A description is given of a set of mobile necks for inserting into the stem(2) of a hip prosthesis, in which the said mobile necks are produced withdifferent inclinations and lengths in such a way that their free ends (3i),when inserted in the said stem, terminate at nine mutually equidistant points(Pi) arranged in three parallel horizontal rows (R0) in such a way that thelines joining the outermost points delineate a square (Q), the length of whosesides is approximately 15 mm, the diagonal (D) of this square coinciding withthe axis (H-H) of a mobile neck (1) set at a neutral inclination, that. isneither varus nor valgus, with respect to a plane (.szlig.) essentiallyperpendicular to the axis of the abovementioned stem (2).
