Supraspinatus atrophy as a predictor of rotator cuff tear size: an MRI study utilizing the tangent sign

HypothesisWe hypothesize that the degree of supraspinatus atrophy, as assessed with the tangent sign will significantly correlate with increasing rotator cuff tear size.MethodsA retrospective review was performed assessing presence of muscle atrophy using the tangent sign, fatty atrophy based on Goutallier classification, and size of rotator cuff tear in 34 patients. A correlation analysis was performed.ResultsAll agreement measures among both evaluators were statistically significant (P < .05). Agreement among the 2 physicians for the tangent sign was consider almost perfect k = 87.2 (95%CI = 51.7, 87.2). Weighted kappa agreement using the Goutallier sign was 75.1 (95%CI = 58.7, 91.4), suggesting substantial agreement. The relationship between the positive tangent sign and coded tear grade was very good with a correlation of R = .84 and R = .87, respectively, showing a strong correlation between the presence of a tangent sign and a larger rotator cuff tear. A strong relationship was also found when comparing the tangent sign to a Goutallier's classification of 2 or greater with a correlation of R = .92 and R = .94 for the 2 physicians. The lowest correlation was found between the Goutallier sign and tear grade from both physicians. All of these findings were statistically significant (P < .05).ConclusionThe tangent sign shows good interobserver reliability and is easily performed to measure rotator cuff atrophy and a positive tangent sign shows an excellent correlation with the size of the rotator cuff tear and may be predictive of the ability of the cuff to be primarily repaired.