Correlation Between Low Triggered Electromyographic Thresholds and Lumbar Pedicle Screw Malposition

Raynor, Barry L.; Lenke, Lawrence G.; Bridwell, Keith H.; Taylor, Brett; Padberg, Anne M.

doi:10.1097/brs.0b013e31815a524f

Cited by 117 publications

(79 citation statements)

References 24 publications

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“…The 7-mA cutoff is based on our own anecdotal experience and the published literature. 14 However, a threshold of less than 7 mA alerts the surgeon to attempt to visualize the medial pedicle intraoperatively and/or revise the screw positioning. A final lateral radiograph is used to confirm screw placement.…”

Section: Electrophysiological Monitoringmentioning

confidence: 99%

Ability of electromyographic monitoring to determine the presence of malpositioned pedicle screws in the lumbosacral spine: analysis of 2450 consecutively placed screws

Parker

Amin²,

Farber³

et al. 2011

SPI

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Object Pedicle screws provide efficient stabilization along all 3 columns of the spine, but they can be technically demanding to place, with malposition rates ranging from 5% to 10%. Intraoperative electromyographic (EMG) monitoring has the capacity to objectively identify a screw breaching the medial pedicle cortex that is in proximity to a nerve root. The purpose of this study is to describe and evaluate the authors' 7-year institutional experience with intraoperative EMG monitoring during placement of lumbar pedicle screws and to determine the clinical utility of intraoperative EMG monitoring. Methods The authors retrospectively studied 2450 consecutive lumbar pedicle screws placed in 418 patients from June 2002 through June 2009. All screws were inserted using a free-hand technique and anatomical landmarks, stimulated at 10.0 mA, and evaluated with CT scanning within 48 hours postoperatively. Medial pedicle screw breach was defined as having greater than 25% of the screw diameter extend outside of the pedicle, as confirmed on CT scanning or intraoperatively by a positive EMG response indicating a medial breach. The sensitivity and specificity of intraoperative EMG monitoring in detecting the presence of a medial screw breach was evaluated based on the following definitions: 1) true positive (a positive response to EMG stimulation confirmed as a breach intraoperatively or on postoperative CT scans); 2) false positive (positive response to EMG stimulation confirmed as a correctly positioned screw on postoperative CT scans); 3) true negative (no response to EMG stimulation confirmed as a correctly positioned screw on postoperative CT scans); or 4) false negative (no response to EMG stimulation but confirmed as a breach on postoperative CT scans). Results One hundred fifteen pedicle screws (4.7%) showed positive stimulation during intraoperative EMG monitoring. At stimulation thresholds less than 5.0, 5.0–8.0, and > 8.0 mA, the specificity of a positive response was 99.9%, 97.9%, and 95.9%, respectively. The sensitivity of a positive response at these thresholds was only 43.4%, 69.6%, and 69.6%, respectively. At a threshold less than 5.0 mA, 91% of screws with a positive EMG response were confirmed as true medial breaches. However, at thresholds of 5.0–8.0 mA or greater than 8.0 mA, a positive EMG response was associated with 89% and 100% false positives (no breaches), respectively. Conclusions When using intraoperative EMG monitoring, a positive response at screw stimulation thresholds less than 5.0 mA was highly specific for a medial pedicle screw breach but was poorly sensitive. A positive response to stimulation thresholds greater 5.0 mA was associated with a very high rate of false positives. The authors' experience suggests that pedicle screws showing positive stimulation below 5.0 mA warrants intraoperative investigation for malpositioning while responses at higher thresholds are less reliable at accurately representing a medial breach.

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Section: Electrophysiological Monitoringmentioning

confidence: 99%

Ability of electromyographic monitoring to determine the presence of malpositioned pedicle screws in the lumbosacral spine: analysis of 2450 consecutively placed screws

Parker

Amin²,

Farber³

et al. 2011

SPI

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“…In a recent review of the literature, we did not identify any study since 2007 where there was a report of malpositioning of pedicular screws associated with neurostimulation in terms of the direct association between the variables of electrical current and the distance of the screw, 23 which persisted in the data collected as it appears in the dispersion in Figure 1 and in the spectrum of values observed in the sample according to Table 3, where the average distance of the screws is categorized by quintiles for the variable electrical current. It can be seen that an increase in the electrical current does not modify the distance of the screws significantly, however the average distances of the screws in the selected sample were all greater than 2 mm, which proves the non-violation of the medial cortical wall of the pedicle, associated with the lowest value of the electrical current being greater than 10mA, which confirms the hypothesis of a quantitative method to evaluate the pedicular integrity in our sample of 50 pedicle screws .…”

