Application of intraoperative evoked EMG monitoring during lumbar pedicle screw fixation / 基础医学与临床

ABSTRACT

Objective The application of intraoperative evoked EMG monitoring during lumbar pedicle screw fixation and to find new stimulus threshold criterion.Methods The validity of the evoked EMG monitoring in detecting the malposition of the pedicle screws was tested again by animal experiment.Nineteen patients was inserted pedicle screws with persistent evoked EMG monitoring via tap stimulator,and the electric current was set at 30% of bone threshold of the same pedicle,all patients were ohecked by CT scan to prove the outcome.Results Thirty-two pedicles of six dogs were inserted Kirchner wires.The stimulate thresholds of mal-position wires had significant difference with those of normal-position wires.During clinical trial,122 screws were inserted in to nineteen patients.Four screws were positive during intraoperative evoked EMG monitoring.Of which one screw was confirmed as mal-position during operation and was then adjusted;another screw was found to be mal-positioned by CT scan post-operation;the other two screws were found normal by CT scan.The sensitivity of this technique was 100% and the specificity was 98%.Conclusion Intraoperative evoked EMG monitoring during lumbar pedicle screw fixation can detect the mal-positioned screws and to protect the nerve roots.The stimulate current may set at 30% of the bone threshold of the relevant pedicle.