The Norwegian Arthroplasty Register was established in 1987. Until January 1994, approximately 200 different implant combinations had been used in total hip replacements (THR) in Norway. About 5,500 THR were performed each year in this period with a total cost of 70 million USD per year. We analyzed the economic consequences related to the use of some inferior primary hip arthroplasties in this period. As the reference arthroplasty, we chose the most commonly used prosthesis in Norway, i.e., the Charnley prosthesis fixed with high viscosity cement containing antibiotic and with systemic antibiotic prophylaxis (n 4,970). We compared this reference group to all other primary THR registered in the same time period (n 24,027), and to the following sub-groups of primary THR: 1) uncemented Ti-Fit/ Bio-Fit (acetabulum/femur) combination (n 173), 2) uncemented Coxa/Femora combination (n 153), 3) THR with low-viscosity cement (n 1,807) and 4) THR with Boneloc cement (n 1,250). We estimated the number of additional revisions compared to the reference arthroplasty after a follow-up of 3-5 years in the different groups, with adjustment for age, sex and diagnosis. The direct extra revision costs were calculated. Compared to the reference arthroplasty, the group of all other primary THR gave an extra revision cost estimated at about 1.7 million USD per year. About 1,000 uncemented Bio-Fit femoral prostheses have been applied in Norway, including those implanted before the registration started (1985-1987). The extra revision costs the first postoperative years for these 1,000 prostheses amount to about 0.7 million USD per year. Corresponding figures in the Coxa/ Femora group were 0.08 million USD, in the group with low-viscosity cement, 0.3 million USD and in the Boneloc group, 0.4 million USD per year.
