Retrospective Study of Nerve Injury and Pedicle Screw Breach after Pedicle Screw Fixation with Intraoperative Triggered Electromyography Monitoring

Abstract

Objective: To evaluate the incidence of nerve injury and pedicle breach after pedicle screw fixation (PSF) with intraoperative triggered electromyography (tEMG) monitoring.Material and Methods: All patients who underwent PSF with intraoperative tEMG at Vajira Hospital between October 2018 and March 2020 were included. Patients with dysmorphic pedicle features, preoperative infection, or incomplete follow-up data were excluded. PSF was done with intraoperative tEMG. The stimulation threshold was recorded. Stimulation threshold <7 mA was not allowed to proceed with the procedure and required reposition of pedicle screw immediately. Post-operative nerve injury was evaluated by physical examination and computer tomography of the spine was done to detect any pedicle breaches. The sensitivity and specificity of intraoperative tEMG to detect pedicle breach were calculated. The risk factors associated with pedicle breach were analyzed.Results: The records of thirty-six patients with 278 pedicle screws were analyzed. No post-operative nerve injuries were found. The incidence of pedicle breach was 2.2%. The sensitivity and specificity were 83.0% and 91.0%, respectively. The risk factors associated with pedicle breach were degenerative disease and tumor(s) (odds ratio (OR) 3.05, 95% confidence interval (CI) 1.11-8.41, p-value=0.030) and stimulation threshold 7-10 mA (OR 0.02, 95% CI 0.00-0.19, p-value< 0.001). Conclusion: PSF with intraoperative tEMG was safe for neural integrity. Intraoperative tEMG had the ability to detect pedicle breaches with fair sensitivity and high specificity. Patients with degenerative disease, tumors, or stimulation threshold less than 11 mA had a higher risk of pedicle breach.