Raynor Barry L, Lenke Lawrence G, Kim Yongjung, Hanson Darrell S, Wilson-Holden Tracy J, Bridwell Keith H, Padberg Anne M
Department of Orthopaedic Surgery, Washington University Medical Center, BJC Health Systems, St. Louis, Missouri 63110, USA.
Spine (Phila Pa 1976). 2002 Sep 15;27(18):2030-5. doi: 10.1097/00007632-200209150-00012.
A prospective clinical study of thoracic pedicle screws monitored with triggered electromyographic testing.
To evaluate the sensitivity of recording rectus abdominis triggered electromyographs to assess thoracic screw placement.
Triggered electromyographic testing from lower extremity myotomes has identified medially placed lumbar pedicle screws. Higher thresholds indicate intraosseous placement because of increased resistance to current flow. Lower thresholds correspond to compromised pedicles with potential for nerve impingement. No clinical study has correlated an identical technique with rectus muscle recordings, which are innervated from T6 to T12.
A total of 677 thoracic screws were placed in 92 consecutive patients. Screws placed from T6 and T12 were evaluated using an ascending method of stimulation until a compound muscle action potential was obtained from the rectus abdominis. Threshold values were compared both in absolute terms and also in relation to other intrapatient values.
Screws were separated into three groups: Group A (n = 650 screws) had thresholds >6.0 mA and intraosseus placement. Group B (n = 21) had thresholds <6.0 mA but an intact medial pedicle border on reexamination and radiographic confirmation. Group C (n = 6) had thresholds <6.0 mA and medial wall perforations confirmed by tactile and/or visual inspection. Thus, 3.9% (27 of 677) of all screws had thresholds <6.0 mA. Only 22% (6 of 27) had medial perforation. Group B screws averaged a 54% decrease from the mean as compared with a 69% decrease for Group C screws (P = 0.0160). There were no postoperative neurologic deficits or radicular chest wall complaints.
To assess thoracic pedicle screw placement, triggered electromyographic thresholds <6.0 mA, coupled with values 60-65% decreased from the mean of all other thresholds in a given patient, should alert the surgeon to suspect a medial pedicle wall breach.
一项采用触发式肌电图测试监测胸椎椎弓根螺钉的前瞻性临床研究。
评估记录腹直肌触发肌电图以评估胸椎螺钉置入情况的敏感性。
来自下肢肌节的触发式肌电图测试已识别出内侧放置的腰椎椎弓根螺钉。较高阈值表明螺钉位于骨内，这是因为电流流动的阻力增加。较低阈值对应于可能压迫神经的受损椎弓根。尚无临床研究将相同技术与腹直肌记录相关联，腹直肌由T6至T12神经支配。
对92例连续患者共置入677枚胸椎螺钉。从T6至T12置入的螺钉采用递增刺激方法进行评估，直至从腹直肌获得复合肌肉动作电位。对阈值进行绝对值比较以及与同一患者的其他值进行比较。
螺钉分为三组：A组（n = 650枚螺钉）阈值>6.0 mA且位于骨内。B组（n = 21枚）阈值<6.0 mA，但再次检查及影像学确认时内侧椎弓根边界完整。C组（n = 6枚）阈值<6.0 mA，经触觉和/或视觉检查确认有内侧壁穿孔。因此，所有螺钉中有3.9%（677枚中的27枚）阈值<6.0 mA。仅有22%（27枚中的6枚）有内侧穿孔。B组螺钉平均值较平均值下降54%，而C组螺钉下降69%（P = 0.0160）。术后无神经功能缺损或胸壁神经根性症状。
为评估胸椎椎弓根螺钉置入情况，触发式肌电图阈值<6.0 mA，且与给定患者所有其他阈值的平均值相比降低60 - 65%，应提醒外科医生怀疑内侧椎弓根壁破裂。
