title: Triggered electromyography for placement of thoracic pedicle screws: is it reliable?
abstract: Reliable electromyography (EMG) thresholds for detecting medial breaches in the thoracic spine are lacking, and there is a paucity of reports evaluating this modality in patients with adolescent idiopathic scoliosis (AIS). This retrospective analysis evaluates the ability of triggered EMG to detect medial breaches with thoracic pedicle screws in patients with AIS. We reviewed 50 patients (937 pedicle screws) undergoing posterior spinal fusion (PSF) with intraoperative EMG testing. Postoperative CT scans were used for breach identification, and EMG values were analyzed. There were 47 medial breaches noted with a mean threshold stimulus of 10.2 mA (milliamperes). Only 8/47 breaches stimulated at 2-6 mA. Thirteen of the forty-seven screws tested at an EMG value ≤6 mA and/or a decrease of ≥65% compared with intraosseously placed screws. The sensitivity and positive predictive value for EMG was 0.28 and 0.21. A subanalysis of T10-T12 screws identified six of seven medial breaches. Using guidelines from the current literature, EMG does not appear to be reliable in detecting medial breaches from T2 to T9 but may have some utility from T10 to T12.
authors.affiliation: Shriners Hospitals for Children, 3551 N Broad Street, Philadelphia, PA 19140, USA. asamdani@shrinenet.org
authors.forename: Amer F
authors.initials: AF
authors.lastname: Samdani
authors.forename: Mark
authors.initials: M
authors.lastname: Tantorski
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Cahill
authors.forename: Ashish
authors.initials: A
authors.lastname: Ranade
authors.forename: Stephen
authors.initials: S
authors.lastname: Koch
authors.forename: David H
authors.initials: DH
authors.lastname: Clements
authors.forename: Randal R
authors.initials: RR
authors.lastname: Betz
authors.forename: Jahangir
authors.initials: J
authors.lastname: Asghar
mesh_terms: D000293:Adolescent; D001863:Bone Screws; D004558:Electric Stimulation; D004576:Electromyography / Q000009:adverse effects* / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000601:surgery; D011859:Radiography; D012189:Retrospective Studies; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000601:surgery*; D012684:Sensory Thresholds; D013123:Spinal Fusion / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D016896:Treatment Outcome