Facet Joint Interventions generally consist of four types of procedures:
Intraarticular (IA) Facet Joint Injections, Medial Branch Blocks (MBB),
Radiofrequency Ablations (RFA) and Facet cyst rupture/aspiration:

Facet Joint Interventions are considered medically reasonable and necessary
for the diagnosis and treatment of chronic pain in patients who meet **ALL**
the following criteria:

  1. Moderate to severe chronic neck or low back pain, predominantly axial, that causes functional deficit measured on pain or disability scale*
  2. Pain present for minimum of 3 months with documented failure to respond to noninvasive conservative management (as tolerated)
  3. Absence of untreated radiculopathy or neurogenic claudication (except for radiculopathy caused by facet joint synovial cyst)
  4. There is no non-facet pathology per clinical assessment or radiology studies that could explain the source of the patient's pain, including but not limited to fracture, tumor, infection, or significant deformity. 

*Pain assessment must be performed and documented at baseline, after each diagnostic procedure using the **same** pain scale for each assessment. A disability scale must also be obtained at baseline to be used for functional assessment (if patient qualifies for treatment).

**A. Diagnostic Facet Joint Procedures (IA or MBB):**

The primary indication of a diagnostic facet joint procedure is to diagnose
whether the patient has facet syndrome. Intraarticular (IA) facet block(s) are
considered reasonable and necessary as a diagnostic test only if medial branch
blocks (MMB) cannot be performed due to specific documented anatomic
restrictions or there is an indication to proceed with therapeutic
intraarticular injections. These restrictions must be clearly documented in
the medical record and made available upon request.

Diagnostic procedures should be performed with the intent that if successful,
radiofrequency ablation (RFA) procedure would be considered the primary
treatment goal at the diagnosed level(s).

A second diagnostic facet procedure is considered medically necessary to
confirm validity of the initial diagnostic facet procedure when administered
at the same level. The second diagnostic procedure may only be performed a
minimum of 2 weeks after the initial diagnostic procedure. Clinical
circumstances that necessitate an exception to the two-week duration may be
considered on an individual basis and must be clearly documented in the
medical record.

For the first diagnostic facet joint procedure:

    1. For the first diagnostic facet joint procedure to be considered medically reasonable and necessary, the patient must meet the criteria outlined under indications for facet joint interventions.
    2. A second confirmatory diagnostic facet joint procedure is considered medically reasonable and necessary in patients who meet **ALL** the following criteria:

  1.     1.       1. The patient meets the criteria for the first diagnostic procedure; **AND**
      2. After the first diagnostic facet joint procedure, there must be a consistent positive response of at least 80% relief of primary (index) pain (with the duration of relief being consistent with the agent used) 

_Frequency limitation_ : For each covered spinal region no more than four (4)
diagnostic joint sessions will be reimbursed per rolling 12 months, in
recognition that the pain generator cannot always be identified with the
initial and confirmatory diagnostic procedure.

**B. Therapeutic Facet Joint Procedures (IA):**

Therapeutic facet joint procedures are considered medically reasonable and
necessary for patients who meet **ALL** the following criteria:

  1. The patient has had two (2) medically reasonable and necessary diagnostic facet joint procedures with each one providing a consistent minimum of 80% relief of primary (index) pain (with the duration of relief being consistent with the agent used); **AND**
  2. Subsequent therapeutic facet joint procedures at the same anatomic site results in at least consistent 50% pain relief for at least three (3) months from the prior therapeutic procedure **or** at least 50% consistent improvement in the ability to perform previously painful movements and ADLs as compared to baseline measurement using the same scale; **AND**
  3. Documentation of why the patient is not a candidate for radiofrequency ablation (such as established spinal pseudarthrosis, implanted electrical device).

Frequency Limitations: For each covered spinal region no more than four (4)
therapeutic facet joint (IA) sessions will be reimbursed per rolling 12
months.

**C. Facet Joint Denervation:**

The thermal radiofrequency destruction of cervical, thoracic, or lumbar
paravertebral facet joint (medial branch) nerves are considered medically
reasonable and necessary for patients who meet **ALL** the following criteria:

  1.     1. Initial thermal RFA: 
      1. After the patient has had at least two (2) medically reasonable and necessary diagnostic MBBs, with each one providing a consistent minimum of 80% sustained relief of primary (index) pain (with the duration of relief being consistent with the agent used) **AND**
      2. Repeat thermal facet joint RFA at the same anatomic site is considered medically reasonable and necessary provided the patient had a minimum of consistent 50% improvement in pain for at least six (6) months **or** at least 50% consistent improvement in the ability to perform previously painful movements and ADLs as compared to baseline measurement using the same scale;

Frequency Limitation: For each covered spinal region no more than two (2)
radiofrequency sessions will be reimbursed per rolling 12 months.

**D. Facet Cyst Aspiration/Rupture**

Intra-articular facet joint injection performed with synovial cyst aspiration
is considered medically necessary when both of the following criteria are met:

  1. Advanced diagnostic imaging study (e.g. MRI/CT/myelogram) confirm compression or displacement of the corresponding nerve root by a facet joint synovial cyst; **AND**
  2. Clinical and physical symptoms related to synovial facet cyst are documented

_Frequency Limitation:_ Cyst aspiration/rupture may be repeated **once** and
only if there is 50% or more consistent improvement in pain for at least three
(3) months.

**Limitations**

  1. Facet joint interventions done without CT or fluoroscopic guidance are considered not reasonable and necessary. This includes facet joint interventions done without any guidance, performed under ultrasound guidance, or with magnetic resonance imaging (MRI).
  2. Use of Moderate or Deep Sedation, General Anesthesia, and Monitored Anesthesia Care (MAC) is not considered medically reasonable and necessary during facet injections1 
  3. The use of Moderate Anesthesia for RFA will be considered in individual cases with documentation of medical necessity such as a longstanding well-documented history of inability to cooperate, medical conditions that would prohibit performance of the procedure, or inability to remain motionless. Patient anxiety or preference alone is not sufficient justification. Routine use of Moderate Sedation or Monitored Anesthesia Care (MAC) or use of General Anesthesia or Deep Sedation for RFA is not considered reasonable and necessary.1 
  4. It is not expected that patients will routinely present with pain in both cervical/thoracic and lumbar spinal regions. Therefore, facet joint interventions (both diagnostic and therapeutic) are limited to one spinal region per session.
  5. It is not routinely necessary for multiple blocks (e.g., epidural injections, sympathetic blocks, trigger point injections, etc.) to be provided to a patient on the same day as facet joint procedures. Multiple blocks on the same day could lead to improper or lack of diagnosis. If performed, the medical necessity of each injection (at the same or a different level[s]) must be clearly documented in the medical record. For example, the performance of both paravertebral facet joint procedures(s) and a transforaminal epidural injection (TFESI) at the same or close spinal level at the same encounter would not be expected unless a synovial cyst is compressing the nerve root. In this situation, TFESI may provide relief for the radicular pain, while the facet cyst rupture allows nerve root decompression. Frequent reporting of multiple blocks on the same day may trigger a focused medical review.
  6. Facet joint intraarticular injections and medial branch blocks may involve the use of anesthetic, corticosteroids, anti-inflammatories and/or contrast agents, and does not include injections of biologicals or other substances not FDA designated for this use.
  7. One to two levels, either unilateral or bilateral, are allowed per session per spine region. Three or four-level procedures are not medically necessary and therefore are non-covered. A session is a time period, which includes all procedures (i.e., medial branch block (MBB), intraarticular injections (IA), facet cyst ruptures, and RFA ablations that are performed during the same day. 
  8. If there is an extended time, two years or more, since the last RFA and there is a question as to the source of the recurrent pain then diagnostic procedures must be repeated.
  9. Therapeutic intraarticular facet injections are not covered unless there is justification in the medical documentation on why RFA cannot be performed. Facet joint procedures in patients for the indication of generalized pain conditions (such as fibromyalgia) or chronic centralized pain syndromes are considered not reasonable and necessary. Individual consideration may be considered under unique circumstances and with sufficient documentation of medical necessity on appeal.
  10. In patients with implanted electrical devices, providers must follow manufacturer instructions and extra planning as indicated to ensure safety of procedure.

The following are considered not reasonable and necessary and therefore will
be denied:

  1. Intraarticular and extraarticular facet joint prolotherapy
  2. Non-thermal modalities for facet joint denervation including chemical, low-grade thermal energy (less than 80 degrees Celsius), laser neurolysis, and cryoablation. 
  3. Intra-facet implants
  4. Facet joint procedure performed after anterior lumbar interbody fusion or ALIF.
  5. Definitive clinical and/or imaging findings pointing to a specific diagnosis other than facet joint syndrome
  6. Diagnostic injections or MMB at the same level as the previously successful RFA procedure

Note: The scales used for measurement of pain and/or disability must be
documented in the medical record. Acceptable scales include but are not
limited to: verbal rating scales, Numerical Rating Scale (NRS) and Visual
Analog Scale (VAS) for pain assessment, and Pain Disability Assessment Scale
(PDAS), Oswestry Disability Index (ODI), Oswestry Low Back Pain Disability
Questionnaire (OSW), Quebec Back Pain Disability Scale (QUE), Roland Morris
Pain Scale, Back Pain Functional Scale (BPFS), and the PROMIS profile domains
to assess function.

**Notice:** Services performed for any given diagnosis must meet all the
indications and limitations stated in this policy, the general requirements
for medical necessity as stated in CMS payment policy manuals, all existing
CMS national coverage determinations, and all Medicare payment rules.