Section: Discussionmentioning

confidence: 99%

Correlation: Impedance and Tomography in Implants Insertion in Lumbar Arthrodesis

et al. 2016

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Objective: To define whether the electroneurophysiological stimulation would be a safe method for reducing injuries in nerve roots during surgery of lumbar spine arthrodesis, as well as verify whether there is a direct correlation between the intraoperative impedance values and the distance from the medial cortical pedicle screw. Methods: Randomized retrospective multicenter study of 10 patients who underwent arthrodesis of lumbar spine after conservative treatment failure, with a total of 50 pedicle screws instrumented. Reliable and safe impedance values were measured in order to reduce the risk of injury to nerve roots in the perioperative period, and these values were compared with the distance between the screw and the medial cortical of the pedicle by CT scan, measured in the immediate post-operative period. Results: There is no direct correlation between the intraoperative impedance values and the distance from the screw to the medial cortical of the pedicle. Conclusion: The electroneurostimulation proved to be a reliable quantitative method to reduce the risk of injury to nerve roots during surgery of lumbar spine arthrodesis when the measured values are greater than 10mA.

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“…A pesar de que la electromiografía (EMG) con tren de impulsos es una técnica aceptada para la correcta monitorización de la instrumentación transpedicular en la columna lumbar 10 , sigue existiendo controversia sobre su fiabilidad a nivel del segmento torácico 1 , si bien otros autores, como Rodríguez-Olaverri 2 , han demostrado su utilidad en la instrumentación de niveles torácicos altos.…”

Section: Discussionunclassified

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

García¹,

Herrera-Pérez²,

Lorensu³

et al. 2012

Coluna/Columna

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RESUMENObjetivo: Demostrar si la técnica de estimulación eléctrica permite la detección de la mal posición medial de los tornillos pediculares torácicos. Resultados: Se analizaron 421 tornillos torácicos. Tuvimos alertas a la estimulación en 25 (5,93%) de los casos. A todos los pacientes se les realizó radiografía posoperatoria demostrando 22 tornillos (5,2%) medializados. Realizamos TAC en 17 pacientes (37%), con ningún tornillo en posición 1 y 10 tornillos en posición 2 (8,5%). Se consideraron tornillos medializados los que tenían respuesta positiva a estimulación inferior a 6 mA. Conclusiones: la estimulación eléctrica nos ha permitido reducir el riesgo de posición medial de los tornillos torácicos, minimizando además el uso de radiografía intraoperatoria. La instrumentación vertebral mediante el uso de tornillos pediculares ha ganado popularidad respecto al tradicional uso de ganchos o sistemas híbridos, debido fundamentalmente a tres característi-cas: poseer mayor capacidad de corrección tridimensional de la deformidad raquídea, mayores índices de fusión de las artrodesis, así como menores índices de revisión 1 . Pero, a pesar de su uso generalizado, la instrumentación transpedicular no está exenta de riesgos, y especialmente en la región torácica, supone un verdadero reto para el cirujano de raquis 1,3 . Por otra parte, la peculiaridad del pedículo de la vértebra torácica es única 2 , siendo más estrechos que a nivel lumbar, con mayores cambios de orientación en caso de deformidades, y con malformaciones congénitas en muchos casos, como la ausencia de canalización de los mismos. Si a esto añadimos la cercanía de estructuras vitales en esta región como son la médula espinal y los grandes vasos, nos encontramos con un recurso quirúrgico de alta complejidad técnica y cuyas complicaciones son potencialmente peligrosas. Como en la columna lumbosacra, la malposición inferior, superior o lateral de los tornillos torácicos puede lesionar raíces nerviosas, sin embargo, es la malposición medial de los mismos la más preocupante, pues la localización intracanal de dicho tornillo puede poner en peligro a la propia médula espinal, amenazando la integridad neurológica de nuestros pacientes.Coluna/Columna. 2012; 11(2): 169-70

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Correlation Between Low Triggered Electromyographic Thresholds and Lumbar Pedicle Screw Malposition

Cited by 117 publications

References 24 publications

Ability of electromyographic monitoring to determine the presence of malpositioned pedicle screws in the lumbosacral spine: analysis of 2450 consecutively placed screws

Ability of electromyographic monitoring to determine the presence of malpositioned pedicle screws in the lumbosacral spine: analysis of 2450 consecutively placed screws

Correlation: Impedance and Tomography in Implants Insertion in Lumbar Arthrodesis

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

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