Objectives To test the hypothesis that intraoperative cone beam computed tomography (CBCT) using the Allura augmented reality surgical navigation (ARSN) system in a dedicated hybrid operating room (OR) matches computed tomography (CT) for identification of pedicle screw breach during spine surgery. Methods Twenty patients treated with spinal fixation surgery (260 screws) underwent intraoperative CBCT as well as conventional postoperative CT scans (median 12 months after surgery) to identify and grade the degree of pedicle screw breach on both scan types, according to the Gertzbein grading scale. Blinded assessments were performed by three independent spine surgeons and the CT served as the standard of reference. Screws graded as Gertzbein 0 or 1 were considered clinically accurate while grades 2 or 3 were considered inaccurate. Sensitivity, specificity, and negative predictive value were the primary metrics of diagnostic performance. Results 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%). Conclusions CBCT, performed intraoperatively with the Allura ARSN system, is comparable and non-inferior to a conventional postoperative CT scan for ruling out misplaced pedicle screws in spinal deformity cases, eliminating the need for a postoperative CT. Key Points • Intraoperative cone beam computed tomography (CT) using the Allura ARSN is comparable with conventional CT for ruling out pedicle screw breaches after spinal fixation surgery. • Intraoperative cone beam computed tomography can be used to assess need for revisions of pedicle screws making routine postoperative CT scans unnecessary. • Using cone beam computed tomography, the specificity was 97.6% and the sensitivity was 90% for detecting pedicle screw breaches and the negative predictive value for ruling out a pedicle screw breach was 99.6%.

Background: To investigate the accuracy of augmented reality (AR) navigation using the Magic Leap head mounted device (HMD), pedicle screws were minimally invasively placed in four spine phantoms. Methods: AR navigation provided by a combination of a conventional navigation system integrated with the Magic Leap head mounted device (AR-HMD) was used. Forty-eight screws were planned and inserted into Th11-L4 of the phantoms using the AR-HMD and navigated instruments. Postprocedural CT scans were used to grade the technical (deviation from the plan) and clinical (Gertzbein grade) accuracy of the screws. The time for each screw placement was recorded. Results: The mean deviation between navigation plan and screw position was 1.9 ± 0.7 mm (1.9 [0.3–4.1] mm) at the entry point and 1.4 ± 0.8 mm (1.2 [0.1–3.9] mm) at the screw tip. The angular deviation was 3.0 ± 1.4° (2.7 [0.4–6.2]°) and the mean time for screw placement was 130 ± 55 s (108 [58–437] s). The clinical accuracy was 94% according to the Gertzbein grading scale. Conclusion: The combination of an AR-HMD with a conventional navigation system for accurate minimally invasive screw placement is feasible and can exploit the benefits of AR in the perspective of the surgeon with the reliability of a conventional navigation system.

ObjectivesTo reduce occupational radiation exposure in a hybrid operating room (OR) used for three-dimensional (3D) image guided spine procedures. The effects of staff positioning, different X-ray imaging systems, and freestanding radiation protection shields (RPSs) were considered.MethodsAn anthropomorphic phantom was imaged with a robotic ceiling mounted hybrid OR C-arm cone beam CT (hCBCT), a mobile O-arm CBCT (oCBCT), and a mobile two-dimensional C-arm fluoroscopy system. The resulting scatter doses were measured at different positions in the hybrid OR using active personal dosimeters and an ionization chamber. Two types of RPSs were evaluated.ResultsUsing the hCBCT system instead of the oCBCT system reduced the occupational radiation dose on average by 22%. At 200 cm from the phantom, scatter doses from the hCBCT were 27% lower compared with the oCBCT. One rotational acquisition with hCBCT or oCBCT corresponded to 12 or 16 min of fluoroscopy with the C-arm, respectively. The scatter dose decreased by more than 90% behind an RPS. However, the protection was slightly less effective at 60 cm behind the RPS, due to tertiary scatter from the surroundings.ConclusionsFor 3D image guided spine procedures in the hybrid OR, occupational radiation exposure is lowered by using hCBCT rather than oCBCT. Radiation exposure can also be decreased by optimal staff positioning in the OR, considering distance to the source and positioning relative to the walls, ceiling, and RPS. In this setting and workflow, staff can use RPSs instead of heavy aprons during intraoperative CBCT imaging, to achieve effective whole body dose reduction with improved comfort.