PURPOSE To determine how different combinations of humeral stem and glenosphere designs for reverse shoulder arthroplasty (RSA) influence range of motion (ROM) and muscle elongation. METHODS A computed tomography scan of a non-pathologic shoulder was used to simulate all shoulder motions, and thereby compare the ROM and rotator cuff muscle lengths of the native shoulder versus 30 combinations of humeral components (1 inlay straight stem with 155° inclination and five onlay curved stems with 135°, 145° or 155° inclinations, using concentric, medialized or lateralized trays) and glenospheres (standard, large, lateralized, inferior eccentric and bony increased-offset (BIO-RSA)). RESULTS Only five of the 30 combinations restored ≥ 50% of the native ROM in all directions: the 145° onlay stem (concentric tray) combined with lateralized or inferior eccentric glenospheres and the 145° stem (lateralized tray) combined with either a large, lateralized or inferior eccentric glenosphere. Lengthening of the supraspinatus and infraspinatus, observed for all configurations, was greatest using onlay stems (7-30%) and BIO-RSA glenospheres (13-31%). Subscapularis lengthening was observed for onlay stems combined with BIO-RSA glenospheres (5-9%), while excessive subscapularis shortening was observed for the inlay stem combined with all glenospheres except the BIO-RSA design (> 15%). CONCLUSIONS The authors suggest implanting 145° onlay stems, with concentric or lateralized trays, together with lateralized or inferior eccentric glenospheres.

中文翻译：

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肱骨干和盂球设计对反向肩关节置换术中运动范围和肌肉长度的影响。


目的 确定用于反向肩关节置换术 (RSA) 的肱骨柄和盂球设计的不同组合如何影响运动范围 (ROM) 和肌肉伸长。方法 使用非病理性肩部的计算机断层扫描来模拟所有肩部运动，从而将自然肩部的 ROM 和肩袖肌肉长度与 30 种肱骨组件组合（1 个倾斜 155° 的嵌体直柄和 5 个嵌体直柄）进行比较。具有 135°、145° 或 155° 倾斜度的镶嵌弯曲柄，使用同心、内侧或侧化托盘）和盂球（标准、大、侧化、下偏心和骨性增加偏移 (BIO-RSA)）。结果 30 种组合中，只有 5 种在所有方向上恢复了 ≥ 50% 的原始 ROM：145° 嵌体柄（同心托盘）与侧向或下偏心盂球组合，以及 145° 柄（侧向托盘）与大的、偏侧或下偏心盂球。在所有配置中观察到，使用高嵌体柄 (7-30%) 和 BIO-RSA 盂球 (13-31%) 时冈上肌和冈下肌的延长效果最大。对于与 BIO-RSA 盂球结合的嵌体柄，观察到肩胛下肌延长（5-9%），而对于与除 BIO-RSA 设计之外的所有盂球结合的嵌体柄，观察到肩胛下肌过度缩短（> 15%）。结论 作者建议植入 145° 高嵌体柄、同心或侧向托盘以及侧向或下偏心盂球。