Accuracy of cortical bone trajectory screw placement using patient-specific template guide system.

ABSTRACT

Cortical bone trajectory (CBT) can facilitate both minimum invasiveness and strong screw fixation; however, ensuring the ideal cortical trajectory is challenging due to the narrow corridor, necessitating high-level surgical skill. A patient-specific template guide for CBT screw placement may be a promising solution to improve accuracy and safety. Little has been reported on the use of a CBT screw guide in clinical practice. The aim of the present study was to evaluate the accuracy of CBT screw placement using the template guide. This study was a retrospective clinical evaluation of prospectively collected patients. Forty-three consecutively enrolled patients who underwent posterior lumbar spinal fusion using the guide system were included. First, three-dimensional planning of CBT screw placement was performed using computer simulation software. The trajectory was directed in a more anterior position of the vertebral body, compared with the original CBT, and the standard size was set as 5-6 mm in diameter and 40-45 mm in length. Then, screw guides were created for each vertebra preoperatively and used. The safety and accuracy of a total of 198 inserted screws (L1 to L5) were analyzed using postoperative computed tomography by evaluation of pedicle perforation and measurement of screw deviations between the planned and actual screw positions. A total of 193 screws (97.5%) were placed completely inside the pedicle and there was no incidence of neurovascular injuries. The mean screw deviation from the planned trajectory on the coronal plane at the midpoint of the pedicle was 0.62 ± 0.42 mm, and the mean angular deviations in the sagittal and transverse planes were 1.68 ± 1.24° and 1.27 ± 0.77°, respectively. CBT screw placement using a patient-specific template guide was accurate enough for clinical application. This technique could be an effective solution to achieve both correct screw insertion and a reduction of complications.