Rotator cuff tears: what have we learned from animal models?

Rotator cuff tendon tears are among the most common soft tissue injuries that occur at the shoulder. Despite advancements in surgical repair techniques, rotator cuff repairs experience a high rate of failure. The common occurrence of tears and the frequency of re-tears require a further understanding of the mechanisms associated with injuries, healing, and regeneration of the rotator cuff. This paper reviews in vivo studies using the various animal shoulder models of the rat, rabbit, sheep, canine, and primate. These animal models have been used to study intrinsic and extrinsic factors leading to shoulder degeneration, various suture techniques, effects of post-surgical treatment, numerous biologic and synthetic scaffolds, and an assortment of biologic augmentations used to accelerate healing. These effects can be examined in a controlled manner using animal models without other confounding factors that sometimes limit clinical studies. The clinically impactful results will be explained to highlight the specific knowledge gained from using animal models in rotator cuff research.