Hamilton Matthew A, Roche Christopher P, Diep Phong, Flurin Pierre-Henri, Routman Howard D
Bull Hosp Jt Dis (2013). 2013;71 Suppl 2:S31-5.
The purpose of this article is to compare the effect reverse shoulder design philosophy has on the lengths and moment arms of the external rotators of the shoulder (i.e. posterior deltoid, infraspinatus, and teres minor). In this study, a single bone model was used to normalize the origin and insertion of each muscle. Four different commercially available designs were virtually implanted into the bones. The assemblies oriented with the arm at the side (0° of abduction) and articulated to 45° internal rotation and 45° external rotation. The muscle length and moment arm for each muscle were analyzed and compared to the anatomic shoulder. The results indicate that all the external rotators are shortened relative to the anatomic shoulder, but the MGLH design shortened the muscles the least. The moment arm analysis showed the teres minor and infraspinatus moment arms increased relative to the normal shoulder in external rotation for all designs. The moment arms are sensitive to the lateral offset of the stem relative to the center of rotation. The MGLH design had the largest moment arm during the external rotation range of motion due to its large humeral offset.
本文的目的是比较反向肩关节设计理念对肩部外旋肌（即三角肌后部、冈下肌和小圆肌）长度和力臂的影响。在本研究中，使用单一骨骼模型来规范每块肌肉的起点和止点。将四种不同的市售设计虚拟植入骨骼中。组件在手臂位于身体一侧（外展0°）时进行定向，并在45°内旋和45°外旋时进行关节运动。分析每块肌肉的肌肉长度和力臂，并与解剖学肩部进行比较。结果表明，相对于解剖学肩部，所有外旋肌均缩短，但MGLH设计对肌肉的缩短程度最小。力臂分析表明，对于所有设计，在进行外旋时，小圆肌和冈下肌的力臂相对于正常肩部均增加。力臂对柄相对于旋转中心的侧向偏移很敏感。由于其较大的肱骨偏移，MGLH设计在运动的外旋范围内具有最大的力臂。
