SAFETY OF PEDICLE SCREW PLACEMENT WITH EVOKED EMG.
Journal Title: Journal of Turkish Spinal Surgery - Year 2006, Vol 17, Issue 4
Abstract
The complication rate associated with pedicle screw insertion in spine surgery varies from 1 to 33 %. Three main utilities are used in the placement of pedicle screw to decrease this potential: probing of the pedicle track, use of fluoroscopy, and evoked EMG. Purpose: To demonstrate whether evoked EMG is a reliable guide for safety of pedicle screw insertion. Study Design/Setting: A retrospective review was undertaken. Patient history, preoperative physical examination, intraoperative anesthesia, spinal cord monitoring records and the postoperative course were reviewed. Methods: A total of 24 consecutive posterior thoracolumbar spine surgeries with transpedicular screws were reviewed. There were 24 patients (9 male and 15 female). A total of 118 pedicle screws were placed. Fifty seven percent of the patients had a principal preoperative diagnosis of idiopathic scoliosis. Other common diagnoses were neuromuscular scoliosis, kyphosis, and spondylolisthesis. All pedicle screws were placed with the assistance of fluoroscopy. After insertion of the transpedicular screws, the integrity of the pedicle cortex was tested by stimulating each screw head and recording evoked EMG. Results: Five of 118 screws (4 %) had evoked EMG potentials of less than 7 uA. This threshold was used based on previous studies to be indicative of pedicle wall breach. There was one patient with postoperative radiculopathy and severe pain in the corresponding nerve root distinct from preoperative presentations. Consequently, this pedicle screw was revised and patient had symptom resolution. Ninety-nine percent of screws that were inserted with evoked EMG and fluoroscopy were without clinical consequence. Conclusion: The use of evoked EMG in evaluating pedicle screw placement is safe and reproducible. A combination of fluoroscopy and EMG monitoring provides excellent intraoperative recognition of neurologic injury.
Authors and Affiliations
Prasit NIMITYONGSKUL, Clinton W. HOWARD
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