The Influence of the Pelvic Bone on the Computational Results of the Acetabular Component of a Total Hip Prosthesis

The computational models developed to evaluate the hip joint performance usually neglect the presence of the pelvic bone. However, deformation depends on the stiffness of the underlying bone, and thus, the inclusion of the pelvic bone in the model influences the computed contact pressure and wear. This work discusses the influence of the pelvic bone, and how it depends on the acetabular component stiffness. It was modeled as two different polyethylene acetabular cups, considering or not a metal-backing for both 28 mm and 32 mm diametric cups. Two finite element models are developed, considering either the acetabular component rigidly fixed or attached to the deformable bone. Results present 28% and 42% difference on the contact pressure for a polyethylene cup without metal-backing when the support conditions are changed, for the 28 mm and 32 mm cups, respectively. Linear wear results present 21% and 31% difference for the same type of cups of 28 mm and 32 mm, correspondingly. The numerical results obtained in the present work show that to model the pelvic bone of the patient with a metal-backed cup did not greatly affect contact pressures and linear wear. However, when a total hip replacement is performed with an all-polyethylene acetabular cup, the presence of the pelvic bone in the model has a major influence.