Depth of Insertion and Radiographic Fate of Non-Holed Cementless Metal Backed Acetabular Components

A retrospective radiographic review of 48 non-holed, factory assembled, cementless metal backed acetabular components, implanted in 45 patients, was performed. Post operative anteroposterior radiographs of the hips were compared to the radiographs at one year follow-up. In addition, measurements were made on 100 post-operative radiographs from patients implanted during the same time period with multiple holed acetabular components whose polyethylene liner was assembled after final impaction of the metal shell. The non-holed cups were implanted at a greater distance from Kohler’s line than the multiple holed acetabular components (1.45 ± 1.83 mm [range 0 – 7.89 mm] vs. 0.69 ± 1.70 mm [range 0 -15.26 mm], p = 0.018). A larger percentage of non-holed cups had gaps between the metal shell and the bone bed (67% vs. 17.5%). Impaction through the polyethylene liner of the non-holed acetabular components leads to a higher incidence of radiographic gaps between the metal shell and the bone bed as well as lateralization of the component, since there were no holes to assess the proper seating at surgery. These radiographic findings did not appear to be detrimental, however, as the cups remained radiographically stable at one year follow-up.