Correlation Between Single-Pulse and Pulse-Train Stimulation During Neuromonitoring of Thoracic Pedicle Screws in Scoliosis Surgery

Abstract

The use of thoracic pedicle screws (TPSs) during scoliosis surgery entails an inherent risk of neurological deficit. Triggered electromyography (t-EMG) is an accurate neuromonitoring test for detection of malpositioned TPSs. However, single-pulse (SP) t-EMG stimulation has shown variable capability for detecting medial pedicle breaches, while pulse-train (PT) t-EMG could be more accurate. The aim of this study was to analyze the correlation between SP t-EMG and PT t-EMG. This retrospective study included 20 patients who underwent scoliosis correction with 294 TPSs placed. A total of 588 tests with both SP t-EMG and PT t-EMG were performed, analyzed, and compared. The results of both t-EMG techniques were stratified into 3 different groups according to threshold obtained: group 1 (≤6 mA), group 2 (6.1-11.9 mA), and group 3 (12 mA). A generalized linear model was used to analyze the correlation between the methods. SP t-EMG elicited response in 5 screws (1.7%) at ≤6 mA, 28 screws (9.5%) at 6.1-11.9 mA, and 261 screws (88.8%) at12 mA. PT t-EMG elicited response in 16 screws (5.4%) at ≤6 mA, 30 screws (10.2%) at 6.1-11.9mA, and 248 screws (84.4%) at12 mA. There is a strong positive and significant association between SP t-EMG and PT t-EMG with a decrease ratio of 2% (95% confidence interval 1% to 3%). SP t-EMG and PT t-EMG stimulation techniques had similar results when the stimuli were applied to TPSs, but PT t-EMG may have better efficacy in low-threshold group.