**Provider Qualifications:**  
  
Medicare Program Integrity Manual states services will be considered medically
reasonable and necessary only if performed by appropriately trained providers.

Patient safety and quality of care mandate that healthcare professionals who
perform facet injections/procedures are appropriately trained and/or
credentialed by a formal residency/fellowship program and/or are certified by
either an accredited and nationally recognized organization or by a post-
graduate training course accredited by an established national accrediting
body or accredited professional training program. If the practitioner works in
a hospital facility at any time and/or is credentialed by a hospital for any
procedure, the practitioner must be credentialed to perform the same procedure
in the outpatient setting. At a minimum, training must cover and develop an
understanding of anatomy and drug pharmacodynamics and kinetics as well as
proficiency in diagnosis and management of disease, the technical performance
of the procedure, and utilization of the required associated imaging
modalities.

In addition to the above requirements, non-physician providers, such as
certified nurse anesthetist, with certain exceptions, may certify, order and
establish the plan of care as authorized by State law. (See Sections
1861[s][2] and 1862[a][14] of Title XVIII of the Social Security Act; 42 CFR,
Sections 410.74, 410.75, 410.76 and 419.22; 58 FR 18543, April 7, 2000.) Each
practitioner must provide only those services within the scope of practice for
each state.

**_Definitions_**

**Acute pain** -The temporal definition of pain persisting for up to 4 weeks
after the onset of the pain.

**Axial** \- Relating to or situated in the central part of the body, in the
head and trunk as distinguished from the limbs, e.g., axial skeleton.

**Biopsychosocial model** \- interdisciplinary model that looks at the
interconnection between biology, pathology and socioenvironmental factors.

**Central neuropathic pain** - Pain, which is causally related to a lesion or
disease of the central somatosensory nerves.

**Centralized Pain** - A neurological chronic pain syndrome of the central
nervous system (brain, brainstem, and spinal cord) which commonly presents
with widespread generalized allodynia which is causally related to the
increased responsiveness of nociceptive nerves in the central nervous system
to the normal threshold or subthreshold simulation from the afferent nerves.
The condition has also been called "central sensitization," "central
amplification," and "central pain syndrome." Fibromyalgia is considered one of
the most common centralized pain syndromes.

**Cervical facet pain** - Pain located in the cervical spine, which may be
characterized by chronic headaches, restricted motion, and axial neck pain,
which may radiate sub-occipitally to the shoulders or mid-back.

**Chronic pain** \- The temporal definition of pain persisting for greater
than or equal to 12 weeks after the onset of the pain.

**Dual diagnostic blocks** \- The diagnostic technique of injecting the same
spinal nerve on two separate occasions to be used as an efficacy comparison to
increase diagnostic accuracy.

**Epidural steroid injection-** The administration via injection of steroid
medicine into the potential epidural space in the spinal column to deliver
steroids to the spinal nerves.

**Facet Joint Intraarticular Injections, Diagnostic -** The placement of local
anesthetic and possibly a corticosteroid into the facet joint to diagnose
facet joint pain.

**Facet Joint Intraarticular Injections, Therapeutic** - The placement of
local anesthetic and possibly a corticosteroid into the facet joint to produce
the beneficial effect of pain reduction.

**Facet joint** \- A diarthrodial joint in the spinal column (also called the
zygapophysial joint or z-joint), producing the articulation of the posterior
elements of one vertebra with its neighboring vertebra. They are bilateral
superior and inferior articular surfaces at each spinal level. The terminology
or nomenclature of the facet joint is classified by the specific vertebrae
level that forms it (e.g., C4-5 or L2-3). There are two (2) facet joints,
right and left, at each spinal level.

**Facet injection** **(also called facet block)** \- A general term used to
describe the injection of local anesthetic and possibly a corticosteroid in
the facet joint capsule or along the medial branch nerves supplying the facet
joints.

**Facet Joint Denervation or Radiofrequency Ablation (RFA)-** A general term
used to describe the minimally invasive procedure that uses thermal energy
generated by the radiofrequency current to deprive the facet joint of its
nerve supply. The procedure is also known as a Medial Branch Radiofrequency
Neurotomy (Ablation) because it is used to thermally remove the medial branch
nerve by using electrical current to create thermal energy to coagulate the
adjacent tissues around the targeted medial branch nerve.

**Facet joint syndrome** -A set of concurrent signs or symptoms to describe
facet joint pain as the pain generator. The typical clinical signs or symptoms
of a facet syndrome may include local paraspinal tenderness; pain that is
brought about or increased on hyperextension, rotation, and lateral bending;
low back stiffness; absence of neurologic deficit; absence of root tension
signs (non- radiating below the knee, absence of paresthesia). Cervical facet
pain is often characterized by chronic headaches, restricted motion, and axial
neck pain, which may radiate sub- occipitally to the shoulders or mid-back.

**Facet Level** -Refers to the zygapophyseal joint or the two medial branch
(MB) nerves that innervate that zygapophyseal joint. Each level has a pair of
facet joints: one on the right side and one of the left side of the spine.

**Intra-articular injection (IA** **)** -The injection of local anesthetic and
possibly a corticosteroid into the facet joint capsule.

**Medial Branch** -The dorsal ramus is the dorsal branch of a spinal nerve
that forms from the dorsal root of the nerve after it emerges from the spinal
cord.

**Medial Branch Block (MBB)** - The placement of local anesthetic and possibly
a corticosteroid near the medial branch nerve which supplies the sensory
innervation to a specific facet joint

**Neuropathic pain** -he pain which is caused by a lesion or disease of the
somatosensory nerves.

**Neurogenic claudication** -intermittent leg pain from impingement of the
nerves emanating from the spinal cord (also called pseuduoclaudication)

**New Onset of Spinal Pain** \- The new onset of the spinal pain must be
materially and significantly different in location, type, duration and
character from the previously treated spine pain.

**Non-invasive conservative management** \- The use of nonsteroidal anti-
inflammatory drugs (NSAIDs), acetaminophen, physical therapy, acupuncture
(applies to only chronic low back pain), or spinal manipulation. This
management should include the application a biopsychosocial treatment
techniques.

**Non-Radicular Back Pain** -The radiating non-neuropathic pain which is not
causally related to a spinal nerve root irritation and does not produce
reproducible neuropathic symptoms in an objective dermatomal pattern.

**Peripheral neuropathic pain** -Pain, which is causally related to a lesion
or disease of the peripheral somatosensory nerves.

**Radicular Back Pain** \- The radiating neuropathic pain causally related to
the spinal nerve root irritation which extends into the distal distribution,
typically the lower extremity, producing neuropathic pain in a dermatomal
pattern

**Radiculopathy** -Radiating neuropathic pain causally related to the spinal
nerve root irritation, which extends distally producing neuropathic pain in a
dermatomal pattern.

**Region** -The segments of the back involved will be defined in this policy
as two regions:

  1. Cervical/Thoracic region= C1-C7/T1-T12
  2. Lumbar/Sacral region= L1-L5/S1-S5

**Session** \- A time period, which includes all procedures (i.e., medial
branch blocks (MBB), intraarticular injections (IA), facet cyst ruptures, and
RFA ablations) performed during one day.

**Subacute Pain** -The temporal definition of pain occurring during the
4-12-week time period.

**Transforaminal epidural steroid injection (TFESI)** -An epidural injection
performed via a paramedian approach to enter the epidural space by placing the
needle in the posterior-superior quadrant of the intervertebral foramen
(neuroforamen) to inject near the dorsal root ganglion and exiting spinal
nerve root (previously known as a selective nerve root block).

**Zygapophysial joint or z-joint** \- see Facet joint

**History/Background and/or General Information**

The spine is the most common source of chronic pain. Chronic axial spinal pain
is one of the major causes of disability and accounts for a substantial US
health burden. Chronic spine pain poses a peculiar diagnostic and therapeutic
challenge due to multiple pain sources, overlapping clinical features, and
nonspecific radiological findings.

The facet joints can cause axial spinal pain and referred pain in the
extremities. The pathology of the pain source is due to facet joints being
richly innervated by the nerve fibers from the medial branch of the dorsal
ramus of spinal nerves. Each facet has a dual nerve supply. One exception is
at the C2-C3 zygapophysial joint, which has a singular nerve supply from the
third occipital nerve (the superficial medial branch of C3 dorsal ramus).1

Facet joint interventions may be used in pain management for chronic
cervical/thoracic and back pain arising from the paravertebral facet joints.
The facet block procedure is an injection of a local anesthetic, with or
without a steroid medication, either into the facet joint (intra-articular) or
outside the joint space around the nerve supply to the joint (the medial
branch nerve) known as medial branch block (MBB). Imaging guidance
(fluoroscopy or CT per code descriptor) is used to assure accurate placement
of the needle for the injection. Paravertebral facet joint denervation is a
therapeutic intervention used to provide both long-term pain relief and reduce
the likelihood of recurrence of chronic cervical/thoracic or back pain
confirmed as originating in the facet joint's medial branch nerve.1

There are various methods that may be used in performing facet joint
denervation. Percutaneous radiofrequency ablation (RFA) is a minimally
invasive procedure done with imaging guidance (fluoroscopy or CT per code
descriptor) and involves using energy in the radiofrequency range to cause
necrosis of specific nerves (medial branches of the dorsal rami), preventing
the neural transmission of pain. Conventional radiofrequency ablation (non-
pulsed or continuous) applies thermal energy of typically 80 to 85 degrees
Celsius. The terms radiofrequency ablation (RFA) and radiofrequency neurotomy
are used interchangeably. Both terms refer to a procedure that destroys the
functionality of the nerve using radiofrequency energy. Non-thermal methods of
denervation include chemical (chemodenervation), low-grade thermal energy
(less than 80 degrees Celsius), pulsed RFA, laser neurolysis, and
cryoablation.1

Throughout this document, societal recommendations with the grading of
evidence are referenced. There are multiple systems to grade or rank the
quality of medical evidence and develop evidence-based recommendations. Not
all grading systems are equivalent, so while there are typically similarities
in the grades or recommendations from various grading systems, they must be
considered independent of the other. The references in this document refer to
the following grading systems.

