Study Links Simultaneous Bilateral TKA to an Increased Risk of Some Complications

Patients undergoing bilateral total knee arthroplasty (TKA) are at an increased risk of several types of complications when compared with a matched cohort of patients undergoing unilateral TKA, according to a study from researchers at the Keck School of Medicine of USC in Los Angeles, California.

“Patients who underwent simultaneous bilateral TKA were at higher risk of experiencing postoperative complications such as pulmonary embolism, stroke, blood loss anemia, and requiring a transfusion,” the study authors said in their paper, which was published online by The Journal of Bone & Joint Surgery

Large Cohort Study

Total knee arthroplasty is a highly effective treatment for patients with advanced osteoarthritis of the knee, providing improved function with decreased pain. When both knees are affected, bilateral TKA offers some advantages over sequential unilateral TKA, including less time in the hospital, a single rehabilitation period, and lower overall costs.

However, some studies have found an increased risk of complications, along with a higher mortality rate, in patients undergoing bilateral TKA. These studies have had important limitations, including a lack of patient matching to account for potential differences between those undergoing bilateral versus those undergoing unilateral TKA.

To address these issues, the study authors compared complications and mortality in a large, nationally representative group of patients undergoing bilateral versus unilateral TKA.

Using the Premier Healthcare Database, the researchers identified more than 21,000 patients who had undergone elective simultaneous bilateral TKA between 2015 and 2020. These patients were matched in a 1:6 ratio for age, sex, race, and comorbidities with a cohort of more than 126,000 patients who had undergone elective unilateral TKA during the same period.

Clarifying Complication Risks

Patients in the simultaneous bilateral TKA group had increased rates of several types of complications compared with those in the unilateral TKA group:

  • Pulmonary embolism (0.27% vs 0.13%, respectively)
  • Stroke (0.13% vs 0.06%)
  • Respiratory failure (0.46% vs 0.34%)

The bilateral TKA patients were also at a higher risk of anemia due to blood loss (26.89% vs 14.86%) and were more likely to undergo a blood transfusion (5.23% vs 0.67%). These risks were increased despite the high use of tranexamic acid to reduce blood loss during surgery in both groups.

In addition, the bilateral TKA patients were more likely to be readmitted to the hospital within 90 days (2.80% vs 2.05%). There was no significant increase in the risk of in-hospital death (0.05% vs 0.04%).

Patients in the bilateral TKA group were at approximately double the risk of pulmonary embolism, stroke, and acute blood loss anemia and at nearly 9 times the risk of blood transfusion than patients in the unilateral TKA group after adjusting for confounders. The risk of readmission within 90 days was 35% higher with bilateral compared with unilateral TKA.

Final Thoughts

“This study presents the largest matched sample size to date comparing the complications and safety between patients treated with simultaneous bilateral TKA and those treated with unilateral TKA,” the study authors said.

And although no significant difference was seen in the rate of in-hospital death, “The risk of mortality following simultaneous bilateral TKA is still a topic of concern.”

The researchers emphasized the need for patient counseling and “thorough medical optimization” in patients selected for bilateral TKA.


Richardson MK, Liu KC, Mayfield CK, Kistler NM, Christ AB, Heckmann ND. Complications and safety of simultaneous bilateral total knee arthroplasty: a patient characteristic and comorbidity-matched analysis. J Bone Joint Surg Am. 2023 Jul 19;105(14):1072-1079. doi: 10.2106/JBJS.23.00112. Epub 2023 Jul 19.

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