Dimensional accuracy of TKA cut surfaces with an active robotic system

Abstract

This is a study of the dimensional accuracy of the bone cut surfaces in robotic TKA. One surgeon performed robotic TKA on four cadaveric knees. A novel technique was developed for measuring the dimensional accuracy of both the femoral and tibial cut surfaces. CT scans were used to create a pre-operative plan and generate nominal cut surfaces on the 3D bone model. After TKA, the cut surfaces were then laser scanned. Two femoral components were also scanned and compared to nominal dimensions. Flatness was computed as the standard deviation between each of the cut surfaces and the best-fit plane. The angles between the five femoral best-fit planes were compared to the nominal values. The point-to-point distances between the femoral cut surfaces and the nominal cut planes were computed to estimate the bone-to-implant gap. The cut surfaces had an average flatness of 0.16 ± 0.06 mm with low variability between different cut planes. The femoral cut surfaces had average angular errors of 0.47 ± 0.39°, which are of similar magnitude as the errors found for the implants. The bone-to-implant gap was within ±1 mm for 97.9% of the surface on average. Using a novel methodology, the dimensional accuracy of an active robotic system for TKA was found to be very high for both the femoral and tibial bone cuts. Comparison studies are needed with other robotic systems as well as studies comparing manual and robotic techniques.