Yearly incidence of unicompartmental knee arthroplasty in the United States.

Our purpose was to estimate the incidence of unicompartmental knee arthroplasty in the United States. Three major implant manufacturers provided data over an 8-year period from 1998 to 2005. In addition, a database from 44 hospitals was used to derive national estimates for implants manufactured by all other companies. The incidence of unicompartmental knee arthroplasty ranged from 6570 implants in 1998 to 44990 in 2005. Unicompartmental knee arthroplasty increased at an average rate of 32.5% during the study period compared with a 9.4% average increase in rate of total knee arthroplasty over the same period. Although unicompartmental arthroplasty is growing at triple the rate of total knee arthroplasty in the United States, the data suggest that unicompartmental implants currently account for less than 8% of all knee arthroplasty procedures.