Acetabular component revision in total hip arthroplasty. Part I: cementless shells.

Magnitude and location of acetabular bone defects dictate the type of reconstruction required. For the majority of reconstructions, a porous-coated hemispheric shell secured to host bone with multiple screws is the implant of choice. This reconstruction is feasible provided at least 50% of the implant contacts host bone. When such contact is not possible, and there is adequate medial and peripheral bone, techniques using alternative uncemented implants can be used for acetabular reconstruction. An uncemented cup can be placed at a "high hip center." Alternatively, the acetabular cavity can be progressively reamed to accommodate extra-large cups. Oblong cups, which take advantage of the oval-shaped cavity resulting from many failed acetabular components, can also be used. The success of these cementless techniques depends on the degree and location of bone loss and on the presence of pelvic discontinuity.