Quantifying Rotator Cuff Atrophy and Fatty Degeneration at the Supraspinatus Origin in the Scapular Fossa

Purpose: The aim of this study was to evaluate the location difference (distance) between the conventional Y-view (CYV) and the bony origin of the supraspinatus, and therefore, to suggest hypotrophy measurement in the CYV could be highly influenced by retraction of a torn tendon.

Methods: Ninety five arthroscopically repaired rotator cuff tears were retrospectively enrolled in this study. The most lateral portion of the osseous origin of the supraspinatus muscle [the Y-view at the level was newly defined as the supraspinatus origin-view (SOV)] and the CYV were determined on the MRI, and location discrepancy between the two levels was measured. Fatty degeneration and cross-sectional areas of rotator cuff muscles were measured on both views. Subgroup analyses were performed in partial-thickness tears and full-thickness tears with tendon retraction.

Results: Distance between the SOV and CYV was 11.2 ± 3.7 mm. Discrepancy of the supraspinatus areas at the two views was greater in full-thickness tears than it was in partial-thickness tears without retraction. In the full-thickness tear group, correlation analysis between retraction and cross-sectional areas of the supraspinatus in both views exhibited statistical significance [Pearson's correlation coefficients = 0.500 (P < 0.001) in the CYV and 0.283 (P = 0.017) in the SOV]; however, the correlation was stronger in the CYV. Ratings of fatty degeneration were similar in both views.

Conclusions: There is considerable location discrepancy between the osseous origin of the supraspinatus at the suprascapular fossa and the CYV in which fatty degeneration and hypotrophy are routinely measured.

Level Of Evidence: Case series, Level IV.