诱发肌电图监测在腰椎椎弓根螺钉内固定术中的应用

Application of intraoperative evoked EMG monitoring during lumbar pedicle screw fixation

目的探讨诱发肌电图监测在腰椎椎弓根螺钉内固定术中的应用,寻找新的阈值判断标准。方法通过动物实验来验证诱发肌电图监测对于术中判断螺钉位置的有效性,并对19例患者进行术中持续诱发肌电图监测,监测电流值采用预先获得的相应椎弓根骨阈值的30%,术后患者行CT检查验证结果。结果6只狗32个椎弓根,异位克氏针和正常克氏针刺激阈值有显著差异。19例患者共122枚椎弓根螺钉,监测结果4例出现阳性,其中1例术中探查发现螺钉异位,进行改道,另一例术后CT扫描发现螺钉出现异位。其余2例术后CT检查螺钉位置正常。该方法敏感性为100%,特异性为98%。结论腰椎椎弓根螺钉内固定术中进行持续诱发肌电图监测能及时发现螺钉位置的异常,从而避免神经损伤的发生,监测电流值最好以相应椎弓根骨阈值的30%为标准。

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.