World's Largest Robotic Knee Surgery Trial Finds No Early Benefit Over Conventional Surgery

Robot-assisted knee replacement surgery can place an artificial joint more precisely than a surgeon operating without robotic help, but that added accuracy did not translate into better patient outcomes in the first year, according to results from RACER-Knee, described as the world's largest randomized trial of its kind. The trial, coordinated by the University of Warwick and University Hospitals Coventry and Warwickshire (UHCW) NHS Trust, was published in The Lancet.

Robotic assistance is already used in about 6% of knee replacements in the UK, compared with 16% in the US and 42% in Australia. The UK-wide trial, funded by the National Institute for Health and Care Research (NIHR) in partnership with Stryker, which makes the robotic system tested, compared conventional total knee replacement with surgery assisted by the Stryker Mako system, the most widely used robotic system of its kind worldwide.

The trial included 339 patients treated by 33 surgeons at 10 hospitals across the UK. One year after surgery, people in the robotic and conventional groups had similar levels of recovery, mobility and pain. On the primary measure, the Forgotten Joint Score, which gauges how much patients notice their artificial joint during everyday activities, there was no meaningful difference between the two groups. Results were also similar for walking ability, pain in the first three months and at 12 months, pain in hospital, and the likelihood of needing a follow-up operation. Serious adverse events were no more common with robotic surgery, suggesting the approach was as safe as conventional treatment.

“Technology such as this could really help the care we give for patients, but for robotic-assisted knee replacements, there is still work to do before we see benefits such as less pain or better movement,” said Andrew Metcalfe, a professor at Warwick Medical School and a chief investigator on the trial. Edward Davis, a consultant orthopedic surgeon at the Royal Orthopaedic Hospital NHS Foundation Trust, said the trial shows robotic assistance allows higher precision and, in theory, lets surgeons customize the procedure to a patient's anatomy, but that more understanding of the ideal implant position is needed before that precision can be turned into an advantage.

Robot-assisted procedures took an average of 10.5 minutes longer and cost about £950 more than conventional surgery. Researchers will continue monitoring the trial's participants for 10 years to see whether meaningful differences emerge over the longer term, including whether one approach reduces the likelihood that patients will need additional knee surgery.