Alterations in function after rotator cuff tears in an animal model.

HYPOTHESIS: This study examined the effect of multiple rotator cuff tendon tears on shoulder function in an animal model.
MATERIALS AND METHODS: Forty-eight Sprague-Dawley rats were divided into uninjured control, supraspinatus tendon detachment, supraspinatus+infraspinatus tendon detachment, or supraspinatus+subscapularis tendon detachment groups. Functional assessment was determined through ambulatory parameters (paw and stride measures) and range of motion prior to tendon detachment and at various time points after tendon detachment.
RESULTS: Ambulatory parameters and total range of motion, representing measures of shoulder function, were significantly altered with rotator cuff tears. The addition of a second torn rotator cuff tendon (infraspinatus or subscapularis)had further detrimental effects on animal shoulder function compared to uninjured control. DISCUSSION: This study demonstrated functional changes in a rat rotator cuff model. Many of the permanent functional changes were likely present because the required motion used for those actions can no longer be performed. For parameters that were transient, compensation with another limb or subsidence of pain may have occurred.
CONCLUSION: The findings in this study are consistent with the alterations in shoulder function observed with rotator cuff and other shoulder injuries in the human. Future studies using this model can begin to examine the root of the functional differences, whether it is pain, mechanical deficiency, or a combination of both, which cannot be fully studied clinically [corrected].