Stimulus-evoked electromyography testing of percutaneous pedicle screws for the detection of pedicle breaches: a clinical study of 409 screws in 93 patients

Presented at the 2009 Joint Spine Section Meeting 

Restricted access

Spine - 1 year subscription bundle (Individuals Only)

USD  $369.00

JNS + Pediatrics + Spine - 1 year subscription bundle (Individuals Only)

USD  $600.00

Object

Percutaneous pedicle screws have recently become popularized for lumbar spinal fixation. However, successful anatomical hardware placement is highly dependent on intraoperative imaging. In traditional open surgery, stimulus-evoked electromyography (EMG) responses can be useful for detecting pedicle screw breaches. The use of insulated sleeves for percutaneous screws has allowed for EMG testing in minimally invasive surgery; however, no reports on the reliability of this testing modality have been published.

Methods

A total of 409 lumbar percutaneous pedicle screws were placed in 93 patients. Levels of instrumentation included L-1 (in 12 patients), L-2 (in 34), L-3 (in 44), L-4 (in 120), L-5 (in 142), and S-1 (in 57 patients). Intraoperative EMG stimulation thresholds were obtained using insulating sleeves over a metallic tap prior to final screw placement. Data were compared with postoperative fine-cut CT scans to assess pedicle screw placement. Data were collected prospectively and analyzed retrospectively.

Results

There were 5 pedicle breaches (3 medial and 2 lateral; 3 Grade 1 and 2 Grade 2 breaches) visualized on postoperative CT scans (1.2%). Two of these breaches were symptomatic. In 2 instances, intraoperative thresholds were the sole basis for screw trajectory readjustment, which resulted in proper placement on postoperative imaging. Thirty-five screw trajectories were associated with a threshold of less than 12 mA. However, all breaches were associated with thresholds of greater than 12 mA. Using thresholds below 12 mA as the indicator of a screw breach, this resulted in a sensitivity of 0.0, specificity of 90.3, positive predictive value of 0.0, and negative predictive value of 0.98. Utilizing a threshold of any decreased stimulus (< 20 mA) would have detected 60% of breaches, with a mean threshold of 16.25 mA.

Conclusions

While these data are limited by the low number of radiographic breaches, it appears that tap stimulation with an insulating sleeve may not be reliable for detecting low-grade radiographically breached pedicles using typical stimulation thresholds (< 12 mA). Imaging-based modalities remain more reliable for assessing percutaneous pedicle screw trajectories until more robust and sensitive electrophysiological testing methods can be devised.

Abbreviations used in this paper: EMG = electromyography; TLIF = transforaminal lumbar interbody fusion.
Article Information

Contributor Notes

Address correspondence to: Michael Y. Wang, M.D., Department of Neurological Surgery, University of Miami Miller School of Medicine, 1095 NW 14th Terrace, Lois Pope Life Center, D4-6, Miami, Florida 33136. email: mwang2@med.miami.edu.
Headings
References
  • 1

    Anderson DGWierzbowski LRSchwartz DMHilibrand ASVaccaro ARAlbert TJ: Pedicle screws with high electrical resistance: a potential source of error with stimulus-evoked EMG. Spine 27:157715812002

    • Search Google Scholar
    • Export Citation
  • 2

    Bose BWierzbowski LRSestokas AK: Neurophysiologic monitoring of spinal nerve root function during instrumented posterior lumbar spine surgery. Spine 27:144414502002

    • Search Google Scholar
    • Export Citation
  • 3

    Bosnjak RDolenc VV: Electrical thresholds for biomechanical response in the ankle to direct stimulation of spinal roots L4, L5, and S1. Implications for intraoperative pedicle screw testing. Spine 25:7037082000

    • Search Google Scholar
    • Export Citation
  • 4

    Calancie BHarris WBroton JGAlexeeva NGreen BA: “Threshold-level” multipulse transcranial electrical stimulation of motor cortex for intraoperative monitoring of spinal motor tracts: description of method and comparison to somatosensory evoked potential monitoring. J Neurosurg 88:4574701998

    • Search Google Scholar
    • Export Citation
  • 5

    Calancie BMadsen PLebwohl N: Stimulus-evoked EMG monitoring during transpedicular lumbosacral spine instrumentation. Initial clinical results. Spine 19:278027861994

    • Search Google Scholar
    • Export Citation
  • 6

    Castro WHHalm HJerosch JMalms JSteinbeck JBlasius S: Accuracy of pedicle screw placement in lumbar vertebrae. Spine 21:132013241996

    • Search Google Scholar
    • Export Citation
  • 7

    Clements DHMorledge DEMartin WHBetz RR: Evoked and spontaneous electromyography to evaluate lumbosacral pedicle screw placement. Spine 21:6006041996

    • Search Google Scholar
    • Export Citation
  • 8

    Darden BV IIOwen JHHatley MKKostuik JTooke SM: A comparison of impedance and electromyogram measurements in detecting the presence of pedicle wall breakthrough. Spine 23:2562621998