  1. GRADE Guidelines used in some systematic reviews, the basis for NASS recommendations aligns with GRADE.
  2. A Modified approach to the grading of evidence2and development of interventional pain management specific instrument3 used in ASIPP Guidelines and some systematic reviews.
  3. US Preventive Services Task Force grading of evidence guidelines used by 2020 Consensus Guidelines by Cohen et al.4
  4. Levels of Evidence for Primary Research Question and Grades of Recommendation for Summaries or Review of Studies adopted by North American Spine Society (NASS).5

A Multi-MAC Subject Matter Expert (SME) Panel on Facet Joint and Medial Nerve
Branch Procedures meeting on was held on 5/28/2020.

_Diagnostic Facet Joint Injections_

Due to the lack of reliable history, physical exam, or imaging to predict
response, providers must rely on facet interventions diagnostic injections
given for diagnostic purposes to determine if the facet joint is the source of
suspected spinal pain. There is controversy over optimal patient selection for
diagnostic injections, which measures successful response and type and number
of diagnostic injections performed.

Numerous investigations have been undertaken to correlate symptoms and
physical exam findings with facet pathology and have concluded conventional
clinical findings are unreliable in identifying facet joint success.5,7,8 A
2020 summary of the literature by Cohen et al. "Consensus practice guidelines
on interventions for lumbar facet joint pain from a multispecialty,
international working group" (2020 Consensus Guidelines) included 21 studies
evaluating the association of physical exam findings with facet block results,
and conclude there was no historical or physical exam findings that could
reliably predict response to facet joint blocks, grade C evidence, low level
of certainly.5 This is consistent with ASIPP 2020 Comprehensive Evidence-Based
Guidelines for Facet Joint Interventions in the Management of Chronic Spinal
Pain: American Society of Interventional Pain Physicians (ASIPP) Guidelines
(2020 ASIPP Guidelines) which rated accurate diagnosis of facet joint pain
with physical examination and symptoms level IV with a weak strength of
recommendation.8 2020 NASS Guidelines reported insufficient evidence to make a
recommendation for or against patient -reported reproduction of pain during a
facet joint injection as a predictor of response to dual diagnostic blocks
with a grade 1 recommendation.6,8 A careful medical history and exam remain an
important component to the evaluation of other etiologies of low back pain and
raise suspicion of facet source.8 Physical findings can help identify levels
for blocks, and maneuvers can aid in the detection of radicular symptoms.5

Imaging studies have been investigated as a marker of painful lumbar facet
joints. While degenerative changes can be found in imaging, they have not been
correlated as a reliable predictor of success with facet interventions.5,8
Nonetheless, imaging studies often play an important role in the exclusion of
other etiologies of back and cervical/thoracic pain. Single-photon emission
computed tomography (SPECT), a nuclear medicine imaging technique, can
identify active inflammatory markers as seen in facet disease but have not
shown consistent results in the prediction of facet joint intervention
success. 2020 Consensus Guidelines reported on 12 studies and concluded
moderate evidence for SPECT (grade C, moderate certainly) and weak evidence
for scintigraphy, MRI, and CT with no to weak supporting evidence.5 2020 ASIPP
Guidelines reported level III evidence for SPECT with weak strength of
recommendation and level V evidence for other imaging modalities, weak
recommendation.8

Conservative treatment, also called medical/interventional treatment, includes
integrative treatments (such as acupuncture (see NCD 30.3) or spinal
manipulation); physical treatments (physical therapy including exercise, heat
and cold modalities, massage), medications (NSAIDS/antidepressants), and
lifestyle modifications (weight loss, sleep hygiene, nutrition, smoking
cessation) are typically perused before interventional procedures. Facet joint
pain is frequently accompanied by other pain etiologies, which may benefit
from conservative modalities or combined therapy, and it is well accepted that
some back pain will resolve spontaneously or with conservative or non-invasive
measures over time. A few studies have had a conservative arm, or investigated
combined modalities that support a combined approach, but did not find a
conservative approach alone consistently lead to improvement.6,9 The Agency
for Healthcare Research released a systematic review of noninvasive
nonpharmacological treatment for chronic pain, including neck and low back.
Two hundred two trials were included which evaluated the spectrum of non-
invasive treatment modalities, concluded durable slight to moderate
improvement in function and pain for specific chronic pain conditions and
support clinical strategies that focus on non-pharmacological and non-invasive
therapies.10 2015 NASS Guidelines recommend a failure of at least four weeks
of non-invasive care,11 2020 Consensus Guidelines recommend a 3-month trial of
different non-invasive treatment,5 2020 ASIPP Guidelines rated level of
evidence II with a strong recommendation for three months after onset and
failure of conservative management8; European Guidelines extend the period to
one year.12 Chronic pain may lead to stress, anxiety, poor sleep and
depression, and other psychological sequalae and treatment beyond the pain
symptoms may be necessary.

Optimally a biopsychosocial model that promotes a multi-disciplinary team
approach addressing physical pain and psychological factors are utilized.13
Patients with chronic pain may also benefit from cognitive behavioral therapy,
biofeedback, and other psychological interventions.14

Due to the lack of reliable history, physical exam, or imaging to predict
response to facet interventions, diagnostic injections may be given for
diagnostic purposes to determine if the facet joint is the source of suspected
spinal pain. The response pattern to diagnostic facet joint injections has
become the gold standard for diagnosing facet syndrome. Temporary or prolonged
abolition of the spinal pain suggests that facet joints were the source of the
symptoms.1 The possibility of false-positive and false-negative reporting is
an inherent risk with facet blocks and challenges identifying the patients
most likely to have a positive response to treatment.5,8 Intra-articular (IA)
and medical branch blocks (MBB) have been evaluated for predictive value for
successful RFA. 2020 ASIPP Guidelines reported on ten studies in the lumbar
spine and found prevalence rates ranged from 27% to 40% with false-positive
rates of 27% to 47%, with =80% pain relief. They conclude level 1-2 evidence
with moderate to strong strength of recommendation of lumbar, diagnostic facet
nerve blocks.7 While both IA and MBB blocks have been shown in studies to be
predictive of success with RFA (2020 Consensus Guidelines grade B
recommendation, low level of certainty)5 five studies comparing lumbar MBB to
IA injections, including two randomized studies14,15 supports MBB as the
preferred modality, largely due to high technical failure rate and pain
associated with the IA injections. One randomized trial focusing on younger
patients shows IA injection with steroids may play a role in patients in which
MBB is contraindicated (Grade C evidence, moderate certainty).5 The Greater
Manchester EUR Policy Statement on Facet Injections no longer commissioned IA
facet injections and recommended medial branch nerve blocks for diagnostic
evaluation for RFA.12 The Spinal Intervention Society (SIS) recommended that
medial branch blocks replace intra-articular injections as a diagnostic
indicator.2

In order to determine if a block is successful, there must be an
assessment/measurement of pain and function. There are three points in which
pain/function must be evaluated: 1. baseline; 2. after a diagnostic block; and
3. at each follow-up to evaluate long term relief. The definition of success
lacks consistency, and there are different cut off values in the literature.
Among the Multi-MAC subject matter expert panel, there was an agreement that
subjective improvement in pain is a valid measurement of improvement in pain
(average voting score of 3.8/5). However, there was not agreement on what the
cut-off should be, if a tool should be used, and if so, which tool. There was
also a consensus that function is the most important indicator of success. A
study assessed the validity of subjective improvement rating improvement after
one IA joint injection and compared subjective rating to use of VAS scoring
and concluded that validity of pain provocation alone as criterion standards
in patients undergoing diagnostic facet injections should be questions with
the positive predictive value of 16% for predicating facet joint as a source
of pain.16 Clinical trials and policy have used multiple standardized tools to
measure pain, including the Numerical Rating Scale (NRS) and Visual Analog
Score (VAS), with pre-set cut off values in attempt to determine a specific
measurement in which patient's may most benefit from intervention. Studies
have evaluated if a specific cut-off value can predict outcomes of RFA and do
report a high correlation between verbal rating scales, NRS and VAS score in
prediction of outcomes with RFA. However, the panel did not agree on a minimum
value that can be used with these tools. The panel did agree that measurement
of function can provide valuable clinical input into improvement, such as the
ability to stand, walk, and the ability to do activities of daily living and
can predict success with future therapeutic procedures. There are multiple
tools to measure function including the Pain Disability Assessment Scale
(PDAS),17 Oswestry Disability Index (ODI),18 Oswestry Low Back Pain Disability
Questionnaire (OSW), Quebec Back Pain Disability Scare (QUE),19 Roland Morris
Pain Scale,20 Back Pain Functional Scale (BPFS),21 and the easy to use PROMIS
profile domains which have been found to correlate well with the ODI scale.22

