Influence of Muscle Fatty Degeneration on Functional Outcomes After Endoscopic Gluteus Medius Repair

Purpose: To report the early outcomes of endoscopic repair of tears of the gluteus medius tendon and to determine whether the fatty degeneration had an influence on clinical results. Methods: Between October 2012 and June 2014, data were prospectively collected and retrospectively reviewed for all patients who underwent endoscopic gluteus medius repair. Patients were assessed pre- and postoperatively using the modified Harris hip score, the nonarthritic hip score, and visual analog scale for pain. The gluteus minimus and the 3 distinct parts of the gluteus medius (anterior, middle, and posterior) were assigned a grade of fatty degeneration on preoperative magnetic resonance imaging scans. Results: Twenty-two hips (in 20 patients) were assessed with the mean follow-up of 31.7 months (range: 24 to 47 months). There were 15 partial-thickness and 7 full-thickness tears. No patient was lost to follow-up. The mean age at the time of surgery was 66 years (range: 45 to 82 years). Of the 20 magnetic resonance imaging-assessed hips included in the study, 14 had fatty degeneration of the gluteus medius (partial-thickness tears: n = 8, full-thickness tears: n = 6). The mean gluteus medius fatty degeneration index was 1.57 (range: 0.33 to 3.33). Postoperative improvement was seen in modified Harris hip score (33.7 points vs 80.2 points, P = .0001), nonarthritic hip score (47.7 points vs 76.8 points, P = .0001), and in the visual analog scale for pain (7.2 vs 3.2, P < .05). Increasing preoperative fatty degeneration index of the gluteus medius correlated with decreased postoperative functional hip score values (regression coefficient, 0.5839; P < .0001). Tear characteristics (partial or full-thickness) did not correlate with fatty degeneration or muscular atrophy and did not affect postoperative outcomes. Conclusions: Endoscopic surgical repair can be an effective treatment of gluteus medius tears in the short term. Fatty degeneration of the gluteus medius and minimus has a negative impact on clinical outcomes of endoscopic gluteus medius repair.