Finite element analyses, 3D-printed guides and navigation system optimizes fragment reorientation for periacetabular osteotomy.

Purpose: Periacetabular osteotomy (PAO) is an effective treatment to correct developmental dysplasia of the hip (DDH). Traditionally, the goal of correction during PAO is based on parameters measured on 2-dimensional images. The aim of the study is to introduce an optimized workflow of PAO in DDH patients by means of personalized correction goal and accuracy of execution.

Methods: Five patients with DDH were prospectively enrolled. Preoperative computed tomography was performed. Surgical planning was done by the treating surgeon and engineers. The planned correction involved reorienting the osteotomized fragment to achieve a target lateral center-edge angle (LCEA) of 25°-40°.The pelvic model with the preoperative and planned correction was analyzed by finite element analysis, which simulated single-leg stance condition. Average and maximal acetabular stresses in different anatomical areas were calculated and are presented as a dashboard at ± 3° increments to help the surgeon determine the ideal correction. To ensure accuracy of the osteotomy and correction as planned, 3D-printed cutting and reorientation guides were used.

Results: Average operation time (101 ± 23 min) and blood loss (651 ± 176 ml) were comparable to previous reports. Radiographic parameters improved significantly, including LCEA (20.0^° ± 6.4^° vs. 30.2^° ± 3.1^°, p = 0.037) and AI (12.5^° ± 3.1^° vs. 0.8^° ± 1.6^°, p = 0.001). The planned correction was similar to the final correction (LCEA planned 31.1^° ± 2.0^° vs. final 30.2^° ± 3.1^°, p = 0.268; AI planned 1.8^° ± 1.5^° vs. final 0.8^° ± 1.6^°, p = 0.349). During an average follow-up period of 1.2 years, all osteotomies healed and these patients reported a significant reduction in mean global pain scale from 70 preoperatively to 23 postoperatively (p = 0.016).

Conclusion: The workflow with FEA simulations to optimize mechanical stress and 3D-printed cutting guides to achieve accurate execution was an effective and safe approach to optimize DDH treatment. Further refinements and further evaluation of navigation systems aimed at obtaining planned correction is necessary.