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Abstract
Background and purpose The number of national arthroplasty registries is increasing. However, the methods of registration, classification, and analysis often differ.
Methods We combined data from 3 Nordic knee arthroplasty registers, comparing demographics, methods, and overall results. Primary arthroplasties during the period 1997–2007 were included. Each register produced a dataset of predefined variables, after which the data were combined and descriptive and survival statistics produced.
Results The incidence of knee arthroplasty increased in all 3 countries, but most in Denmark. Norway had the lowest number of procedures per hospital—less than half that of Sweden and Denmark. The preference for implant brands varied and only 3 total brands and 1 unicompartmental brand were common in all 3 countries. Use of patellar button for total knee arthroplasty was popular in Denmark (76%) but not in Norway (11%) or Sweden (14%). Uncemented or hybrid fixation of components was also more frequent in Denmark (22%) than in Norway (14%) and Sweden (2%).
After total knee arthroplasty for osteoarthritis, the cumulative revision rate (CRR) was lowest in Sweden, with Denmark and Norway having a relative risk (RR) of 1.4 (95% CI: 1.3–1.6) and 1.6 (CI: 1.4–1.7) times higher. The result was similar when only including brands used in more than 200 cases in all 3 countries (AGC, Duracon, and NexGen). After unicompartmental arthroplasty for osteoarthritis, the CRR for all models was also lowest in Sweden, with Denmark and Norway having RRs of 1.7 (CI: 1.4–2.0) and 1.5 (CI: 1.3–1.8), respectively. When only the Oxford implant was analyzed, however, the CRRs were similar and the RRs were 1.2 (CI: 0.9–1.7) and 1.3 (CI: 1.0–1.7).
Interpretation We found considerable differences between the 3 countries, with Sweden having a lower revision rate than Denmark and Norway. Further classification and standardization work is needed to permit more elaborate studies.
Acknowledgments
All authors participated in the planning and design of the study and in interpretation of the results. The data from the respective national registers were prepared by OR, AMF, and FM. The databases were merged and initially analyzed by OR and SB, after which the dataset was distributed to the other authors for analysis locally. OR was responsible for writing of the manuscript, and all the authors contributed actively during its preparation.
We thank the orthopedic surgeons in Sweden, Denmark, and Norway, and their staff, whose faithful work has made the study possible.