Introduction: We evaluate our 3-year experience with intraoperative EMG monitoring during placement of lumbar pedicle screws and determine the clinical utility of intraoperative EMG monitoring.
Methods: We studied 2012 consecutive patients who underwent posterior lumbar fusion surgery from January 2010 to December 2012. Screws were inserted under fluoroscopic guidance using anatomical landmarks. We calculated the sensitivity and specificity of IOM with pedicle screw stimulation at </= 10mAmp to predict a new root injury related neurodeficit.
Results: Of 2012 patients, 84 (4.2%) patients had screws which stimulated at </= 10mAmp. In 37 out of these 84 (44%) patients, the screws were replaced or removed. A total of 42 new neurodeficits were seen in the 2012 patients under study, incidence of 2 % (CI95% 1.51-2.81%). Two of 42 (5%) new neurodeficits occurred in patients in whom the pedicle screws stimulated at </= 10mAmp and 40 (95%) new neurodeficits were seen in patients whose pedicle screws stimulated at > 10mAmp. The sensitivity of predicting a new root injury related neurodeficit was found to be 4.76% while the specificity was 95.84%. The positive predictive values was 2.38% (CI95% 0.29-8.34%) and the negative predictive value 97.79% (CI95% 97.19-98.51%)
Conclusions: When using IOM with EMG, a positive screw response at screw stimulation thresholds </= 10mAmp was highly specific for predicting a new root related neurodeficit but was poorly sensitive.
Patient Care: My research helps identify the limitations of the EMG technique to identify a mis-placed pedicle screw. This helps the surgeon be aware of the limitations of this technique in interpreting the intraoperative findings.
Learning Objectives: By the conclusion of this session, participants should be able to 1)identify the role of EMG in pedicle screw placement, 2) realize the limitation of the EMG technique, 3) be aware of the cost implications of the technique.