The incidence of knee arthroplasty for primary osteoarthritis grows rapidly among baby boomers: a population-based study in Finland.

OBJECTIVE: Total knee arthroplasty (TKA) is a commonly used treatment for severe primary knee osteoarthritis (OA) that is refractory to conservative treatment. Despite the presumed increase in the use of this treatment modality in younger patients, there are few published data concerning this. The aim of our study was to examine the changes in the age- and sex-standardized incidence of TKA and unicondylar knee arthroplasty (UKA) in Finland during 1980-2006 and to identify factors that might affect the incidence during this period.

METHODS: We obtained data on UKAs and TKAs from the Finnish Arthroplasty Registry and population data from Statistics Finland to analyze the incidence of UKAs and TKAs in Finland for the period 1980-2006. The effects of sex, age group, and hospital volume on the incidence of these procedures were also evaluated.

RESULTS: The annual cumulative incidence of UKAs and TKAs has increased rapidly from 1980 to 2006 among 30-59-year-old inhabitants of Finland. For UKAs, the incidence increased from 0.2 per 100,000 inhabitants to 10 per 100,000, and for TKAs, the incidence increased from 0.5 per 100,000 to 65 per 100,000. The incidence remained higher among women during the entire study period. Most of the increase occurred among patients ages 50-59 years. The incidence grew more rapidly in low-volume and intermediate-volume hospitals.

CONCLUSION: We demonstrated a rapid increase in the incidence of arthroplasty among patients with primary knee OA in Finland, especially in those ages 50-59 years. There was no single explanatory factor behind this finding, although some of the growth might be due to the increased incidence noted in low- and intermediate-volume hospitals.