(HealthDay News) – From 1991–2010 there was a 161.5% annual volume increase in primary total knee arthroplasty (TKA) among Medicare enrollees as well as an increase in per capita utilization, according to research published in the Sept 26 issue of the Journal of the American Medical Association.

Peter Cram, MD, from the University of Iowa in Iowa City, and colleagues used Medicare Part A data files to identify 3,271,851 patients age 65 years or older who underwent primary TKA and 318,563 patients who underwent revision TKA.

The researchers found that, from 1991–2010, there was a 161.5% increase in annual primary TKA volume. Per capita utilization increased 99.2%, from 31.2 procedures per 10,000 enrollees in 1991 to 62.1 procedures per 10,000 enrollees in 2010. The volume of revision TKA also increased over the study period by a 105.9% volume increase and a 59.4% per capita utilization increase. Length of stay (LOS) decreased significantly, from 7.9 days in 1991–1994 to 3.5 days in 2007–2010 for primary TKA, while rates of adverse outcomes resulting in readmission remained stable from 1991–2010. However, rates for all-cause 30-day readmission increased significantly, from 4.2–5%. There was a decrease in hospital LOS for revision TKA, but a significant increase in all-cause 30-day readmission, from 6.1–8.9%, and a significant increase in readmission for wound infection, from 1.4–3%.

“Increases in TKA volume have been driven by both increases in the number of Medicare enrollees and in per capita utilization,” the authors write.

Several authors disclosed financial ties to pharmaceutical and health care companies.

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