Background: While a number of studies have documented the very good clinical results of arthroscopic rotator cuff repair, very few authors have specifically assessed cuff integrity, supraspinatus atrophy, and fatty infiltration and their influence on the clinical outcome.

Methods: We evaluated fifty-three consecutive patients (average age, 60.9 years) who had undergone arthroscopic repair of an isolated supraspinatus tendon tear. After an average duration of follow-up of 26.4 months, all patients were evaluated clinically with use of the Constant score and underwent standardized magnetic resonance imaging at our institution. The preoperative and postoperative magnetic resonance images were evaluated by two independent observers who were blinded to the clinical outcome of the patient. Evaluation criteria were cuff integrity; atrophy of the supraspinatus; and fatty infilitration of the supraspinatus, infraspinatus, and subscapularis. These findings were correlated to the clinical outcome.

Results: Regardless of the tendon integrity, every parameter of the Constant score was significantly improved after the repair. The overall average Constant score was improved from 53.5 to 83.4 points (p < 0.001). The retear rate in our series was 25% (thirteen of fifty-three). Patients who had a retear had significantly less abduction strength (p = 0.043) and a significantly lower total Constant score (p = 0.012) than those who had an intact repair. A higher degree of preoperative supraspinatus atrophy and Stage-2 fatty infiltration of the supraspinatus were positive predictors of a retear. Also, an older age was an important predictor of a retear (p = 0.011). Progression of structural changes in the rotator cuff was halted when the repair remained intact, but there was no significant reversal of fatty infiltration or muscle atrophy. When the repairs failed, there was significant progression of fatty infiltration and atrophy of the supraspinatus.

Conclusions: The clinical and structural results of arthroscopic repairs of isolated supraspinatus tears are equal to those reported following open repair. Fatty infiltration and muscle atrophy cannot be reversed by successful arthroscopic repair. Higher degrees of muscular atrophy and fatty infiltration preoperatively are associated with recurrence of the tear as well as progression of fatty infiltration and muscular atrophy and an inferior clinical result.

Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.