Preoperative Quadriceps Muscle Quality Predicts Early Ambulation After Hip Fracture Surgery

OBJECTIVES: To investigate whether preoperative muscle characteristics measured on CT scans could predict early ambulation capacity after hip fracture surgery. METHODS: Design: Retrospective cohort study. Setting: Single Level I academic trauma center. Patient Selection Criteria: 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. Outcome Measures and Comparisons: 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. RESULTS: 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 R 2 =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. CONCLUSION: 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.