Triggered electromyography (tEMG) in the lumbar spine It́s reliable? Correlation of tEMG with postoperative CT images in lumbar instrumentation. / Electromiografía evocada (tEMG) en la columna lumbar. ¿Es confiable? Correlación de tEMG con imágenes de TC posoperatorias en la instrumentación lumbar.

INTRODUCTION: Instrumentation with pedicle screws (PS) can compromise the adjacent neural structures. Triggered electromyography (tEMG) is a modality of intraoperative neuromonitoring, used to assist in the placement of these. The objective of the present study is to evaluate the reliability of this tool. METHOD: Retrospective review of patients underwent posterior lumbar fusions from January 2017 to December 2019, correlating postoperative CT images (postop CT) with tEMG results for each PS with a threshold of 10mA, establishing sensitivity and specificity of this tool. Diagnostic test and receiver operating characteristic curve were performed to evaluate the area under the curve. RESULT: A total of 275 PS were evaluated between L1 to S1; 5 PS showed concordance for an inadequate trajectory, while 10PS, with tEMG <10mA, were correctly positioned. The postoperative CT identified 17 pedicle gaps not noticed by the tEMG. Sensitivity and specificity were 23% (95% CI: 8-45) and 96% (95% CI: 93-98), respectively, with a PPV of 33.3% and a NPV of 93.6%. The area under the curve was 0.74 (95% CI: 0.62-0.86) with a cut-off point of 24mA, showing a sensitivity of 77% (95% CI: 0.55-0.92) and specificity of 69% (95% CI: 0.63-0.75). CONCLUSION: Given its low sensitivity, we do not recommend tEMG as the sole test in the verification of PS. We recommend using a cut-off point ≤8mA as it demonstrated the highest levels of sensitivity and specificity. We do not recommend using high thresholds to increase sensitivity.

Electromiografía evocada (tEMG) en la columna lumbar. ¿Es confiable? Correlación de tEMG con imágenes de TC posoperatorias en la instrumentación lumbar / Triggered electromyography (tEMG) in the lumbar spine Its reliable? Correlation of tEMG with postoperative CT images in lumbar instrumentation

Introducción: La instrumentación con tornillos pediculares (TP) puede comprometer las estructuras neurales adyacentes. La electromiografía evocada (tEMG) es una modalidad del neuromonitoreo intraoperatorio utilizada para asistir la colocación de estos. El objetivo del presente estudio es evaluar la confiabilidad de esta herramienta. Método: Revisión retrospectiva de pacientes intervenidos de artrodesis lumbar posterolateral instrumentada desde enero del 2017 hasta diciembre del 2019. Se correlacionaron las imágenes de TC postoperatorias (TC-postop) con los resultados de la tEMG para cada TP con un umbral de 10mA, y se establecieron la sensibilidad y especificidad de esta herramienta. Se realizó test diagnóstico y la curva característica operativa del receptor para evaluar el área bajo la curva. Resultado: Se evaluaron 275 TP entre L1 y S1; 5 TP presentaban concordancia para una trayectoria inadecuada, mientras que 10TP, con tEMG <10mA, se encontraban correctamente posicionados. La TC-postop identificó 17 brechas pediculares no advertidas por la tEMG. La sensibilidad y la especificidad fue del 23% (IC 95%: 8-45) y 96% (IC 95%: 93-98), respectivamente, con un VPP del 33,3% y un VPN del 93,6%. El área bajo la curva fue de 0,74 (IC 95%: 0,62-0,86) con punto de corte de 24mA, que mostró una sensibilidad del 77% (IC 95%: 0,55-0,92) y una especificidad del 69% (IC 95%: 0,63-0,75). Conclusión: Dada su baja sensibilidad, no aconsejamos la tEMG como prueba única en la verificación de TP. Recomendamos la utilización de un punto de corte ≤8mA, ya que ha demostrado los niveles más altos de sensibilidad y especificidad. No recomendamos el uso de umbrales elevados para aumentar la sensibilidad.(AU)

