Pedicle violation and Navigational errors in pedicle screw insertion using the intraoperative O-arm: A preliminary report

Abstract

Background: Use of computer-assisted insertion of pedicle screws has some advantages owing to the reportedly decreased incidence of pedicle breach and clinical events. Registration-based methods based on preoperative computed tomography imaging, 2D fluoroscopy, and 3D fluoroscopy are the most popular, however each has its limitations. O-arm-based navigation, which uses intraoperative acquisition and registration of navigated images, may overcome many of these disadvantages. We set out to study the clinical accuracy and navigational accuracy for pedicle screw insertion using our recently acquired O-arm and present our preliminary findings.

Methods: The first 26 patients operated consecutively for L4-5 fusion were included in the study. O-arm-based navigation was used to insert the pedicle screws. Postoperative computed tomography images were acquired and assessed for pedicle breach and anterior cortical perforation. Planned trajectories of each screw were compared with the actual trajectories in the postoperative images to assess navigational accuracy in both axial and sagittal planes.

Results: A total of 104 screws were inserted. One screw (1%) breached the pedicle laterally. Nonsignificant anterolateral cortical perforations were noted in 7 screws (6.7%), all of which occurred at L5 level. The mean axial and sagittal navigational error was 2.3° (±1.7) and 3.1° (±2.3), respectively. There were no significant differences in the errors between L4 or L5 level. The occurrence of anterior perforation correlated with the degree of axial (P = .02) but not sagittal (P = .12) navigational error. There were no clinical events related to the screw insertion.

Conclusion: Use of O-arm-guided pedicle screw insertion was associated with low incidence of pedicle breach (1%) and a low range of navigational error in both sagittal and axial planes. Anterolateral vertebral body perforation was higher at L5 without any negative clinical events. Despite the high need for technical support, we found that O-arm was a very efficient tool for accurate pedicle screw insertion.

Keywords: Clinical accuracy; Computer-assisted navigation; Navigational accuracy; O-arm; Pedicle screw.

Figures

Fig. 1

(A) Axial angle on the O-Arm images. The arrow represents the midsagittal plane of L4, which is defined as 0°. The planned screw makes a 13.1° angle with the midsagittal plane of L4. (B) Axial angle on the postoperative images. The actual screw made 11.2° angle with the midsagittal plane of L4. (Color version of figure is available online.)

Fig. 2

(A) Sagittal angle on the O-Arm images. The arrow is the superior end plate of L4 defined as 0°. The planned screw makes a 10.1° angle with the end plate of L4. (B) Sagittal angle on the postoperative images. The actual screw makes a 10.7° angle with the end plate of L4. (Color version of figure is available online.)

Fig. 3

Shows an example of anterolateral perforation. The adjacent image shows the planned L5 trajectory almost parallel to the midline sagittal vertebral axis. The triangle-shaped L5 body and proximity of the planned screw to the cortical margin can be noted. (Color version of figure is available online.)