Electrical Stimulation for Intraoperative Evaluation of Thoracic Pedicle Screw Placement

Abstract

These results are consistent with previous studies of lumbosacral pedicle screws. In this series, stimulation thresholds >11 mA have a 97.5% negative predictive value, suggesting that cortical violation is highly unlikely. Although judgment of screw placement should not depend solely on stimulation thresholds, pedicle screw stimulation may provide rapid and useful intraoperative information on screw placement during procedures involving the use of thoracic pedicle screws.

Recording triggered EMG thresholds from axillary chest wall electrodes: a new refined technique for accurate upper thoracic (T2–T6) pedicle screw placement

“…Screws located inside the spinal canal exhibited a mean threshold of 10.38 ± 3.33 mA (range, 6-16 mA). These data are in agreement with the 11-mA threshold limit proposed by Shi et al [17]. Five out of six screws located inside the spinal canal showed thresholds below 12 mA, a much higher limit than the 6 mA described in our previous study [7].…”

“…2 Mean EMG thresholds according to the post-operative position of the pedicle screws on both sides of the thoracic curve recording has been reported to be unreliable due to the significant overlap of intercostal muscle innervation. Monitoring EMG responses in these muscles requires electrodes at all levels to ensure adequate coverage of the appropriate myotome [17]. A similar concern exists for t-EMG responses in the rectus abdominis and the external oblique muscle, since they share common intercostal and subcostal nerves (T7-T12) [4,18].…”

“…A recent study described a series of thoracic screws in humans and reported that stimulation thresholds [11 mA had a 97.5% negative predictive value, suggesting that cortical violation is highly unlikely above this threshold intensity [17]. Although these authors did not recommend judging screw placement solely on stimulation thresholds, they concluded that pedicle screw stimulation might provide rapid and useful intraoperative information in humans.…”

Valor predictivo de la estimulación eléctrica de los tornillos pediculares torácicos en la mal posición medial de los mismos en la instrumentación de cirugía de columna

“…Los estudios de conducción eléctrica están basados en la premisa de la resistencia eléctrica dentro del pedículo intacto 2 . Su eficacia ha sido bien documentada en pedículos lumbares 7 , mientras que la literatura muestra resultados variables en la columna torácica 4,5 . Actualmente, es posible evaluar el orificio del tornillo dentro del pedículo electrofisiológicamente, existiendo guías publicadas de umbrales de estimulación para la cirugía de columna lumbosacra 4,5 .…”

“…En el año 2003, Shi y cols. describieron el uso de guías similares para la instrumentación torácica 5 , recomendando usar la musculatura intercostal para monitorizar las vértebras torácicas superiores.…”