High degree of accuracy of a novel image-free handheld robot for unicondylar knee arthroplasty in a cadaveric study

Abstract

Background: Surgical robotics has been shown to improve the accuracy of bone preparation and soft tissue balance in unicondylar knee arthroplasty (UKA). However, although extensive data have emerged with regard to a CT scan-based haptically constrained robotic arm, little is known about the accuracy of a newer alternative, an imageless robotic system.

Questions/purposes: We assessed the accuracy of a novel imageless semiautonomous freehand robotic sculpting system in performing bone resection and preparation in UKA using cadaveric specimens.

Methods: In this controlled study, we compared the planned and final implant placement in 25 cadaveric specimens undergoing UKA using the new tool. A quantitative analysis was performed to determine the translational, angular, and rotational differences between the planned and achieved positions of the implants.

Results: The femoral implant rotational mean error was 1.04° to 1.88° and mean translational error was 0.72 to 1.29 mm across the three planes. The tibial implant rotational mean error was 1.48° to 1.98° and the mean translational error was 0.79 to 1.27 mm across the three planes.

Conclusions: The image-free robotic sculpting tool achieved accurate implementation of the surgical plan with small errors in implant placement. The next step will be to determine whether accurate implant placement translates into a clinical and functional benefit for the patient.

Fig. 1

The Navio™ handpiece includes a blue clamshell central unit for the user to grip, an array to allow it to be tracked by the system, and a metal guard covering the burr. Calibration of the burr to the end of the guard means that the system registers when the burr is covered by the guard or cutting. Reprinted with permission from Blue Belt Technologies Inc (Plymouth, MN, USA).

Fig. 2A–C

(A) The planning stage screen shows where the user can adjust the implant size and move the position of the implant in all three planes to best match the patient’s condyle. (B) The gap planning screen shows the position of the implant on the patient’s condylarsurface (yellow overlay). The graph at the bottom of the screen illustrates the virtual gap balance through a range of flexion predicted from implementing the planned implant position and tensioning the ligaments. (C) Contact point screen, illustrates the contact points on both the tibial and femoral component as the knee goes through a range of flexion.

Fig. 3A–B

(A) Femur and (B) tibia cutting screens show midcutting. The yellow surface is the “target” surface, green surface indicates 1 mm of bone still to be removed, blue surface indicates 2 mm of bone still to be removed, and the purple surface indicates 3 mm or more bone still to be removed.