For the diagnostic block, the pain relief achieved is temporary and used as a
predictor of success for subsequent RFA. The objective is to reduce false-
positives that would not be predictive of success with RFA and avoid false-
negative patients who could benefit but would not be offered treatment. Most
studies have used a cut-off of pain relief greater than 80% to consider MBB as
positive. Ten studies assessing the prevalence of lumbar facet joint pain
using a cut-off value of 80% relief reported with a prevalence rate of 27% to
40% with false-positive rates of 27% to 47% receiving a moderate to strong
recommendation from 2020 ASIPP Guidelines.8 One paper reports dual comparative
blocks are advocated as a means of identifying true-positive cases and
excluding placebo responders and have been shown to have a sensitivity of 100%
and a specificity of 65%.23

As stated in the 2020 Consensus Guideline: "the cut-off designating an MBB as
positive is one of the most controversial areas in pain medicine."5 Cohen et
al in 2013, prospective study to evaluate predictive values and reported no
difference in the predictive value of = 50% to <80% pain reduction vs. =80%
pain reduction. The guidelines advocate for using =50% for clinical trials and
clinical practice. The guidelines acknowledge that the existing evidence does
not adequately address the 50-80% group and that this cut-off was selected to
maximize access to care given the lack of reliable alternative treatment
options in this population and potential benefit of treatment in this group.4
On the contrary, there are studies that show patients with =80% relief are
more likely to show a positive response to RFA. 2020 ASPP Guidelines report
Level I to II evidence based on ten diagnostic accuracy studies (using =75%
and =80% criterion) and offer moderate to strong strength of recommendation.
They cite the literature using the 50% cut-off is conflicting due to internal
inconsistencies.8

There is controversy regarding the number of diagnostic blocks needed to
ensure an accurate diagnosis before proceeding with RFA. Derby et al.
evaluated the correlation of lumbar MMB with diagnostic MMB cutoff values to
optimize therapeutic outcomes and a failure of single MMB and conclude with a
dual block protocol a 70% cut-off value was acceptable. With a single block,
80% or higher was optimal.24,25 Three systematic reviews also showed
significantly better improvement with dual MBB with 80% cut off value.26-28
Two randomized controlled trials (one in the cervical region) demonstrated
positive results with dual blocks.29,30 SIS and ASIPP advocate for dual
diagnostic blocks, and diagnostic accuracy is reduced if lower cut-off
criteria are used. In contrast, the 2020 Consensus Guidelines advocate for
single blocks using a 50% cut-off. One RCT compares outcomes of stratified by
different prognostic values and reported the success rate in those who
underwent RFA in the zero (no block), single and double block groups were 33%,
39%, and 64%, respectively.31 Another study reporting on success rates of RFA
based on the number of blocks concludes no difference in outcomes based on the
number of blocks.34 A meta-analysis of five RCT using zero or one block
favored RFA.35 However, a meta-analysis is challenging given the high
heterogenicity of the literature. The 2020 Consensus Guidelines suggest the
number of blocks depends on the goals with dual blocks preferable for research
where diagnostic accuracy is critical while single (or no) blocks reduce the
number of procedures and access to care. Balancing these factors, they
recommend a single block reporting moderate evidence that dual blocks result
in higher success with RFA, but zero-block results in the highest number of
patients with a positive response to RFA.5 The result of voting from the
Multi-MAC SME Panel was a score of 3.2/5, stating confidence in the clinical
literature to support two MMB needed to diagnose facet pain.11 North American
Spine Society (NASS) Guidelines recommend dual MBB blocks on two separate
occasions and second block administered only if >80% relief with the first
block due to an unacceptably high false-positive rate of single diagnostic
injection.11 In the 2020 NASS Evidence-Based Clinical Guidelines for
Multidisciplinary Spine Care, they state a single diagnostic IA injection with
50% pain relief provides no clinically meaningful improvement at six months
(Grade of Recommendation B) and insufficient evidence to make a recommendation
for or against the use of RFA (Grade of Recommendation I(Insufficient)).6

The literature and societal guidance report that diagnostic injections should
be medial branch blocks, not intraarticular injections. This is agreed upon in
the 2020 Consensus Guidelines, 2020 ASIPP Guidelines, and NASS Guidelines.
NASS Guidelines state IA facet injections have not been validated for
diagnostic use, and the false positive rate is unknown as well as lack of
effectiveness studies comparing IA vs. MBB in the cervical spine11. The
exceptions in the case of the occipitoatlantal and atlantoaxial joints, since
there are no medial branch or other intervention to block readily. In these
cases, dual blocks with 80% relief are supported by most guidelines.6

_Therapeutic joint injections_

Intra-articular injections into the facet joint have been used as a treatment
modality for facet related pain and remains controversial. Therapeutic
injections typically include a corticosteroid as there would not be
anticipated long-acting pain relief from a short-term local anesthetic. Among
the Multi-MAC Subject Matter Expert (SME) panel, the average voting was 2.70,
with a range from 1-4. There is clinical evidence against the use of IA
therapeutic facet joint injection. Lilius et al. conducted an RCT including
109 patients who failed to show a difference between saline, steroids, and
anesthetic injected around two facet joints.32 Carette et al. conducted an RCT
including 101 patients with IA lumbar facet pain showed a non-significant
difference between the injection of saline and depo-corticosteroid with 22% in
steroid group compared to 5% in saline group reporting benefit at six
months.33 A small RCT, including 41 patients, reported return of pain in 3
days after IA steroid injection compared to 3.5 days in the control.34 Kennedy
et al. performed a small RCT comparing IA facet injections with a steroid to
saline and did not find a change in need for RFA.35 In the FACTS study, a
double-blinded RCT, Cohen et al. found no significant difference for pain
relief or functional outcome change between lumbar facet IA injection with
steroid or anesthetic or MBB with steroid, anesthetic or saline for up to 6
months post-injection. Five patients made it to the 6-month follow-up, of
which two had RFA. The FACTS study also found that MBB for anesthetic or
steroids did not perform better than saline.15

On the contrary, a systematic review by Manchikanti et al. (2015)26 using a
modified approach to the grading of evidence and reported 20 RCT assessed with
moderate to high-quality methodological criteria. For therapeutic
interventions, the evidence was variable from level II to III, with level II
evidence for lumbar facet joint nerve blocks and radiofrequency neurotomy for
long-term improvement (greater than six months), and level III evidence for
lumbosacral zygapophysial joint injections for short-term improvement only.
This review provides evidence for the diagnostic validity of facet joint nerve
blocks, and moderate evidence for therapeutic radiofrequency neurotomy and
therapeutic facet joint nerve blocks in managing chronic low back pain.6 These
two studies have been criticized for a high proportion of patients taking
opioids and prior back surgery, lack of control groups, and the absence of
blinding.5 Schneider et al reported in rigorously selected patients, 56% of
patients had 100% pain relief at six months.36 A systematic review by Engel
reported sustained relief of 6 months, and 1/3 had relief at one year.28

This is in contrast with another systematic review during the same period that
looked at the evidence supporting the use of therapeutic IA facet joint
injections for patients with suspected facet joint pain. The review focused on
IA facet joint injections with active drug or placebo/inactive injection are
more effective in reducing back pain and back pain-related disability than
conservative treatment. A total of 391 records were screened, and six trials
were included. The trials included were small (range 18-109 participants), and
overall in terms of pain and disability outcomes, most were inconclusive. Only
two of the trials report any significance between the groups' differences in
pain or disability outcomes. The authors addressed the limitations and flaws
in these trials that were clinically diverse and precluded any meta-analysis.
Several methodological issues were identified. The positive results are
interpreted with caution and suggest that there is a need for further high-
quality work in this area.37

Many societal recommendations that do not support the use of therapeutic facet
joint injections include:

  * The 2020 Consensus Guidelines developed by a multispecialty international working group recommend against the routine use of therapeutic facet injections giving it a grade D, moderate level of certainty.4
  * National Institute for Health and Care Excellence (NICE) guideline on Low back pain and sciatica in over 16s: assessment and management42 recommendations are based on systematic reviews of best available evidence and explicit consideration of cost effectiveness. The NICE recommendation for image-guided facet joint injections "Do not offer spinal injections for managing low back pain. The Guideline Development Group (GDG) agreed that health-related quality of life, pain severity, function, and psychological distress were the outcomes that were critical for decision making. Responder criteria (greater than 30% improvement in pain or function), adverse events, and healthcare utilization were also considered as important. Evidence was reported for all the outcomes except for psychological distress and healthcare utilization. For image-guided facet joint injections, evidence was only available for pain, function, and responder criteria. There was no evidence for any of the other outcomes." The NICE summary concludes: "Overall, the GDG agreed that there was no consistent good quality evidence to recommend the use of spinal injections for the management of low back pain. There was minimal evidence of benefit from injections, and reason to believe that there was a risk of harm, even if rare.

The GDG consequently agreed that it was appropriate to recommend against the
use of spinal injections for people with low back pain."

