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

Abstract

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. 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. Twenty-two hips (in 20 patients) were assessed with the mean follow-up of 31.7months (range: 24 to 47months). 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 66years (range: 45 to 82years). 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. 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. Level IV, therapeutic case series (no control group).