Torsional Fixation of the Femoral Component in Cementless Total Hip Arthroplasty: Newly Designed Funnel Shape Femoral Component

Rotational stability of the femoral component is now regarded as the most important factor in the minimization loosening in artificial hip joints. In this study, we report the development of a new type of femoral component from which excellent rotational stability is expected. The design of the new Jikei total hip funnel shape femoral component is characterized by the curvature of the proximal part of the stem being the same on both the lateral and medial sides. By fitting the shape of the stem so that its greatest diameter fits snugly into the greatest diameter of the proximal femoral canal, excellent rotational stability is obtained. Using the finite element method (FEM), we compared the rotational stability of this component with that of other femoral component designs. In the newly designed Jikei femoral component stem, the rotational stresses were distributed to the cortical bone, with less stress concentration being transmitted to the cancellous bone in the middle portion of the stem and without the occurrence of micromotion. Superior rotational stability was found in this extended breadth funnel-shaped stem.