  * The American Association of Neurological Surgeons (AANS) and the Congress of Neurological Surgeons (CNS) 2014 Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine: Part 13: injection therapies, low-back pain, and lumbar fusion. Lumbar intraarticular facet injections are not recommended for the treatment of chronic lower-back pain. The literature does suggest the use of lumbar medial nerve blocks for short-term relief of facet-mediated chronic lower-back pain without radiculopathy.43
  * The North American Spine Society (NASS) Evidence-Based Clinical Guidelines for Multidisciplinary Spine Care: Diagnosis and Treatment of Degenerative Lumbar Spondylolisthesis 2nd Edition (2014) reports that there is insufficient evidence to make a recommendation for or against the use of injections for the treatment of degenerative lumbar spondylolisthesis. Grade of Recommendation: I (Insufficient Evidence).11 The 2020 NASS Low Back Pain Guidelines states there is insufficient evidence to make a recommendation for or against the use of steroid injections for suspected facet-mediated pain (Grade 1 Recommendation) nor sufficient evidence for or against the use of 50% reduction in pain following MBB for diagnosis of facet joint pain (Grade 1 Recommendation). The guidelines also state that the outcomes of RFA become more reliable when more stringent diagnostic criteria are used, and relief is durable for at least six months following procedure (Grade B Recommendation).6 NASS Guidelines state while there is some evidence in the literature when compared to RFA, RFA offers longer-term pain relief, and long-term outcomes have not been reported in adequately designed trials. They state that if therapeutic IA injections are used, they should be used in patients whose initial injections resulted in pain relief >50% for at least three months and not be repeated more than three times annually. The guidelines address concern of the majority of research on therapeutic MBBS comes from a single-center, reports on prospective studies and one RCT which had unspecified intervals and cannot determine the true duration of treatment and concern with lack of studies comparing therapeutic MBBs to medial branch RFA.6,11
  * Agency for Healthcare Research and Quality (AHRQ) Technology Assessment Program: Pain Management Injection Therapies for Low Back Pain (2015) authors used predefined criteria and selected randomized trials of patients with lumbosacral radiculopathy, spinal stenosis, nonradicular back pain, or chronic postsurgical back pain that compared effectiveness or harms of the epidural, facet joint, or sacroiliac corticosteroid injections versus placebo or other interventions. Also included were randomized trials that compared different injection techniques and large (sample sizes greater than 1000) observational studies of back injections that reported harms. Seventy-eight randomized trials of epidural injections, 13 trials of facet joint injections, and one trial of sacroiliac injections were included. Limited evidence suggested that epidural corticosteroid injections are not effective for spinal stenosis or nonradicular back pain and that facet joint corticosteroid injections are not effective for presumed facet joint pain.39
  * A 2009 American Pain Society guideline recommends against the use of corticosteroids into the facet joint.40

Some societal recommendation that supports the use of therapeutic facet joint
injections include:

  * 2020 ASIPP Guidelines7: Therapeutic Facet Joint Interventions in Lumbar Spine states:
  * The level of evidence is II with moderate strength of recommendation for therapeutic lumbar facet joint nerve blocks with the inclusion of three relevant randomized controlled trials with long-term improvement.
  * The level of evidence is IV with a weak strength of recommendation for lumbar facet joint intraarticular injections with inclusion of nine relevant randomized controlled trials, with most of them showing lack of effectiveness without the use of local anesthetic.

The American Society of Anesthesiologists (ASA) Task Force on Chronic Pain
Management and the American Society of Regional Anesthesia and Pain Medicine
(ASRA) Practice Guidelines for Chronic Pain Management (2010)41:

  * Recommendations for joint blocks: Randomized controlled trials (RCT) report equivocal findings regarding the efficacy of facet joint steroid injections compared with facet saline injections regarding pain relief for patients with low back pain (LBP). However, studies with observational findings for facet joint injections indicate that pain scores are improved over baseline scores for assessment periods of 1-6 months. Intraarticular facet joint injections may be used for symptomatic relief of facet-mediated pain. Medial branch blocks may be used for the treatment of facet-mediated spine pain.
  * The American Association of Neurological Surgeons (AANS) and the Congress of Neurological Surgeons (CNS) 2014 Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 13: injection therapies, low-back pain, and lumbar fusion states lumbar intraarticular facet injections are not recommended for the treatment of chronic lower-back pain. The literature does suggest the use of lumbar medial nerve blocks for short-term relief of facet-mediated chronic lower-back pain without radiculopathy.42

  * _Radiofrequency Ablation_

Radiofrequency neurotomy is described as radiofrequency lesioning performed
utilizing either a heat lesion or pulsed mode radiofrequency. A thermal
radiofrequency neurotomy lesion for facet denervation is performed at 80 to
85C. Clinically, a higher temperature allows for a larger lesion to be made.
The size of the lesion is influenced by the vascularity of the surrounding
tissue: the greater the vascularity of the tissue, the smaller the lesion.
Overall, the mechanism of radiofrequency neurotomy is described as denaturing
of the nerves. Consequently, with radiofrequency, the pain returns when the
axons regenerate, requiring repetition of the radiofrequency procedure. The
pulsed mode radiofrequency is an application of a strong electric field to the
tissue that surrounds the electrode, and the temperature of the tissue
surrounding the tip of the electrode does not exceed 42C and heat is
dissipated during the silent period.8

The effectiveness of radiofrequency ablation to improve pain and function for
facet joint mediated back pain in carefully selected individuals has been
explored in the medical literature. Clinical trials report conflicting data on
the effectiveness of RFA. Most clinical trials defined success with RFA as 50%
pain relief at six months.

A 2015 Cochrane review by Maas et al., including 23 RCTs (n=1309), evaluated
patients who had a positive response to diagnostic block and underwent RFA
found moderate evidence on the effectiveness of RFA compared to placebo for
pain management of facet origin over the short term (mean difference (MD)
-1.47, 95% confidence interval (CI) -2.28 to -0.67). Low-quality evidence that
facet joint RFA is more effective than placebo for function over the short
term (MD -5.3, 95% CI -8.66 to -.20) and over the long term (MD -3.9, 95% CI
-6.94 to 0.47). RFA for disc pain did not show effects compared to placebo
over the short or long term (MD -1.63, 95% CI -2.58 to -.68). They concluded
no high-quality evidence to suggest RFA procedure provides pain relief for
patients with chronic low back pain.43

Juch et al. reported on 125 patients in the treatment arm and 126 in the
control arm (exercise). Patients had a single diagnostic block with at least
50% or more pain reduction before RFA. The mean difference for the primary
outcome pain intensity at three months was -0.18 (95% CI, -0.76 to 0.40). The
mean difference for functional status at three months was -2.45 (95% CI, -5.53
to 1.03); the RR for global perceived recovery at three months was 1.35 (95%
CI, 0.81 to 2.05). This study has been challenged, stating that the lack of
efficacy was due to the treatment arm using the perpendicular technique.47
Perpendicular electrode placement has been questioned with concern it may fail
to reach the target nerve or only capture a segment, while parallel electrode
placement reliably captures the target nerve and does so along a substantial
length of the nerve. Those who challenge these studies report there are three
studies (1999-2008) that utilized the parallel technique that would result in
positive outcomes and report support for RFA from these trials.44 There are no
recent trials that address this controversy.

Leggett et al. (2014) conducted a systematic review to determine the efficacy
of RFA for chronic low back pain associated with lumbar facet joints,
sacroiliac joints, discogenic low back pain, and the coccyx. Included articles
were sham-controlled randomized controlled trials (RCTs), assessed the
efficacy of RFA, reported at least one month of follow-up, and included
participants who had experienced back pain for at least three months. Eleven
sham controlled RCTs were included: three studies involving discogenic back
pain, six studies involving lumbar facet joint pain, and two studies involving
sacroiliac joint pain. No studies were identified assessing the coccyx. The
evidence supports RFA as an efficacious treatment for lumbar facet joint and
sacroiliac joint pain, with five of six and both of the RCTs demonstrating
statistically significant pain reductions, respectively. The evidence
supporting the RFA for the treatment of discogenic pain is mixed. Future
studies should examine the clinical significance of the achieved pain
reduction and the long-term efficacy of RFA.45

The systematic review (2015) by Manchikanti et al. looked at both therapeutic
injections, and RFA in lumbar, cervical and thoracic regions evaluated 21 RCTs
and five observational trials, using a modified approach to the grading of
evidence2 reported Level II evidence for RFA in the lumbar and cervical spine,
and level IV in the thoracic region.26 A systematic review by Engel et al.
2016, which serves as the basis for NASS recommendations, "The Effectiveness
and Risks of Fluoroscopically-Guided Cervical Medial Branch Thermal
Radiofrequency Neurotomy: A Systematic Review with Comprehensive Analysis of
the Published Data" using the GRADE system for rating. They conclude the
majority of patients were pain-free at six months and over a third pain-free
at one year.27 In 2017, Lee et al. conducted a meta-analysis that included
seven trials with 454 patients comparing RFA (n=231) to sham or epidural
(n=223) and reported greater improvement in the RFA group.46

2020 ASIPP consensus guidelines7 Table 22 reports on 11 studies on RFA
effectiveness and concludes:

Lumbar Spine: The level of evidence is II with moderate strength of
recommendation for lumbar radiofrequency ablation with the inclusion of 11
relevant randomized controlled trials (RCTs) with two negative studies and
four studies with long-term improvement.

The American Society of Anesthesiologists (ASA) Task Force on Chronic Pain
Management and the American Society of Regional Anesthesia and Pain Medicine
(ASRA) Practice Guidelines for Chronic Pain Management (2010) Recommendations
for Ablative Techniques45: The Task Force notes that other treatment
modalities should be attempted before consideration of the use of ablative
techniques.

