Mendias Christopher L, Roche Stuart M, Harning Julie A, Davis Max E, Lynch Evan B, Sibilsky Enselman Elizabeth R, Jacobson Jon A, Claflin Dennis R, Calve Sarah, Bedi Asheesh
Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, MI, USA; Department of Molecular & Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA.
Department of Orthopaedic Surgery, University of Michigan Medical School, Ann Arbor, MI, USA.
J Shoulder Elbow Surg. 2015 Jan;24(1):111-9. doi: 10.1016/j.jse.2014.06.037. Epub 2014 Sep 3.
A persistent atrophy of muscle fibers and an accumulation of fat, collectively referred to as fatty degeneration, commonly occur in patients with chronic rotator cuff tears. The etiology of fatty degeneration and function of the residual rotator cuff musculature have not been well characterized in humans. We hypothesized that muscles from patients with chronic rotator cuff tears have reduced muscle fiber force production, disordered myofibrils, and an accumulation of fat vacuoles.
The contractility of muscle fibers from biopsy specimens of supraspinatus muscles of 13 patients with chronic full-thickness posterosuperior rotator cuff tears was measured and compared with data from healthy vastus lateralis muscle fibers. Correlations between muscle fiber contractility, American Shoulder and Elbow Surgeons (ASES) scores, and tear size were analyzed. Histology and electron microscopy were also performed.
Torn supraspinatus muscles had a 30% reduction in maximum isometric force production and a 29% reduction in normalized force compared with controls. Normalized supraspinatus fiber force positively correlated with ASES score and negatively correlated with tear size. Disordered sarcomeres were noted, along with an accumulation of lipid-laden macrophages in the extracellular matrix surrounding supraspinatus muscle fibers.
Patients with chronic supraspinatus tears have significant reductions in muscle fiber force production. Force production also correlates with ASES scores and tear size. The structural and functional muscle dysfunction of the residual muscle fibers is independent of the additional area taken up by fibrotic tissue. This work may help establish future therapies to restore muscle function after the repair of chronically torn rotator cuff muscles.
肌肉纤维持续性萎缩和脂肪堆积，统称为脂肪变性，常见于慢性肩袖撕裂患者。脂肪变性的病因以及残留肩袖肌肉组织的功能在人类中尚未得到充分阐明。我们推测，慢性肩袖撕裂患者的肌肉存在肌纤维力产生减少、肌原纤维紊乱以及脂肪空泡堆积的情况。
测量了13例慢性全层后上肩袖撕裂患者的活检标本中冈上肌肌纤维的收缩性，并与健康股外侧肌肌纤维的数据进行比较。分析了肌纤维收缩性、美国肩肘外科医师协会（ASES）评分和撕裂大小之间的相关性。还进行了组织学和电子显微镜检查。
与对照组相比，撕裂的冈上肌最大等长力产生减少30%，标准化力减少29%。标准化冈上肌纤维力与ASES评分呈正相关，与撕裂大小呈负相关。观察到肌节紊乱，以及冈上肌纤维周围细胞外基质中富含脂质的巨噬细胞堆积。
慢性冈上肌撕裂患者的肌纤维力产生显著降低。力产生也与ASES评分和撕裂大小相关。残留肌纤维的结构和功能肌肉功能障碍与纤维化组织占据的额外面积无关。这项工作可能有助于建立未来的治疗方法，以恢复慢性撕裂肩袖肌肉修复后的肌肉功能。
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