The purpose of this study is to clarify the relationship between clinical, MRI and pathological findings, associated with torn rotator cuff muscles. Materials of this study were Twenty-nine shoulders in twenty-eight patients with rotator cuff tears, treated surgically in our hospital from March (2008) to April (2009). 19 were males, and 10 were females. The mean age at surgery was 63 years. The average periods, onset to the operation, was 18.2 months. The mean size of the tear was 3.3 cm. The mean JOA score was 69.9 points before operation. Needle biopsy was done in all cases at the supraspinatus and infraspinatus muscle, using the 14G needle biopsy kit. The biopsy organization was fixed by fresh freezing and paraffin, and stained using the H-E and Sudan III methods. We evaluated fatty infiltration between muscle fibers and graded 0 to 2, (Grade 0: fat cell (-) at H-E and fat (-) at Sudan III, Grade 1: fat cell (+) at H-E and fat (±) at Sudan III or fat cell (-) at H-E and fat (+) at Sudan III, Grade 3: fat cell (+) at H-E and fat (+) at Sudan III). MRI was enforced one to seven days before the operation in all cases, and we classified the fatty degeneration of rotator cuff muscles, using Nakagaki and Goutallier's Classification. We evaluated and analyzed the relationship between the clinical, MRI and pathological findings statistically. There were fat cells between the muscle fibers, in H-E (paraffin). In the supraspinatus and infraspinatus, there was a relationship between the size of the tear and the fatty degeneration on MRI. In the supraspinatus, there was a relationship between the fatty degeneration on MRI and fatty infiltration between muscle fibers on pathology.
