Intraoperative Electromyography Monitoring In Minimally Invasive Transforaminal Lumbar Interbody Fusion

Objective:To determine the effectiveness and clinical result of intraoperative electromyography(EMG) monitoring for detecting a perforation of the pedicle cortex irritation of nerve root during minimally invasive transforaminal lumbar interbody fusion(TLIF).Methods:Between February 2008 and October 2009, 16 consecutive patients(18 levels,66 pedicles)who underwent minimally invasive TLIF received intraoperative EMG monitoring. Spontaneous EMG monitoring was performed during decompression and interbody graft placement. Stimulus-evoked EMG monitoring was performed during the placement of the pedicle access needle,testing of the pedicle tap and screw. We need adjustment with stimulating intensity below 10 mA. All patients underwent postoperative computed tomography (CT) scanning.Results:In no patient did the authors observe significant EMG activation during decompression. Intermittent nerve root firing was noted after the interbody graft was placed in two cases. Using the active stimulation protocol, 23(34.8% ) of screw placements required one or more changes to the trajectory of the pedicle access needle.3(4.5%) pedicle taps induced EMG thresholds less than 10mA, prompting repositioning. Two was repositioned with improvement>15mA and one with improvement at 12mA. After surgery, no new neurologic deficits were found in all patients. Postoperative computed tomography (CT) scanning revealed three cases of pedicle medially breach and one case laterally.Conclusions: Intraoperative EMG monitoring helps to incorrect medial screw trajectories, allowing for early adjustment and confirmation of improved placement. Intraoperative nerve root monitoring is a useful adjunct to minimally invasive TLIF.