Dramatic rise in total knee arthroplasty, associated infection rates over past 20 years

By Ingrid Grasmo, medwireNews Reporter

Study findings document a steep rise in total knee arthroplasty (TKA) procedures over the past 20 years, being driven by both an increase in the number of patients enrolled in Medicare and greater per capita utilization.

Worryingly, the study published in JAMA also revealed increased rates of hospital readmission and infectious complications despite a decrease in the total length of stay (LOS) in hospital.

Peter Cram (University of Iowa, USA) and colleagues say the findings are of particular clinical and economic significance, given that approximately 600,000 TKA procedures are performed annually in the USA at a cost of approximately US$ 15,000 (€ 11,600) per procedure.

The observational 20-year study of 3,271,851 registered Medicare patients aged 65 years and older who underwent primary TKA, and 318,563 who underwent revision TKA, showed that primary TKA volume increased 161.5% from 93,230 to 243,802, while per capita utilization increased 99.2% from 31.2 to 62.1 procedures per 10,000 patients. Similarly, revision TKA volume increased 105.9% from 9650 to 19,871 with a 59.4% increase in per capita utilization.

"These figures suggest that growth in primary and revision TKA volume is being driven by both an increase in the number of Medicare enrolees and an increase in per capita arthroplasty utilization," say the authors, adding that the growth is likely driven by a combination of factors including an expansion of the patient population indicated for TKA, an aging population, and an increasing prevalence of conditions such as obesity that predispose patients to osteoarthritis.

Additional research findings also showed a significant shift in the pattern of care between 1991 and 2010, where LOS for primary TKR decreased significantly from 7.9 to 3.5 days and revision TKR from 8.9 to 5.0 days.

Despite this encouraging finding, 30-day all-cause readmission rates after primary TKR increased significantly from 4.2% during 1991 to 1994 to 5.0% during 2007 to 2010. The same trend was observed for revision TKR, showing a respective increase of 6.1% to 8.9%. In addition to the increase in readmission rates, the study also revealed an important increase in infection rates for revision cases, increasing from 1.4% to 3.0%.

The researchers suggest that the increase in infections may be associated with the reduction in hospital LOS and the consequent reduced vigilance for early signs of superficial wound infections.

In an associated editorial, James Slover and Joseph Zuckerman (Hospital for Joint Diseases, New York, USA) said: "In the currently challenging and dynamic healthcare environment, critical evaluation and systematic data collection about total knee replacements will be needed to optimize outcomes and ensure access to these life-improving procedures."

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