  * Chemical denervation: Chemical denervation (e.g., alcohol, phenol, or high-concentration local anesthetics) should not be used in the routine care of patients with chronic non-cancer pain.
  * Cryoablation: Cryoablation may be used in the care of selected patients (e.g., post-thoracotomy pain syndrome, low back pain (medial branch), and peripheral nerve pain).
  * Radiofrequency ablation: Conventional (e.g., 80C) or thermal (e.g., 67C) radiofrequency ablation of the medial branch nerves to the facet joint should be performed for low back (medial branch) pain when previous diagnostic or therapeutic injections of the joint or medial branch nerve have provided temporary relief. Conventional radiofrequency ablation may be performed for neck pain. Conventional or thermal radiofrequency ablation of the dorsal root ganglion should not be routinely used for the treatment of lumbar radicular pain.

National Institute for Health and Care Excellence (NICE) guideline on Low back
pain and sciatica in over 16s: assessment and management (2016) Evidence
Statement47:

Radiofrequency denervation compared with placebo/sham for low back pain:
Evidence from four studies demonstrated clinical benefit in pain for
radiofrequency denervation compared to placebo/sham at both the short and
long-term follow-ups of less than and greater than four months (low to
moderate quality, n=160). In contrast, there was no difference in function
between treatments at any time point. Conflicting evidence from one study for
quality of life at less than four months follow-up showed clinical benefit for
radiofrequency denervation compared to placebo/sham for the SF-36 domains of
general health and vitality. Radiofrequency denervation was inferior to sham
for the domains of mental health, pain, and social function. There was no
difference between treatments for the physical domain (low quality, n=81).

Evidence from a single study reporting adverse events at less than four months
follow-up demonstrated an increase in adverse effects for radiofrequency
denervation in terms of the number of patients with moderate or severe
treatment- related pain (low quality, n=79). There was no difference in other
adverse events (change of sensibility and loss of motor function) at short
term follow-up when radiofrequency denervation was compared to placebo/sham in
the same study (very low quality). Additionally, when compared with
placebo/sham, a benefit for radiofrequency denervation in responders to pain
reduction measured by global perceived effect was demonstrated by two studies
at both the less than and greater than four months follow-up time points.
However, this was not seen for pain reduction measured by visual analog scale
(VAS) at less than four months reported by a single study (low quality, n
equal to 111).

  * Radiofrequency denervation versus medial branch block:

Evidence from a single study demonstrated clinical benefit in terms of pain
for radiofrequency denervation compared to medial branch blocks at both the
short- and long-term follow-ups of less than and greater than 4 months (very
low quality, n=100). Radiofrequency denervation has evolved as a treatment for
spinal pain over the last 40 years and is a minimally invasive and
percutaneous procedure performed under local anesthesia or light intravenous
sedation. Radiofrequency energy is delivered along an insulated needle in
contact with the target nerves. This focused electrical energy heats and
denatures the nerve. This process may allow axons to regenerate with time,
requiring the repetition of the radiofrequency procedure.

  * The duration of pain relief following radiofrequency denervation is uncertain. Data from randomized controlled trials suggests relief is maintained for at least 6-12 months, but no study has reported longer-term outcomes. Pain relief for more than 2 years would not be an unreasonable clinical expectation. 
  * The de novo economic model undertaken for this guideline for radiofrequency denervation suggested that the treatment is likely to be cost-effective, provided the duration of effect exceeds 16 months.
  * If radiofrequency denervation is repeated, we do not know whether the outcomes and duration of these outcomes are like the initial treatment. If repeated radiofrequency denervation is to be offered, we need to be more certain that this intervention is both effective and cost effective.

NASS Guidelines state that therapeutic medial branch RFA is a validated
treatment for facet mediated pain, and repeat procedures are equally
successful if the response to the initial RFA lasted at least three months.
These guidelines advocate dual diagnostic MBB with =80% relief of the primary
(index pain), and the onset, and minimum duration of relief is consistent with
the agent employed. Also, RFA should be performed at the same level no more
than twice annually, and only if the initial radiofrequency lesion results in
significant pain relief (> 50%) for at least six months. In those situations,
a repeat procedure in that year is appropriate.15 2020 NASS Low Back Pain
Guidelines states there is insufficient evidence to make recommendations for
or against the use of cryodenervation for treatment of zygapophyseal (facet)
joint pain.10

The American Association of Neurological Surgeons (AANS) and the Congress of
Neurological Surgeons (CNS) 2014 Guideline update for the performance of
fusion procedures for degenerative disease of the lumbar spine. Part 13:
injection therapies, low-back pain, and lumbar fusion. Lumbar intraarticular
facet injections are not recommended for the treatment of chronic lower-back
pain. The literature does suggest the use of lumbar medial nerve blocks for
short-term relief of facet-mediated chronic lower-back pain without
radiculopathy. Lumbar medial nerve ablation is suggested for 3-6 months of
relief for chronic lower-back pain without radiculopathy. Diagnostic medial
nerve blocks by the double-injection technique with an 80% improvement
threshold are an option to predict a favorable response to medial nerve
ablation for facet-mediated chronic lower-back pain without radiculopathy.
Still there is no evidence to support the use of diagnostic medial nerve
blocks to predict the outcomes in these same patients with lumbar fusion.43

_Cervical and Thoracic Spine_

Most of the literature focuses on the lumbar region regarding interventional
facet joint diagnosis, and the 2020 Consensus Guidelines are specific for the
lumbar region. The 2020 ASIPP Guidelines include the cervical and thoracic
regions. The 2020 ASIPP Guidelines report level I-II with moderate to strong
strength of recommendation for lumbar, diagnostic blocks report ten diagnostic
accuracy studies to support the recommendation. ASIPP report level II evidence
for the cervical spine with moderate strength or recommendation citing ten
diagnostic accuracy studies. Two systematic reviews support reliance on dual
diagnostic blocks with 100% relief of the index pain to select patients for
the procedure reporting more than 60% selected using this stringent criterion
had 100% relief of index pain. They were pain-free at six months and nearly
40% pain free at one year with functional improvement in neck pain.27,28

ASIPP (2020)8 Therapeutic Facet Joint Intervention Cervical Spine:

  * The level of evidence is II with moderate strength of recommendation for therapeutic cervical facet joint nerve blocks with the inclusion of one relevant randomized controlled trial and three observational studies, with long-term improvement.
  * The level of evidence is V with weak strength of recommendation for cervical intraarticular facet joint injections with the inclusion of three relevant randomized controlled trials, with two observational studies, the majority showing lack of effectiveness. In contrast, one study with a six-month follow-up showed a lack of long-term improvement.
  * The level of evidence is II with moderate strength of recommendation for cervical radiofrequency ablation with the inclusion of one randomized controlled trial with positive results and two observational studies with long-term improvement.

Evidence to support use in thoracic region is further supported by one 2012
systematic review report evidence for diagnostic accuracy of the thoracic
facet joint injection, and one 2018 study comparing thoracic IA vs. MBB
reporting significant pain relief with thoracic joint injection.48 NASS
guidelines state the lack of supporting literature for the use of IA
injections for thoracic pain, however, states the lack of other effective
alternative therapies.11

_Imaging_

Image guidance has become standard care for facet blocks and RFA procedures,
allowing accurate needle placement, monitor contrast and anesthetic spread,
and improve safety by direct visualization of bony elements and avoiding
surrounding structure. Studies dating back to the 1980s comparing "blind"
injections to image-guided concluded that the procedure should not be
performed without radiographical imaging. Fluoroscopy is considered the gold
standard for facet block procedures, and most studies were conducted with
fluoroscopic guidance and consistent with societal recommendations. The US
Department of Health and Human Services OIG report in 2008 asserted
radiographic guidance is recommended.49 One cadaveric study showed improved
accuracy with fluoroscopy over CT.50 2020 Consensus Guidelines recommend CT or
preferably fluoroscopy for lumbar MBB (grade B recommendation), CT scanning
for IA placement (grade C recommendation), and fluoroscopy for medial branch
RFA (grade B recommendation, low level of evidence). The Guidelines state
fluoroscopy is preferred to CT due to lower cost, faster times, and less
radiation exposure than CT.5

The use of ultrasound has been explored as an alternative imaging modality.
Cadaveric, retrospective studies, and review of RCT and non-RCT suggest that
there is little difference between ultrasound and fluoroscopy guided
procedures, however, there are no well-designed studies to report the safety
of this approach. Limitations for ultrasound guidance include reduced
visibility in obese patients, more challenging to target the proper segment,
and not being able to visualize facet joint.5 NASS Guidelines state
insufficient evidence to support use of ultrasound guidance.11 Subject matter
experts score low confidence that the facet joint procedures can be performed
under ultrasound guidance (score 1.7/5).

_Facet Joint Cyst Rupture_

Facet joint cysts have been found to have a prevalence of 6.5% and are thought
to play a role in facet mediated pain. In these cases, nerve root compression
or irritation is associated with radicular pain like other neuro-compressive
lesions. Rupture of the cyst has been associated with pain improvement and may
potentially avoid more invasive open surgical procedures. In these cases, IA
injection is used and often with TFESI to treat radicular pain.11 A systematic
review of 870 patients report cyst resolution to be 58% for the percutaneous
procedure, and 90% for decompressive procedures concluding advantage of
surgical intervention as compared to percutaneous procedures and pain relief
with surgical management is estimated 83.5%. Shuang et al. systematic review
of 29 studies reported overall the satisfactory results (after short- or long-
term follow-up) were achieved in 55.8% [49.5, 62.08] (pooled mean and 95% CI)
of the 544 patients subjected to percutaneous lumbar facet joint cyst
resolution procedures. 38.67% [33.3, 43.95] of this population underwent
surgery subsequently to achieve durable relief.51 However, the analysis
consisted largely of small retrospective studies and case reports with low-
quality evidence. In one prospective, non-randomized study, 120 patient's
satisfaction was reported as 75%, with 25% requiring repeat surgery.55 NASS
Guidelines address the concern of cyst reoccurrence, which occurs about 50% of
the time and does not recommend repeating the procedure more than once and
only if the first procure produces satisfactory results, which they define as
50% improvement for at least three months.11 The subject matter expert panel
voted 3.9/5 in support of facet joint cyst rupture for pain relief.

