Skeletal Muscle Atrophy and Fatty Infiltration after Massive Rotator Cuff Tears in a Novel Rat Model

INTRODUCTION: Rotator cuff tears (RCT) are the most common tendon injury seen in orthopedic patients. Although small tears are amenable to arthroscopic repair, massive RCT repairs can result in re-tears and poor clinical outcomes. Muscle atrophy and fatty infiltration in rotator cuff muscles are major complications of chronic massive RCT and are thought to be among the factors responsible for the failure of attempted massive RCT repair. The pathophysiology of rotator cuff muscle atrophy and fat infiltration remains largely unknown, and no small animal model has been demonstrated to reproduce the histologic and molecular changes seen in massive RCT. In this study, we have successful generated a massive RCT injury in rat by complete transection of supraspinatus (SS) and infraspinatus (IS) tendons. Significant and consistent muscle atrophy and fat infiltration were observed in rotator cuff muscles after massive RCT in our novel model. Furthermore, we have investigated the role of denervation in muscle atrophy and fat infiltration after RCT in this model.