Preoperative Quadriceps Muscle Quality Predicts Early Ambulation After Hip Fracture Surgery.

Abstract

To investigate whether preoperative muscle characteristics measured on CT scans could predict early ambulation capacity after hip fracture surgery. Design: Retrospective cohort study. Single Level I academic trauma center. Patients aged ≥55 years who underwent surgical fixation for hip fractures (OTA/AO types 31A, 31B) between January 2015 and December 2024 were included. Inclusion required preoperative CT imaging and documented ambulation assessments at postoperative day 1 (POD1) and discharge. Patients with neuromuscular disorders affecting muscle mass were excluded. Primary outcome was distance walked (feet) during physical therapy at POD1 and discharge. Preoperative CT scans were opportunistically analyzed for muscle quality (Hounsfield Units, HU) and size (cross-sectional area, CSA) in psoas, gluteal, and quadriceps muscles. Associations were analyzed using linear mixed-effects models adjusted for BMI, Charlson Comorbidity Index, pre-injury wheelchair use, time to surgery, and fixation method. 140 patients (mean age 75±8 years, 59% female) contributed 210 ambulation observations. Ambulation improved from 0 (IQR 0-20) feet at POD1 to 20 (IQR 0-86) feet at discharge (p<0.001). In the fully adjusted mixed-effects model, quadriceps quality was the only muscle metric that independently predicted ambulation (β=0.042, 95% CI: 0.012-0.072, p=0.007; marginal R2=0.272). Among clinical covariates, higher BMI was associated with reduced ambulation (β=-0.060, p=0.029); Charlson Index was not significant (β=-0.062, p=0.189). No other muscle quality (gluteus medius, gluteus maximus, psoas; all p>0.16) or size metric (all p>0.33) reached significance. In patients after hip fracture surgery: Preoperative quadriceps muscle quality was the primary muscle-based predictor of early postoperative ambulation. Muscle quality outperformed size in predicting early functional recovery. Opportunistic CT-based HU assessment identified patients at risk for limited early mobilization. Therapeutic Level III.