Lateral Transpsoas Approach

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Dilator Technique

  • Connect the Sentio dilator probe and set current to 6mA.
  • Advance the dilator probe through the psoas while stimulating.
  • If Sentio triggers a ‘STOP’, reposition the dilator probe to locate a safe entry point by achieving a ‘GO’ at 6mA.
  • If Sentio stays ‘GO’ and the probe is in good position on fluoro, insert the dilators and retractor.
  • Sweep field with 6mA to confirm absence of nerve by maintaining a ‘GO’.
  • {Optional} Confirm the nerve is located behind the retractor blades by positioning the probe behind the retractor blades and obtaining a ‘STOP’.

Dissection Technique

  • Connect the Sentio probe and set current to 6mA.
  • Advance the probe through the psoas while stimulating.
  • If Sentio triggers a ‘STOP’, reposition the probe to locate the nerve. The MMG signal will increase if you are moving toward the nerve. Otherwise, the MMG signal will decrease and turn to ‘GO’ as you move away from the nerve.
  • Locate a safe entry point by achieving a ‘GO’ at 6mA. If Sentio stays ‘GO’ and probe is in good position on fluoro, retract muscle fibers and position retractor.
  • Sweep field with 6mA to confirm absence of nerve by maintaining a ‘GO’.
  • {Optional} Confirm the nerve is located behind the retractor blades by positioning the probe behind the retractor blades and obtaining a ‘STOP’.

Advanced Applications

  • In difficult cases, especially at the L4-5 level, there may be multiple nerves present. You can use the Sentio probe to map these nerves precisely by starting with 1mA and adjusting the current up until a ‘STOP’:
    • ‘STOP’ at 1mA = Probe in contact with nerve
    • ‘STOP’ at 2-6mA = Probe within approximately 2-6mm of nerve
    • ‘STOP’ at >6mA = Safe distance
    • Once the nerves are precisely located, you may be able to establish a safe entry point by gently retracting the nerves posterity.
    • Confirm the nerve is located behind the retractor blades by positioning the probe behind the retractor blades and obtaining a ‘STOP’.

LATERAL NOTE: Surgeons less familiar with this technique may consider working at a slightly higher current level such as 10mA rather than 6mA to establish a safe working distance.