Abstract
Stereotactic principles used primarily for brain surgery have been developed further and introduced into spine surgery at the beginning of the 1990’s. The system solutions available consist of three components: the surgical object (vertebra), the virtual object (CT-image data of the vertebra), and the navigatorallowing the surgeon to localise the position of the instrument inside the surgical object in real-time. Optoelectronic systems using infrared light emitting diodes and magnetic field based navigators are in use.
Lumbar pedicle screw insertion was the first clinical application for this technique. Screws can be positioned safely following a preplanned optimal trajectory or according to the anatomic situation utilising the real-time module intraoperatively.
The effectiveness of this new technique has been shown in prospective studies (Schwarzenbach et al 1997, Laine et al 1997, 1999).
In a a prospective randomised clinical trial one-hundred consecutive patients were randomly allocated for either conventional (Group 1) or computer assisted (Group 2) pedicle screw insertion. From the computer assisted group nine patients were dropped out. There was no statistical difference between the groups. CT-based optoelectronic navigation was used for screw insertion in Group 2. The screw position in the pedicle was assessed postoperatively by an independent observer with CT.
The pedicle perforation rate was 13.4% (37/277 screws) in the conventional group and 4.6% (10/219 screws) in the computer assisted group (P=0.006). The majority of perforations was less than 4 mm. A pedicle perforation of 4 to 6 mm was found in 1.4% (4/277) of the screws in Group 1, and none in Group 2. Intraoperatively, eleven screws were repositioned in Group 1 and none in Group 2. There were no postoperative complications related to screw placement.
We conclude that higher accuracy of pedicle screw insertion with computer assisted navigation than with conventional methods could be demonstrated under clinical conditions in a randomised controlled clinical trial.
At present CAOS Systems are used also for localisation of intraosseous pathologic processes during biopsies in spine and pelvis, sacroiliac screw fixation and vertebral osteotomies.
Refinement of the method for use in minimal invasive and percutaneous procedures is in progress.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
