In 35,000 TKA Patients, What’s the Mortality Rate?

How many total knee arthroplasty patients die from the operation, is bilateral simultaneous arthroplasty a contributing factor and, finally, will using robotic assist technologies lower that rate?

These provocative questions were the basis of an interesting new study about the use of technology-assisted instrumentation in bilateral simultaneous total knee arthroplasty (BSTKA) surgeries which, as its outcome measure, chose the rate of early postop death when compared with conventional instrumentation.

A group of Australian researchers published the results of this study titled “Increased Early Mortality in Bilateral Simultaneous TKA Using Conventional Instrumentation Compared with Technology-Assisted Surgery: A Study of 34,908 Procedures from a National Registry” in the December 1, 2021, edition of The Journal of Bone and Joint Surgery.

Co-author Ian Harris A.M., M.B.B.S., Ph.D., director of the Whitlam Orthopaedic Research Centre, Ingham Institute for Applied Medical Research at the University of New South Wales in Sydney, Australia, explained the timing of their work to OTW. “It took time for the registry to have enough data to be able to detect a difference. Testing for treatment effects using mortality as an outcome requires large numbers because of the infrequency of the event.”

The authors wrote, “The overall odds ratio of 30-day mortality for technology-assisted versus conventional BSTKA, adjusted for age, sex, and procedure year, was 0.26. The odds ratio of 90-day mortality for these procedures was 0.25. Among the 15,408 bilateral simultaneous TKA procedures performed with technology-assisted versus conventional instrumentation from 2015 to 2019, the odds ratio of 30-day mortality, further adjusted for ASA and BMI, was 0.26. The odds ratio of 90-day mortality for these procedures was 0.26.”

Clarifying, Dr. Harris explained to OTW, “The odds ratios are for mortality following technology-assisted bilateral simultaneous TKA, and the comparator is conventional instrumentation. The odds ratio < 1 means that the mortality with technology-assisted BSTKA is lower than for conventional. You can reverse it, (inverse of 0.26 is 3.85) and say that for conventional instrumentation (this time with technology-assisted as the comparator) is 3.85.”

“It appears that the use of conventional instrumentation is associated with a much higher rate of early death after bilateral total knee replacement. Given that the only main difference between groups is that one instruments the intramedullary canal, and the other doesn’t, it is reasonable to hypothesize that the difference in mortality is due to fat emboli at the time of surgery.”

Harris also discussed how this data might change his and other surgeons’ day-to-day practice. “This means that post-operative mortality can be reduced (and therefore the procedure made safer) by using modern techniques of instrumentation (like computer-assisted and robotic-guided). This should lead to an increase in the use of these techniques, where feasible, as cost, availability and training are the obstacles to widespread introduction.”