Robotic assessment of patella tracking in total knee arthroplasty.

Objectives: Robotic tools have been developed to improve planning, accuracy and outcomes in total knee arthroplasty (TKA). The purpose of this study was to describe and illustrate a novel technique for assessing the patellofemoral (PFJ) in TKA using an imageless robotic platform.

Methods: A consecutive series of 30 R-TKA was undertaken by a single surgeon utilising the described technique. A technique to dynamically assess the PFJ intra-operatively, pre- and post-implantation was developed. A full set of data from 9 cases was then collected and reviewed for analysis. A series of dynamic PFJ tracks collected intra-operatively pre- and post-implantation are presented. Furthermore, a full assessment of PFJ over and under-stuffing through a 90° arc of flexion is illustrated. Finally, a pre- and post-centre of rotation for the PFJ was defined and measured.

Results: The described technique was defined over a series of 30 R-TKA using the described robotic platform. Nine cases were analysed to determine what data could be measured using the robotic platform. Intra-operative real-time data allowed a visual assessment of PFJ tracking through a range of motion of 0°-90° flexion pre- and post-implantation. PFJ over and under-stuffing was also assessed intra-operatively through a range of motion of 0°-90° flexion. Post-operative analysis allowed a more detailed study to be performed, including defining a pre- and post-implantation centre of rotation (COR) for the patella. Defining the COR allowed the definition of a patella plane. Furthermore, patella mediolateral shift in full extension, and end flexion could be measured.

Conclusion: Intra-operative assessment of the PFJ in TKA is challenging. Robotic tools have been developed to improve measurement, accuracy of delivery and outcomes in TKA. These tools can be adapted in novel ways to assess the PFJ, which may lead to further refinements in TKA techniques.