Acetabular defect classification and surgical reconstruction in revision arthroplasty. A 6-year follow-up evaluation.

From 1982 to 1988, 147 cemented acetabular components were revised with cementless hemispheric press-fit components, with an average follow-up period of 5.7 years (range, 3-9 years). Acetabular defects were typed from 1 to 3 and reconstructed with a bulk or support allograft. Type 1 defects had bone lysis around cement anchor sites and required particulate graft. Type 2A and B defects displayed progressive bone loss superiorly and required particulate graft, femoral head bulk graft, or cup superiorization. Type 2C defects required medial wall repair with wafer femoral head graft. Type 3A and B defects demonstrated progressive amounts of superior rim deficiencies and were treated with structural distal femur or proximal tibia allograft. Six of the 147 components (4.0%), all type 3B, were considered radiographically and clinically unstable, warranting revision. Three of the six were revised. Moderate lateral allograft resorption was noted on radiographs, but host-graft union was confirmed at revision. Size, orientation, and method of fixation of the allografts play an important role in the integrity of structural allografts, while adequate remaining host-bone must be present to ensure bone ingrowth.