The Double-Cup Construct: A Novel Treatment Strategy for the Management of Paprosky IIIA and IIIB Acetabular Defects.

BACKGROUND: Treatment of massive acetabular bone loss in revision total hip arthroplasty is complex, and various treatment strategies have been described. We describe a novel technique of using a Trabecular Metal Revision Shell as a buttress augment creating a "double-cup" construct rather than the use of custom triflanges or cup-cage constructs for Paprosky types IIIA and IIIB acetabular defects.

METHODS: We retrospectively reviewed 20 double-cup cases at a mean of 2.4 years follow-up at a single institution between 2005 and 2014. We evaluated postoperative radiographic evidence of acetabular loosening and complication rates, restoration of hip center of rotation, preoperative and postoperative modified Harris Hip Score, and Merle d'Aubigne-Postel pain and walking scores.

RESULTS: There were no revisions for acetabular loosening and no cases of aseptic loosening. We observed a 25% dislocation rate, which was the most common complication. Most dislocations occurred within the first year after surgery and most were acetabulum only revisions. Hip center of rotation was restored to an average of 22.5 mm within the interteardrop line. Average Harris Hip Score improved from 28.2 to 68.7 (P < .001) and Merle d'Aubigne-Postel pain and walking scores improved from 2.7 to 5.1 and 2.4 to 4, respectively (P < .001).

CONCLUSION: The double-cup construct is a reliable option for reconstruction of Paprosky type IIIA and IIIB acetabular defects with no cases of acetabular loosening both clinically and radiographically at a mean of 2 years follow-up. The most common complication was dislocation in the acetabulum-only revisions, and clinical outcome measures were reliably improved in surviving cases.