Evoked and spontaneous electromyography to evaluate lumbosacral pedicle screw placement.
METHODS
A prospective study was performed to evaluate the effectiveness of evoked and spontaneous electromyography in predicting pedicle wall breakthrough and subsequent lumbar radiculopathy occurring after placement of pedicle screw instrumentation of the lumbar spine.


OBJECTIVE
To correlate cortical breakthrough of the pedicle wall with an electrically evoked electromyography threshold of stimulation, to assess the sensitivity of mechanically evoked electromyography for nerve root irritation, and to correlate postoperative nerve root irritation with intraoperative findings.


BACKGROUND
Pedicle wall breakthrough has been evaluated by radiographic means and found to be difficult to evaluate. Methods to perform both electrically evoked and mechanically evoked electromyography have been developed more sensitive tests for breakthrough.


METHODS
Twenty-five patients receiving 112 pedicle screws were evaluated.


RESULTS
Cortical breakthrough was associated with electrically evoked electromyography threshold of less than 11 milliAmps. Not all screws that had broken through the pedicle wall caused a postoperative radiculopathy. Electromyographic activity was sensitive to nerve root stimulation.


CONCLUSIONS
Measuring the electrically evoked electromyography threshold of stimulation helps to assess pedicle screw placement. Mechanically evoked electromyography indicates intraoperative nerve root displacement. Postoperative radiculopathy correlated with pedicle wall breakthrough, but did not occur in every case.
Clements
D H
DH
Department of Orthopaedic Surgery, Temple University Hospital, Philadelphia, Pennsylvania, USA.
Morledge
D E
DE
Martin
W H
WH
Betz
R R
RR
D000293:Adolescent; D000328:Adult; D000368:Aged; D001863:Bone Screws / Q000009:adverse effects; D004576:Electromyography; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D007866:Leg; D008159:Lumbar Vertebrae / Q000503:physiopathology / Q000601:surgery*; D008161:Lumbosacral Region / Q000601:surgery; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology*; D009408:Nerve Compression Syndromes / Q000175:diagnosis / Q000517:prevention & control; D011446:Prospective Studies