Triggered EMG (T-EMG) Values of Pedicle Screws with a Powered Screwdriver vs A Standard Probe in Adolescent Idiopathic Scoliosis Do Not Agree: A Prospective Validation Study.

Triggered electromyography (t-EMG) is a common technique used during spinal instrumentation in surgery for adolescent idiopathic scoliosis. This study tests the validity of t-EMG values obtained with a standard ball-tipped probe after completion of screw placement versus t-EMG values obtained during screw insertion with a powered screwdriver. t-EMG values were collected for screws spanning T7-L5 using both a standard probe and a powered screwdriver. A power analysis determined that a sample size of 300 screws would provide enough precision to estimate limits of agreement within ±2 mA. A monopolar constant current stimulation technique (0.2 ms duration and 3.11 Hz stimulation rate) was used at each level. EMG was acquired with placement of bipolar pairs of subdermal needle electrodes. A Bland-Altman plot was used to assess agreement between threshold readings from the two techniques. Twenty-nine patients were enrolled in this study with 305 screws. t-EMG values measured using a powered screwdriver were on average 1 mA lower than values from a standard probe. When readings less than or equal to 20 mA were considered, the limits of agreement were approximately 4 and 7 mA overall. In total, 28/305 (9%) screws were removed and reinserted, 9/305 (3%) screws were redirected, and 3/305 (1%) screws were aborted based on t-EMG readings. Despite a small overall difference in t-EMG value between the standard probe and screwdriver, there was still large variability in agreement between the two techniques. t-EMG values obtained with a powered screwdriver during screw insertion are not interchangeable with values measured by a probe.

Standard Probe Endoscopic Ultrasonography before Endoscopic Submucosal Dissection Avoids Misjudging the Size of Esophageal and Gastric Stromal Tumors by Miniprobe Sonography / 胃肠病学

Endoscopic ultrasonography (EUS)is routinely performed before endoscopic submucosal dissection (ESD)for treatment of upper gastrointestinal stromal tumors.However,when a miniprobe sonography (12,15 and 20 MHz)was used,the size of tumor revealed by EUS was often inconsistent with what it actually was,which might increase the difficulty of ESD and the risk of perforation and massive bleeding.Aims:To investigate the value of standard probe (5 and 7.5 MHz)EUS in detecting the size of upper gastrointestinal stromal tumors before ESD.Methods:Clinical data of patients who were suspicious of esophageal and gastric stromal tumors by gastroscopy and EUS from Jan.2012 to Oct.2014 at the Renmin Hospital of Wuhan University were collected.Of them,195 cases treated by ESD were retrospectively analyzed.Results:Of 195 cases treated by ESD,37 cases diagnosed by standard probe EUS and 108 cases diagnosed by miniprobe EUS were confirmed as stromal tumors by pathology.Fourteen cases were failure for ESD and then transferred to surgical treatment,one was due to misjudgement of the origin of tumor by standard probe EUS and 9 were due to misjudgement of the size of tumor by miniprobe EUS.The misjudgement rate of standard probe EUS was lower than that of miniprobe EUS with an insignificant difference (2.7%vs.8.3%,P>0.05).In 9 cases misjudged by miniprobe EUS, the size of tumor presented by miniprobe EUS was significantly smaller than its real size [(1.22 ±0.51)cm vs.(3.97 ±1.06)cm,P<0.01].ESD was avoided or terminated in 3 cases because of the accurate estimation of tumor origin, structure and blood flow by standard probe EUS.Conclusions:For patients who are going to receive ESD for suspected upper gastrointestinal stromal tumors,it would be best to select standard probe EUS to detect the size,origin and blood flow of the tumor before ESD.It will decrease the risk and improve the success rate of ESD.