Twelve anatomical values of the proximal femur and theirs variations in rotation (internal 12 degrees, neutral, external 12 degrees) have been measured radiologically by digitalization on a group of ten anatomical units. A computerized analysis has been performed considering the errors in the X-ray amplification and dispersion factors, as well as the methodological imprecisions. It came out that, except for the width of the medullary canal in AP view, all anatomical parameters were very sensitive to the different positions of the femur in rotation and were subject to significant variations. These fluctuations lead the authors to the following conclusion: during the pre-operating planning of cementless hip arthroplasties, the radiology still allows to choose the size of the femoral component so as to improve the fitting with the internal geometry of the femur. However, the radiology still remains insufficient as a basis to conceive and design a custom implant.