Computer-assisted femoral head reduction osteotomies an approach for anatomic reconstruction of severely deformed Legg-Calvè-Perthes hips

Abstract

Background: Legg–Calvé–Perthes (LCP) is a common orthopedic childhood disease leading to a deformity of the femoral head and to an adaptive deformity of the acetabulum. The altered joint biomechanics can result in early joint degeneration requiring total hip arthroplasty. In 2002 Ganz et al. introduced the femoral head reduction osteotomy (FHRO) as a direct joint-preserving treatment. The procedure remains one of the most challenging in hip surgery. Computer-based 3D preoperative planning and patient-specific navigation instruments have been successfully used to reduce technical complexity in other anatomies. The goal of this study was to evaluate the feasibility and anatomic reconstruction of such an approach for FHRO. Methods: In this pilot study 6 LCP patients were treated by FHRO in multiple centers between May 2017 and June 2019. Based on patient-specific 3D models of the hips, the surgeries were simulated in a step-wise fashion. Patient-specific intstruments tailored to FHRO were designed 3D-printed and used in the surgeries for navigating the osteotomies. The results were assessed radiographically and time and costs recorded. Results and Interpretation: The clinical feasibility of our approach for FHRO surgery has been demonstrated. The results showed significant improvement compared to the preoperative situation. The sphericity index improved postoperatively by 20% (p=0.028), the postoperative head diameter differed by only 1.8% (p = 0.043) from the contralateral side and Stulberg classification improved from 4.33 poor coxathrosis outcome to 1.5 good outcome (p = 0.026). The average time (minutes) for preliminary analysis, computer simulation, and patient-specific instrument design was 63 (±48), 156 (±64), and 105 (±68.5), respectively. All operations were performed by experienced surgeons, still three complications occurred, showing that FHRO remains one of the most complex hip surgeries, even with computer assistance; however none was directly related to simulation or navigation technique.