Muscle atrophy as a consequence of rotator cuff tears: should we compare the muscles of the rotator cuff with those of the deltoid?
OBJECTIVE
The quantitative assessment of muscle atrophy has a degree of importance in prognosticating rotator cuff treatment. However, it has been conjectured that muscle fat increases with aging. Therefore, we thought that the quantitative assessment of the supraspinatous would be better if made in comparison with a standard of reference such as the deltoid. Consequently, we performed a two-part study, first evaluating supraspinatous changes compared with the deltoid in "normals" with aging, and second, determining if in patients with cuff tears the supraspinatous fat exceeds that of the deltoid.


METHODS
In part 1, we studied 50 patients stratified by decade. In the first sitting, two blinded independent observers quantitatively graded the deltoid (with the supraspinatous obscured) and in the second sitting the same two observers quantitatively graded the supraspinatous (with the deltoid obscured). In part 2 of the study, we evaluated patients with moderate rotator cuff tears (>2 cm) and performed the same blinded, two-sitting, quantitative assessment (with the comparison muscle obscured).


RESULTS
We found that muscle atrophy increases with age in patients without tears (0.011/0.028 U/year), although to a greater degree in the deltoid (p = 0.032). Also, in similarly aged patients, quantitative scores of the deltoid closely matched those of the supraspinatous (p = 0.071). Notably, however, in patients with large tears, the supraspinatous showed significant changes disproportionate to those of the deltoid, regardless of patient age (p = 0.044).


CONCLUSIONS
In the presence of a normal rotator cuff, fatty infiltration increases with age. Age-related changes occur more frequently in the deltoid, verifying this muscle's potential as a standard of reference. With cuff tears, supraspinatous atrophy was disproportionate to that of the deltoid. Therefore, systematic assessment of supraspinatous muscle atrophy may be more reliable using the deltoid as a control for comparison than assessing it in isolation.
Ashry
Reem
R
Department of Radiology, Hospital for Joint Diseases, NYU Medical Center, 301 E17th Street, New York, NY 11228, USA. Reem.ashry@gmail.com
Schweitzer
Mark E
ME
Cunningham
Patricia
P
Cohen
Jodi
J
Babb
James
J
Cantos
Andrew
A
D000273:Adipose Tissue / Q000473:pathology; D000328:Adult; D000367:Age Factors; D000368:Aged; D006801:Humans; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology*; D009133:Muscular Atrophy / Q000175:diagnosis* / Q000209:etiology*; D012189:Retrospective Studies; D017006:Rotator Cuff / Q000473:pathology; D000070636:Rotator Cuff Injuries; D012737:Sex Factors; D012782:Shoulder / Q000473:pathology*