• Stephen J Lewis, Randolph Gray, Laura M Holmes, Samuel Strantzas, Subir Jhaveri, Christian Zaarour, and Sofia Magana.
• Hospital for the Sick Children, Toronto, Canada. Stephen.Lewis@uhn.on.ca
• Spine. 2011 Sep 15;36(20):1627-38.

Study DesignRetrospective review of 36 consecutive patients undergoing coronal plane deformity correction with intraoperative skull-femoral traction between 2005 and 2008 with motor evoked potential (MEP)/somatosensory evoked potential monitoring.ObjectiveTo determine the prevalence and significance of neurophysiological changes with intraoperative skull-femoral traction in adolescent idiopathic scoliosis.Summary Of Background DataIntraoperative skeletal traction can be associated with spinal cord stretching and ischemia with resultant electrophysiological changes. The prevalence and risks of such changes and their clinical significance is unknown.MethodsThirty-seven procedures involving 36 patients (27 females and 9 males) with a mean age of 14.8 (12-18) years were divided into two groups on the basis of the presence (group 1, n = 18 procedures) or absence (group 2, n = 19) of significant MEP changes with surgery. They were compared with patients undergoing correction without traction (group 3).ResultsSignificant differences among the groups were observed in mean preoperative Cobb angle (86° vs. 70° vs. 59°), mean intraoperative posttraction Cobb angle (50.0° vs. 34.6°), traction index (0.41 vs. 0.50), flexibility index (0.14 vs. 0.27 vs. 0.25), and presence of primary lumbar curves (0% vs. 32% vs. 14%). Initial onset of MEP amplitude loss (group 1) occurred at a mean of 94 (1-257) minutes from the onset of surgery, was bilateral in 13 procedures, and improved at a mean of 5.5 (1-29) minutes after decreasing or removing the traction. At closure, complete bilateral recovery to baseline was observed in 10 procedures, recovery to >50% baseline in five, and recovery to <50% baseline in three procedures. There were no neurologic deficits in this series.ConclusionIntraoperative traction is associated with frequent changes in MEP monitoring. The thoracic location of the major curve, increasing Cobb angle, and rigidity of major curve are significant risk factors for changes in MEP with traction. The presence of any MEP recordings irrespective of its amplitude at closure was associated with normal neurological function. Somatosensory evoked potential monitoring did not correlate with the traction induced MEP amplitude changes.

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