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Related Experiment Videos

Can triggered electromyograph thresholds predict safe thoracic pedicle screw placement?

Barry L Raynor1, Lawrence G Lenke, Yongjung Kim

  • 1Department of Orthopaedic Surgery, Washington University Medical Center, BJC Health Systems, St. Louis, Missouri 63110, USA.

Spine
|March 14, 2003
PubMed
Summary

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This study found that triggered electromyography using rectus abdominis muscles can effectively assess thoracic pedicle screw placement. Lower EMG thresholds (<6.0 mA) may indicate medial breaches, guiding surgeons to potential complications.

Area of Science:

  • Spinal surgery
  • Neurosurgery
  • Orthopedic surgery

Background:

  • Triggered electromyography (tEMG) using lower extremity myotomes has identified misplaced lumbar pedicle screws.
  • Higher tEMG thresholds suggest intraosseous placement due to increased resistance.
  • Lower thresholds indicate compromised pedicles and potential nerve impingement.

Purpose of the Study:

  • To evaluate the sensitivity of rectus abdominis triggered electromyography (tEMG) for assessing thoracic pedicle screw placement.
  • To correlate tEMG findings with screw position and potential pedicle wall breaches.

Main Methods:

  • A prospective study involving 677 thoracic pedicle screws in 92 patients (T6-T12).
  • Ascending stimulation of rectus abdominis muscles to obtain compound muscle action potentials.

Related Experiment Videos

  • Comparison of threshold values, both absolute and relative to intrapatient means.

    • Main Results:

    • 3.9% of screws (27/677) had thresholds <6.0 mA.
    • Only 22% (6/27) of low-threshold screws had confirmed medial wall perforations.
    • Screws with <6.0 mA thresholds showed significant decreases from the mean threshold (54-69%).

    Conclusions:

    • tEMG thresholds <6.0 mA in the rectus abdominis may indicate medial pedicle wall breaches.
    • A decrease of 60-65% from the mean threshold within a patient is a key indicator of potential breach.
    • This technique can alert surgeons to suspected medial pedicle wall breaches during thoracic screw placement.