Accuracy of lower cervical pedicle screw placement with assistance of distinct navigation systems: a human cadaveric study

Abstract

Purpose: Evaluate the accuracy of five different techniques for lower cervical pedicle screw placement.

Methods: Forty human cadaveric cervical spines were equally divided into five groups, and each group had eight specimens. Pedicle screws with dia. 3.5 mm were used. Group 1 was blind screw placement without any assistance; Group 2-5 was assisted by the X-ray fluoroscopy, virtual fluoroscopy navigation system, CT-based navigation system, and Iso-C 3D navigation system, respectively. Thereafter, cortical integrity of each pedicle was evaluated by anatomic dissection of the specimens.

Results: A total of 398 pedicle screws were inserted. In the Group 1-5, the average operation time per sample was 27 ± 3.0, 112 ± 10.3, 69 ± 6.4, 98 ± 11.0, and 91 ± 6.0 min, respectively. The outcome for excellent, fair and poor were 29 (36.3 %), 21 (26.2 %) and 30 (37.5 %) in Group 1; 35 (44.9 %), 29 (37.2 %) and 14 (17.9 %) in Group 2; 34 (42.5 %), 36 (45.0 %) and 10 (12.5 %) in Group 3; 70 (87.5 %), 10 (12.5 %) and 0 (0.0 %) in Group 4; 72 (90.0 %), 8 (10.0 %) and 0 (0.0 %) in Group 5.

Conclusions: Blind screw placement was surely unsafe. Lower cervical pedicle screw placement assisted by the CT-based navigation system or the Iso-C 3D navigation system significantly improved the accuracy compared to the fluoroscopy assistance and the virtual fluoroscopy navigation assistance.

Figures

Fig. 1

Virtual fluoroscopy navigation system assisted pedicle screw placement. The pedicle screw placement is inducted by the 2D images (A–P view, lateral view and bi-oblique view), with the pointer to determine the entry point, the sagittal angle and a protractor to determine the transverse angle

Fig. 2

Preoperative design of CT-based navigation system. The preoperative design of the left pedicle of C5 is taken as an example, the ideal entry point, sagittal angle, transverse angle and the appropriate length and diameter of the screw are illustrated

Fig. 3

CT-based navigation system assisted cervical pedicle screw placement. According to the preoperative reconstructed 3D images, a pointer is used to determine the entry point and direction

Fig. 4

Iso-C 3D navigation system assisted cervical pedicle screw placement. The pedicle screw placement is inducted by the instantaneous reconstructed 3D images

Fig. 5

Evaluation of accuracy of the pedicle screw placement in gross view. a Excellent: the screw is totally in the pedicle without penetration. b Fair: there is penetration in the isthmus by the screw thread, and the penetrated part is no more than 1 mm. c Poor: there is penetration in the isthmus by the screw and the penetrated part is more than 1 mm