Evaluation with evoked and spontaneous electromyography during lumbar instrumentation: a prospective study

Abstract

The neuroanatomical structures that approximate the bony pedicles of the lumbar spine allow little room for technical error or compromise of the bone during pedicle screw insertion. Currently available neurophysiological monitoring techniques detect compromised bone and nerve root injury after it occurs. The purpose of this prospective study is to evaluate the reliability and efficacy of a unique neurophysiological monitoring technique. This technique provides immediate evaluation of pedicle cortical bone integrity in patients undergoing lumbar fusion with instrumentation by using electrified surgical instruments throughout the pedicle screw fusion procedure. Spontaneous electromyographic (EMG) activity was also monitored. Intraoperative evoked EMG stimulation was performed using a pedicle probe and feeler as monopolar stimulators during the insertion of 164 pedicle bone screws in 32 patients. The EMG response to subthreshold stimulation intensities indicated cortical bone compromise. Immediate and conclusive feedback via evoked EMG activity using stimulating pedicle probes in appropriate muscle groups was successful in identifying pedicle cortical bone compromise in four patients. One false-negative evoked EMG study was noted but was identified via spontaneous EMG activity. Intraoperative EMG monitoring alerted the surgeon that redirection of the pedicle probe or screw was necessary to avoid nerve root irritation or injury and served as an early warning system. Evoked EMG stimulation proved to be reliable and efficacious, especially when used in combination with spontaneous EMG. This technique may provide an added safeguard during implant placement procedures at centers where intraoperative neurophysiological monitoring is routinely performed.

Multimodal intraoperative monitoring (MIOM) during 409 lumbosacral surgical procedures in 409 patients

“…All the studies including [2,4,6,12,13]. In our institution, we introduced a multimodal intraoperative monitoring with sensory and motor-evoked potentials and particularly selective nerve root monitoring for each miotom in a side-by-side comparison.…”

“…Among these techniques, continuous EMG recording, somatosensoryevoked potentials and compound muscle action potentials by electrical stimulation of the motor cortex or the spinal cord are the most frequently used [2,4,6,12,13]. Bose et al [2] concluded that continuous intraoperative electromyographic monitoring provided a real-time measurement of impending spinal nerve root injury during instrumented posteriolumbar fusion, allowing for timely intervention and minimizing the risk of nerve root damage.…”

Posterior approach to ventrally located spinal meningiomas

“…Although SSEPs are easily recordable without adjusting the anesthetic regimen, there are reports of false negative results in up to 25% [15,19,20]. TcMEPs have been used as an alternative with favorable results [21]. TcMEPs evaluate the pyramidal motor pathways and in combination with continuous EMG monitoring give an immediate and conclusive feedback of motor tract integrity.…”

Cost-effectiveness of confirmatory techniques for the placement of lumbar pedicle screws

“…3,30 Use of intraoperative image guidance, such as the O-arm (Medtronic, Inc.), improves accuracy of screw positioning. 26 Considerable controversy exists regarding the optimal method of monitoring pedicle screw placement.…”