Finite element analysis of mechanical stability of ceramic acetabular components and evaluation of ROM in articulating hip joints

Ceramic articular surfaces are now widely used as total hip replacements for young and active patients. However, while the excellent tribological properties and high biocompatibility of ceramic articular surfaces prevent loosening and osteolysis, their high stiffness and low ductility occasionally result in ceramic surface fractures. Therefore, this study investigated the effect of varying the sizes of the acetabular components on the mechanical stability. Three femoral head models and 27 acetabular cup models were designed following three size parameters: ball head diameter (28, 32, and 36 mm), acetabular cup thickness (3, 4, and 5 mm), and liner thickness (9, 10, and 11 mm). For all these models, the mechanical stability was evaluated using 3D finite element analyses. Plus, the motion of the 3 femoral head models was measured in six directions using a motion study. The results showed that the maximum stress was decreased when increasing the sizes of the cup, liner, and femoral head, where the 36 mm ball head, 5 mm cup, and 11 mm liner showed the lowest maximum stress, while the 36 mm femoral head exhibited the largest range of motion. The acetabular cup stability was also shown to be affected by the stiffness of the components, where increasing the head size or thickness of the cup and liner increased the component stiffness and range of motion. Thus, the mechanical simulation demonstrated that increasing the size of the acetabular components decreased the ceramic surface stress and risk of impingement.