Two knee replacements may be better than one

(SAN DIEGO, Calif.)Replacing both knees in one surgery — or simultaneous total knee replacement — was associated with significantly fewer prosthetic joint infections and fewer revision knee operations within one year after surgery, compared with total knee replacements performed in two separate procedures, according to a study presented today at the American Academy of Orthopaedic Surgeons’ annual meeting. Simultaneous replacement, however, was associated with a moderately higher risk of adverse cardiovascular outcomes within 30 days.

“We feel that the simultaneous surgery resulted in fewer infections because it involved fewer trips to the operating room,” said John P. Meehan, the study author who conducted the research when he was an associate professor of orthopaedic surgery at UC Davis Health System.

The study analyzed 11,445 patients who underwent simultaneous bilateral knee replacement and 23,715 patients who had both knees replaced in two stages several months apart. Patients’ mean ages were 67.2 years in the group who underwent simultaneous surgery and 67.7 years in the group who underwent two surgeries. The majority of patients in both groups were women: 53.9 percent of those who underwent simultaneous surgery and 61.3 percent of those who underwent two procedures.

In this study, patients who underwent simultaneous knee replacements had:

• higher risk of heart attack and pulmonary embolism
• similar risk of death and stroke
• lower risk of major joint infection or major mechanical malfunction

“Our study found that the risk of developing a serious joint infection that required an additional knee revision surgery was two times higher in patients who had staged knee replacements compared to the patients who had both knees replaced at the same time (2.2 percent after staged knee replacements and 1.2 percent after bilateral knee replacements),” said Meehan.

Revision knee surgeries for problems unrelated to infection were also more common using the staged approach.

“These findings indicate that performing simultaneous knee replacements would significantly reduce the incidence of major orthopaedic complications, and at the same time reduce the number of hospitalizations and the number of operating room sessions,” he added.

Similar to previous studies, this study found that the risk of adverse cardiovascular events such as having a heart attack or developing a blood clot that travels to the lungs was higher after undergoing simultaneous knee replacements, but there was no significant difference in overall mortality.

Meehan, who now is in private practice in Sacramento, Calif., added that further research is needed to define the specific cardiac risk factors that would preclude patients from undergoing the dual surgeries. His collaborators on the current study were Richard White, chief of general medicine at UC Davis Health System, and Sunny Kim, director of outcomes and patient safety with the UC Davis Department of Orthopaedic Surgery. Their work was funded by a UC Davis Board of Advisors Vision Grant.

UC Davis Health System is advancing the health of patients everywhere by providing excellent patient care, conducting groundbreaking research, fostering innovative interprofessional education and creating dynamic, productive partnerships with the community. The academic health system includes one of the country’s best medical schools, a 645-bed acute-care teaching hospital, an 800-member physician’s practice group and the new Betty Irene Moore School of Nursing. It is home to a National Cancer Institute-designated cancer center, an international neurodevelopmental institute, a stem cell institute and a comprehensive children’s hospital. Other nationally prominent centers focus on advancing telemedicine, improving vascular care, eliminating health disparities and translating research findings into new treatments for patients. Together, they make UC Davis a hub of innovation that is transforming health for all. For more information, visit