[Computer-assisted surgery: automated screw placement in the vertebral pedicle]

Previous studies of conventional surgical procedures have shown a significant rate of incorrect pedicle screw placement ranging from 10 to 40%. Transpedicle screw insertion may cause three types of complications: neurologic, vascular and mechanical. The aim of this prospective study is to improve the reliability of pedicle screwing with computer assistance.

A new and original technique that combines preoperative computed tomography imaging with intraoperative passive navigation has been used to perform 48 pedicle screwings in the thoracolumbar region. In the same time, 48 pedicle screwings were performed manually in the same region and on the same vertebral levels. With postoperative X-rays and computed tomography examination, screw position related to pedicle position could be assessed and comparison could be made between the two groups (with and without computer assistance).

Two screws in 48 vertebra (4%) had incorrect placement with computer assisted technique whereas 18 screws in 48 vertebra (37%) had incorrect placement with manual insertion. The intraoperative accuracy provided by the computer after registration was better than 1 mm. The difference between the two groups was statistically highly significant (P < 0.0001). The cortex penetration observed with the computer assisted technique was not imputed to computer failures. Errors in acquiring data by the surgeon in the pre and peroperative steps may explain the two incorrect placements of the screws.

This clinical experience confirms that the accuracy and reliability of this computer assisted technique are very good.