A need for functionally graded stiffness femoral stem for reduction in stress shielding and promoting bone growth: Computational analysis

Abstract

Total Hip Arthroplasty (THA) is an orthopaedic procedure that is available to reduce pain and restore the functionality of hip joints. THA has been successfully implemented for the last 40 years. However, after more than 40 years of design and implementation, premature loosening of the femoral stem still occurs due to the stress shielding. Stress shielding can be reduced by using implants with lower stiffness. This however, could increase the micromotion and interface debonding between the stem and femur bone. The aim of this study is to investigate stress and micromotion distribution across the length of the stem and to develop a bone in growth simulation model. To achieve this, a bone growth mechano-regulation algorithm based on deviatoric strain was applied to study the tissue differentiation process. The initial outcome of the study indicates that the stiffness of the implant should not be uniform rather graded from the distal to proximal and lateral to medial directions of the implant. With such graded stiffness, bone growth density was possible across the entire length of the stem, hence reducing aseptic loosening due to stress shielding. Copyright 2017 ASME.