Development of neuromonitoring pedicle screw-results of electrical resistance and neurophysiologic test in pig model

Objective: To analyze the electrical resistance of a newly developed neuromonitoring pedi-cle screw (Neuro-PS) and to verify the electrophysiologic properties of the Neuro-PS in a pig model. Methods: We developed 2 types of the Neuro-PS in which a gold lead was located internally (type I) and externally (type II). We measured the electrical resistance of the Neuro-PS and the conventional screw and analyzed the electrical thresholds of triggered EMG (t-EMG) of each screw by intentionally penetrating the medial pedicle wall and contacting the exiting nerve root in a pig model. Results: The electrical resistances of the Neuro-PS were remarkably lower than that of the conventional screw. In electrophysiologic testing, only the type II Neuro-PS under the lead-nerve contact condition showed a significantly lower stimulation threshold as compared to the conventional screw. Conclusion: The Neuro-PS demonstrated lower electrical resistances than the conventional screw. The type II Neuro-PS under the lead-nerve contact condition showed a significantly lower stimulation threshold compared to that of the other screws in the t-EMG test.