Comparison of the Malposition Rates of the Vertebral Pedicle Screws Using the PediGuard Technique: PediGuard Technique Associated With Fluoroscopy and Fluoroscopy Alone

It is a guide for the perforation of the pedicular channel, with a probe at its extremity. This probe allows a real time measurement of the electric conductivity of the tissues that are being crossed. The conductivity measure is translated in a sound signal. Because the cortical bone has a low conductivity, the probe will emit a low intensity sound signal. The cancellous bone has a medium conductivity. Therefore, the probe will emit a medium sound signal. However, in the event of a breach in the pedicular cortical, as blood and periost have a high conductibility, the probe will emit a intense, rapid pace, sound signal.The Pediguard technique helps thus to anticipate a cortical effraction, by detecting the proximity of the cortical wall.

The placing of pedicular screws under fluoroscopic control is the most common technique as it is both reproducible and accessible. It is a two dimensional imaging technique. The profile incidence at the level of the spine is mostly used to spot the vertebral pedicle and the direction of the screw in the sagittal plane. However, there is no real control of the direction of the pedicular screw in the horizontal or frontal plane and it is an irradiating imaging technique.