Acetabular revision with a modular anti-protrusio acetabular component.

Current anti-protrusio cages are non-porous-coated and 1 piece and they require liner cementation. These factors limit bone ingrowth, trials, and modularity. Results of a completely modular porous-coated anti-protrusio component (MAPC) are presented. Sixty-three acetabular revisions with MAPC were performed from 1998-2001 by 2 surgeons. Average follow-up was 29 months (range, 24-50). 30/63 (48%) had Paprosky type 3A or B defects. 55/63 (87%) MAPCs remain in place. Four components were removed for infection, 3 for loosening, and 1 for malposition. Eight hips dislocated, requiring 6 reoperations. Two MAPCs are radiographically loose but asymptomatic. At short-term follow-up, these results are comparable to conventional 1-piece anti-protrusio cages. Advantages include the potential for bone ingrowth and long-term fixation, surgical technique similar to large hemispherical components, ability to trial, and modularity.