What is the rate and degree of deformity in femoral diaphyseal nonunion? A CT-based retrospective cohort study

BACKGROUND: This study investigated the rate and degree of deformity in femoral diaphyseal nonunion using preoperative bilateral CT-scans. METHODS: A retrospective cohort study was conducted at a single Level 1 trauma center. Patients aged > 18 years who underwent operative treatment for femoral diaphyseal nonunion between 2015 and 2025 and had preoperative bilateral femur CT-scans were included. Axial, sagittal, coronal, and length differences between the femoral nonunion and the contralateral healthy femur were measured. Torsional deformity ≥ 15° and length discrepancy ≥ 20 mm were considered clinically relevant. Thresholds of ≥ 5° and ≥ 10° were used to identify outliers in coronal and sagittal plane deformity, respectively. RESULTS: Thirty-two patients met the inclusion criteria (median age 57 years, 63% male). Torsional deformity ≥ 15° was present in 10 patients (31%), including internal rotation in 4 (13%) and external rotation in 6 (19%). Sagittal plane deformity ≥ 10° was observed in 5 patients (16%), with apex anterior angulation in 1 (3%) and apex posterior angulation in 4 (13%). Mean sagittal plane angulation was 9.7° ± 6.7° in the affected limb and 12.5° ± 2.6° in the unaffected limb (p = 0.017). Coronal plane deformity ≥ 5° was present in 10 patients (31%), including varus in 8 (25%) and valgus in 2 (6%). Mean coronal angulation was 5.3° ± 6.0° in the affected limb and 3.3° ± 2.5° in the unaffected limb (p = 0.099). Mean femoral length was 439 ± 31 mm in the affected limb and 445 ± 28 mm in the unaffected limb (p = 0.015), with a length discrepancy ≥ 20 mm in 5 patients (16%). CONCLUSIONS: Clinically relevant torsional deformity was present in one in three patients undergoing femoral shaft nonunion surgery, while femoral length discrepancy ≥ 20 mm occurred in one in six. A small but significant decrease in apex anterior angulation was observed, and most coronal plane outliers were in varus. These findings underline the importance of recognizing deformity in femoral nonunion.