Neurophysiological characteristics of carbon PEEK screws in patients with spinal metastatic disease

Introduction: Carbon fibre-reinforced polyetheretherketone (CFR-PEEK) pedicle screws have gained attention in spinal oncology because of their radiolucency and compatibility with radiotherapy. While their biomechanical characteristics have been studied, their neurophysiological performance remains unclear. Methods: This prospective observational study was conducted between 2020 and 2024 and included 14 patients with vertebral metastases. A total of 202 pedicle screws (101 titanium, 101 CFR-PEEK) were analysed. For each trajectory, a titanium trial screw with a diameter 0.5 mm smaller than the definitive CFR-PEEK implant was inserted once as a tap-equivalent device to measure the baseline stimulation threshold and was subsequently replaced by the CFR-PEEK screw along the same trajectory to record the corresponding value. Intraoperative stimulation thresholds were measured in milliamperes (mA) and stratified by implant type, anatomical side, and spinal level. Results: The mean thresholds were 21.43 mA for titanium and 20.27 mA for CFR-PEEK (p = 0.435). Compared with the thoracolumbar level, the thoracic level was associated with significantly greater conductivity (p = 0.002). A significant threshold difference (> 5 mA) was observed in 35.64% of the trajectories. Conclusion: CFR-PEEK screws are safe and reliable but require titanium-assisted monitoring to ensure consistent intraoperative stimulation thresholds.