Advanced XLIF Monitoring Multicenter Study
Condition: Degenerative Lumbar Disc Disease
Study type: Observational

Summary: 
      The objective of this study is to evaluate the utility of localized stimulation of the
      lumbosacral nerve roots during XLIF through correlation of observed changes in the response
      latency, amplitude, waveform morphology, and/or response threshold with surgical events.
      Additionally, correlation between neuromonitoring findings and postoperative neural status
      will be evaluated.
    

Detailed description: 
      The utility of NVM5 neuromonitoring by stimulating within the surgical site during XLIF has
      been previously demonstrated; however, it is possible that depending on the site of injury,
      this method of monitoring may stimulate nerves at a location that is distal to the site of
      injury along the nerve conduction pathway. In this example, the site of injury would not
      disrupt the stimulus and a normal muscle response may occur, providing a false negative
      result. With this in mind, it has been hypothesized that more accurate information may be
      gathered by stimulating the lumbar roots or spinal nerves cranial to the surgical site and
      recording the subsequent muscle response in the lower limbs. Using this technique, the
      response to the stimulus would traverse the surgical site, including the site of any nerve
      injury. Currently, the only described method of stimulating cranial to the surgical site is
      with transcranial motor evoked potentials (tcMEP); stimulating the lumbosacral nerve roots
      locally has not been demonstrated. Though tcMEP monitoring is a well-documented technique,
      there are several limitations associated with its use. For example, tcMEP requires adherence
      to total intravenous anesthesia (TIVA), thereby restricting the use of inhalational agents.
      This restriction may require additional training and coordination with the anesthesiologist,
      as well as added cost to the hospital.6 Additional challenges with tcMEP include the
      requirements for high voltage stimulation to successfully transmit a stimulus across the
      skull. In rare instances this can cause seizures, tongue lacerations, and other
      complications. Finally, due to inclusion of the central nervous system, monitoring with tcMEP
      may be less reproducible and specific than a more localized stimulation.

      To address these challenges, recent adaptations to standard MEP and EMG monitoring protocols
      have used local stimulation of the lumbosacral nerve roots at the level of the conus, with
      recorded responses from the relevant innervated muscle groups of the lower limbs. Early
      experience using this technique has shown the feasibility and reproducibility of obtaining
      reliable baseline and longitudinal responses throughout a surgical procedure, and
      incorporation of this monitoring modality has become common practice at certain surgical
      sites performing XLIF, although determination of clinically meaningful changes in those
      responses have yet to be determined.
    

Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Patients who, in the investigator's opinion, require lateral approach spinal fusion surgery
        at spinal level L4-5 (though may include any number of levels from L2 through L5), and have
        consented to XLIF surgery for their condition will be included. All subjects must meet the
        inclusion/exclusion criteria below in order to be considered for enrollment.