Finite Element Analysis of Normal and Dysplastic Hip Joints in Children

From a surgical point of view, quantification cannot always be achieved in the developmental deformity in hip joints, but finite element analysis can be a helpful tool to compare normal joint architecture with a dysplastic counterpart. CT scans from the normal right hip of an 8-year-old boy and the dysplastic left hip of a 12-year-old girl were used to construct our geometric models. In a three-dimensional model construction, distinctions were made between the cortical bone, trabecular bone, cartilage, and contact nonlinearities of the hip joint. The mathematical model incorporated the consideration of the linear elastic and isotropic properties of bony tissue in children, separately for the cortical bone, trabecular bone, and articular cartilage. Hexahedral elements were used in Autodesk Inventor software version 2022 ("Ren") for finite element analysis of the two hips in the boundary conditions of the single-leg stance. In the normal hip joint on the cartilaginous surfaces of the acetabulum, we found a kidney-shaped stress distribution in a 471,672 mm² area. The measured contact pressure values were between 3.0 and 4.3 MPa. In the dysplastic pediatric hip joint on a patch of 205,272 mm² contact area, the contact pressure values reached 8.5 MPa. Furthermore, the acetabulum/femur head volume ratio was 20% higher in the dysplastic hip joint. We believe that the knowledge gained from the normal and dysplastic pediatric hip joints can be used to develop surgical treatment methods and quantify and compare the efficiency of different surgical treatments used in children with hip dysplasia.