Purpose: When repairing retracted rotator cuff tears, the tear pattern (eg, crescent-shaped, L-shaped) is best determined intraoperatively by evaluating the mobility of the tendon in multiple directions. The purpose of our study was to evaluate the location of the supraspinatus (SSP) muscle belly on magnetic resonance imaging (MRI) in patients undergoing arthroscopic repair of retracted rotator cuff tears. We hypothesized that the location of the rotator cuff muscle would move after tendon repair, and that the perioperative change in muscle position would correlate with the tear pattern.
Methods: A series of primary arthroscopic repairs for rotator cuff tears with >3 cm of medial retraction from 2015 to 2016 was reviewed. MRIs were performed preoperatively and within 10 days postoperatively. The SSP muscle was assessed on sagittal MRI and evaluated for the “occupation ratio”, “tangent sign”, and the “location index” proposed in this study. Pre and postoperative MRIs were compared, and correlated with intraoperatively determined tear patterns. Fifty shoulders without rotator cuff pathology were also assessed for the “location index” as control.
Results: Fifty-nine shoulders (mean age 65.0 years) were included, among which five reverse L-shaped tears were identified. The occupation ratio and tangent sign improved postoperatively. Preoperatively, in the majority of tears, the SSP muscle was located more posteriorly in the SSP fossa, compared to the control group, and shifted anteriorly after repair. However, in reverse L-shaped tears the SSP muscle was located more centrally in the fossa, and shifted posteriorly following repair.
Conclusion: Rotator cuff tearing and arthroscopic rotator cuff repair change the location of the SSP muscle. Although repair usually results in shifting of the muscle belly from posterior to anterior, reverse L-shaped tears demonstrated an opposite pattern. The location of the SSP muscle belly may be useful in predicting tear patterns of retracted rotator cuff tears.
Level of evidence: Level IV (case series).

Keywords: shoulder, rotator cuff, muscle belly, muscle location, MRI, muscle atrophy, tendon retraction, location index


中文翻译：

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关节镜下旋转袖套修复后上睑肌位置改变：术前预测泪液类型的潜在来源

目的：在修复缩回的肩袖撕裂时，最好在术中通过评估肌腱在多个方向上的活动性来确定撕裂类型（例如，月牙形，L形）。我们研究的目的是评估接受关节镜修复肩袖缩回撕裂的患者在磁共振成像（MRI）上棘上肌（SSP）肌肉腹部的位置。我们假设肌腱修复后肩袖肌的位置会移动，围手术期肌肉位置的变化将与泪液类型相关。
方法：回顾了2015年至2016年的一系列关节内镜修复，修复了肩袖撕裂且内侧缩回> 3 cm的情况。术前和术后10天内进行MRI。在矢状面MRI上评估了SSP肌肉，并评估了本研究中提出的“占有率”，“切线符号”和“位置指数”。比较术前和术后MRI，并将其与术中确定的泪液类型相关联。还评估了五十个没有肩袖病理的肩膀作为“位置指数”的对照。
结果：包括59个肩膀（平均年龄65.0岁），其中5个倒L型眼泪被确定。术后占位率和切线符号改善。与对照组相比，术前大部分泪液中，SSP肌肉位于SSP窝的后方，并且在修复后向前方移动。然而，在反向的L形眼泪中，SSP肌肉位于窝的中央，在修复后向后移动。
结论：肩袖撕裂和关节镜下肩袖修复改变了SSP肌肉的位置。尽管修复通常会导致肌肉腹部从后部转移到前部，但反向的L形眼泪表现出相反的模式。SSP肌肉腹部的位置可能有助于预测缩回的肩袖撕裂的撕裂类型。
证据级别：第四级（案例系列）。

关键词：肩，肩袖，肌肉腹部，肌肉位置，MRI，肌肉萎缩，腱收缩，位置指数