    • Search Google Scholar
    • Export Citation
  • 9

    Darden BV IIWood KEHatley MKOwen JHKostuik J: Evaluation of pedicle screw insertion monitored by intraoperative evoked electromyography. J Spinal Disord 9:8161996

    • Search Google Scholar
    • Export Citation
  • 10

    Dhall SSWang MYMummaneni PV: Clinical and radiographic comparison of mini-open transforaminal lumbar interbody fusion with open transforaminal lumbar interbody fusion in 42 patients with long-term follow-up. Clinical article. J Neurosurg Spine 9:5605652008

    • Search Google Scholar
    • Export Citation
  • 11

    Dickerman RDGuyer R: Intraoperative electromyography for pedicle screws: technique is the key!. J Spinal Disord 19:4632006. (Letter)

    • Search Google Scholar
    • Export Citation
  • 12

    Glassman SDDimar JRPuno RMJohnson JRShields CBLinden RD: A prospective analysis of intraoperative electromyographic monitoring of pedicle screw placement with computed tomographic scan confirmation. Spine 20:137513791995

    • Search Google Scholar
    • Export Citation
  • 13

    Guyer DWYuan HAWerner FWFrederickson BEMurphy D: Biomechanical comparison of seven internal fixation devices for the lumbosacral junction. Spine 12:5695731987

    • Search Google Scholar
    • Export Citation
  • 14

    Holland NRLukaczyk TARiley LH IIIKostuik JP: Higher electrical stimulus intensities are required to activate chronically compressed nerve roots. Implications for intraoperative electromyographic pedicle screw testing. Spine 23:2242271998

    • Search Google Scholar
    • Export Citation
  • 15

    Holly LTFoley KT: Percutaneous placement of posterior cervical screws using three-dimensional fluoroscopy. Spine 31:5365412006

  • 16

    Khoo LTPalmer SLaich DTFessler RG: Minimally invasive percutaneous posterior lumbar interbody fusion. Neurosurgery 51:5 SupplS166S1812002

    • Search Google Scholar
    • Export Citation
  • 17

    Masferrer RGomez CHKarahalios DGSonntag VK: Efficacy of pedicle screw fixation in the treatment of spinal instability and failed back surgery: a 5-year review. J Neurosurg 89:3713771998

    • Search Google Scholar
    • Export Citation
  • 18

    Owen JHKostuik JPGornet MPetr MSkelly JSmoes C: The use of mechanically elicited electromyograms to protect nerve roots during surgery for spinal degeneration. Spine 19:170417101994

    • Search Google Scholar
    • Export Citation
  • 19

    Raynor BLLenke LGBridwell KHTaylor BAPadberg AM: Correlation between low triggered electromyographic thresholds and lumbar pedicle screw malposition: analysis of 4857 screws. Spine 32:267326782007

    • Search Google Scholar
    • Export Citation
  • 20

    Roy-Camille RSaillant GBerteaux DMarie-Anne SMamoudy P: [Vertebral osteosynthesis using metal plates. Its different uses (author's transl).]. Chirurgie 105:5976031979. (Fr)

    • Search Google Scholar
    • Export Citation
  • 21

    Steffee ADBiscup RSSitkowski DJ: Segmental spine plates with pedicle screw fixation. A new internal fixation device for disorders of the lumbar and thoracolumbar spine. Clin Orthop Relat Res 203:45531986

    • Search Google Scholar
    • Export Citation
  • 22

    Wang MYAnderson DGPoelstra KALudwig SC: Minimally invasive posterior fixation for spinal deformities. Neurosurgery 63:3 Suppl1972042008

    • Search Google Scholar
    • Export Citation
  • 23

    Wang MYKim KALiu CYKim PApuzzo MLJ: Reliability of three-dimensional fluoroscopy for detecting pedicle violations in the thoracic and lumbar spine. Neurosurgery 54:113811432004

    • Search Google Scholar
    • Export Citation
  • 24

    Weinstein JNSpratt KFSpengler DBrick CReid SSpengler D: Spinal pedicle fixation: reliability and validity of roentgenogram-based assessment and surgical factors on successful screw placement. Spine 13:101210181988

    • Search Google Scholar
    • Export Citation
  • 25

    Welch WCRose RDBalzer JRJacobs GB: Evaluation with evoked and spontaneous electromyography during lumbar instrumentation: a prospective study. J Neurosurg 87:3974021997

    • Search Google Scholar
    • Export Citation
  • 26

    Wiesner LKothe RSchulitz KPRüther W: Clinical evaluation and computed tomography scan analysis of screw tracts after percutaneous insertion of pedicle screws in the lumbar spine. Spine 25:6156212000

    • Search Google Scholar
    • Export Citation
Metrics

Metrics

All Time Past Year Past 30 Days
Abstract Views 339 214 11
Full Text Views 153 25 5
PDF Downloads 153 22 2
EPUB Downloads 0 0 0
PubMed
Google Scholar