Mako trial reignites debate over value of robotic-assisted surgery

The largest double-blind randomised comparison of robotic-assisted total knee replacement (rTKR) versus conventional instrumental total knee replacement (cTKR) has found that greater surgical precision does not translate into better patient outcomes at one year.

TKR remains one of the most successful operations in modern orthopaedics, yet 10%-20% of patients continue to report residual pain, dissatisfaction, or awareness of their artificial joint. Robotic-assisted surgery has therefore been rapidly adopted as a route to greater surgical precision and improved patient outcomes.

The RACER-Knee trial, using Stryker’s Mako platform, delivers the most rigorous test of this claim.

At one year, the mean Forgotten Joint Score (FJS) was similar between the rTKR and cTKR groups (p=0.62). Secondary patient-reported outcomes, including Oxford Knee Score, EQ-5D-5L, pain scores and activity measures, showed no meaningful differences at three, six or 12 months. Early postoperative pain, opioid consumption and time to discharge were also similar, suggesting that the additional technical precision offered by robotic assistance did not confer a measurable short-term recovery advantage.

The pragmatic design of the RACER-Knee trial, which allowed surgeons to choose their alignment strategy, is particularly significant. Rather than testing robotics under an artificial, protocol-driven ideal, the trial sought to reflect how the technology is actually used in day-to-day clinical practice.

Robotic assistance did, however, deliver greater radiographic precision. The absolute difference between achieved and planned hip–knee–ankle alignment was smaller with robotics, at 2.0° versus 2.8°. That additional precision came with practical and financial trade-offs. Operative time was longer by an average of 10.5 minutes, while the robotic pathway cost approximately £950 more per case. Serious adverse events were evenly distributed between the groups. Under standard UK willingness-to-pay thresholds, rTKR was not cost-effective within the first year.

The RACER-Knee findings also sit within a broader body of evidence from Australia questioning whether the increased precision of robotic assistance necessarily produces superior clinical outcomes.

The Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) has collected data on more than 1.1 million knee replacements, with robotic assistance used in 40.1% of patella/trochlea knee procedures and 53.4% of unicompartmental knee procedures. When adjusted for age, gender, ASA, BMI, and mobility, there is no difference in the rate of revision when robotic assistance is used in patella/trochlea knee replacement or when used in unicompartmental knee replacement.

Further evidence comes from the recently published results of the RASKAL trial from Australia, which found that robotic-assisted surgery and functional alignment were not superior to computer-assisted surgery and mechanical alignment, respectively, in improving clinical and functional outcomes up to two years after TKA.

“The additional costs of robotic-assisted TKA have been estimated to be approximately US$2,000 per case compared with computer-assisted TKA, and an extra US$2,600 per case compared with manual instrumentation,” the authors said. “These additional costs need to be balanced against reduced operating times, reduced PCL [posterior cruciate ligament] trauma, and perceived ease of surgical execution reported with this newer technology.”

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