Virtual Bernese osteotomy using three-dimensional computed tomography in hip dysplasia

Background Accurate assessment of acetabular morphology and its relationship to the femoral head is essential for planning a periacetabular osteotomy. We observed the acetabular coverage after virtual Bernese osteotomy using computer-aided technique. Methods Three-dimensional computed tomography of 18 normal hips and 3 symptomatic dysplastic hips were analyzed. Through the center of the femoral head, vertical images were obtained at 10 degrees intervals from 0 degrees to 180 degrees of rotation, using multiplanar reformation technique. Subsequently we measured 19 center-edge angles (CEAs) from each acetabulum. Four types of virtual osteotomy were performed on the three dysplastic hips. The adequacy of acetabular coverage after osteotomy was determined by comparing CEAs after correction with normal CEAs. Results Pearson correlation coefficients between the CEAs measured from normal cases and postoperative cases after lateral rotation of osteotomized fragments were 0.906 in case 1, 0.975 in case 2, 0.976 in case 3. Additional anterior rotation increased anterior acetabular coverage and simultaneously decreased posterior coverage in all three cases. Conclusion Computer-aided virtual surgery technique based on three-dimensional computed tomography information enabled acetabular coverage to be quantified preoperatively in Bernese osteotomy. Lateral rotation of osteotomized acetabular fragments improved anterior and posterior coverage as well as lateral coverage.