Factors affecting stability of press fit acetubular cups

Press fitting cementless porous coated acetabular components without screw fixation is desirable to minimize debris-related problems. Compression between the bone and periphery of an acetabular component which is slightly larger than the reamed acetabulum provides implant fixation while oversizing at the dome may adversely affect stability. In most primary total hip arthroplasties, the acetabulum can be reamed to a hemispherical cavity and assessed using acetabular sizing trials prior to implanting the cup. Use of an implant with a hemispherical dome and gradual transition to a wider peripheral dimension maximizes peripheral bone strains and implant stability with less impaction force and overall deformation than a larger oversized hemispherical cup.