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Updated: Aug 18, 2026
An Anesthesia, Surgery, and Harvest Method for the Evaluation of Transpedicular Screws Using an In Vivo Porcine Lumbar Spine Model
Published on: May 31, 2017
Evaluation of intrapedicular screw position using intraoperative evoked electromyography
J Maguire1, S Wallace, R Madiga
1Knoxville Orthopedic Clinic, St. Mary's Medical Center, Tennessee, USA.
Study Design:
This study analyzed the parameters needed for electrical stimulation of vertebral pedicle drill bits and screws.
Objectives:
The feasibility of using electrically evoked electromyography was studied.
Summary Of Background Data:
Considerable potential for damage of adjacent nerve roots with incorrectly placed bits and screws exists with pedicular fixation of the lumbar spine.
Methods:
Ninety-five drill bits, one hundred forty-four screws, and thirty-four exposed nerve roots were electrically stimulated in thirty-six patients. Simultaneous evoked electromyographic activity was recorded from four muscle groups in each lower extremity during partial neuromuscular blockade.
Results:
A constant current threshold of 6 mA or less correlated with misplaced drill bits and screws that broached the cortex. Evoked electromyography was 93% sensitive whereas radiography was only 63% sensitive to detecting bits and screws that had broached the cortex.
Conclusions:
Evoked electromyography is a valuable sensitive adjunct to radiographic examination of pedicle drill bit and screw placement.
