ACCURACY OF ROBOTICALLY ASSISTED UKA

Abstract

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.