[Precision and safety of positioning pedicle screws in the thoracic and lumbar spine using a hand-guided aiming sleeve : A CT control study].

Background: For the implantation of pedicle screws, navigation-supported systems are nowadays used more and more to avoid screw misalignment by making the direction of the screw more predictable.

Objective: Examination of the precision after instrumentation of the pedicle screw with the hand-guided aiming sleeve. The aim was to verify that the implementation of the pedicle screws is plannable and precise by using 2D X‑ray only.

Method: This retrospective study analyzed 27 consecutive trauma patients (17-84 years, 13f/14m) with vertebral body fractures. The position and precision of 108 screws, implanted using the hand-guided aiming sleeve was investigated. To determine the position the actual course of the screws was examined using the postoperative 3D CT data set (GE Optima 540, General Electric Company Boston, MA, USA; slice thickness 1.25 mm). The screws were then compared to the previously defined ideal position of the tip of the screw. In addition to the absolute and relative deviation from the ideal target point, the convergence angle and the parallelism to the cover plate were determined.

Results: Of 108 implanted pedicle screws, 90 (83%) were within target. The remaining 18 (17%) represented a clinically irrelevant screw deviation: A lateral deviation was found in 17 pedicle screws (16%) and a medial deviation in 1 (1%). The average deviation from the ideal target point in the vertebral body was 2.3 mm ventrally with a standard deviation of ± 2.3 mm. No screw misalignment or pedicle perforation was found.

Conclusion: The transcutaneous implantation of pedicle screws with a hand-guided aiming sleeve in the thoracic and lumbar spine represents a safe and precise procedure. The risk of misalignment needing a revision is lower compared to other methods of navigated screw implantation reported in the literature [1-6]. A CT-based preliminary planning is not necessary. The method is economical, special technical equipment is not required.