Navigation accuracy and assessability of carbon fiber-reinforced PEEK instrumentation with multimodal intraoperative imaging in spinal oncology

Radiolucent carbon-fiber reinforced PEEK (CFRP) implants have helped improve oncological follow-up and radiation therapy. Here, we investigated the performance of 3D intraoperative imaging and navigation systems for instrumentation and precision assessment of CFRP pedicle screws across the thoraco-lumbar spine. Thirty-three patients with spinal tumors underwent navigated CFRP instrumentation with intraoperative CT (iCT), robotic cone-beam CT (rCBCT) or cone-beam CT (CBCT) imaging. Two different navigation systems were used for iCT-/rCBCT- and CBCT-based navigation. Demographic, clinical and outcome data was assessed. Four blinded observers rated image quality, assessability and accuracy of CFRP pedicle screws. Inter-observer reliability was determined with Fleiss` Kappa analysis. Between 2018 and 2021, 243 CFRP screws were implanted (iCT:93, rCBCT: 99, CBCT: 51), of which 13 were non-assessable (iCT: 1, rCBCT: 9, CBCT: 3; *p = 0.0475; iCT vs. rCBCT). Navigation accuracy was highest using iCT (74%), followed by rCBCT (69%) and CBCT (49%) (*p = 0.0064; iCT vs. CBCT and rCBCT vs. CBCT). All observers rated iCT image quality higher than rCBCT/CBCT image quality (*p < 0.01) but relevant pedicle breaches were reliably identified with substantial agreement between all observers regardless of the imaging modality. Navigation accuracy for CFRP pedicle screws was considerably lower than expected from reports on titanium implants and CT may be best for reliable assessment of CFRP materials.