Mechanical Loading in Rotator Cuff Tendon Healing

Rotator cuff tendon tears are a common cause of pain and decreased shoulder function. Although surgical repair is typically beneficial, re-tearing at the insertion site frequently occurs. The role that mechanical loading plays in rotator cuff injury, repair, and healing is unclear. Therefore, an animal model has been developed to investigate this role, as well as guide the design of clinical studies in humans. There are wide varieties of methods, both in vitro and in vivo, used to evaluate and enhance rotator cuff tendon healing in the rat model. The objective of this article is to summarize the use of the rat model in studies evaluating the role mechanical loading plays in healing of the rotator cuff tendons, specifically the supraspinatus, after injury and surgical repair. We will discuss studies using both the acute and chronic tear models. Specifically, these studies are ones that measure the tension required to repair the supraspinatus tendon in acute and chronic tears, investigate the role of postoperative activity level on tendon healing, and evaluate parameters of in vivo shoulder mechanics and rat ambulation after different injuries. Finally, future directions that can be taken from these results, both clinically and in animal models, will be discussed.