Automated intraoperative EMG testing during percutaneous pedicle screw placement.
BACKGROUND
EMG screw testing has been shown to be sensitive and reliable in open spinal instrumentation cases. However, there is little evidence to show its applicability to percutaneous screw placement.


OBJECTIVE
To demonstrate the utility of EMG testing in percutaneous techniques, where lack of direct visualization poses an added risk to nerve injury.


METHODS
Summary of intraoperative EMG results during percutaneous pedicle screw placement.


METHODS
Percutaneous pedicle screws were placed in twenty patients (22 levels, 88 pedicles). The initial fluoroscopically-guided k-wires and the subsequent taps were insulated and stimulated via an automated EMG system. Low threshold values prompted repositioning of the pedicle trajectory.


RESULTS
Four (5%) k-wires induced EMG thresholds less than 10mA, prompting repositioning. One was repositioned without improvement, but with improvement upon tapping. One k-wire with very low threshold (3mA) was repositioned with an improved result (13mA). In 78 pedicles (89%) the tap threshold was greater than the k-wire.


CONCLUSIONS
EMG testing helps to identify suboptimal screw trajectories, allowing for early adjustment and confirmation of improved placement. Tapping often improved thresholds, perhaps by compressing the bone and creating a denser, more insulative pedicle wall. EMG testing may improve the safety of percutaneous screw techniques, where the pedicle cannot be visually inspected.
Ozgur
Burak M
BM
Division of Neurosurgery, University of California, San Diego Medical Center, 200 West Arbor Drive, San Diego, CA 92103-8893, USA. bozgur@ucsd.edu
Berta
Scott
S
Khiatani
Vishal
V
Taylor
William R
WR
D001331:Automation; D001863:Bone Screws; D001864:Bone Wires; D004576:Electromyography / Q000379:methods*; D006801:Humans; D019060:Minimally Invasive Surgical Procedures; D016343:Monitoring, Intraoperative / Q000379:methods*; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*