AVERAGE 12-YEAR OUTCOME OF A CHROME-COBALT, BEADED, BONY INGROWTH ACETABULAR COMPONENT

Seventy-two hips (67 patients) were reconstructed with the Acetabular Reconstruction Component (ARC, Howmedica, Rutherford, NJ), a chrome-co balt component with sintered ingrowth beads and peripheral flanges for screw fixation. All the materials used in the ARC (metal, porous laye r, and polyethylene) are identical to those used in the Porous Coated Anatomic (PCA) acetabular component (Howmedica), but the design is dif ferent. To determine the importance of design features alone, clinical results obtained with the 2 different designs made of identical mater ials were compared. The average follow-up period for patients with the ARC was 12 years (range, 10-13.3 years). Seven patients (7 hips) with the ARC died prior to the minimum 10-year follow-up period, none havi ng undergone revision procedures. Overall, 3 acetabular components (4% ) in 3 patients were revised, at an average of 8.5 years (range, 7.6-9 .3 years) from the index operation. The reasons for revision were asep tic loosening third-body polyethylene wear observed during a revision for femoral lysis, and acetabular component malposition and recurrent dislocation. The total incidence of acetabular aseptic loosening was 4 % (3 of 72 hips). Pelvic osteolysis occurred in 3 cases (4%). In contr ast, the incidence of acetabular revision of the PCA acetabular compon ent at follow-up periods of 2-10 years is reported to be as high as 11 % (range, 3-11%). Rates of aseptic loosening are as high as 30% (range , 3-30%) at substantially shorter follow-up periods, and the incidence of pelvic osteolysis associated with the PCA component is also as hig h as 30% (range, 5-30%). These differences may reflect differences in design between the 2 acetabular components, as the materials used were identical. In this, the longest reported average follow-up study of a successful cementless acetabular component, the aseptic loosening rat e of 4% contrasts with the 42% rate at similar follow-up duration for cemented acetabular components placed by the same surgeon in patients of similar age.