Technical Efficacy of a Direction Specific Radiofrequency Device in the Performance of Lumbar Medial Branch Neurotomies

Study Timeline, Outline, and Methods

• Initial evaluation with physician and study eligibility determination
• Presentation of study to patient and informed consent obtained
• Baseline paraspinous muscle EMG performed
• MB (medial branch)/DR (dorsal ramus) radiofrequency neurotomy with Nimbus MEE probe (start date)
• Post-operative soreness managed with oral and topical medications and possibly 1-4 physical therapy sessions, as needed
• MD visit at intake evaluation and at 3 and 6 weeks following the procedure.
• Paraspinal needle electromyography, using the mini-paraspinal mapping ("miniPM") technique of Haig will be carried out at baseline (pre-procedure) and between 3 and 6 weeks post-procedure.
• MRI, with sequencing which allows for volumetric calculations (see Appendix III), will be obtained on all of the ten chosen subjects at 7 days post-procedure. If there is any evidence of edema or coagulation changes with volume of greater than 600 cubic mm, or evidence of bony edema or other changes believed to be due to the procedure, then a follow up MRI will be obtained at 14 days post-procedure. If bony edema changes are present at 14 days, repeat MRI will be obtained at 6 weeks post-procedure.
• Procedural details, including procedural and fluoroscopy times, will be collected for each subject. A matched cohort of patients who have undergone MB RFN (radiofrequency neurotomy) using the previous/current method have had the same data obtained for group comparisons.

Lumbar Paraspinal Mapping:

The adequate cauterization of the targeted medial branches will be confirmed using the paraspinal mapping (PM) technique of Haig. This testing will be carried out on all subjects at 3-6 weeks post radiofrequency neurotomies, by electromyographers blinded to the side and levels of the procedure. Subjects found to have reliable evidence of spontaneous electrical activity, as detailed in, will be deemed to have had a successful denervation of the medial branch in question.

Baseline PM will also be carried out at enrollment to document a normal baseline and to rule out the presence of spontaneous activity from other underlying pathology. Those found to have findings of spontaneous activity, upon baseline needle EMG of the lumbar paraspinals, will be excluded from the study.

Lumbar MRI - Post-Procedure

The ten study participants in this study will undergo lumbar MRI, using sequencing that will allow volume calculations of any soft tissue or bony findings of edema or coagulation. Experience thus far would indicate that the zone of edema can be identified, but that the zone of tissue coagulation (smaller than the zone of edema) cannot be reliably demarcated. Bench research using the Nimbus MEE probe indicates a zone of coagulation of 550 cubic mm or less, and the expected findings on MRI would consist of a zone of edema in this range, although MRI evidence of edema may be found in a larger volume of soft tissue, given that edema changes would be expected to be present in an area larger than the area of coagulation. The intention is to provide evidence that the area treated includes the known location of the targeted medial branch, but that bone edema or other unintended findings are not encountered. These MRIs will be obtained at 7 days post-procedure. If there is evidence for unintended bony edema, then these subjects will return for repeat MRI at 14 days post-procedure. If any of these unexpected findings are still present at 14 days post-procedure, then these subjects will be asked to undergo a third MRI at 6 weeks post-procedure. Images will be interpreted by a radiologist who is board certified in diagnostic radiology. Post-procedure MRI scoring will include documentation of the presence or absence of lesions, calculated volume of lesions, whether the lesion covers the anatomical location of the medial branch, and whether there is any evidence of bone edema at the lesion site(s).

Inclusion criteria

• Patients with a low back pain episode greater than three months in duration, unresponsive to non-interventional care, have had a lumbar MRI which is available for review, who have been selected to undergo lumbar medial branch RF lesioning and who have agreed to undergo pre and post procedure EMG and post procedure lumbar magnetic resonance imaging (LMRI).
• Age 18 or greater
• Appropriately selected patients using at least one set of diagnostic medial branch blocks

Exclusion criteria

• Inability to attend EMG, MRI assessments within the defined assessment time windows
• Radicular pain or evidence of neurological compromise in the lower limbs (see clarification above - Target Population).
• Those unable to read English and complete the informed consent process
• Spondylolysis or lytic spondylolisthesis, degenerative spondylolisthesis which is Grade II+ or unstable.
• Systemic inflammatory, toxic, corticosteroid induced or congenital myopathy, or inflammatory arthritis
• Possible pregnancy or other reason that precludes the use of fluoroscopy, MRI, or EMG
• Significant lumbar scoliosis (Cobb angle > 15 degrees).
• Radicular/neurological deficits or focal disc herniation and/or stenosis, with correlating radicular symptoms (defined as pain or paresthesias below the knee; pain reproduction with straight leg raising; leg > back pain with extension/rotation maneuvers; radicular strength, reflex, or sensory changes consistent with their level of nerve root impingement).
• Immunologically suppressed, or has received steroids at any dose daily for > 1 month within last 12 months
• Currently involved in another study or treatment that may affect the outcome of this study
• Evidence of spontaneous activity (denervation potentials) on baseline EMG