E1767. Intraoperative Cone Beam CT is as Reliable as Conventional CT for Identification of Pedicle Screw Breach in Thoracolumbar Spine Surgery
  1. Gustav Burström; Karolinska Institutet
  2. Paulina Cewe; Karolinska Institutet
  3. Erik Edstrom; Karolinska Institutet
  4. Anastasios Charalampidis; Karolinska Institutet
  5. Rami Nachabe; Philips
  6. Adrian Elmi-Terander; Karolinska Institutet
To test the hypothesis that intraoperative cone beam computed tomography (CBCT) using the Philips Allura Augmented Reality Surgical Navigation (ARSN) system in a dedicated hybrid OR, matches computed tomography (CT) for identification of pedicle screw breach during spine surgery.

Materials and Methods:
In this retrospective study, 20 patients (260 pedicle screws; overall mean age 30.5 years; 11 women and 9 men) underwent intraoperative CBCT as well as conventional postoperative CT scans to identify and grade the degree of pedicle screw breach. All patients had undergone spinal fixation surgery that included placement of pedicle screws. Two hundred and sixty screws were graded according to the Gertzbein grading scale on both the intraoperative CBCT and the postoperative conventional CT scans. Blinded assessments were performed by three spine surgeons and the CT served as the standard of reference. Screws graded as 0 or 1 according to the Gertzbein grading scale were considered clinically accurate while grades 2 or 3 were considered clinically inaccurate. Sensitivity, specificity and negative predictive value were the primary metrics of diagnostic performance.

For this patient group, the negative predictive value of an intraoperative CBCT to rule out pedicle screw breach was 99.6% (CI: 97.75% - 99.99%). Among 10 screws graded as inaccurate on CT, 9 were graded as such on the CBCT, giving a sensitivity of 90.0% (CI: 55.5% - 99.75%). Among the 250 screws graded as accurate on CT, 244 were graded as such on the CBCT, giving a specificity of 97.6% (CI: 94.85% - 99.11%). The absolute interrater agreement was 72.7% in the CT-group and 63.1% in the CBCT-group.

CBCT, performed with the Allura ARSN system (Philips), is comparable to a conventional postoperative CT scan for ruling out misplaced pedicle screws in spinal deformity cases.