Preoperative Quadriceps Muscle Quality Predicts Early Ambulation after Hip Fracture Surgery

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Abstract
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: The primary outcome was distance walked (feet) during physical therapy at POD1 and discharge. Preoperative CT scans were opportunistically analyzed for muscle quality (Hounsfield units) and size (cross-sectional area) in psoas, gluteal, and quadriceps muscles. Associations were analyzed using linear mixed-effects models adjusted for body mass index, Charlson Comorbidity Index, preinjury wheelchair use, time to surgery, and fixation method. RESULTS: A total of 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 body mass index 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 Hounsfield units assessment identified patients at risk of limited early mobilization. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

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