STRESS ANALYSIS OF POROUS INGROWTH HIP SURFACE REPLACEMENTS.

We examined three new interfaces for porous ingrowth hip surface replacements using linear and nonlinear contact finite element analysis. The results indicate that a flatter interface than is usually used, similar to the epiphyseal line, may improve surface replacement longevity. In addition we find that linear analysis of the pressure at the prosthesis-bone interface gives significantly different results than does an analysis which models the interface as a slip surface. This means that the stress patterns at the interface immediately post-implantation, before bony ingrowth occurs, can not be accurately determined from a simple linear analysis.