Advanced XLIF Monitoring Multicenter Study

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.

Inclusion Criteria:

1. Male and female spine surgery patients who are at least 18 years of age;

2. Persistent back and/or leg pain unresponsive to conservative treatment for at least
six (6) months, unless surgical treatment is clinically indicated earlier;

3. Surgical candidates for extreme lateral approach lumbar spine surgery at spinal levels
L2 to L5, inclusive of L4-5;

4. Able to undergo surgery based on physical exam, medical history and surgeon judgment;

5. Patients who understand the conditions of enrollment and are willing to sign an
informed consent to participate in the evaluation.

Exclusion Criteria:

1. Patient has a mental or physical condition that would limit the ability to comply with
study requirements;

2. Currently undergoing any surgical treatment at any spinal level other than L2 to L5;

3. Currently undergoing surgical treatment for significant deformity correction (e.g.,
osteotomy, anterior longitudinal ligament release, or other significant manipulation
of the spinal column);

4. Underlying neurological disease or neurological deficit that is not associated with
the condition for which he/she is seeking surgical intervention (e.g., diabetic
peripheral neuropathy);

5. Implanted pacemaker, defibrillator, or other electronic devices;

6. Involved in active litigation relating to the spine (worker's compensation claim is
allowed if it is not contested);

7. Pregnant women;

8. Patient is a prisoner;

9. Patient is participating in another clinical study that would confound study data.