Classification and reconstruction in revision acetabular arthroplasty with bone stock deficiency.

Revision acetabular surgery with bone stock loss is a difficult problem. Defects are classified into contained cavitary (Type-1) defects and noncontained defects (Type 2A and 2B) based on preoperative radiographs and intraoperative findings. Fifty-four hips with Type-1 defects were treated with morsellized allograft. The overall success rate was 90% at 6.78 year followup. Type-2 defects are reconstructed with structural grafts. Twenty-nine hips with Type-2A defects (the allograft supports <50% of the cup) were reviewed at 7.1 years' followup. The success rate was 90)%. In all but 1 case the allograft united to host bone. No resorption or minor resorption was seen in 26 of 29 hips with minor column structural grafts. Type-2B defects all had structural allografts that supported >50% of the cup. There were 33 hips in this group observed for an average of 7.1 years. The rerevision rate in this group was 45%. However, 7 of 15 hips were reconstructed without additional graft at rerevision. The only factor that was clinically significant for success in Type-2B defects was choice of acetabular component. In hips that received roof rings with cemented cups, the success rate was 100% (excluding 1 infection). The authors support the use of allograft bone in revision acetabular surgery. When structural grafts are required, every attempt should be made to achieve >50% support from host bone. If this is not possible, then a roof reinforcement ring with a cemented cup is the acetabular component of choice.