Structural Allograft Supporting a Trabecular Metal Cup Provides Durable Results in Complex Revision Arthroplasty

Background: Revision total hip arthroplasty (THA) is challenging specially in the presence of severe acetabular bone deficiency. We report the use of a highly porous revision shell augmented by structural allograft to provide structural support and coverage to the acetabular component. Methods: We identified 56 patients (58 hips) undergoing revision THA, where a trabecular metal revision cup was supported by structural allograft. Mean follow-up was 5.4 years (range 2-12 years). Preoperatively acetabular bone defects were classified as Paprosky 2A in 6 hips (10%), 2B in 12 hips (21%), 2C in 12 hips (21%), 3A in 11 hips (19%), and 3B in 17 hips (29%). Structural allograft configuration was classified as type 1 (flying buttress) in 13 hips, type 2 (dome support) in 23 hips, and type 3 (footings) in 17 hips, with 5 hips having combined configurations. Results: All hips showed evidence of union between the allograft and host bone at latest follow-up, 14 hips had partial resorption of the allograft that did not affect cup stability. Three acetabular components demonstrated failure of ingrowth. Survivorship-free from radiographic acetabular loosening as end point was 94% at 5 years. The 5-year survivorship with revision for any reason as end point was 90%. Conclusion: Trabecular metal shells combined with structural bone allograft in revision THA demonstrate excellent midterm survival, with 94% of acetabular components obtaining stable union onto host bone at 5 years. Allograft restored bone stock with minimal resorption, and when it occurred did not alter the survivorship of the acetabular component.