Clinical outcomes of UKA procedures are sensitive to malalignment of the components, and thus show significant variability in the literature. This study evaluates the early clinical results of a new surgical procedure designed to significantly increase the accuracy and precision of the alignment of the components, and thus increase post-operative functional outcomes.

A new UKA technique has been developed, which combines tactile guided robotic technology with image guided surgery. Three-dimensional planning of the implant positioning is followed by precise resection of the bony surfaces. 223 patients have received a UKA from three clinical sites using this new technology. To date, 14 patients are 1 year and 84 patients are 6 months postoperative. Clinical data from all patients are included in an IRB approved registry.

From 223 UKAs, there have been no revisions and 6 reoperations; 2 for infection, 1 for arthrofibrotic band release, 1 for quad tendon arthrotomy separation, 1 for a femoral fracture at the navigation pin site and 1 for unexplained medial pain. Data for patients one year postoperative showed significant improvements, compared to pre-operative values, in range of motion (p< 0.02), Knee Society Scores (p< 0.0001) and WOMAC scores (p< 0.01), particularly pain (p< 0.01) and stiffness (p< 0.01).

This initial series of robotically guided UKA implantations provided significant improvement in the postoperative function of patients in every functional measurement with no revisions to date. The introduction of new procedures and technologies in medicine is routinely fraught with issues associated with learning curves and unanticipated pitfalls. Because the explicit objectives of this novel technology are to optimize surgical procedures to provide more safe and more reliable outcomes, these favorable results provide the potential for significant improvements in orthopedic surgery.

Literature has shown that the outcomes of UKA are significantly improved by correct component alignment. With the desire to minimize the surgical exposure and the limitations of manual instrumentation, this goal has proven difficult to achieve consistently. This study evaluates the accuracy of a new technique that replaces manual instrumentation with a robotically guided cutting instrument designed to implement a three-dimensional pre-operative plan.

Forty-three UKAs were implanted using a robotically guided system that creates virtual boundaries defining the depth and volume of bone resection for a specific implant. The boundaries were based on a three-dimensional pre-operative plan. Post-operative lateral and AP radiographs were evaluated for four different aspects of component to host bone alignment for the tibia and four for the femur. Ten patients also underwent a post-operative CT to compare the resultant versus the planned three-dimensional component placements.

Radiographically, we identified an outlier as any specific measurement outside a particular range set by an independent clinical advisory board of orthopedic surgeons. Of the 344 radiographic measurements, only 4 (1%) were identified as outliers, with none of these deemed clinically significant. On average, the components were placed in 0.6° less varus (SD = 1.9°) and 0.1° less posterior slope (SD = 1.8°) compared with the pre-operative plan, with RMS errors of 1.9° in the coronal plane and 1.7° in the sagittal plane.

Robotically assisted implementation of a pre-operative plan for UKA is accurate and precise with very few outliers. This is particularly impressive as these patients were from the inaugural series of patients undergoing a technologically innovative procedure. This technology has great potential to improve accuracy and enhance safety for surgeons with procedures that are less forgiving and technically difficult.