Computer Assisted Planning, Simulation and Navigation of Periacetabular Osteotomy

Periacetabular osteotomy (PAO) is an effective approach for surgical treatment of hip dysplasia in young adults. However, achieving an optimal acetabular reorientation during PAO is the most critical and challenging step. Routinely, the correct positioning of the acetabular fragment largely depends on the surgeons experience and is done under fluoroscopy to provide the surgeon with continuous live x-ray guidance. To address these challenges, we developed a computer assisted system. Our system starts with a fully automatic detection of the acetabular rim, which allows for quantifying the acetabular 3D morphology with parameters such as acetabular orientation, femoral head Extrusion Index (EI), Lateral Center Edge (LCE) angle, total and regional femoral head coverage (FHC) ratio for computer assisted diagnosis, planning and simulation of PAO. Intra-operative navigation is used to implement the pre-operative plan. Two validation studies were conducted on four sawbone models to evaluate the efficacy of the system intra-operatively and post-operatively. By comparing the pre-operatively planned situation with the intra-operatively achieved situation, average errors of 0.6◦ ± 0.3◦, 0.3◦ ± 0.2◦ and 1.1◦ ± 1.1◦ were found respectively along three motion directions (Flexion/Extension, Abduction/Adduction and External Rotation/Internal Rotation). In addition, by comparing the pre-operatively planned situation with the post-operative results, average errors of 0.9◦ ± 0.3◦ and 0.9◦ ± 0.7◦ were found for inclination and anteversion, respectively.