With 3D CT data of proximal femora it is possible to develop a computer programme for optimising femoral component fit and simulation of implantation. The implantation of the femoral stem can be simulated with any femoral component that has cortical press fit.

Five different currently used femoral components were virtually “implanted” in over 200 different femoral bone data. Optimal femoral fit was defined, when the component showed best diaphyseal and metaphyseal congruent contact with all CT data available. Position of neck and head were secondary, since an optimal press fit situation had priority in our set-up. Best fit was considered taken cortical contact and reconstruction of joint geometry into account.

There were numerous failures in all tested standard components, when correct angle of antetorsion, off-set, and leg length were expected. There were considerably better results with the use of CTX standard prosthesis (CTX-S).

The data of this study indicate a high proportion of less optimal fit with femoral standard components tested in this series. Indication for choosing CTX-S femoral components is dependent upon the individual geometry of dysplastic hip joint and the simulation results of standard components using the VIP method.