Modified cups.

Late results of structural allografting of the acetabulum are quite variable. In order to reduce or avoid the necessity for bone grafting, some modified cups have been developed. The deep cup with or without a lateralized polyethylene liner reduces the problem of the protrusio socket. Oblong or bilobed ingrowth cups significantly reduce the need for grafting of the roof-deficient acetabulum. Constrained or capture polyethylene liners are useful in the unstable hip.