Fatty infiltration in the intact supraspinatus tendon; a normal physiological response with increasing age and female gender.

Background: Fatty infiltration and muscle atrophy of supraspinatus are used as markers of chronicity in rotator cuff tears and are known to both be independently related to poorer outcomes following surgical repair.1 We hypothesized that supraspinatus muscle atrophy and fatty infiltration increases with age irrespective of whether the rotator cuff is intact and therefore cannot be used as accurate markers for chronicity. Method: Retrospective review of 280 patients who underwent 3.0 T shoulder MRI's with either a normal scan or rotator cuff tear. Two independent observers reviewed the images. Data collected included intact rotator cuff tendons looking specifically at supraspinatus muscle height/length: suprascapular fossa ratio, tangent sign and Goutallier grade for fatty infiltration.
Results: There were 90 scans with intact rotator cuff tendons. Mean age was 51 years (range 17-86); 52 males, 38 females. On multiple regression analysis, there was a positive correlation of age with fatty infiltration and muscle atrophy on all parameters in the normal intact cuff. Females were significantly more likely than males to have a higher grade of fatty infiltration.
Conclusion: Age and female gender are risk factors for rotator cuff atrophy and fatty infiltration in patients with normal rotator cuffs. Therefore, these parameters should be used with caution by surgeons when deciding on tear chronicity and the potential to repair the torn rotator cuff.