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

HYPOTHESIS: We hypothesize that the degree of supraspinatus atrophy, as assessed with the tangent sign will significantly correlate with increasing rotator cuff tear size.

METHODS

A 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.

RESULTS

All 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).

CONCLUSION

The 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.