An acetabular cup 10 comprises an inner articulating surface 14 having a polar axis 26, an arcuate outer surface 12, an annular rim 16 there between, and at least one elongate passage 22 which extends from the rim 16 to the outer surface 12. A longitudinal extent of the said at least one passage 22 extends in a direction which is non-parallel with the polar axis 26. The said at least one passage 22 may in part define a slot in the outer surface.
