Can triggered electromyography thresholds assure accurate pedicle screw placements? A systematic review and meta-analysis of diagnostic test accuracy

- Triggered electromyography (t-EMG) by direct pedicle screw stimulation was introduced two decades ago and its efficacy remains disputed.
- The diagnostic accuracy of t-EMG was weak in the condition of overall thresholds.
- Using titanium-alloy pedicle screws, a stimulation threshold of ⩽8 mA in the lumbar spine has high accuracy (sensitivity, 0.82; specificity, 0.97; diagnostic odds ratio (DOR), 147.95) as an indication of possible pedicle screw malpositioning.

ObjectiveTriggered electromyography (t-EMG) for pedicle screw placement was introduced to prevent the misplacement of screws; however, its diagnostic value is still debated. This study aimed to clarify the diagnostic value of t-EMG and to compare thresholds.MethodsWe searched MEDLINE, EMBASE, and the Cochrane Library, and 179 studies were identified. Among them, 11 studies were finally enrolled. The pooled sensitivity, specificity, diagnostic odds ratio (DOR), and summary receiver operating characteristics (SROC) plots were analyzed.ResultsThe enrolled studies included 13,948 lumbar and 2070 thoracic screws. The overall summary sensitivity/specificity/DOR values of t-EMG were 0.55/0.97/42.16 in the lumbar spine and 0.41/0.95/14.52 in the thoracic spine, respectively, indicating a weak diagnostic value. However, subgroup analysis by each threshold value showed that the cutoff value of 8 mA in the lumbar spine indicated high sensitivity (0.82), specificity (0.97), and DOR (147.95), thereby showing high diagnostic accuracy of identifying misplaced screws.ConclusionThe most useful application of t-EMG may be as a warning tool for lumbar pedicle screw malpositioning in the presence of positive stimulation at a threshold of ⩽8 mA.Significancet-EMG by screw stimulation may be valuable in the lumbar region at a threshold of ⩽8 mA.