*Corresponding author:Yunfen Wu, Department of Intraoperative Neurophysiology, University of Cantabria, Spain
Received: August 09, 2018; Published: August 16, 2018
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Background: Stimulus evoked electromyography (EMG) is commonly used to identify clinically relevant misplaced pedicle screws in the lumbosacral spine. This monitoring modality is more meaningful in minimally invasive surgery. In minimally invasive surgery, the pedicle screws are usually not tested, only the pedicle access needle and the tapscrew are tested by using the same stimulation threshold. No studies have compared the electrical resistance of cannulated pedicle screws and tapscrews. This study is designed to measure and to compare the resistance of cannulated tapscrews and noncoated pedicle screws of similar electroconductive characteristics and of different diameters to determine whether the same stimulation threshold can be applied for tapscrews and pedicles screws in minimally invasive lumbosacral fixation.
Materials and Methods: Resistance measurements were obtained three times across the shank from a random sampling of nine commonly used cannulated titanium noncoated pedicle screws and nine cannulated tapscrews (three composed of titanium and six of stainless steel), one of each diameter.
Results: Resistance of all tested pedicle screws ranged from 0.1ohms to 0.3ohms and tapscrews ranged from 0.1ohms to 0.3ohms. No significant differences in resistance values were observed between the cannulated noncoated titanium pedicle screws and, titanium and stainless steel tapscrews of different diameters (P > 0.05).
Conclusion: Using non-metallic dilators, the authors propose the same stimulation threshold can be used for the testing of the cannulated tapscrew and noncoated pedicle screw of similar electroconductive characteristics to optimize the accuracy of the stimulus-evoked EMG.
Keywords: Electrical Resistance; Electromyography; Pedicle Screw; Tapscrew; Thresholds; Minimally Invasive; Lumbar Fixation