Standard multiplanar fluoroscopy versus a fluoroscopically based navigation system for the percutaneous insertion of iliosacral screws - A cadaver model

Objectives: To compare the safety and efficiency of standard multiplanar fluoroscopy (StdFluoro) and virtual fluoroscopy (VirtualFluoro) for use in the percutaneous insertion of iliosacral screws. Design: Human cadaver study comparing 2 imaging modalities during iliosacral screw insertion; imaging randomized from side to side. Setting: Bioskills laboratory in a medical school. Participants: Twenty-nine embalmed whole human cadavers without prior hip or pelvic surgery. Intervention: Iliosacral screws were inserted into the SI bodies using a percutaneous insertion technique. Screws were inserted on one side using StdFluoro, and on the other side, screws were placed using VirtualFluoro. Main Outcome Measurements: Time necessary for imaging preparation, screw insertion, and actual fluoroscopy were recorded. Accuracy and safety of screw placement was assessed using computed tomography and an anatomic dissection of the pelvis. Results: Fifty-six of 58 iliosacral screws were placed within the desired bony corridor of the posterior pelvis. One screw placed using each method was inserted erroneously, but both were relatively minor deviations. There were no obvious injuries to major vessels or nerve roots. The total surgical time required for preparation of imaging and screw insertion averaged 7.3 minutes using StdFluoro and 6.7 minutes using VirtualFluoro (P = 0.4). Although the time necessary for screw insertion using VirtualFluoro averaged only 3.5 minutes, compared to 7.0 minutes for StdFluoro (P < 0.05), this time savings was offset by that required for application and calibration of tracking devices when using VirtualFluoro. The average fluoroscopy time using StdFluoro method was 26 seconds, whereas that for the VirtualFluoro was only 6 seconds (P < 0.01). Conclusions: Most of the percutancous iliosacral screws were safely inserted using StdFluoro and VirtualFluoro, and total surgical times were similar using both methods. As VirtualFluoro continues to evolve, improved efficiency in operative times may be expected. Currently, the most beneficial aspect of using VirtualFluoro during the insertion of percutaneous ihosacral screws appears to be significantly decreased use of fluoroscopy when compared to StdFluoro.