A Comparison of Drill Guiding and Screw Guiding 3D-Printing Techniques for Intra- and Extrapedicular Screw Insertion.

Study Design: Screw randomized cadaveric study.

Objective: To compare the accuracy of three-dimensional (3D)-printed drill guides versus additional screw guiding techniques for challenging intra- and extrapedicular screw trajectories.

Summary Of Background Data: Pedicle screw placement can be technically demanding, especially in syndromic scoliosis with limited bone stock. Recently, 3D-printing and virtual planning technology have become available as new tools to improve pedicle screw insertion. Differences in techniques exist, while some focus on guiding the drill, others also actively guide subsequent screws insertion. The accuracy of various 3D-printing-assisted techniques has been studied; however, direct comparative studies have yet to determine whether there is a benefit of additional screw guidance.

Methods: Two cadaveric experiments were conducted to compare drill guides with two techniques that introduce additional screw guiding. The screw guiding consisted of either k-wire cannulated screws or modular guides, which were designed to guide the screw in addition to the drill bit. Screws were inserted intra- or extrapedicular using one of each methods according to a randomization scheme. Postoperative computed tomography scanning was performed and fused with the preoperative planning for detailed 3D screw deviation analysis.

Results: For intrapedicular screw trajectories malpositioning was low (2%) and the modular guides revealed a statistically significant increase of accuracy (P  = 0.05) compared with drill guides. All techniques showed accurate cervical screw insertion without breach. For the extrapedicular screw trajectories both additional screw guiding methods did not significantly (P = 0.09) improve accuracy and malpositioning rates remained high (24%).

Conclusions: In this cadaveric study it was found that the additional screw-guiding techniques are not superior to the regular 3D-printed drill guides for the technically demanding extrapedicular screw technique. For intrapedicular screw insertion, modular guides can improve insertion; however, at cervical levels regular 3D-printed drill guides already demonstrated very high accuracy and therefore there is no benefit from additional screw guiding techniques.

Level Of Evidence: 3.