The Norwegian Arthroplasty Register

Abstract

In 1985, the Norwegian Orthopaedic Asso- ciation decided to establish a national hip register, and the Norwegian Arthroplasty Register was started in 1987. In January 1994, it was extended to include all artificial joints. The main purpose of the register is to detect inferi- or results of implants as early as possible. All hospitals participate, and the orthopedic surgeons are supposed to report all primary operations and all revisions. Using the patient's unique national social security number, the revi- sion can be linked to the primary operation, and survival analyses of the implants are done. In general, the survival analyses are performed with the Kaplan-Meier method or using Cox multiple regression analysis with adjust- ment for possible confounding factors such as age, gen- der, and diagnosis. Survival probabilities can be calculat- ed for each of the prosthetic components. The end-point in the analyses is revision surgery, and we can assess the rate of revision due to specific causes like aseptic loosen- ing, infection, or dislocation. Not only survival, but also pain, function, and satisfaction have been registered for subgroups of patients. We receive reports about more than 95% of the pros- thesis operations. The register has detected inferior im- plants 3 years after their introduction, and several unce- mented prostheses were abandoned during the early 1990s due to our documentation of poor performance. Further, our results also contributed to withdrawal of the Boneloc cement. The register has published papers on economy, prophylactic use of antibiotics, patients' satisfaction and function, mortality, and results for dif- ferent hospital categories. In the analyses presented here, we have compared the results of primary cemented and uncemented hip pros- theses in patients less than 60 years of age, with 0-11 years' follow-up. The uncemented circumferentially po- rous- or hydroxyapatite (HA)-coated femoral stems had better survival rates than the cemented ones. In young patients, we found that cemented cups had better sur- vival than uncemented porous-coated cups, mainly be- cause of higher rates of revision from wear and osteoly- sis among the latter. The uncemented HA-coated cups with more than 6 years of follow-up had an increased revision rate, compared to cemented cups due to aseptic loosening as well as wear and osteolysis. We now present new findings about the six common- est cemented acetabular and femoral components. Gen- erally, the results were good, with a prosthesis survival of 95% or better at 10 years, and the differences among the prosthesis brands were small. Since the practice of using undocumented implants has not changed, the register will continue to survey these implants. We plan to assess the mid- and long-term results of implants that have so far had good short-term results. n