Experiments on robot-assisted navigated drilling and milling of bones for pedicle screw placement.

BACKGROUND: This article presents experimental results for robot-assisted navigated drilling and milling for pedicle screw placement. The preliminary study was carried out in order to gain first insights into positioning accuracies and machining forces during hands-on robotic spine surgery. Additionally, the results formed the basis for the development of a new robot for surgery.
METHODS: A simplified anatomical model is used to derive the accuracy requirements. The experimental set-up consists of a navigation system and an impedance-controlled light-weight robot holding the surgical instrument. The navigation system is used to position the surgical instrument and to compensate for pose errors during machining. Holes are drilled in artificial bone and bovine spine. A quantitative comparison of the drill-hole diameters was achieved using a computer.
RESULTS: The interaction forces and pose errors are discussed with respect to the chosen machining technology and control parameters. Within the technological boundaries of the experimental set-up, it is shown that the accuracy requirements can be met and that milling is superior to drilling.
CONCLUSIONS: It is expected that robot assisted navigated surgery helps to improve the reliability of surgical procedures. Further experiments are necessary to take the whole workflow into account. Copyright 2006 John Wiley & Sons, Ltd.