A Prospective Trial of Cooled Radiofrequency Ablation of Medial Branch Nerves Versus Facet Joint Injection of Corticosteroid for the Treatment of Lumbar Facet Syndrome

Chronic, non-neurogenic low back pain (CLBP) is a common condition that affects many
individuals across their lives. The lumbar facet joint has been implicated as an important
source of CLBP, with a prevalence of 15-45%. Elements of clinical history, physical
examination, and imaging (radiographs, standard CT scan, standard MRI sequences) provide poor
diagnostic specificity for pain of lumbar zygapophysial joint (Z-joint) origin. Thus,
clinicians have traditionally relied upon MBN blocks to confirm or refute this diagnosis. The
reference standard for the diagnosis of lumbar Z-joint pain is a positive response to dual
comparative MBN blocks, which requires pain reduction of great than or equal to 80% of
concordant duration to that expected of two different local anesthetics on independent
occasions. Further, dual comparative MBN blocks have a high positive predictive value for
determining the clinical outcome of lumbar MBN RFA for the treatment of lumbar Z-joint pain;
when patients are appropriately selected using this reference standard and rigorous MBN RFA
technique is implemented according to practice guidelines, studies demonstrate excellent
clinical outcomes.

In additional to MBN RFA, lumbar facet joint injection of corticosteroid is another commonly
used treatment strategy for lumbar facet joint pain related to osteoarthritis. While clinical
outcome studies of facet joint injection with corticosteroid have generally shown only modest
outcome improvements, this literature is generally flawed by invalid selection protocols that
do not require dual comparative MBN blocks in order to confirm the diagnosis of pain specific
to the lumbar facet joint(s).

Despite the widespread use of these two techniques (lumbar MBN RFA vs. facet joint
corticosteroid injection), the two techniques have never been compared in an
appropriately-designed head-to-head study. The sole outcome study comparing these two
treatment methods used an invalid selection protocol of one positive MBN block, requiring
only 50% relief in pain and not of concordant duration with that expected by the local
anesthetic used; in addition, a single RFA lesion was applied with a 20g conventional RFA
electrode and fluoroscopic images were not published, so it is unclear if parallel electrode
technique was used, as is necessary with conventional RFA. This invalid patient selection and
RFA technique protocol is similar to that used in the Mint Trials, which has led to a broad
call for improving such standards in research and clinical care by a multitude of experts
representing interventional pain, spine, and radiology specialty societies. As such, an
appropriately designed head-to-head trial in warranted.

Furthermore, while the conventional RFA modality has been studied extensively for MBN RFA,
minimal outcome literature on the effectiveness of C-RFA technology has been published. C-RFA
is similar in mechanism to conventional RFA: a thermal lesion is created by applying
radiofrequency energy through an electrode placed at a target structure. In C-RFA, a constant
flow of ambient water is circulated through the electrode via a peristaltic pump, maintaining
a lowered tissue temperature by creating a heat sink. By removing heat from tissues
immediately adjacent to the electrode tip, a lower lesioning temperature is maintained,
resulting in less tissue charring adjacent to the electrode, less tissue impedance and more
efficient heating of target tissue. The volume of tissue heated, and the resultant thermal
lesion size is substantially larger with C-RFA, conferring an advantage over conventional
RFA. Further, given the spherical geometry and forward projection the C-RFA lesions beyond
the distal end of the electrode, the RFA probe can be positioned at a range of possible
angles and still capture the target neural structure, whereas more fastidious, parallel
positioning is required with conventional RFA. These technical advantages increase the
probability of successful denervation of neural pain generators that have variability in
anatomic location, as is the case with facet syndromes in which significant osteoarthritis is
present, which is associated with joint hypertrophy and osteophyte formation. Additionally, a
longer lesion of the MBN may be more reliably achieved with C-RFA compared to conventional
RFA, potentially resulted in greater treatment durability, as the recurrent of facetogenic
pain after successful denervation is related to reinnervation by nerve re-growth to bridge
the gap created by the lesion. Consistent with this technical advantage, there is preliminary
evidence for superiority of C-RFA compared to both conventional RFA and other novel RFA
techniques in the treatment of sacroiliac joint-mediated pain.

Lumbar facet joint pain is a common and costly cause of chronic low back pain. Lumbar MBN RFA
and facet joint injection of steroid are two commonly used treatment strategies for lumbar
facet-mediated pain, yet the two techniques have never been compared in an
appropriately-designed head-to-head trial. Further there is minimal clinical outcome
literature describing the effectiveness of MBN C-RFA despite its technical advantages over
conventional MBN RFA. We will determine if individuals with lumbar facet syndrome who are
treated with MBN C-RFA compared to face joint injection of corticosteroid have a greater
likelihood of experiencing meaningful relief of low back pain symptoms, functional
improvement, and reduction of analgesic medication use at both short and long-term follow-up.
Answering this clinical question will help determine which standard of care technique is
superior, such that patients with lumbar facet syndrome can get be offered the best treatment
available.

As such, the goal of the proposed study is to determine if individuals with lumbar facet
syndrome who are treated with C-RFA of the MBNs compared to face joint injection of
corticosteroid have a greater likelihood of experiencing meaningful relief of low back pain
symptoms, functional improvement, and reduction of analgesic medication use at both short and
long-term follow-up.

Inclusion Criteria:

- Adult patients aged > 40 capable of understanding and providing consent in English and
capable of complying with the outcome instruments used.

- Axial (non-radicular) back pain for at least 3 months (ie Chronic Low Back Pain), with
pain lasting at least half of the days within those 3 months, that did not respond to
conventional treatment such as physical therapy, oral analgesic agents, and
non-invasive adjunctive treatments. The pain can be unilateral or bilateral. The pain
can also include referred lower limb pain.

- 7-day worst numeric pain rating score (NPRS) for back pain of 5/10 or greater at
baseline evaluation.

- Positive responses to dual comparative diagnostic MBN blocks using 0.5mL of 0.5%
bupivacaine and 4% lidocaine, on respective encounters on separate days, at each of
the appropriate MBNs. The blocks are administered in a double-blind fashion so that
neither the subject nor the independent assessor is aware of the local anesthetic
used.

Exclusion Criteria:

- Focal neurologic signs or symptoms.

- Radiologic evidence of a symptomatic herniated disc or nerve root impingement related
to spinal stenosis.

- Active systemic or local infections at the site of proposed needle and electrode
placement.

- Coagulopathy or other bleeding disorder.

- Receipt of remuneration for their pain treatment (e.g. disability, worker's
compensation, auto injury in litigation or pending litigation).

- History of prior spine surgery.

- Grade 2 Spondylolisthesis at an affected or adjacent level.

- BMI >35.

- Incarceration.

- Cognitive deficit affecting ability to complete the assessment instruments.

- Inability to read English and complete the assessment instruments.

- Allergy to local anesthetics.

- Chronic widespread pain or somatoform disorder (e.g. fibromyalgia).

- Prior lumbar MBN radiofrequency neurotomy.

- Addictive behavior, severe clinical depression, anxiety, or any mental health
condition with psychotic features.

- Possible pregnancy or other reason that precludes the use of fluoroscopy.

- Daily chronic opiate use of >50 morphine equivalents.