Effective in vivo radiation dose with image reconstruction controlled pedicle instrumentation vs. CT-based navigation

Abstract

There is a rapid increase of computer-assisted surgery (CAS) in the spine for insertion of pedicle screws. In contrast to the traditional technique using fluoroscopy, CT is the primary source for surgical navigation systems. To compare organ and effective doses of fluoroscopy-controlled versus computer-assisted pedicle screw insertion under the aspect of risk reduction and number needed to treat. In 20 consecutive cases of traditional pedicle screw instrumentation under fluoroscopic control the effective doses were recorded in vivo and the organ doses then calculated. Simulating a spiral CT necessary for the 3-D-model for navigation we defined a spiral CT protocol for the instrumented levels and calculated organ and effective doses from Monte Carlo Results from CT examinations. Organ doses were clearly higher for the CT model than in any of the fluoroscopic procedures in vivo. The mean effective dose for the CT model was fifteen times higher than the fluoroscopic dose: 7.27 mSv versus 0.48 mSv. In experienced hands open pedicle screw insertion in the thoracic and lumbar spine using fluoroscopy-control requires a fifteen times lower radiation dose than do CT scans necessary for computer-assisted surgery. Regarding the published small percentage of neurological complications in traditional screw insertion technique the use of computer-assisted surgery in pedicle screw insertion using CT scan should be limited to carefully chosen indications. The development of navigation systems based on other data sources than CT should be encouraged.