Markerless robotic pedicle screw placement based on structured light tracking.

Purpose: Most existing robot systems for pedicle screw placement rely on optical markers to establish the spatial relationship between the surgical tool and the surgical path. Marker installation and registration are time-consuming, and error may also accumulate along the complicated coordinate transformation chain. Therefore, we proposed a markerless structured light-based method to simplify the surgery workflow and the coordinate transformation chain.

Methods: Firstly, a structured light camera is used to directly track both the surgical tool and the bone anatomy without using markers. Secondly, a markerless "two-direction" approach for robot-camera registration together with a feedback robot control method is developed. Lastly, a prototype system is built and examined with precision validation experiments and pedicle screw drilling experiments.

Results: Precision validation experiments show satisfactory positioning accuracy of the system. In drilling experiments, 42 paths were drilled on three synthesized cervical vertebrae phantoms and all the paths successfully went through the pedicles. The mean position error of the entry point was 0.28 ± 0.16 mm, and the mean angle error was 0.49 ± 0.24°, which can meet the clinical requirement.

Conclusion: The results show the feasibility of the proposed structured light-based method for pedicle screw placement, which has a simple workflow and can achieve good accuracy without using optical markers.