Trunk Muscle Cross-Sectional Areas at Hip Fractures and Their Association With Recovery of Postoperative Gait Ability: A Multicenter, Retrospective Cohort Study

Abstract

Purpose To determine the relationship between trunk muscle cross-sectional area (CSA) measured using trunk computed tomography at the time of injury and gait ability at discharge. Methods This multicenter retrospective cohort study was performed in comprehensive rehabilitation units of four hospitals in Japan. The study included 442 patients with hip fractures who underwent surgery (bipolar hip arthroplasty or open reduction and internal fixation) and were hospitalized for treatment between January 2020 and January 2023. The main outcome measure was bilateral trunk muscle CSA (multifidus, erector spinae, psoas major, lateral abdominal muscles, and rectus abdominis). Participants who met the eligibility criteria were classified into two groups based on gait ability at the time of hospital discharge: those who maintained their gait ability (the maintenance group) and those who declined (the decline group). Results The CSA of the multifidus muscle was 0.015 ± 0.005 (CSA/Weight/fourth lumbar vertebrae) and 0.013 ± 0.004 (CSA/Weight/fourth lumbar vertebrae) in the maintenance and decline groups, respectively, being significantly lower in the decline group ( P = 0.028, effect size = 0.457). The CSA of the psoas major was 15.3 [13.1⁠–⁠18.0] (CSA/Weight/fourth lumbar vertebrae) and 13.4 [11.9⁠–⁠16.0] (CSA/Weight/fourth lumbar vertebrae) in the maintenance and decline groups, respectively, being significantly lower in the decline group ( P = 0.020, effect size = 0.335). Conclusion Smaller CSAs of the multifidus and psoas major muscles before injury were associated with decreased gait ability after hip fractures.