Loosening of cobalt chrome beads from a porous-coated acetabular component. A report of ten cases.

Seventy consecutive total hip arthroplasties were performed using a porous-coated acetabular component consisting of a cobalt chrome substrate to which cobalt chrome beads were sintered. Fifty-six were primary arthroplasties and 14 were revisions. The authors analyzed the immediate postoperative roentgenographs of all 70 hips and the follow-up roentgenographs of the 66 hips that were followed for a minimum of two years, the average follow-up period being 30 months. Loose cobalt chrome beads were diagnosed in ten of the 70 hips (14.3%), five (8.9%) in the primary arthroplasties, and five (35.7%) in the revision arthroplasties. In two of the primary arthroplasties and three of the revision arthroplasties, the loose beads were observed on the immediate postoperative roentgenographs. None of the acetabular components appeared loose by other roentgenographic criteria. The sintering technique used in the manufacture of these implants did not prevent loosening of cobalt chrome beads from porous-coated cobalt chrome acetabular components. A longer follow-up period is required to assess fully the clinical significance.