Radiographic Predictors of Leg Shortening After Curved Intertrochanteric Varus Osteotomy in Osteonecrosis of the Femoral Head.

Purpose: Curved intertrochanteric varus osteotomy (CVO) is a joint-preserving option for young patients with osteonecrosis of the femoral head (ONFH), but postoperative leg length discrepancy (LLD) remains a concern. This study investigated factors associated with leg shortening in both the early postoperative phase (P1) and the healing phase until bone union (P2).

Methods: This retrospective study included 48 patients (51 hips) with non-traumatic ONFH who underwent CVO. Radiographic evaluations were performed preoperatively, immediately postoperatively, and at bone union. Pearson's correlation coefficient was used to correlations between radiographic parameters and leg shortening in P1 and P2. Patients were divided into groups based on whether leg shortening ≥ 5 mm was observed in each phase, and statistical comparisons were conducted. Multivariate logistic regression analyses were performed to identify independent risk factors for leg shortening ≥ 5 mm.

Results: Leg shortening ≥ 5 mm occurred in 17.6% of hips in P1 and 47.1% in P2. Lateral shift of the osteotomy arc center correlated with leg shortening in P1 (r = 0.689, p < 0.0001). Varus angle and changes in femoral anteversion were also correlated in both P1 and P2 (P1: r = 0.362/0.322; P2: r = 0.404/0.754, all p < 0.05). Greater varus angle and lateral/distal shift of the osteotomy center were significantly associated with P1 shortening. In P2, greater changes in femoral anteversion, increased osteotomy distance from the midpoint of the lesser trochanter, and larger varus angle were significant factors. Multivariate analysis identified lateral shift of the osteotomy center as an independent predictor in P1 (OR, 1.30; 95% CI, 1.06-1.81; p = 0.004). In P2, change in femoral anteversion was an independent predictor of leg shortening ≥ 5 mm (OR: 1.24, 95% CI: 1.07-1.51; p = 0.003).

Conclusion: Leg shortening post-CVO progresses during surgery and bone healing. Careful surgical planning and postoperative management, particularly in cases requiring extensive varus correction or anteversion changes, is essential for minimizing LLD and optimizing outcomes.