Race- and Sex-Specific Incidence Rates and Predictors of Total Knee Arthroplasty: Seven-Year Data From the Osteoarthritis Initiative

Abstract

Objective: To determine race- and sex-specific rates of total knee arthroplasty (TKA) and to document independent effects of demographic factors on TKA incidence in a population with radiographically confirmed osteoarthritis (OA).

Methods: We used data from the Osteoarthritis Initiative, a US-based, multicenter longitudinal study of knee OA. We selected subjects with radiographic symptomatic OA at baseline and determined TKA incidence rates (ratio of TKAs to time at risk for TKA) over 84 months of followup. We used multivariable Poisson regression to identify independent associations between demographic factors and TKA utilization.

Results: During the study period there were 223 TKAs among 1,915 subjects for an incidence of 1.9% (95% confidence interval [95% CI] 1.7-2.2%). The overall rate was 1.9% (95% CI 1.5-2.3%) in men versus 2.0% (95% CI 1.7-2.3%) in women, and 2.2% (95% CI 1.9-2.6%) in whites versus 1.0% (95% CI 0.7-1.5%) in nonwhites. We observed a statistically significant interaction between sex and age (stratified at <65 and ≥65 years at end of followup), wherein male sex was associated with decreased risk of TKA for younger participants (relative risk [RR] 0.32) but not for older participants. Nonwhite race was associated with a decreased risk of TKA for both younger (RR 0.32) and older (RR 0.43) participants.

Conclusion: Our finding that nonwhites were less likely to undergo TKA than whites in adjusted analyses confirms racial differences observed in population-based studies and underscores the need for interventions to address lower use of TKA among nonwhites with OA.

Trial registration: ClinicalTrials.gov NCT00080171.

Figure 1. Kaplan-Meier Survival Estimates with 95% Confidence Bands

Follow-up time is along the x-axis and percent with TKA is along the y-axis. Each line represents the probability of undergoing TKA over time, stratified by race (blue line for Whites, red line for non-Whites). The shaded area around each line is the 95% confidence band. The log-rank p-value for the difference in the survival curves is <0.001.

Figure 2. Kaplan-Meier Survival Estimates for Age-Sex Subgroups by Baseline KL. (A) Those less 65 years at 7-years follow-up; (B) Those greater than 65 years at 7-years follow-up

Follow-up time is along the x-axis and percent with TKA is along the y-axis. Each line represents the probability of undergoing TKA over time, stratified by baseline KL (red lines are baseline KL 2, green lines are baseline KL 3, and blue lines are baseline KL 4) and sex (lighter lines are males and darker lines are females). Figure A includes participants in the younger age group (<65 at follow-up) and Figure B includes participants in the older age group (>65 at follow-up). In Figure A, within each baseline KL grade (within each color), the dark line is substantially above the light line, indicating that women are more likely to undergo TKA as compared to men. In Figure B, within each baseline KL grade (within each color), the light and dark lines are much closer together, indicating that there is not a substantial difference in TKA utilization over time between men and women.