Alumina ceramic bearings for hip endoprostheses - The Austrian experiences

The current anthors review clinical and retrieval experiences with hemisphe ric monolithic alumina ceramic sockets (Group 1), implanted between 1976 an d 1979, and similar modular titanium sockets with alumina ceramic inlays (G roup 2), implanted between 1990 and 1995. Both cementless sockets articulat ed with alumina ceramic femoral ball heads for total hip joint replacements , Clinical followup of patients with hemispheric monolithic alumina ceramic sockets (Group 1, 138 sockets) resulted in a total failure rate of 19.6% a fter 5 to 20 years. Radiologic analysis of eight stable sockets showed migr ation of 0.2 mm to 2.89 mm, but in four sockets at risk for late aseptic fa ilure after an average followup of 12.5 years as much as 13.4 mm of migrati on was seen. Histologic evaluation revealed pseudosynovial membranes as thi ck as 1 mm with fine birefringent wear particles within mononuclear macroph ages around two stable retrieved sockets. The membranes around four loose s ockets were 6 to 10 mm thick and also heavily loaded with larger alumina we ar particles. After 7 years followup clinical analysis of patients with mod ular titanium sockets with alumina ceramic inlays (Group 2, 30 sockets) res ulted in four revisions, compared with one revison of 50 identical sockets (control group) with polyethylene instead of alumina ceramic inlays, Wear p article analyses in scanning electron microscopy showed significantly more particles (X10(9) +/- standard deviation/g dry tissue) from the control gro up (4.26 +/- 6.38), compared with alumina ceramic bearings of Group 1 (0.70 +/- 0.79), and of Group 2 (1.62 +/- 2.13). The alumina particle sizes rang ed between 0.13 and 78.38 mu m. The mean annual linear wear of 38.8 mu m wa s calculated for the bearings in Group 1, and of 26.94 mu m for bearings in Group 2, These results support the good tribologic and biologic performanc e of alumina ceramic bearings for total hip arthroplasty.