The role of impaction grafting: the when and how.

The challenges of acetabular revision include bone loss and poor bone biology. Favorable 10-year reports exist of uncemented acetabular revision using hemispherical uncemented sockets. In the presence of bone stock deficiency, adjunctive morsellized impaction bone grafting is a recognized means of restoring bone stock. We attempt to restore bone stock with impaction grafting beneath a cementless cup for contained defects, defects that can be rendered contained, and whenever there is capacity for rim fixation. The technique of bone graft preparation is important. We use a mixture of bone milling and bone chips of various sizes. Morsellized allograft is inserted, packed, and/or reverse reamed into any defects. The reconstruction relies on the ability to gain biological fixation of the component to the underlying host bone. This requires intimate host bone contact and rigid implant stability. The fixation is therefore augmented with screws in all cases. It is important to achieve host bone contact in a least part of the dome and posterior column. When this is possible, and particularly when there is a good rim fit, we have not found it absolutely necessary to have contact with host bone over >50% of the surface. Stability of primary fixation is a better predictor of outcome than volume of graft or percentage of host bone contact. The advantages of bone grafting in acetabular reconstruction include the ability to restore bone stock, rebuild a normal hip center and hip biomechanics, and increase bone stock for future revisions.