A retrospective review of 25 patients who underwent 28 acetabular revisions with the Burch-Schnieder antiprotrusio cage (Protek, Berne, Switzerland) and cancellous allograft bone was performed. Follow-up periods averaged 33 months. Patients had averaged 2.1 prior operations per hip. Twenty-two hips had American Academy of Orthopaedic Surgeons type III (combined segmental and cavitary bone loss) acetabular deficiency. Five hips had type II (cavitary bone loss) and one hip had type I (segmental bone loss) acetabular deficiency. After surgery, 80% of the patients had mild or no pain and 80% functioned as at least a community ambulator. Radiographic analysis included a detailed study of implant migration and the degree to which the hip center and bone stock were restored. Significant component migration was documented in 14% of the acetabular reconstructions. The hip center was improved from a preoperative side-to-side difference of 12.5 mm to 4.9 mm at final evaluation (P = .01). Average medial wall bone stock was improved from 1.9 mm before surgery to 10.1 mm postrevision (P < .01). No patients required revision of the antiprotrusio cage for problems related to the acetabular reconstruction. For failed acetabular components associated with moderate to massive bone loss, the antiprotrusio cage reliably reconstituted the hip joint center and acetabular bone stock. The short-term incidence of mechanical loosening parallels that of previously reported acetabular reconstruction techniques.