title: Evaluation of pedicle screw insertion monitored by intraoperative evoked electromyography.
abstract: The insertion of pedicle screws monitored by evoked electromyography (EMG) was prospectively evaluated in the 132 consecutive patients. The technique involved constant-voltage stimulation and was statistically evaluated at both the arbitrary 20- and 40-V settings. The patients were postoperatively evaluated clinically and radiographically. Computed tomography (CT) scanning was performed for new neurologic deficits. Results were divided into three groups: type 1, a negative EMG response; type 2, a positive EMG response, but no corrective action taken; and type 3, a positive EMG response and corrective action undertaken. Nonparametric statistics were used to evaluate the results at both the 20- and 40-V settings. In the type 3 group, in which corrective action was undertaken, there were no neurologic injuries or screw removals, a statistically significant result. Looking at the two intensity levels, at 20- and 40-V settings, there were no statistically significant differences in the three classifications at either intensity level. We concluded the evoked EMG for monitoring pedicle screw insertion is an efficacious adjunct. A positive response at < 20 V with the constant-voltage technique warrants corrective action.
authors.affiliation: Charlotte Spine Center, North Carolina 28207, USA.
authors.forename: B V
authors.initials: BV
authors.lastname: Darden
authors.forename: K E
authors.initials: KE
authors.lastname: Wood
authors.forename: M K
authors.initials: MK
authors.lastname: Hatley
authors.forename: J H
authors.initials: JH
authors.lastname: Owen
authors.forename: J
authors.initials: J
authors.lastname: Kostuik
mesh_terms: D000328:Adult; D000368:Aged; D001863:Bone Screws; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D013122:Spinal Diseases / Q000503:physiopathology* / Q000601:surgery