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Do Nerve Blocks Work for Neck Pain and Low Back Pain?

Analysis of the science of stopping the pain of facet joint syndrome with nerve blocks, joint injections, and nerve ablation

by Paul Ingraham, Vancouver, Canada BIO
Credentials & qualifications. I am a science journalist, and I was a massage therapist for ten years. I’m close to the end of a Health Sciences degree — 2 courses left! — and I am on the editorial team of Science-Based Medicine. I have spent many years studying therapy science, and my work is greatly enriched by thousands of conversations with readers and experts from around the world. I make a living from this website, selling some of my most detailed tutorials as ebooks. For more, see Who Am I to Say?

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The source of neck pain and back pain is a particularly difficult clinical problem to solve. As the neck and back pain tutorials explain in detail, the bottom line is that therapists and doctors really should not be diagnosing the source of neck and back pain with much confidence — it’s usually just not possible. There are too many possible causes, and too many of them are poorly understood.

One possible source of pain is the knuckle-like facet joints. You have a pair of facet joints for each vertebra. These are the joints that pop in many people as you twist and flex your spine. Each facet joint moves only a little, sliding on dime-sized cartilaginous surfaces. There are many possible ways that facet joints may cause pain, and a certain amount of facet joint pain is probably a factor in many cases of spinal pain. If facet joints are hurting, we call it “facet joint syndrome.”

In a sense it doesn’t even matter what, exactly, might be going wrong with a facet joint — not if you can numb the whole thing, turning off all sensation like flicking a light switch. Because facet joints are a nicely specific anatomical structures with good clear “edges,”1 they have become the target of several minimally invasive treatment procedures that aim to temporarily or permanently silence any pain noise coming from them:

These procedures would all be provided a medical specialist, most likely either a physiatrist or an orthopedic surgeon. Do they work? Are they safe?

Nerve blocks as a pretty good diagnostic tool

Here’s an interesting (if somewhat drastic) way to find out if a facet joint is the origin of low back or neck pain: cut off the nerve supply to the facet joint! If your pain stops, voila: presumably that’s where the pain was coming from.

This is called a “medial branch block” (MBB), often simplified to a “nerve block.” The medial branch nerves are the wee nerves that carry pain sensation from the facet joints.2 Without those nerves, the facet joint just can’t hurt you. It’s an anatomical convenience that each little facet joint just happens to be served by a specific bit of nerve that can be anaesthetized without too much difficulty.

Thus, if an MBB relieves pain, it provides a fairly high degree of diagnostic confidence.

But it’s not a perfect diagnostic tool

Don’t for a second think it’s as straightforward as it seems! Many other factors tend to confuse the issue. For example:

Or here’s a particular good one: what if you’re kind of, um, messed up in the head? No offense. Researchers found that the amount of relief the low back pain patients got from facet joint injections could be predicted by psychological factors.3 So much for a simple equation.

An MBB should be considered as a diagnostic tool in basically every case of stubborn neck or back pain. But nothing is ever as simple as it seems.

An overview of the evidence as of mid-2010

There’s been quite a bit of scientific attention to this topic lately. In 2010, Physical Therapy published a small but clear study showing a strong benefit to one type of nerve block for sciatica (selective nerve root blocks, or SNRB). The study showed that the nerve blocks worked quite well — “significant reductions in pain and disability.”4 (It also knocked physical therapy, but that’s another story.5)

And the journal Pain Physician has published not one, not two, but three articles in the last two years analyzing facet joint treatments for the neck,6 low back7 and thoracic8 spine — see the footnotes for their full abstracts and (delightfully) the full text of all three papers are also available. As this weren’t enough, this year also saw a more general Cochrane Collaboration review of injection therapies.

So what did all of this reviewing amount to? The low back pain review concluded quite negatively:

There is insufficient evidence to support the use of injection therapy in subacute and chronic low-back pain.

However, that was for low back pain only, and the authors acknowledged that benefits of some types of injection therapy for certain patients “cannot be ruled out.” So what do the more specific reviews in Pain Physician have to say?

So there’s some good news in there. A treatment does not have to be perfect to be worthwhile, and there is almost certainly some good being done here.

Medial branch nerve blocks are rocking the house

Medial branch nerve blocks in particular are looking good. The reviews above gave them a pretty definite thumbs up. This is particularly due to a 2008 experiment in which researchers gave medial branch nerve blocks to 120 chronic neck pain patients,9 and found that they produced “significant relief and functional improvement” in “over 83% of patients.”

This study is widely cited as virtual proof that nerve blocks “work,” and it is the main reason that anyone is enthusiastic about needles for neck pain in recent history. I think it is pretty good evidence, and MBB is absolutely an option chronic neck pain patients should consider.

