Triggered Electromyography is a Useful Intraoperative Adjunct to Predict Postoperative Neurological Deficit Following Lumbar Pedicle Screw Instrumentation

STUDY DESIGN: Systematic review and meta-analysis. OBJECTIVES: Malposition of pedicle screws during instrumentation in the lumbar spine is associated with complications secondary to spinal cord or nerve root injury. Intraoperative triggered electromyographic monitoring (t-EMG) may be used during instrumentation for early detection of malposition. The association between lumbar pedicle screws stimulated at low EMG thresholds and postoperative neurological deficits, however, remains unknown. The purpose of this study is to assess whether a low threshold t-EMG response to lumbar pedicle screw stimulation can serve as a predictive tool for postoperative neurological deficit. METHODS: The present study is a meta-analysis of the literature from PubMed, Web of Science, and Embase identifying prospective/retrospective studies with outcomes of patients who underwent lumbar spinal fusion with t-EMG testing. RESULTS: The total study cohort consisted of 2,236 patients and the total postoperative neurological deficit rate was 3.04%. 10.78% of the patients incurred at least 1 pedicle screw that was stimulated below the respective EMG alarm threshold intraoperatively. The incidence of postoperative neurological deficits in patients with a lumbar pedicle screw stimulated below EMG alarm threshold during placement was 13.28%, while only 1.80% in the patients without. The pooled DOR was 10.14. Sensitivity was 49% while specificity was 88%. CONCLUSIONS: Electrically activated lumbar pedicle screws resulting in low t-EMG alarm thresholds are highly specific but weakly sensitive for new postoperative neurological deficits. Patients with new postoperative neurological deficits after lumbar spine surgery were 10 times more likely to have had a lumbar pedicle screw stimulated at a low EMG threshold.