Custom Acetabular Cages Offer Stable Fixation and Improved Hip Scores for Revision THA With Severe Bone Defects

Background: Revision THA is particularly challenging in hips with severe acetabular bone loss. When the extent or geometry of the acetabular bone loss precludes more-straightforward techniques such as jumbo hemispheric cementless shells, reconstruction with morselized allograft protected by a custom cage may offer an alternative, but, to our knowledge, few series have reported on results with this approach.

Questions/purposes: For patients with severe (Paprosky IIIB) defects, we asked: do individualized custom cages result in (1) improved Harris hip scores; (2) restoration of hip center; and (3) a low incidence of surgical complications?

Methods: Twenty-six patients (26 hips) with a massive acetabular defect were involved in this study from 2003 to 2013. During this period, one patient was lost to followup and one died, leaving 24 patients (eight males, 16 females) in this retrospective analysis. The customized cages were individualized to each patient's bone defect based on rapid-prototype three-dimensional printed models. Mean followup was 67 months (range, 24-120 months). Harris hip scores were assessed before surgery and at each followup. Postoperative radiographs were evaluated for cage position, migration, and graft incorporation. Complications and reoperations were assessed by chart review.

Results: The mean Harris hip score improved from 36 (SD, 8; range, 20-49) to 82 (SD, 18; range, 60-96) (p < 0.001). Individualized custom cages resulted in generally reliable restoration of the hip center. No rerevisions have been performed. None of the cups showed radiographic migration, but one cage was believed to be loose, based on a circumferential 2-mm radiolucent line. Cancellous allografts appeared to be incorporated in 23 of 24 patients. One deep infection and one superficial infection were observed and treated with irrigation, débridement, and vacuum-sealing drainage. One dislocation and one suspected injury of the superior gluteal nerve also were observed and treated conservatively.

Conclusions: Individualized custom cages using rapid prototyping and three-dimensional printing appeared to provide stable fixation and improved hip scores at short-term followup in this small, single-center series. As further improvements in the design and manufacturing process are made, future studies should evaluate larger patient groups for longer times, and, ideally, compare this approach with alternatives for these complex bone defects.

Level Of Evidence: Level IV, therapeutic study.