Relative Femoral Neck Lengthening in Legg-Calvé-Perthes Total Hip Arthroplasty

BACKGROUND: Total hip replacement (THR) in patients with a history of Legg-Calvé-Perthes disease can be a technically challenging procedure due to the distorted hip morphology. We propose a technique in which THR is preceded by a modified relative femoral neck lengthening (RFNL) procedure. Hereby, we aim to restore the biomechanical parameters. METHODS: Twenty-eight patients underwent RFNL in preparation of a second-stage THR between December 2011 and September 2019. The mean age was 38.1 ± 11.4 years. Radiographs were analyzed for centrotrochanteric distance, lateral displacement of the greater trochanter, and leg length discrepancy to assess the biomechanical restoration. Complication rate, reoperation rate, and patient-reported outcome measures were measured. RESULTS: Mean centrotrochanteric distance increased from −18.7 ± 6.7 mm preoperatively to 1.9 ± 9.0 mm (P < .001) after RFNL and to 11.4 ± 10.4 mm after THR (P < .001). Mean lateral displacement of the greater trochanter increased from 34.2 ± 8.1 mm preoperatively to 42.4 ± 5.2 mm (P < .001) after RFNL and to 49.9 ± 8.3 mm after THR (P < .001). Leg length discrepancy decreased from 17.5 ± 10.5 mm to 2.7 ± 2.2 mm after THR (P < .001). Mean Harris Hip Score improved from 56.9 ± 17.6 preoperatively to 89.4 ± 10.7 at the latest follow-up (P < .001). Eight patients (8 hips) postponed THR because of sufficient clinical improvement, at a mean follow-up of 4.2 ± 2.1 years. Two hips needed a revision RFNL due to non-union (7.1%), and 1 hip replacement was revised due to a deep infection (5.0%). CONCLUSIONS: RFNL prior to THR in patients with end-stage osteoarthritis following Legg-Calvé-Perthes disease allows for utilizing regular implants with straight access to the femoral canal, with restored biomechanics and restoration of leg length. The prominent overhanging greater trochanter is reduced to prevent postoperative extra-articular impingement.