Musculoskeletal Research Unit, Department of Molecular Mechanisms of Disease, Vetsuisse Faculty ZH, University of Zurich, Zurich, Switzerland.
Competence Center for Applied Biotechnology and Molecular Medicine, Department of Molecular Mechanisms of Disease, Vetsuisse Faculty ZH, University of Zurich, Zurich, Switzerland.
Am J Sports Med. 2024 Apr;52(5):1319-1327. doi: 10.1177/03635465241226961. Epub 2024 Mar 8.
Muscle edema formation and inflammatory processes are early manifestations of acute rotator cuff lesions in sheep. Histological analysis of affected muscles revealed edema formation, inflammatory changes, and muscle tissue disruption in MRs.
Edema contributes to inflammatory reactions and early muscle fiber degeneration before the onset of fatty infiltration.
Controlled laboratory study.
Osteotomy of the greater tuberosity, including the insertion of the infraspinatus tendon, was performed on 14 sheep. These experimental animal models were divided into 2 groups: a nontrauma group with surgical muscle release alone (7 sheep) and a trauma group with standardized application of additional trauma to the musculotendinous unit (7 sheep). Excisional biopsy specimens of the infraspinatus muscle were taken at 0, 3, and 4 weeks.
Edema formation was histologically demonstrated in both groups and peaked at 3 weeks. At 3 weeks, signs of muscle fiber degeneration were observed. At 4 weeks, ingrowth of loose alveolar and fibrotic tissue between fibers was detected. Fatty tissue was absent. The diameter of muscle fibers increased in both groups, albeit to a lesser degree in the trauma group, and practically normalized at 4 weeks. Immunohistology revealed an increase in macrophage types 1 and 2, as well as inflammatory mediators such as prostaglandin E2 and nuclear factor kappa-light-chain-enhancer of activated B cells.
Early muscle edema and concomitant inflammation precede muscle fiber degeneration and fibrosis. Edema formation results from tendon release alone and is only slightly intensified by additional trauma.
This study illustrates that early edema formation and inflammation elicit muscle fiber degeneration that precedes fatty infiltration. Should this phenomenon be applicable to human traumatic rotator cuff tears, then surgery should be performed as soon as possible, ideally within the first 21 days after injury.
肌肉水肿的形成和炎症过程是羊急性肩袖病变的早期表现。受影响肌肉的组织学分析显示，MR 中出现水肿形成、炎症变化和肌肉组织破坏。
水肿会导致炎症反应，并在脂肪浸润发生之前导致早期肌肉纤维变性。
对照实验室研究。
对 14 只绵羊进行了肱骨大结节截骨术，包括冈下肌腱的插入。这些实验动物模型分为 2 组：仅行手术肌肉松解的非创伤组（7 只绵羊）和对肌肌腱单位行标准化附加创伤的创伤组（7 只绵羊）。在 0、3 和 4 周时取冈下肌的切除活检标本。
两组均在组织学上显示出水肿形成，且在 3 周时达到高峰。在 3 周时，观察到肌肉纤维变性的迹象。在 4 周时，检测到纤维之间疏松肺泡和纤维组织的侵入。没有脂肪组织。两组的肌肉纤维直径均增加，尽管创伤组的程度较小，但在 4 周时几乎恢复正常。免疫组织化学显示 1 型和 2 型巨噬细胞以及炎症介质（如前列腺素 E2 和核因子 kappa-轻链增强子的 B 细胞）增加。
早期肌肉水肿和伴随的炎症先于肌肉纤维变性和纤维化发生。水肿的形成仅由肌腱松解引起，并且仅由附加创伤略微加剧。
本研究表明，早期水肿形成和炎症引发的肌肉纤维变性先于脂肪浸润。如果这种现象适用于人类外伤性肩袖撕裂，那么应尽快进行手术，理想情况下在受伤后 21 天内进行。
