Correlation between single-pulse and pulse-train stimulation during neuromonitoring of thoracic pedicle screws in scoliosis surgery

Abstract

Objective: 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.

Methods: 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 tEMG techniques were stratified into 3 different groups according to threshold obtained: group 1 (£6 mA), group 2 (6.1e11.9 mA), and group 3 (12 mA). A generalized linear model was used to analyze the correlation between the methods.

Results: SP t-EMG elicited response in 5 screws (1.7%) at £6 mA, 28 screws (9.5%) at 6.1e11.9 mA, and 261 screws (88.8%) at 12 mA. PT t-EMG elicited response in 16 screws (5.4%) at £6 mA, 30 screws (10.2%) at 6.1e11.9mA, and 248 screws (84.4%) at 12 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%).

Conclusions: 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.