Large Diameter Heads Can Be Anatomically Contoured for Soft-Tissue Relief Without Affecting Their Contact Area

IntroductionLarge diameter femoral heads provide increased range-of-motion and reduced dislocation rates compared to smaller diameter femoral heads. However, several recent studies have reported that contemporary large head prostheses can directly impinge against the local soft tissues leading to anterior hip pain. To address this we developed a novel Anatomically Contoured large diameter femoral Head (ACH) that maintains the profile of a large diameter femoral head over a hemispherical portion and then contours inward the distal profile of the head for soft-tissue relief. We hypothesized that the distal contouring of the ACH articular surface would not affect contact area. The impact of component placement, femoral head to acetabular liner radial clearance, and joint loading during different activities was investigated.MethodsA finite element model was used to assess the femoroacetabular contact area of a 36 mm diameter conventional head and a 36 mm ACH (Fig. 1). It included a rigid acetabular shell, pla...