Use of 3D Printed Models to Determine Accurate Bone Cuts during a Periacetabular Osteotomy for Developmental Hip Dysplasia

Abstract

AbstractThe periacetabular osteotomy (PAO) is a powerful tool to delay the progression of hip arthritis by reorienting the acetabulum. This study aimed to use three-dimensional (3D)-printed models of the pelvis, reconstructed from the computed tomography (CT) scans of patients, to model how the level of dysplasia and its location ilium osteotomy affect radiographic outcomes following PAO. This pilot study aims to determine if preoperative 3D printing/planning can assist in predicting radiographic outcomes. We performed a retrospective review of five patients with differing levels of hip dysplasia for whom we had obtained CT scans before PAO surgery. For each patient, we printed two pelvis models that would undergo standardized cuts of the PAO procedure, with variations only in the distance of the ilium start point (one-third of the distance between the anterior superior iliac spine and anterior inferior iliac spine [AIIS] vs. two-thirds of the distance). We then mobilized the acetabular fragment into eight reproducible positions in space by moving the ilium cut a combination of 0, 1, or 2 cm anterior/lateral. Each position of the newly realigned acetabula was examined under fluoroscopy to obtain a standardized anteroposterior view, and to obtain standardized radiographic measurements in the form of lateral center edge angle (CEA), acetabular depth, Tonnis angle, and acetabular inclination. We performed 80 simulations of the PAO with varying degrees of acetabular mobilization. On average, in the models where the supra-acetabular cut was closer to the AIIS, we found more significant degrees of radiographic correction, regarding Tonnis angles (12.91 vs. 7.95, p = 0.0175), acetabular inclination (20.25 vs. 9.875, p = 0.027), and lateral CEA (11.75 vs. 2.5, p = 0.061). Patients who had greater dysplasia also had more significant degrees of radiographic Tonnis angle correction with the same mobilization movements of the acetabula (p = 0.005). When utilizing 3D printing to model PAO in dysplasia pelvises, we found that both a higher level of preoperative dysplasia and starting the supra-acetabular osteotomy closer to the AIIS were associated with more powerful corrections following smaller manipulations.