_Centralized Pain Syndrome_

Facet procedures by nature treat a local pain condition, while a centralized
pain syndrome, such as fibromyalgia, is a generalized pain condition. Patients
with centralized pain syndromes are thought to have alternations in central
neurotransmission. A prospective study with 548 patients diagnosed with
primary spine pain were also evaluated for fibromyalgia criteria before spinal
interventions. 42% of the patients meet diagnostic criteria for fibromyalgia.
They determined a profound phenotypic difference in those with fibromyalgia as
compared to those with spinal pain alone associated with more neuropathic pain
descriptors, anxiety, greater pain interference and lower physical function.

The authors concluded that the phenotypical factors found in the fibromyalgia
group may be predictive of poor outcomes in spine intervention procedures.52
Exploration of factors associated with poor outcomes from lumbar RFA and long
duration pain was correlated with treatment failure.53 There is insufficient
literature that addresses if facet joint procedures are beneficial for
centralized pain conditions.

_Intrafacet Implants_

Intrafacet implants have been proposed as an alternative technique to surgical
fusion. They involve the placement of an allograft dowel made from bone (from
femur or tibia) and placed surgically or via the minimally invasive procedure.
The allograft, which is processed by licensed tissue banks, which must be
compliant with FDA requirements for tissue processing, are not subject to FDA
510K clearance and can be marketed. There are no clinical trials that address
the efficacy and safety of these implants. The report on six cases did not
indicate efficacy.54

_Nonthermal modalities_

__

Several alternatives to percutaneous radiofrequency denervation have been
proposed, including pulsed radiofrequency, cryoablation, laser ablation, and
chemical ablation, in which a neurolytic substance (e.g., alcohol, phenol,
glycerol) is injected into the affected nerve root. An alternative method of
denervation using an endoscopic approach (i.e., endoscopic dorsal ramus
rhizotomy) has also been proposed.55 The literature on these modalities is
largely limited to case reports or small series with mixed results.14,56-58
One RCT (n=80) comparing pulsed radiofrequency ablation to steroid injections
concluded it may be more effective than steroids.59 A RCT (n=50) compared
study of continuous to pulsed radiofrequency ablation and did not report
significant differences.60 Long term safety and efficacy data is lacking. The
American Society of Anesthesiologists (ASA) Task Force on Chronic Pain
Management and the American Society of Regional Anesthesia and Pain Medicine
(ASRA) Practice Guidelines for Chronic Pain Management (2010) Recommendations
for Ablative Techniques: The Task Force notes that other treatment modalities
should be attempted before consideration of the use of ablative techniques.41

Anesthesia

The American Society of Anesthesiologists provides definitions on the
continuum of the depth of sedation. Minimal sedation anxiolysis is defined as
a drug-induced state during which patients respond normally to verbal
commands. Although cognitive function and physical coordination may be
impaired, airway reflexes, and ventilatory and cardiovascular functions are
unaffected. Progressing depth of sedation beyond minimal is moderate or
"conscious", deep and general. Monitored Anesthesia Care or "MAC" is not a
depth of sedation, but a specific anesthetic service allowing a deeper level
of analgesia than can be provided by moderate sedation. Statement on Continuum
of Depth of Sedation: Definition of General Anesthesia and Levels of
Sedation/Analgesia.61

The increases risk associated with the use of anesthesia, including sedation,
in the elderly population must be considered. A 2020 review reports a
substantial increase in the use of non-operating room anesthesia (NORA) for
elderly patients and that advanced age is an independent risk factor for
anesthesia-related adverse events in this population. The authors explain
there are significant changes in pharmacological effects of anesthetic agents
with aging requiring reduced dosing and careful titration and monitoring to
reduce adverse events. They also report that increasing age increases the risk
of aspiration and cognitive complications even during sedation. The paper
discusses that older and frailer patients may benefit greatly from less
invasive procedures, but this must be balanced against safety outside of a
high acuity operating suite and increased risk associated with anesthetic in
this population.62 A retrospective analysis from the 2008-2012 Premier
Database reviewed 21,276,691 inpatient discharges seeking a better
understanding of the risk of cardiopulmonary resuscitation (CPRA). They found
96,554 patients suffered CPRA and reported patients who received opioids and
sedatives had an adjusted odds ratio for CPRA of 3.47 (95% CI: 3.40- 3.54;
p<0.0001) compared with patients not receiving opioids or sedatives.
Therefore, opioids alone and sedatives alone were associated with a 1.81-fold
and a 1.82-fold (p<0.0001 for both) increase in the odds of CPRA,
respectively. They found 42% survived CPRA and only 22% were discharged to
home calling for further research in this area and efforts to investigate
opioid sparing anesthesia and reduced sedative use and improved monitoring
given this risk.63

The American Society of Anesthesiologist committee opinion for anesthetic care
during interventional pain procedures for adults stating that when sedation is
provided during the performance of pain procedures it is important that the
patient can be responsive during critical portions of the procedure to report
potential procedure related paresthesia, acute changes in pain intensity or
function for potential toxicity. The committee opinion states that
interventional pain procedures generally only require local anesthetic however
patients may elect to also receive supplemental sedation but must remain
conscious. Exceptions may include a well-documented history of inability to
cooperate, medical conditions that would prohibit performance of the
procedure, or inability to remain motionless.1

The Spine Intervention Society Factfinder for patient states that sedation is
not intrinsically necessary for interventional spine procedures and that the
decision should be considered on case-by-case basis.64 This report focused on
moderate sedation and expresses concern of over-sedation impairing the ability
to "of the patients to respond adequately to any potential pain, discomfort,
or paresthesia during a procedure and warn the physician accordingly of a
potential impending serious complication". The use of heavy sedation has been
associated with increased risk of neurological injuries, such as spinal cord
injury. Moderate sedation has been associated with apnea and hypoxemia. While
some reports common use of sedation There is limited evidence of isolated
situations where sedation may provide medical benefit. A RCT with 73 subjects
with crossover design reported sedation did not predict satisfaction with care
or improved pain.65 A report of 6897 patients with transforaminal epidural
steroid injections without sedation reported only a 3% dissatisfaction rate.66
He reports concluded the default use of sedation is not associated with clear
health/outcome benefits and associated with rare but serious increased risk.
That most patients are satisfied with care when sedation without sedation and
that it should be used judiciously and under circumstances with careful
monitoring and administered by trained providers and with appropriate
monitoring.

Reconsideration Request

A reconsideration request was received requesting therapeutic facet joint
injections be considered as a first line treatment option for facet pain and
include both intraarticular injections or medial branch blocks. Most of the
submitted literature was already in the evidence section of the LCD.
Additional submitted studies published prior to 2016 were not cited
individually in the LCD and many were included in at least one of the
systematic reviews that were evaluated in the LCD.26,37 Literature evaluated
with this request include:

  * A 2022 retrospective report comparing 99 patients who received lumbar facet joint nerve blocks compared to 227 receiving radiofrequency neurotomy with one year follow up. Pain improvement was reported in both groups with 100%, 99% and 79% reporting improvement in the nerve block group as compared to 100%, 74% and 65% in the RFA group at 3, 6 and 12 months respectively. Patients received between 1-4 nerve blocks and 1-2 RFAs. The authors conclude that the outcome from therapeutic facet joint nerve blocks is comparable to RFA. Missing data with 48 of the original 99 and 148 of the original 227 reported at 12 months data limits this data set.67 A similar study was conducted to evaluate 132 patients who received cervical medial branch blocks and 163 patients receiving cervical RFA. Of the original group 107 in the injection group and 105 in the RFA the group completed 12 month follow up and reported 100%, 94%, and 81% of the patients in the medial branch blocks group, and 100%, 69%, and 64% in the radiofrequency neurotomy group at 3-, 6-, and 12-month follow-up, respectively. Both studies are limited by the retrospective design and without a control group cannot determine if the procedures are equivalent.68
  * A European systematic review explores the management of facet joint osteoarthritis with medial branch blocks. Eight articles were included in the review. The studies were challenged by small sample sizes ranging from 8 to 60 and the majority having less than 30 subjects, short term follow-up with a maximum of 6 months, significant variability in treatments, different tools to measure pain and other limitations leading the authors to conclude that the role of facet injection in the management of low back pain has a positive trend but is non-conclusive.69
  * A small RCT compared 60 subjects with a single positive diagnostic block receiving 1-2 level treatment with IA injection or RFA for 6 months. They reported a decrease in NRS score at 2 weeks, and 1,3, and 6 months for both groups. They report similar outcomes at six months for both groups. The authors reported steroid related side effects in the injection group and no adverse events in the RFA group suggesting that the RFA may be a better option for management to reduce the potential adverse events related to steroids.70
  * A small RCT with 40 subjects randomized patients with cervical facet joint pain to IA injection or RFA. They report both groups had a decrease in NRS at 1, 3 and 6 months (p=0.000). They report both groups reported 50% and the author concludes that RFA is an effective treatment for cervical facet pain while avoiding the adverse effects of steroids.71
  * A small prospective study administered a sham block followed by MBB with presumed facet mediated pain to 104 subjects. Patients who experienced improvement with the saline solution were excluded from the study for presumed placebo effect (16.7%) and patients who did not experience at least 50% improvement after the lidocaine injection were referred for evaluation for other potential etiologies (31.7%). The remaining 54 patients were followed with VAS score measurements and 67% reported improvement maintained at 3 months. The remaining 33% reported worsening pain scores over this duration. The authors concluded that this group was the true facet mediated pain while the group that experienced improvement after a single diagnostic medial branch block had myofascial pain which resolved during this three month follow up. This is consistent with data that suggests a high false positive rate with a single medial branch block and supports the use of dual diagnostic blocks and encourages a three-month follow-up injections to ensure correct diagnosis.72

The new evidence to support the role of therapeutic injections as first line
therapy was very low quality. Additional literature supports the coverage
position of RFA if dual diagnostics blocks are positive for facet mediated
pain. Therefore, there was not sufficient evidence submitted with this
reconsideration to change the policy's coverage position.

