Hip Gluteus Medius Tears Are Associated With Lower Femoral Neck-Shaft Angles and Higher Acetabular Center-Edge Angles

Abstract

1) To assess the possible relationship between the morphology of femur or acetabulum and the gluteus medius pathology. 2) To analyze the outcome of isolated arthroscopic treatment of femoroacetabular impingement (FAI) for patients with radiographic gluteus medius tear. We performed a retrospective study of FAI patients who underwent arthroscopy between January 2016 to December 2019. Demographic data, such as sex, age, body mass index (BMI), symptom duration, were collected. Radiographic parameters, including alpha angle, lateral center-edge angle (LCEa), femur neck-shaft angle (NSa), gluteus medius pathology, were also collected. Exclusion criteria were previous hip conditions, such as osteoarthritis (Tönnis grade > 1), rheumatoid arthritis, ankylosing spondylitis, snapping hip, previous surgery on the ipsilateral hip, or incomplete data. We followed up these patients with radiographic gluteus medius tear. No surgical procedure for gluteus medius was performed. The minimum follow-up period was 13 months. Patient-reported outcomes, such as modified Harris Hip score (mHHS), visual analog scale (VAS), and patient acceptable symptom state (PASS), as well as physical examination data, including tenderness at the greater trochanter, abductor weakness, limping gait, and positive Trendelenburg sign or test, were gathered preoperatively and postoperatively. A total of 569 hips (314, 55.2% male) were collected eventually, with a mean age of 36.5 ± 10.4 years (range: 13.0 to ∼65.0). Gluteus medius pathology was found in 209 (36.7%) hips, including 41 (7.2%) partial-thickness tears and 10 (1.8%) complete tears. The NSa of the normal, tendinosis, partial tear, and complete tear groups was 133.8 ± 4.7°, 130.6 ± 3.8°, 129.4 ± 3.9°, and 129.6 ± 3.4°, respectively (P < .001). The LCEa of each group was 31.7 ± 35.7°, 33.3 ± 6.5°, 34.9 ± 6.8°, and 33.7 ± 8.1°, respectively (P= .004). On multivariable logistic regression analysis, lower NSa and higher LCEa were identified as risk factors for developing gluteus medius pathology (P < .001). For patients with gluteus medius tear, two cases were lost to follow-up and two cases had incomplete data. The mean follow-up period of the remaining 47 hips was 29.5 ± 12.9 (range: 13 to 59) months. The mHHS improved from 54.8 ± 19.1 to 90.1 ± 6.7 points (P < .001), and VAS decreased from 6.8 ± 1.6 to 3.0 ± 1.6 points (P < .001). Forty-two cases met the threshold of PASS, with a rate of 89%. The abductor strength increased from 4.1 ± 1.00 to 4.6 ± .7 grades (P= .002). However, for patients with a completely torn gluteus medius, improvement of abductor strength was not significant statistically (3.4 ± .9 to 3.9 ± .9, P= .234). There was a correlation between lower NSa/higher LCEa and gluteus medius pathology. Isolated arthroscopic treatment of FAI for patients with radiographic gluteus medius tear can gain satisfactory patient-reported outcomes. Therapeutic case series, IV.