Robotic vertebral puncture system for percutaneous vertebroplasty

A robotic system with an X-ray-translucent end-effector and a passive failsafe mechanism is proposed for percutaneous vertebroplasty (PVP). The proposed system consists of a puncture robot with five degrees of freedom, a workstation for the navigation system, and an optical tracking device. The end-effector of the robot is partially X-ray translucent to allow the needle insertion process to be monitored by an X-ray fluoroscope. The robot has a passive failsafe mechanism for safety purposes. A needle assembly is attached to the robot by four asymmetric contacting parts supported by four springs. To evaluate the puncture accuracy of the system, puncture tests were conducted on 50 pedicles of five polyurethane phantoms simulating human lumbar vertebrae from L1 to L5. Pre-operative computed tomography (CT) volumes were acquired for the respective phantoms and segmented. Surgical plans were made for the respective pedicles by a surgeon. After the system was placed at the experimental table's side and the phantom was fixed on the table, robot calibration and phantom registration were performed. During the experiments, no needles were found to be protruding from the pedicles. The positioning accuracy measured by the optical tracking device was 0.64 mm root-mean-square (RMS) and 1.09° RMS (error range = 0.1-0.98 mm, 0.96-1.36°). After the tests, post- operative CT volumes of the respective phantoms were acquired and the puncture trajectories were analyzed. The puncture errors between the planned and actual trajectories were 1.66 mm RMS and 1.62° RMS (error range = 0.13-4.21 mm, 0.36-2.73°). The results demonstrate the feasibility of safe and accurate punctures with the proposed system.