Abstract: A cementless acetabular implant intended for use in instances of a bony defect in the pelvis at the acetabular cavity requiring substantial rebuilding of the acetabulum by use of bone graft material. It includes a substantially rigid metallic hemispherically shaped support cup for contiguous reception with the bone within the acetabular cavity. A flange extends outwardly from a peripheral rim of the support cup for supportive engagement on bone stock located beyond the acetabular cavity. The flange also serves to contain the bone graft material. The outer convex surface of the support cup is porous, as is a medial surface of the flange, to accept bone ingrowth. A bearing insert of low friction material for receiving the ball of a femoral prosthetic component is mounted in contiguous engagement with an inner surface of the support cup.