Wang Hongwei, Liao Xinhua, Ma Xianguang, Li Changqing, Han Jianda, Zhou Yue
Department of Orthopaedics, Xinqiao Hospital, Chongqing, China.
Indian J Orthop. 2013 Jul;47(4):352-6. doi: 10.4103/0019-5413.114915.
Although stimulus evoked electromyography (EMG) is commonly used to confirm the accuracy of pedicle screw placement. There are no studies to differentiate between solid screws and hollow screws to the electrical resistance of pedicle screws. We speculate that the electrical resistance of the solid and hollow pedicle screws may be different and then a potential source of error with stimulus-evoked EMG may happen.
Resistance measurements were obtained from 12 pedicle screw varieties (6 screws of each manufacturer) across the screw shank based on known constant current and measured voltage. The voltage was measured 5 times at each site.
Resistance of all solid screws ranged from 0.084 Ω to 0.151 Ω (mean =0.118 ± 0.024 Ω) and hollow screws ranged from 0.148 Ω to 0.402 Ω (mean = 0.285 ± 0.081 Ω). There was a significant difference of resistance between the solid screws and hollow screws (P < 0.05). The screw with the largest diameter no matter solid screws or hollow screws had lower resistance than screws with other diameters. No matter in solid screws group or hollow screws group, there were significant differences (P < 0.05) between the 5.0 mm screws and 6.0 mm screws, 6.0 mm screws and 7.0 mm screws, 5.0 mm screws and 7.0 mm screws, 4.5 mm screws and 5.5 mm screws, 5.5 mm screws and 6.5 mm screws, 4.5 mm screws and 6.5 mm screws. The resistance of hollow screws was much larger than the solid screws in the same diameter group (P < 0.05).
Hollow pedicle screws have the potential for high electrical resistance compared to the solid pedicle screws and therefore may affect the EMG response during stimulus-evoked EMG testing in pedicle screw fixation especially in minimally invasive percutaneous pedical screw fixation surgery.
尽管刺激诱发肌电图（EMG）常用于确认椎弓根螺钉置入的准确性，但尚无研究区分实心螺钉和空心螺钉对椎弓根螺钉电阻的影响。我们推测实心和空心椎弓根螺钉的电阻可能不同，进而可能导致刺激诱发肌电图出现潜在误差来源。
基于已知的恒定电流和测量的电压，在12种椎弓根螺钉型号（每个制造商6枚螺钉）的整个螺钉杆部进行电阻测量。每个部位测量5次电压。
所有实心螺钉的电阻范围为0.084Ω至0.151Ω（平均值 = 0.118±0.024Ω），空心螺钉的电阻范围为0.148Ω至0.402Ω（平均值 = 0.285±0.081Ω）。实心螺钉和空心螺钉之间的电阻存在显著差异（P < 0.05）。无论实心螺钉还是空心螺钉，直径最大的螺钉电阻均低于其他直径的螺钉。无论在实心螺钉组还是空心螺钉组中，5.0mm螺钉与6.0mm螺钉、6.0mm螺钉与7.0mm螺钉、5.0mm螺钉与7.0mm螺钉、4.5mm螺钉与5.5mm螺钉、5.5mm螺钉与6.5mm螺钉、4.5mm螺钉与6.5mm螺钉之间均存在显著差异（P < 0.05）。相同直径组中，空心螺钉的电阻远大于实心螺钉（P < 0.05）。
与实心椎弓根螺钉相比，空心椎弓根螺钉具有较高电阻的可能性，因此在椎弓根螺钉固定尤其是微创经皮椎弓根螺钉固定手术的刺激诱发肌电图测试过程中，可能会影响肌电图反应。
