  The variability in width, height, and spatial orientation of a spinal pedicle
makes pedicle screw insertion a delicate operation. The aim of the current
paper is to describe a computer-assisted surgical navigation system based on
fluoroscopic X-ray image calibration and three-dimensional optical localizers
in order to reduce radiation exposure while increasing accuracy and reliability
of the surgical procedure for pedicle screw insertion. Instrumentation using
transpedicular screw fixation was performed: in a first group, a conventional
surgical procedure was carried out with 26 patients (138 screws); in a second
group, a navigated surgical procedure (virtual fluoroscopy) was performed with
26 patients (140 screws). Evaluation of screw placement in every case was done
by using plain X-rays and post-operative computer tomography scan. A 5 per cent
cortex penetration (7 of 140 pedicle screws) occurred for the computer-assisted
group. A 13 per cent penetration (18 of 138 pedicle screws) occurred for the
non computer-assisted group. The radiation running time for each vertebra level
(two screws) reached 3.5 s on average in the computer-assisted group and 11.5 s
on average in the non computer-assisted group. The operative time for two
screws on the same vertebra level reaches 10 min on average in the non
computer-assisted group and 11.9 min on average in the computer-assisted group.
The fluoroscopy-based (two-dimensional) navigation system for pedicle screw
insertion is a safe and reliable procedure for surgery in the lower thoracic
and lumbar spine.
