Cousiño Juan P Cabrera, Luna Francisco, Torche Máximo, Vigueras Sebastián, Torche Esteban, Valdés Guillermo
Department of Neurosurgery, Hospital Clínico Regional de Concepción, Concepción, Bio-Bio, Chile.
Surg Neurol Int. 2020 Mar 6;11:42. doi: 10.25259/SNI_4_2020. eCollection 2020.
The standard of care is to utilize intraoperative neurophysiological monitoring (IOM) of triggered electromyography (tEMG) during posterior lumbosacral instrumented-fusion surgery. IOM should theoretically signal misplacement of S1 screws into the neural L5-S1 foramen or spinal canal, utilizing screw stimulation, and recording of the lower limb muscles and the anal sphincter. Here, we evaluated when and whether anterolateral S1 screw malposition could be detected by IOM/tEMG during open posterior lumbosacral instrumented fusion surgery.
tEMG, somatosensory-evoked potential (SSEP), and transcranial electrical motor-evoked potential (TcMEP) data were retrospectively reviewed from 2015 to 2017 during open posterior lumbosacral instrumented fusions. We utilized screw stimulation alert thresholds of <14 mA (tEMG) and recorded from the lower extremity muscles and anal sphincter. Furthermore, all patients underwent routine postoperative computed tomography (CT) scans to confirm the screw location.
There were 106 S1 screws placed in 54 patients: 52 bilateral and 2 unilateral. In 6 patients (11.1%), 7 screws (6.6%) registered at low tEMG thresholds. In 1 patient, the postoperative CT scan documented external malposition of the screw despite no intraoperative IOM/tEMG alert. When S1 misplaced screws were stimulated, the most sensitive muscle was the tibialis anterior; the sensitivity of the IOM/tEMG was 87.5%, the specificity was 97.9%, the positive predictive value was 77.8%, and the negative predictive value was 98.9%. TcMEP and SSEP did not change during any of the operations. Notably, no patient developed a new neurological deficit.
Anterolateral S1 screw malposition can be detected accurately utilizing IOM/tEMG stimulation of screws. When alerts occur, they can largely be corrected by partially backing out the screw (e.g., a few turns) and/ or changing the screw trajectory.
护理标准是在腰骶部后路器械融合手术中使用触发式肌电图（tEMG）进行术中神经生理监测（IOM）。理论上，IOM应通过螺钉刺激并记录下肢肌肉和肛门括约肌的反应，来提示S1螺钉误置入神经所在的L5-S1椎间孔或椎管。在此，我们评估了在开放性腰骶部后路器械融合手术中，IOM/tEMG能否以及何时检测到S1螺钉的前外侧位置异常。
回顾性分析2015年至2017年期间开放性腰骶部后路器械融合手术中的tEMG、体感诱发电位（SSEP）和经颅电刺激运动诱发电位（TcMEP）数据。我们采用<14 mA的螺钉刺激警报阈值（tEMG），并记录下肢肌肉和肛门括约肌的反应。此外，所有患者术后均接受常规计算机断层扫描（CT）以确认螺钉位置。
54例患者共置入106枚S1螺钉：52例双侧置入，2例单侧置入。6例患者（11.1%）的7枚螺钉（6.6%）在低tEMG阈值时被记录到。1例患者术后CT扫描显示螺钉外置，但术中IOM/tEMG未发出警报。当刺激误置入的S1螺钉时，最敏感的肌肉是胫前肌；IOM/tEMG的敏感性为87.5%，特异性为97.9%，阳性预测值为77.8%，阴性预测值为98.9%。在任何手术过程中，TcMEP和SSEP均未发生变化。值得注意的是，没有患者出现新的神经功能缺损。
利用IOM/tEMG对螺钉进行刺激可准确检测S1螺钉的前外侧位置异常。当发出警报时，很大程度上可通过将螺钉稍微退出（例如，几圈）和/或改变螺钉轨迹来纠正。
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