Abstract: The invention relates to a femoral prosthesis part, the metaphyseal part of which comprises a series of geometric sections (SA to SG) which are disposed in parallel to the transverse plane at equidistant levels. The aforementioned geometric sections are provided with a quadrilateral shape having strongly rounded summits. The two long sides of said sections converge in the medial direction and each section lies inside a geometric quadrangle which is located in the plane. The four sides of said quadrangle intercept, respectively, four geometric lines (m, l, a, p) which are obtained by projecting the profiles of the internal surface of the cortical bone. The above-mentioned geometric sections pivot in relation to one another in internal rotation from the bottom upwards in order to obtain the desired helitorsion angle.