While the risk of revision after total knee replacement is low overall at about 1 to 2%, Black patients have a higher risk than white patients. The underlying factors driving this disparity and whether it holds true when looking at separate groups of patients who had aseptic revision to address mechanical problems such as pain, instability or loosening, or septic revision to treat infection complications, have been unclear.

Now, researchers at Hospital for Special Surgery (HSS) have examined racial disparities separately for aseptic and septic revision total knee replacement using data from three large states. In their study published July 21 in JAMA Network Open, they found that Black patients had a 39% higher risk of aseptic revision and an 11% higher risk of septic revision than white patients.

“As we predicted, the risk factors were very different for patients needing aseptic versus septic revision,” says lead and corresponding study author Anne R. Bass, MD, rheumatologist at HSS. “But we were totally surprised to find Black race was one of the only risk factors associated with aseptic revision and that this disparity was so much higher for patients treated at high-volume hospitals.”

Dr. Bass and HSS colleagues analyzed data from statewide databases from California, Florida and New York for almost 725,000 patients who had total knee replacement between 2004 and 2014. The investigators looked at an extensive range of variables that have been linked to risk of revision total knee replacement in previous studies, including age; sex; insurance status; presence of other conditions such as diabetes, obesity, renal disease and chronic obstructive pulmonary disease (COPD); inflammatory arthritis; surgical site complications; infection on admission for knee replacement surgery; and hospital factors, including non-government, not-for-profit, teaching hospital, rural location, number of beds, and annual total knee replacement volume.

In addition to being Black, other factors associated with a higher risk of septic revision total knee replacement were diabetes, obesity, renal disease, COPD, inflammatory arthritis, surgical site complications, Medicaid insurance and low hospital total knee replacement volume. Similarly, for aseptic revision, additional risk factors were male sex, workers’ compensation insurance and low hospital total knee replacement volume.

When the researchers analyzed the data according to different categories of hospital volume, they discovered Black patients had a 20% higher risk of aseptic revision total knee replacement than white patients if they underwent replacement at low-volume hospitals, defined as 89 or fewer total knee replacements annually. However, the relative risk was 68% higher for those who had knee replacements at very high-volume hospitals, defined as 645 or more procedures per year.

“The question now is why do these disparities exist,” says Dr. Bass. “Our study did not reveal causes, but we can use this learning to develop theories for further investigation.”

“We know that Black patients tend to bypass larger, higher-volume hospitals and have surgery at lower-volume hospitals,” says study co-author Michael L. Parks, MD, a hip and knee surgeon at HSS. “One of the reasons why they may have higher revision rates at higher-volume hospitals is that they tend to present later with more advanced disease and require more complicated surgeries than white patients.”

“The other hypothesis is that care is not being delivered equally across patient groups at high-volume hospitals,” says Dr. Bass. “If that’s the case, hospitals should review and ensure care processes are accessed and applied equally across racial groups to improve surgical outcomes.”

Dr. Bass, Dr. Parks and colleagues are currently conducting further research to look for a relationship between revision total knee replacement risk, hospital volume and annual volume by surgeon to see if they can learn more about racial disparities.

The study was supported by funding provided by the Stavros Niarchos Complex Joint and Reconstruction Center at HSS.