Facet joint procedures are a challenging area due to variability in the
literature, lack of consensus among experts, differences in societal
guidelines and a historical pattern that demonstrates high risk for over
utilization. When there is a lack of consensus on best practices, careful
evaluation of the medical literature and utilization of the best available
evidence serves as the basis for our determinations in coverage and
guidelines. This is supplemented with the knowledge shared from our subject
matter expert panel.

The literature and consensus of the expert panel and societal guidelines agree
that there is there is no specific history, physical exam findings, or imaging
studies that can diagnose facet joint mediated pain and predict response to
treatment. For this reason, diagnostic facet joint injections are indicated.
Medial branch blocks are the preferred technique for these injections, which
is validated and supported by literature as compared to the IA injections,
which lack validation, are technically more difficult, and more painful. There
is consensus that all facet procedures should be performed under image
guidance, CT or fluoroscopy, with a preference for fluoroscopy.

The controversial areas are the number of blocks and the percentage of pain
relief required to consider a block successful. For the diagnostic block, the
pain relief achieved is temporary and used as a predictor of success for
subsequent RFA. The objective is to reduce false-positives that would not be
predictive of success with RFA and avoid false-negative patients who could
benefit but would not be offered treatment. Many studies have used a cut-off
of pain relief greater than 75-80% to consider a diagnostic block as positive.
Ten studies assessing the prevalence of lumbar facet joint pain using a cut-
off value of 80% relief reported with a prevalence rate of 27% to 40% with
false-positive rates of 27% to 47% received a moderate to a strong
recommendation from 2020 ASIPP Guidelines.7

The 2020 Consensus Guideline advocate for using single blocks with =50% for
clinical trials and clinical practice while acknowledging that the existing
evidence does not adequately address the 50-80% group and that this cut-off
was selected to maximize access to care given lack of reliable alternative
treatment options in this population and potential benefit of treatment in
this group.4 On the contrary, there are studies that show patients with dual
blocks using =80% relief are more likely to show a positive response to RFA.
This aligns with ASIPP and SIS guidelines1.1,11 Given the lack of clear
evidence, the consensus among experts and societies there is uncertainty
regarding the cut off values and number of blocks. Most of the evidence and
societal guidance supports the use of a more stringent diagnostic cut off. The
Multi-MAC SME Panel was a score of 3.2/5 favoring the dual block regimen. Once
a patient begins treatment, the treatments often continue without repeat
diagnostic studies, so the correct diagnosis initially is important. The
existing evidence is clear there is a high risk of false positives with a
single block and 50% cut off and that a dual block and higher cut-off (75-80%)
improves diagnostic accuracy. The evidence also supports that improved
diagnostic accuracy predicts greater improvement with RFA treatments. While
this must be balanced against excluding some patients for treatment who may
potentially benefit, given the lack of supporting literature to define this
population, current evidence supports dual blocks at 75-80% improvement is
more strongly supported than the alternative less stringent approach.

The effectiveness and clinical utility of therapeutic facet blocks is another
controversial area. In this case, we are referring to injections with
corticosteroids as injections as local anesthetic would not be expected to
have any sustained effect. There is support for the use of therapeutic
injections in the form of a systematic review and societal guidelines. Most of
this support is from a single center that utilizes a published, modified
grading criterion they developed. Grading from one grading criteria to another
often have similarities but cannot be extrapolated to another so we must
consider each grading criteria individually. There is some additional
literature from other sites and societal support for therapeutic injections
offered by ASA and ASRA. The overwhelming majority of other guidelines and
evidence do not support therapeutic IA injections, and this includes multiple
studies, systematic reviews, and guidelines by 2020 Consensus Guidelines,
NASS, NICE, AHRQ, AANS, and CNS. Their use received a "D" rating from 2020
Consensus Guidelines. The current consensus is that diagnostic injections are
to select patients who may be candidates for RFA, and not for therapeutic
injections. Clinically since the reported efficacy of therapeutic injections
(if a true benefit exists) would be around three months compared to six months
or longer for RFA, so there is an obvious benefit for selection of RFA as a
treatment over injections. The Multi-MAC SME voting was 3.4/5 that subsequent
therapeutic IA or MBB are effective. The evidence does support several special
circumstances when RFA cannot be performed, and therapeutic injections may be
appropriate. Therefore, the policy allows therapeutic injections in
circumstances when RFA is not feasible.

The goal procedure for facet joint interventions is radiofrequency ablation.
The strongest available data related to facet interventions is to support the
use of RFA for facet joint pain. Still, even that is mixed and lacks a clear
consensus on proper patient selection and effectiveness. A 2015 Cochrane
review showed a moderate benefit for RFA for pain, but lack of benefit for
function.46 However, the patient selection used the less stringent criteria of
a single block with a 50% reduction in pain. Other studies have shown this
criterion is associated with a higher false-positive rate and less success
with RFA procedures, so this conclusion may not be represented if the stricter
criteria were used. The FACTS study, an RCT that compared outcomes stratified
by different prognostic values and reported the success rate in those who
underwent RFA in the zero (no block), single and double block groups were 33%,
39%, and 64%, respectively.33 While this served as the basis for recommending
a single block at 50% in the 2020 Consensus Guidelines, it also demonstrates
the improved success rate for the dual block group, which increased to 64%.20
A systematic review that used the GRADE system for rating which is a more
standardized grading system and allows both RCT and observational studies to
be evaluated, concluded the majority of patients were pain free at six months
and over a third pain free at one year.29 This conclusion was supported by a
2017 meta-analysis.35 The overall societal consensus is in support of the use
of RFA with ASIPP, ASA/ASRA, NICE, 2020 Consensus Guidelines, and AANS/CNS,
all having guidelines that support RFA use. Even the NASS Guidelines that
report insufficient evidence for RFA provided guidelines for use. There remain
concerns as the clinical studies of RFA for chronic low back pain have
significant methodological limitations that can affect the interpretation of
the data. Uncertainties regarding several aspects of RFA for spinal pain,
necessitate additional research. The validation of radiofrequency for chronic
spinal pain management relies upon the resolution of these technical issues,
as well as issues regarding patient selection and long-term efficacy.48 While
the literature is not complete in terms of efficacy and patient selection for
RFA facet procedures, the procedure offers the potential to avoid more
invasive surgery. It may potentially reduce opioid use, justifying maintaining
RFA as an option in the management of back pain in properly selected patients
despite these limitations.

Limitations, such as number of levels and frequency, are challenging as there
is little evidence on these factors. Lack of consensus in the medical
community about frequency of injections has been a challenge.49 Societies have
begun to offer recommendations on frequency. The NASS Coverage Recommendations
recommends dual blocks, does not recommend therapeutic procedures, recommends
limiting RFA to maximum of twice per year and procedures for facet joint cyst
rupture to be repeated not more than once.11 The 2020 Consensus Guidelines
report recommends single diagnostic blocks, does not recommend therapeutic
injections and recommends limiting RFA to no more than two times per year.5
The Multi-MAC SME panel also provided input on frequency. The panel voted
1.8/5 that diagnostic injections should be a minimum of 28 days apart and
recommended allowing sooner may be beneficial. The panel voted 3.5/5 that
therapeutic injections should be a minimum of 3 months apart, and during
treatment phase interventional procedures should be repeated only if medically
necessary, and not to exceed four times per year was scored as 3.4/5. The
panel voted RFA should be repeated only if medically necessary at a minimum of
6 months apart with score a of 3.9/5. The panel supported allowing three
levels (diagnostic or therapeutic) in one session with score of 3.8/5, however
prevalence data demonstrates that three diagnostic levels are not routine and
would be under unusual circumstances. There is currently no evidence to
support that facet mediated pain may extend routinely beyond 2 levels. The
purpose of the dual diagnostic blocks is to further identify the pain
generator and successfully treat the impacted region. This correlates with
literature when the number of levels is reported, Medicare national data and
MAC local data, which demonstrates that most facet procedures involve 1 or 2
levels only.49

Several alternatives to percutaneous radiofrequency denervation have been
proposed, including pulsed radiofrequency, cryoablation, laser ablation, and
chemical ablation, in which a neurolytic substance (e.g., alcohol, phenol,
glycerol) is injected into the affected nerve root. An alternative method of
denervation using an endoscopic approach (i.e., endoscopic dorsal ramus
rhizotomy) has also been proposed. There is insufficient evidence in the
published medical literature to determine the safety and efficacy of these
emerging alternative modalities or approaches compared to thermal
radiofrequency denervation for the treatment of spinal pain.