Image-Based vs Imageless Robotics: Does the Platform Affect Femoral Rotation in TKA?

“Equivalent accuracy of image-based and imageless robotic platforms in achieving planned femoral rotation in primary total knee arthroplasty: A CT-based study” was published in the Knee Surgery, Sports Traumatology, Arthroscopy (KSSTA) Journal in July 2026.

As robotic-assisted total knee arthroplasty (TKA) becomes increasingly established in contemporary practice, an important question remains: does the type of robotic platform - image-based or imageless - influence the accuracy of femoral rotation?

The aim

The study aimed to determine whether image-based and imageless robotic platforms differed in their ability to achieve planned femoral rotation in primary TKA. The researchers hypothesised that the platforms would be equivalent, with any difference falling within ±1°.

The protocol

This single-surgeon retrospective cohort study included 150 patients undergoing robotic-assisted TKA for primary osteoarthritis - 79 using an imageless platform and 71 using an image-based platform.

All patients underwent pre- and postoperative CT scans. Femoral rotation was planned intraoperatively relative to the posterior condylar axis (PCA), while postoperative CT was used to measure the achieved rotation relative to the transepicondylar axis (TEA). Accuracy was defined as the difference between planned and achieved rotation. Measurements were independently performed by two blinded, fellowship-trained knee surgeons.

What did the research show?

The research showed a mean rotational error of 1.3° for imageless TKA and 1.2° for image-based TKA, with no statistically significant difference between the groups.

Equivalence testing confirmed that the two platforms were statistically equivalent within the predefined ±1° margin. Although analysis identified a small adjusted difference of 0.51°, this explained very little of the overall variation and was not considered clinically meaningful.

There were also no differences in patient-reported outcomes, apart from lower pain scores in the image-based group at 12 months.

What does this mean for surgeons and patient care?

The findings suggest that both image-based and imageless robotic platforms can achieve comparable accuracy in femoral rotation. For surgeons, the choice of robotic platform alone does not appear to provide a clinically meaningful advantage in rotational accuracy.

This is an important consideration as robotic technology continues to evolve. The value of a platform should ultimately be assessed in the context of surgical planning, execution, component positioning, soft-tissue balance and patient outcomes - rather than technology alone.

For patients, the findings provide reassurance that both approaches can accurately reproduce planned femoral rotation in primary TKA.

The take-home message: when it comes to femoral rotational accuracy, image-based and imageless robotic TKA appear to be clinically equivalent. Surgical planning, technique and an understanding of individual knee biomechanics remain central to achieving an optimal outcome.