Study design: Prospective, randomized, controlled study.
Objective: To report the results of using the PediGuard (SpineGuard, Inc., San Francisco, CA), a local electrical conductivity measurement device, to reduce radiation exposure while drilling the pilot hole for pedicle screw placement.
Summary of background data: Reports of pedicle screw placement in the lumbar spine have shown medial pedicle perforations with nerve root impingement in addition to lateral pedicle and vertebral body perforations that can impinge the nerve root within the psoas. Routine use of fluoroscopy (fluoro) is thought to reduce the risk of perforations but is associated with increased radiation. A new pedicle-drilling device (PediGuard) which uses electrical conductivity differentiation at the tip for assessing bone versus soft tissue, has been developed to improve the safe positioning of pedicle screws. This device not only warns of an impending medial breach but also is the only device available to, in real time, nonradiographically detect a lateral breach. METHODS.: Eighteen patients with a diagnosis of lumbar degenerative spine who had a posterior spinal fusion were enrolled. The average age of the patients was 55 ± 12 years. Postoperative computed tomographic scans were reviewed by an independent reviewer. Screws were considered "in" (<2 mm of breach) or "out" (≥ 2 mm of breach). In a randomized fashion, the surgeon placed a pilot hole either with a standard technique (manual probe) or the PediGuard, and used fluoro for each drilling as a guidance assist as necessary. Electromyographic testing was not done by the surgeon. A total of 78 screws (39 via standard probe and 39 with PediGuard assist) were analyzed.
Results: There was no significant difference in breach rate of 2 mm or more by either of the 2 methods (P = 1.000), with 1 screw out in each group. Fluoro shots averaged 5.2 (range, 0-15) per screw in the PediGuard group versus 7.5 (range, 2-17) in the standard group (P < 0.001). This represents an average decrease of 2.3 (30%) fluoro shots per screw with the PediGuard. There were 202 total fluoro shots used in the PediGuard group versus 293 in the standard group.
Conclusion: In this prospective, randomized trial of a pedicle drilling device that uses electrical conductivity differentiation at the tip for assessing bone versus soft tissue, the number of fluoro shots was reduced by 30% compared with a standard drilling probe while maintaining a 97.5% accurate, safe screw placement.