Pre-operative Surgical Simulation Of An Acetabular Press Fit: Assembly Strains In Bone

Abstract

An idealized axisymmetric finite element model of the acetabulum and acetabular implant was analyzed. The assembly strains induced in the bone by the press fit insertion of an oversized cementless acetabular implant were examined. The interaction between implant and bone was modeled as a nonlinear contact-coupled interface to simulate the actual process of press fitting the oversized implant into the prepared acetabular bone bed.

INTRODUCTION
Initial implant stability of the cementless acetabular implant is commonly achieved by press fitting oversized acetabular components. Implicit in this concept is “pre-straining” of the bone which must occur at the time of implantation. Assembly strains are expected to be very different in both magnitude and direction from the strains induced by normal joint forces. and can greatly change the mechanical environment and load transfer patterns. The mechanical consequences of an interference fit and the development of these assembly strains in bone are critical to our understanding of both the biologic response of bone to mechanical stimuli and the way in which the bond implant construct may be modeled. The purpose of this study was to determine the effect of the amount of press fit and the size of the implant on the magnitude of resultant assembly strains.