TAPERED DESIGN FOR THE CEMENTLESS TOTAL HIP-ARTHROPLASTY FEMORAL COMPONENT

The long term behavior of total hip arthroplasty ultimately is determi ned by adaptive bone remodeling. Stress adaptation creating various de grees of metaphyseal bone atrophy has occurred with prostheses designe d for tight distal fit and fill. This phenomenon has been explained as bone adaptation resolving the conflict between femoral component stif fness and bone flexibility. However, clinical observations indicate th at a different premise may be operational when prostheses with tapered geometries are used. The results of four published reports (748 arthr oplasties) using cementless femoral components of a tapered design wer e reviewed. The review found a low incidence of aseptic loosening (0.5 %) and significant thigh pain (0.5%), and a radiographic incidence of proximal bone atrophy of 6%. In no case was the metaphyseal bone atrop hy described as severe or extensive. These findings challenge the prem ise that reactive bone adaptation is related to the issues of femoral component stiffness exclusively and propose that femoral component geo metry may have an influence on bone adaptation.