与脊柱导航联合应用于椎弓根钉置入过程中的肌电图监测:敏感和有效吗?

Sensitivity and efficacy of intraoperative electromyography monitoring in combination with 3D imaging modality during complex lumbosacral procedures

背景：脊柱外科手术中已广泛应用术中肌电图监测,但肌电图监测标准仍有待深入研究,而术中肌电图监测在国内的应用报道十分有限。目的：分析电诱发肌电图监测在椎弓根螺钉置入内固定过程中的敏感程度以及可靠性。设计、时间、地点：回顾性病例分析,于2008-07/2009-05在北京中医药大学东直门医院骨科完成。对象：选择北京中医药大学东直门医院骨科收治的腰椎间盘突出症及腰椎管狭窄症患者74例,男31例,女43例;年龄22～83岁,平均58岁。方法：于椎弓根螺钉内固定和椎管内手术操作中全程使用电诱发肌电图监测,刺激电流为2Hz、时程0.2ms的方波脉冲电刺激,打入椎弓根螺钉时刺激强度限制为0～60mA,电刺激强度为逐级递增。腰椎板切除减压、髓核摘除、神经根探查松解等椎管内手术操作时刺激强度限制为2～4mA。于双侧长收肌、股直肌、股二头肌、胫骨前肌和腓肠肌内侧头的肌腹中部及肛门括约肌记录分析肌电反应。主要观察指标：实时监测和记录自由肌电反应及触发肌电反应中动作电位出现的时间、频率、振幅、肌群,以及术后神经根功能损伤及恢复情况。结果：74例患者在术中肌电图监测和3-D脊柱导航系统帮助下共置入378只椎弓根螺钉内固定,仅有3只椎弓根螺钉（L42只,L51只）置入过程中,当电流强度小于10mA时即出现肌电反应,及时提醒术者,经术中C臂X射线透视证实椎弓根骨皮质穿透,而予以重新置入,置入准确率达99.2%。电诱发肌电图监测下进行椎管内手术操作,仅2例患者术中进行L5,S1节段减压、松解时反复出现下肢明显肌电反应,术后出现下肢神经症状较术前加重,经2～4周保守治疗后恢复,神经根误损伤率为2.7%。所有患者术后未出现不可逆的相关神经根损伤症状。结论：椎弓根螺钉置入腰椎椎管内手术过程中电诱发肌电监测可最大限度地保证安全操作、预防神经根损伤。与术中脊柱导航系统的联合应用可增加监测的敏感性,在复杂腰骶椎术中是目前最为有效的监测方法。

BACKGROUND： Electromyogram （EMG） monitoring during operation has been widely used in spinal surgery. However, some questions remain poorly understood. EMG monitoring in domestic application is rarely reported. OBJECTIVE： To evaluate the sensitivity and reliability of EMG monitoring during pedicle screw placement and laminectomy. DESIGN, TIME AND SETTING： A retrospective analysis of cases. The study was performed at Department of Orthopedics, Dongzhimen Hospital, Beijing University of Chinese Medicine from July 2008 to May 2009. PARTICIPANTS： A total of seventy-four cases of lumbar intervertebral disc protrusion and/or lumbar spinal stenosis were selected from Department of Orthopedics, Dongzhimen Hospital, Beijing University of Chinese Medicine, including 31 males and 43 females, aged 58 years （ranging 22-83 years）. METHODS： The cases were treated with laminectomy for decompression, never root exploration and solution, pedicle screw fixation with the assistance of 3D imaging modality and EMG monitoring. Monophasic constant current （0.2 ms, 2 Hz） was used as stimulation signal. The stimuli amplitude for pedicle screw placement and laminectomy for decompression and never root solution was （0-60 mA） and （2-4 mA）, respectively. The compound muscle action potential was recorded in different muscles （adductor Iongus, rectus femoris muscle, biceps femoris, tibialis anterior muscle, gastrocnemius muscle） of bilateral lower limb. MAIN OUTCOME MEASURES： Free running EMG and stimulus triggered EMG, including time, frequency, amplitude, muscle group were observed and recorded simultaneously. Never root functional injury and restoration after surgery were detected. RESULTS： 378 pedicle screws in 74 patients were monitored intraoperatively, and only 3 pedicle screw malposition （2 of L4. 1 of L5） was detected and then replaced with the help of C-arm fluoroscopic examination. Myoelectricity appeared when the current intensity was less than 10 mA. The correct rate of implantation was 99.2%. Nerve root impingement was found in two cases during laminectomy for L5 and Sldecompression and never root solution, which alerted the surgical team of critical neural structures. Nerve symptoms of the lower limb were aggravated after surgery and restored following 2-4 weeks of conventional treatment. The error injury rate of nerve root was 2.7%. In all reported cases, no irreversible neurological deficit was observed 2-4 weeks after operation. CONCLUSION： Intraoperative EMG monitoring can find improperly placed screws and detect impending nerve root injury promptly. Combined EMG and 3-D imaging modality monitoring is a reliable and practicable method that can be used to protect neural structures during complex lumbosacral surgery.