Deformation of Press-Fit Metal Acetabular Components following Impaction into Physiologically Relevant Models

INTRODUCTION For a stable uncemented acetabular shell or monoblock cup post implantation, the acetabula cavity is reamed to a smaller diameter (up to 4 mm) than that of the component, resulting in an interference fit [1]. Press-fit cups and shells have a range of porous coatings on their outer surface to promote bone ingrowth which support long-term stability. A number of previous FE and experimental studies [2, 3] have reported that if the components experience a pinching force, due to varying support from the underlying cavity, their diametrical deformation following insertion is measurable. However a limitation of these studies has been their use of uniform polyurethane foam blocks to mimic the human acetabulum. In this study CT scans of the pelvis were used to develop cup and shell impaction models, where the definition of appropriate non-uniform material properties, realistic bony support and physiologically relevant implant methods was implemented.