A cup component of an orthopaedic joint prosthesis comprises a hollow shell wherein the head part of a mating component of the joint can be received. The shell has a flange at its open face extending around at least part of its periphery with at least two major threaded bores extending through the flange. The flange also provides at least one minor threaded bore, wherein the diameter of the minor bore is less than that of the major bores and the pitch of the thread in the minor bore is less than that of the thread in the major bores. The cup component includes at least two fixation screws whose shanks have approximately equal diameters, each of which is threaded on its external surface (i) to engage the thread a respective one of the bores in the shell flange, and (ii) to threadingly engage the bone, and a temporary screw having a self-drilling tip for forming a bore in a bone, and a diameter and a thread which are suitable for threadingly engaging the thread in the minor bore.