Better positioning should, in theory, reduce both early and long-term failure. Yet the new data suggest that technical precision does not necessarily yield better overall early results.

Implant malpositioning means the new joint sits at the wrong angle or depth. A poorly placed implant can wear out faster, loosen, or cause pain that sends patients back to the operating table. The hip study hints that robotic tools do what their makers promise on this narrow front. They do not appear to fix the broader set of reasons a joint replacement fails.

For hips, the specific gain seen with robotic surgery — fewer revisions caused by malpositioning — was offset elsewhere, leaving the total repeat-surgery rate unchanged.

How much does robotic surgery cost?

The technology carries substantial upfront expense. Robotic systems cost around £1 million to introduce into a hospital. Each procedure adds between £1,000 and £2,500 to the bill.

These figures land at a sensitive moment for the NHS. The health service plans a major expansion of robotic surgery, aiming to increase the number of procedures sevenfold by 2035.

How did the researchers reach these conclusions?

The teams used a method called target trial emulation. This statistical approach balances patients according to known differences in their characteristics, making comparisons between large patient groups more closely resemble those of a randomized clinical trial.

Hasan Mohammad, an academic clinical lecturer in trauma and orthopedics at Queen Mary and lead author of the study, said: "This study, which uses novel methodology and represents the largest real-world analysis of its kind worldwide, provides important independent evidence for patients, surgeons and policymakers at a time when robotic hip and knee replacement surgery is being adopted rapidly. New technology should deliver meaningful benefit for patients and represent good value for a publicly funded health service."

What are the limitations?

The studies tracked only early outcomes. Longer follow-up may reveal whether differences in implant survival emerge over time.

Registry data, while comprehensive, cannot capture every clinical detail that matters. Surgeon experience with robotic systems also varied across hospitals, and outcomes may improve as operators become more practiced — a possibility the early data cannot yet rule out.

The knee study, titled "Are robotic knee replacements superior? An early national comparison of robotic versus conventional knee replacements for arthritis using registry data," appeared in The BMJ in 2026 (DOI: 10.1136/bmj-2026-100691).