Use of rapid prototyping drill guide template for pedicle screw placement

Abstract

Background: Pedicle screw placement using free hand technique has high incidence of pedicle perforation. The said risk can be reduced with intra-operative fluoroscopy or navigation, which have some disadvantages. A promising principle for solving most of the issues is the rapid prototyping technology. By this technique it is possible to manufacture patient specific drill guide templates that enable optimal pedicle screw placement. In the last decade, many studies have featured relatively successful implantations of pedicle screws through the use of drill guide templates, though mostly on cadavers. We performed a similar clinical study involving the manufacture of templates for the lumbar and sacral regions that enable simultaneous multiple- level screw implanting. Methods: A randomized clinical trial was performed in 15 patients. In the lumbar and sacral spine 30 screws were implanted using drill guide template and 36 screws using free hand technique under fluoroscopy supervision. Preoperative CT-scans were taken for drill guide template design and manufacture using selective laser sintering method. According to postoperative CTscan analysis, pedicle perforation incidence was estimated. Results: The incidence of cortex perforation was significantly reduced in the drill guide template group. Conclusions: Drill guide templates have turned out to be a reliable solution that importantly reduces pedicle perforation incidence and complications related to it. However, there are shortcomings: a relatively lengthy manufacturing process, possible manufacturing faults and incorrect positioning during the operation. Owing to mentioned disadvantages, templates have not replaced free hand and navigation technique yet, but could represent a useful tool in some selected cases.