Introduction: Instrumentation with pedicle screws (PS) can compromise the adjacent neural structures. Triggered electromyography (tEMG) is a modality of intraoperative neuromonitoring, used to assist in the placement of these. The objective of the present study is to evaluate the reliability of this tool. Method: Retrospective review of patients underwent posterior lumbar fusions from January 2017 to December 2019, correlating postoperative CT images (postop CT) with tEMG results for each PS with a threshold of 10mA, establishing sensitivity and specificity of this tool. Diagnostic test and receiver operating characteristic curve were performed to evaluate the area under the curve. Result: A total of 275 PS were evaluated between L1 to S1; 5 PS showed concordance for an inadequate trajectory, while 10PS, with tEMG <10mA, were correctly positioned. The postoperative CT identified 17 pedicle gaps not noticed by the tEMG. Sensitivity and specificity were 23% (95% CI: 8-45) and 96% (95% CI: 93-98), respectively, with a PPV of 33.3% and a NPV of 93.6%. The area under the curve was 0.74 (95% CI: 0.62-0.86) with a cut-off point of 24mA, showing a sensitivity of 77% (95% CI: 0.55-0.92) and specificity of 69% (95% CI: 0.63-0.75). Conclusion: Given its low sensitivity, we do not recommend tEMG as the sole test in the verification of PS. We recommend using a cut-off point ≤8mA as it demonstrated the highest levels of sensitivity and specificity. We do not recommend using high thresholds to increase sensitivity.(AU)

Triggered electromyography (tEMG) in the lumbar spine it's reliable? Correlation of tEMG with postoperative CT images in lumbar instrumentation / Electromiografía evocada (tEMG) en la columna lumbar. ¿Es confiable? Correlación de tEMG con imágenes de TC posoperatorias en la instrumentación lumbar

Introduction: Instrumentation with pedicle screws (PS) can compromise the adjacent neural structures. Triggered electromyography (tEMG) is a modality of intraoperative neuromonitoring, used to assist in the placement of these. The objective of the present study is to evaluate the reliability of this tool. Method: Retrospective review of patients underwent posterior lumbar fusions from January 2017 to December 2019, correlating postoperative CT images (postop CT) with tEMG results for each PS with a threshold of 10mA, establishing sensitivity and specificity of this tool. Diagnostic test and receiver operating characteristic curve were performed to evaluate the area under the curve. Result: A total of 275 PS were evaluated between L1 to S1; 5 PS showed concordance for an inadequate trajectory, while 10PS, with tEMG <10mA, were correctly positioned. The postoperative CT identified 17 pedicle gaps not noticed by the tEMG. Sensitivity and specificity were 23% (95% CI: 8-45) and 96% (95% CI: 93-98), respectively, with a PPV of 33.3% and a NPV of 93.6%. The area under the curve was 0.74 (95% CI: 0.62-0.86) with a cut-off point of 24mA, showing a sensitivity of 77% (95% CI: 0.55-0.92) and specificity of 69% (95% CI: 0.63-0.75). Conclusion: Given its low sensitivity, we do not recommend tEMG as the sole test in the verification of PS. We recommend using a cut-off point ≤8mA as it demonstrated the highest levels of sensitivity and specificity. We do not recommend using high thresholds to increase sensitivity.(AU)

Introducción: La instrumentación con tornillos pediculares (TP) puede comprometer las estructuras neurales adyacentes. La electromiografía evocada (tEMG) es una modalidad del neuromonitoreo intraoperatorio utilizada para asistir la colocación de estos. El objetivo del presente estudio es evaluar la confiabilidad de esta herramienta. Método: Revisión retrospectiva de pacientes intervenidos de artrodesis lumbar posterolateral instrumentada desde enero del 2017 hasta diciembre del 2019. Se correlacionaron las imágenes de TC postoperatorias (TC-postop) con los resultados de la tEMG para cada TP con un umbral de 10mA, y se establecieron la sensibilidad y especificidad de esta herramienta. Se realizó test diagnóstico y la curva característica operativa del receptor para evaluar el área bajo la curva. Resultado: Se evaluaron 275 TP entre L1 y S1; 5 TP presentaban concordancia para una trayectoria inadecuada, mientras que 10TP, con tEMG <10mA, se encontraban correctamente posicionados. La TC-postop identificó 17 brechas pediculares no advertidas por la tEMG. La sensibilidad y la especificidad fue del 23% (IC 95%: 8-45) y 96% (IC 95%: 93-98), respectivamente, con un VPP del 33,3% y un VPN del 93,6%. El área bajo la curva fue de 0,74 (IC 95%: 0,62-0,86) con punto de corte de 24mA, que mostró una sensibilidad del 77% (IC 95%: 0,55-0,92) y una especificidad del 69% (IC 95%: 0,63-0,75). Conclusión: Dada su baja sensibilidad, no aconsejamos la tEMG como prueba única en la verificación de TP. Recomendamos la utilización de un punto de corte ≤8mA, ya que ha demostrado los niveles más altos de sensibilidad y especificidad. No recomendamos el uso de umbrales elevados para aumentar la sensibilidad.(AU)