Midterm Results Of Flanged Acetabular Cup Used In Severe Acetabular Defects

BACKGROUND: Revision hip arthroplasty complicated by massive acetabular defects and/or pelvic discontinuity has remained difficult to manage, with no definite option to produce predictable results. Acetabular cages and reinforcement rings have high failure rates because of lack of biological fixation. Custom triflange cups are economically demanding like cup-cage constructs, and require time to be fabricated. Cementless acetabular cup having an ischial hook and three iliac flanges is a technically simple but effective option to be used in such situations. QUESTIONS/PURPOSES: We sought to determine (1) mid-term Kaplan-Meier survival; (2) clinical outcomes based on HSS and WOMACscores; (3) radiological outcomes based primarily on component migration; (5) mean operative time and (4) the complication rate for a series of 18 procedures. METHODS: We conducted a retrospective review of all the revision hip arthroplasty procedures performed between January 2013 and May 2015 and identified 18 procedures in 18 patients where a cementless porous-coated hemispherical cup (Combicup-R, Link) was used. According to AAOS classification, 8 of the 18 (44%) acetabuli had Type 3 defect and 10 of 18 (56%) acetabuli had Type 4 defect. Structural bone allografts were used in 7 cases and all cases required morsellized allograft. The minimum followup was of 49 months and average was of 58 months (range, 49–67 months; SD, 34.3). Postoperative clinical evaluation was done at 6 weeks, 3, 6, and 12 months, and annually thereafter. HSS and WOMAC scores were recorded at follow up and radiographs were taken. Serial radiographs were compared with the 6-week postoperative radiographs to evaluate for component loosening/migration and structural graft resorption. RESULTS: The 6-year Kaplan-Meier survival rate with revision for any cause representing failure was 93% (95% confidence interval [CI], 83.1–97.4). HSS and WOMAC score improved significantly from a preoperative value of 54 and 43 respectively to 87 and 85 postoperatively (p < 0.001). One patient had resorption of structural allograft and subsequent cup migration, which needed re- revision surgery. CONCLUSIONS: Porous coated acetabular cup supplemented with flanges and hooks is a suitable option to treat severe acetabular defects and pelvic discontinuity in acetabular revision reconstructions, than cages which do not provide biological fixation. Compared to custom triflange cups, they are more economical, technically easier to implant and do not require any waiting period to be fabricated.