Computer assisted planning of periacetabular osteotomy with biomechanical optimization: Constant thickness cartilage models vs. patient-specific cartilage models

Abstract

Periacetabular osteotomy (PAO) is an effective approach for surgical treatment of hip dysplasia in young adults. The aim of PAO surgery is to increase acetabular coverage of the femoral head and to reduce contact pressures by reorienting the acetabulum fragment during PAO. The success of PAO significantly depends on the surgeon’s experience. Previously, we have developed a computer assisted planning and navigation system for PAO, which allows for not only quantifying the 3D hip morphology with geometric parameters such as acetabular orientation (expressed as inclination and anteversion angles), lateral center edge (LCE) angle and femoral head coverage for a computer assisted diagnosis of hip dysplasia but also virtual PAO surgical planning and simulation. In this paper, we extend our system with a patient-specific 3D finite element (FE) model to estimate the optimal acetabulum reorientation for planning PAO. One key factor that may influence the biomechanical optimization results is the cartilage models used in the FE simulation. In the literature, both constant thickness cartilage models and patient-specific cartilage models have been suggested. Another contribution of our paper is the investigation of the effect of these two different cartilage models on the biomechanical optimization results. Regression analysis showed that the results obtained by the constant thickness cartilage models are significantly correlated with those obtained by using the patient-specific cartilage models. Furthermore, biomechanical optimization-based planning of PAO using these two different cartilage models achieved the same optimal orientations.