a plurality of canine acetabular cups designed to fit within different sized spherical reamed bone cavities to produce controlled interference without use of cements , screws or nails . each of the canine acetabular cups , regardless of size , mates with a common femoral head , providing interchangeability . the controlled interference is obtained through use of a multiple curvature ti — al — v shell having a porous coating . the interference starts from zero at 50 degrees from the apex of the shell and extends to full interference value at 90 degrees from the apex . the ti — al — v shell carries a uhmw polyethylene insert , which is locked by interference , a non - circular post mated with an elongated opening and a circumferential locking groove mated with an interior projection . initial stability is provided immediately after surgery due to the interference arrangement ; long term stability is afforded by bone ingrowth .