A Mouse Model of Massive Rotator Cuff Tears

Background: Rotator cuff tears are the most common tendon injury seen in orthopaedic patients. Muscle atrophy and fatty infiltration in rotator cuff muscles are considered among the key factors responsible for the failure of attempted repair of a massive rotator cuff tear. However, the pathophysiology of rotator cuff muscle atrophy and fatty infiltration remains largely unknown, partly because of the lack of appropriate small animal models. The goal of this study was to develop a mouse model of muscle atrophy and fatty infiltration after a rotator cuff tear. We also sought to study the role of denervation on muscle atrophy and fatty infiltration after a rotator cuff tear. Methods: Adult wild-type FVB/N mice were randomly divided into three groups. Mice in different groups received unilateral complete supraspinatus and infraspinatus tendon transection, suprascapular nerve transection, or both procedures. Sham surgery was performed on the contralateral shoulder to serve as a control. Mice were killed twelve weeks after surgery. Histological analysis and high-resolution magnetic resonance imaging were used to evaluate muscle atrophy and fat infiltration after a rotator cuff tear. Results: Significant and consistent muscle atrophy and fatty infiltration were observed in the rotator cuff muscles after rotator cuff tendon transection. We further found that denervation significantly increases the amount of muscle atrophy and fatty infiltration after a rotator cuff tear. Conclusions: We successfully developed a novel mouse model of a massive rotator cuff tear, which simulates major pathological changes, including muscle atrophy and fatty infiltration after massive rotator cuff tears seen in patients. Clinical Relevance: Successful development of this novel mouse model of rotator cuff tears will provide a powerful tool to study the molecular mechanisms of muscle atrophy and fatty infiltration by introducing transgenic and knockout mice in the future. This model may also serve as a powerful in vivo model in developing new treatments for this common disease.