 3 个 RC 撕裂模型：冈上肌撕裂 （Tear I）;冈上肌和冈下肌联合撕裂 （Tear II）;冈上肌、冈下肌和肩胛下肌上三分之一的合并撕裂（撕裂 III）。通过增加每个 RC 撕裂模型中剩余 RC 肌肉的负荷来模拟代偿条件。在正常和高三角肌负荷的每种情况下，在不同的外展和中立旋转角度下测量肱骨头平移。结果在外展和旋转过程中三角肌的高负荷下，与完整状态相比，在撕裂 II 和 III 中观察到肱骨头的显着优越翻译。在 Tear II 中，涉及增加小圆肌和肩胛下肌负荷的代偿条件有效地降低了上平移，因此即使在高三角肌负荷下，与完整状态相比也没有观察到显着差异。然而，在 Tear III 中，无论代偿条件如何，仍然观察到显着的优越翻译。 结论在后上 RC 撕裂模型中，剩余 RC 肌肉，特别是小圆肌和肩胛下肌的补偿，有效地减少了肱骨头的上平移，而如果撕裂也涉及肩胛下肌的上三分之一，则这种补偿策略是不够的。临床意义 后上 RC 撕裂患者可能会发现专注于加强剩余 RC 肌肉的保守治疗是有益的，尤其是肩胛下肌和小圆肌。相反，同样累及肩胛下肌腱的可修复大块 RC 撕裂患者可能受益于手术干预，这些手术干预主要是为了修复肩胛下肌腱以恢复横向力对。被认为无法修复的大面积撕裂应评估关节置换术或其他手术。