ABSTRACT
OBJECTIVES: To assess if hydroxyapatite (HA)-coated titanium pedicle screws exhibit the same electroconductive characteristics as non-HA-coated screws. METHODS: Resistance measurements were obtained from a random sampling of 10 HA-coated pedicle screws and 10 non-HA-coated screws, and surgical conditions simulated. Surface resistivity measurements were taken for each screw to determine voltage drop over its entire length. RESULTS: The non-HA-coated screws tested showed low resistive properties and proved to be an ideal conductor of electrical current. The resistive properties associated with the HA-coated pedicle screws were found to be similar to those of commonly used insulators removing the effectiveness of triggered electromyographic responses. CONCLUSIONS: Based on test results, these data suggest that the resistance value of the HA-coated screw is large enough to prevent modern Intra-Operative Monitoring (IOM) equipment from delivering the necessary current through the shank of the screw to create a diagnostic electromyographic response. Any response that would be produced would be because of shunting of electric current from the non-coated head of the screw into adjacent tissue and not through the shank of the screw. These study results suggest that HA-coated screws cannot be stimulated to assist in determining the accuracy of pedicle screw placement.
