Trends in epidemiology of knee arthroplasty in the United States, 1990-2000.

OBJECTIVE There is little information on longitudinal trends in the epidemiology of total knee arthroplasty (TKA). This study was undertaken to determine whether, during the past decade, TKA rates increased in younger adults and older adults, whether utilization of TKA increased among minorities, and whether more patients underwent surgery at high-volume hospitals. METHODS TKA cases (n = 443,008) were extracted from the 1990-2000 Nationwide Inpatient Sample database. TKA trends for 3 time periods were obtained (1990-1993 [period I], 1994-1997 [period II], and 1998-2000 [period III]). RESULTS Between period I and period III, the proportion of TKAs performed increased by 95.2% in the 40-49-year age group and by 53.7% in the 50-59-year age group. Black patients and Hispanic patients were more likely to undergo TKA in period III than in period I (odds ratio [OR] = 1.6, 95% confidence interval [95% CI] 1.5-1.6 and OR 2.7, 95% CI 2.5-2.9, respectively). However, white patients accounted for 93.0%, 89.9%, and 87.5% of TKAs in the 3 time periods, respectively. In period III, the proportion of patients undergoing surgery in high-volume hospitals increased compared with periods I and II. Both mortality and length of hospital stay diminished significantly in period III, but the rate of discharge to an inpatient facility increased by 89.7% (period I to period III). CONCLUSION Over the past decade, TKA was increasingly performed in younger patients, which suggests a broadening of indications for this procedure. Although utilization of TKA increased among minorities, the vast majority of TKAs were performed in white patients. Further efforts to narrow this disparity are required. The shift toward TKAs being increasingly performed at high-volume centers may improve surgical outcomes. Finally, the effect of increased discharge to inpatient facilities on TKA outcomes needs to be ascertained.