Bone-mounted miniature robotic guidance for pedicle screw and translaminar facet screw placement: Part I - Technical development and a test case result

OBJECTIVE: To introduce a new miniature robot (SpineAssist; MAZOR Surgical Technologies, Caesarea, Israel) that has been developed and tested as a surgical assistant for accurate percutaneous placement of pedicle screws and translaminar facet screws. METHODS: Virtual projections in three planes-axial, lateral, and anteroposterior-are reconstructed for each vertebra from a preoperative computed tomographic (CT) scan. On a specially designed graphic user interface with proprietary software, the surgeon plans the trajectory of the screws. Intraoperative fluoroscopic x-rays with targeting devices are then matched with the CT-based virtual images, as well as the surgeon's plan. A clamp is attached to the spinous process or a minimally invasive frame (Hover-T frame; MAZOR Surgical Technologies) is mounted to the iliac crest and one spinous process. The miniature robot is then attached to the clamp and/or frame. On the basis of combined CT scan and fluoroscopic data, the robot aligns itself to the desired entry point and trajectory, as dictated by the surgeon's preoperative plan. RESULTS: A test case in a cadaver lumbar spine was performed in which four screws and two rods were inserted, using a minimally invasive technique, combining the SpineAssist system and Hover-T frame in conjunction with the PathFinder system (Spinal Concept Inc., Austin, TX). The discrepancy between the planned and actual screw trajectories was measured by means of postprocedural CT scan. Overall, the four screws were implanted with an average deviation of 1.02 +/- 0.56 mm (range, 0-1.5 mm) from the surgeon's plan. CONCLUSION: These preliminary results confirm the system's accuracy and support its use in minimally invasive spine surgery applications.