The gluteal muscles in end-stage osteoarthritis of the hip: intra- and interobserver reliability and agreement of MRI assessments of muscle atrophy and fatty degeneration

AIM: To assess the intra-and interobserver reliability and agreement of muscular atrophy and fatty degeneration of the gluteal muscles on magnetic resonance imaging (MRI) in patients with end-stage osteoarthritis of the hip. MATERIALS AND METHODS: Thirty-nine patients with end-stage osteoarthritis of the hip, who scheduled for hip replacement surgery, were included in the study. The cross-sectional areas of the gluteus medius and minimus muscles were manually circumscribed and automatically calculated, while intramuscular fatty degeneration was assessed using the semiquantitative classification system of Goutallier. Two independent observers performed all the evaluations. RESULTS: Good agreement and excellent reliability were found for the cross-sectional areas of the gluteus medius and gluteus minimus (intraclass correlation coefficient [ICC] for intraobserver 0.97 and 0.93, ICC for interobserver 0.98 and 0.95). Fair reliability was found for fatty degeneration of the gluteus muscles (mean kappa 0.23 and mean prevalence-adjusted kappa 0.53). The average proportion of agreement for the raters was 0.71. CONCLUSION: The present study demonstrated substantial agreement and excellent intra- and interobserver reliability for the measurements of the cross-sectional areas of the gluteus medius and gluteus minimus. Assessment of fatty degeneration had fair intra-and interobserver reliability, but acceptable agreement. (C) 2018 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.