Geographic Differences in Rates of Primary Total Knee Arthroplasty in Young and Older Adults: A Comparison of 3 US States

Objective. Rates of total knee arthroplasty (TKA) among Medicare beneficiaries (adults aged >= 65 yrs) vary across the United States, with higher rates in the Midwest and West than in the South. It is not known if a similar variation is present among younger patients, or if findings in Medicare reflect selective postponement of TKA in some regions. Methods. Data on all primary TKA performed in adults aged >= 20 years in 3 states (Iowa, Utah, and Florida) in 2016 were obtained from state inpatient databases. Rates of TKA were computed based on population census data. Age-, sex-, and race-standardized rates were compared between Iowa and Florida, and between Utah and Florida, among adults aged 20-64 years and adults aged >= 65 years. Results. There were 10,074, 8954, and 43,908 primary TKAs in Iowa, Utah, and Florida, respectively. Standardized rates were higher in Iowa and Utah than in Florida among both adults aged 20-64 years (Iowa:Florida rate ratio [RR] 1.89, 95% CI 1.79-1.99; Utah:Florida RR 2.31, 95% CI 2.18-2.45) and those aged >= 65 years (Iowa:Florida RR 1.41, 95% CI 1.35-1.47; Utah:Florida RR 1.77, 95% CI 1.70-1.85). Results were similar in sensitivity analyses limited to White patients, urban residents, and those with a diagnosis of knee osteoarthritis. Conclusion. TKA rates were higher in Iowa and Utah than in Florida among both younger adults and those aged >= 65 years, indicating that geographic differences are not specific to elderly patients.