Healthcare News & Insights

Total knee arthroplasty study: Length of stay decreased, readmissions increased

Total knee arthroplasty (TKA) is a popular procedure at most hospitals and the majority of facilities are doing a good job at reducing length of stay. But a new study shows not all is well when it comes to TKAs.

The study, which was published in the Journal of the American Medical Association, found the rate of primary TKA procedures increased significantly (162%) from 1991 to 2010. And the rate of revision TKA procedures rose 106%.

The researchers attributed the growth to a combination of factors:

  • an expansion in the types of patients considered likely to benefit from TKA
  • an aging population, and
  • an increase in certain conditions that predisposes patients to osteoarthritis, such as obesity.

In addition, the procedure’s growth can be looked at from the standpoint it’s been very successful in safely reducing pain and improving function and quality of life for an aging population.

Problem is, the growth in TKA procedures isn’t going to slow down any time soon. The researchers predict a “profound increase” in TKA procedures over the next 30 years. And with a price tag of around $15,000 per procedure, this will put a major strain on Medicare and other carriers.

Reduced length of stay

But the popularity of TKAs isn’t the only factor the study revealed.

After analyzing data for 3.3 million Medicare Part A beneficiaries 65 years of age and older who had primary TKA, and 318,563 who had a revision TKA, Dr. Peter Cram of the University of Iowa in Iowa City and colleagues identified two other important trends.

For one thing, there was a decrease in the hospital length of stay (LOS) for both procedures. Primary TKA saw a drop in LOS from 7.9 days in 1991-1994 to 3.5 days in 2007-2010. Revision TKA saw a drop from 9 days to 5 days for over the same time periods.

Researchers believe the drops in LOS were due to the propensity at the time to discharge patients as quickly as possible to their home or other post-acute care settings, such as skilled nursing facilities.

Increase in readmission rates

While reducing the length of stay helped keep costs down for hospitals, it probably led to the next finding — an increase in readmission rates.

For primary TKA, the readmission rates for adverse outcomes were stable between 1991-2010. But for all-cause 30-day readmissions, the rate increased from 4.2% in 1991-1994 to 5% in 2007-2010.

For revision TKA, the all-cause 30-day readmission rate rose from 6.1% in 1991-1994 to 8.9% 2007-2010. And these procedures were associated with a more than double rate of readmission for wound infection (1% to 3%) and a more than 100% increase in readmissions for hemorrhage, sepsis and heart attack.

The researchers gave the following explanations for the increase in infections:

  • an increase in revision TKAs being performed specifically to treat infected prostheses — noting that the infections were “present on admission”
  • a consequence of the increasingly resistant organisms colonizing hospitals, and
  • reduced hospital LOS which may lead to reduced vigilance for early signs of superficial wound infection in the postoperative period.

Note: While this study has important findings to think about, the researchers did point out it also has the following limitations:

  • only looked at fee-for-service Medicare beneficiaries who make up about 60% of the TKA population
  • relied upon administrative data, which means they were unable to evaluate functional status and patient satisfaction
  • lacked clinical detail and were unable to determine the indications for TKA at the level of the individual patient
  • lacked chart review data for identification of TKA outcomes and complications, and
  • focused the analysis on TKA adverse outcomes resulting in hospital readmission within 30 days of discharge, which didn’t capture late complications.

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