Association between Degree of Gluteus Minimus Muscle Atrophy and the Japanese Forgotten Joint Score-12 at 3 Months after Total Hip Arthroplasty using the Direct Anterior Approach

Abstract

Objective: This study aimed to assess how the degree of atrophy in gluteus muscles affects the Japanese Forgotten Joint Score-12 (JFJS-12) after total hip arthroplasty (THA).
Methods: The study included 217 patients who underwent unilateral THA at our hospital between April 2015 and March 2020. Patient-reported outcomes were analyzed using the JFJS-12. To measure the cross-sectional area (CSA) of the gluteus muscles, horizontal cross-sectional images at the lowest end of the sacroiliac joint were used for the gluteus minimus and gluteus medius, whereas horizontal cross-sectional images on the top of femoral head were used for the gluteus maximus. Based on the obtained CSA, we calculated the percentage of atrophy in each gluteus muscle according to the following formula: (1–muscle volume on the affected side/muscle volume on the unaffected side) × 100. Multiple regression analysis was performed to determine the factors affecting the JFJS-12, at 3 months postoperatively.
Results: The findings suggested that the degree of gluteus minimus atrophy was significantly associated with the JFJS-12.
Conclusion: The degree of preoperative gluteus minimus atrophy may influence the JFJS-12 after THA.