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

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. 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. 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. CFR-PEEK screws are safe and reliable but require titanium-assisted monitoring to ensure consistent intraoperative stimulation thresholds.