Relationship Between Preoperative Psoas Major Muscle Quality and Forgotten Joint Score-12 in Patients After Total Hip Arthroplasty

BACKGROUND: There are limited reports on the factors affecting the Forgotten Joint Score-12 (FJS-12) in patients after total hip arthroplasty (THA). Therefore, this study aimed to determine whether the quantity and quality of the preoperative psoas muscle are related to the FJS-12 in post-THA patients. METHODS: This retrospective cohort study used mailed questionnaires and medical records. Questionnaires containing the FJS-12 were mailed to 752 patients who underwent THA at our hospital between April 2015 and August 2020. The quantity and quality of the psoas major muscle were measured by computed tomography. The association between FJS-12 and the quantity and quality of the psoas major muscle was assessed by logistic regression analysis adjusted for potentially relevant factors. RESULTS: In total, 484 patients were included in the analysis. The FJS-12 score of the analyzed subjects was 75 points. Poor psoas major muscle quality was associated with a poor group of patients scoring <50 on the FJS-12. This association was independent of the adjustment factors. However, the quantity of psoas muscle was not associated. CONCLUSIONS: The quality of the psoas major muscle is associated with FJS-12. In the rehabilitation of patients undergoing THA, focusing on the quality of the psoas major muscle may help achieve the ultimate goal.