However, as always, you have to read the fine print. A more detailed look at this paper is quite educational …

6 reasons to curb your enthusiasm for medial branch blocks as a treatment option

I can see at least 6 reasons why the Manchikanti paper is not exactly a slam dunk, and MBBs are no miracle cure:

  1. “Over 83%” of patients sounds awfully good — and it is, for a neck pain treatment — but it’s hardly everyone. More than 1 in 10 people were not helped, even after a facet joint was “confirmed” as the source of pain by an earlier nerve block.
  2. In science, the words “significant improvement” do not mean “cured”: they mean statistically significant. And statistical significance is not really all that exciting. Those who were helped were not necessarily helped a lot — just enough that we can say, “Yep, that treatment was better than nothing.” So many of those people almost undoubtedly had results that were somewhat less than miraculous. And it gets worse …
Those who were helped were not necessarily helped a lot — just enough that we can say, “Yep, that treatment was better than nothing.”
  1. These patients didn’t just get one needle in the neck and then walk out the door with their “significant improvement.” They walked out the door … and then came back again a few weeks later for another dose. And another. The average number of treatments over the course of the year they were studied was, wait for it … three and a half, plus or minus one. That’s off to the pain clinic with you three, maybe even four or five times per year to get your “significant results.” That’s a fair amount of getting stabbed in the neck, I have to say. Is this procedure starting to sound a little less awesome than it did at first?
  2. As implied by the repeat treatments, the benefits of treatment were not exactly long term. The average duration of average pain relief was 14–16 weeks, and with massive variation of up to half that time. Some patients were getting their statistically significant but probably not stellar symptom relief for only half that time — about a couple of months. No wonder they needed repeat treatments.
  3. And, of course, it’s a minimally invasive procedure, and all invasive procedures have higher costs and risks, and should be avoided unless absolutely necessary.
  4. Last and definitely not least, these patients were not compared to patients receiving any other kind of treatment or no-treatment or a placebo, which I find really strange. It leaves us wondering how well they would have done with no treatment at all. Spinal pain is notoriously unpredictable. People who receive no treatment routinely experience “significant relief” for no apparent reason. Thus, this study just doesn’t fully answer the question it asks — it can’t.

If all that doesn’t curb your enthusiasm for nerve blocks, then nothing can.

So what does the salamander say?

After all those caveats, the SaveYourself.ca salamander says “meh” to most nerve blocks (especially for low back pain). And the salamander is even less impressed by injections right into the joint: while not completely ruled out, so far tests of this treatment have totally failed the impress me test.

Is it worth considering? Certainly. Diagnostically useful? Yep. Great for some patients? Probably.

It is a big deal? The end of all spinal pain? No — it really is not.

On the bright side, a treatment does not have to be perfect to be worthwhile. (Good thing, too, or there’s an awful lot we’d have to dispose of.) MBBs show a much clearer benefit than many other popular treatments. They may not be the holy grail of spinal therapies, but they are arguably more promising than acupuncture10 or chiropractic adjustment.11 Similarly, it looks like SNRBs for sciatica are worth considering as well.


What’s New In this Article?

Friday, October 1, 2010 — Updated with reference to Thackeray.

July 24, 2009 — Original publication.

Notes

  1. For contrast, consider muscle pain — which is definitely a factor in low back and neck pain — which may be extremely difficult to locate anatomically. Where is muscle pain? Compared to facet joints, the anatomical location of muscle pain is like trying to find a smoke signal in the fog. BACK TO TEXT
  2. Let me explain “wee little nerves” with a bit more jargon for my professional readers: the nerves in question here are the medial branches of the dorsal ramus nerves that innervate the facet joints. BACK TO TEXT
  3. Wasan et al. Psychopathology predicts the outcome of medial branch blocks with corticosteroid for chronic axial low back or cervical pain: a prospective cohort study. BMC Musculoskeletal Disorders. 2009. PubMed #19220916. BACK TO TEXT
  4. Thackeray et al. A Pilot Study Examining the Effectiveness of Physical Therapy as an Adjunct to Selective Nerve Root Block in the Treatment of Lumbar Radicular Pain From Disk Herniation: A Randomized Controlled Trial. Physical Therapy. 2010. PubMed #20864600. BACK TO TEXT
  5. The purpose of the experiment as actually to test both the effectiveness of nerve blocks and to see if providing physical therapy as well was of any value. It wasn’t. Patients got the same amount of better, with or without the physical therapy. BACK TO TEXT
  6. Falco et al. Systematic review of diagnostic utility and therapeutic effectiveness of cervical facet joint interventions. Pain Physician. 2009. PubMed #19305483. Abstract:
    BACKGROUND: Chronic, recurrent neck pain is common and is associated with high pain intensity and disability, which is seen in 14% of the adult general population. Controlled studies have supported the existence of cervical facet or zygapophysial joint pain in 36% to 67% of these patients. However, these studies also have shown false-positive results in 27% to 63% of the patients with a single diagnostic block. There is also a paucity of literature investigating therapeutic interventions of cervical facet joint pain.
    STUDY DESIGN: A systematic review of cervical facet joint interventions.
    OBJECTIVE: To evaluate the accuracy of diagnostic facet joint nerve blocks and the effectiveness of cervical facet joint interventions.
    METHODS: Medical databases and journals were searched to locate all relevant literature from 1966 through December 2008 in the English language. A review of the literature of the utility of facet joint interventions in diagnosing and managing facet joint pain was performed according to the Agency for Healthcare Research and Quality (AHRQ) criteria for diagnostic studies and observational studies and the Cochrane Musculoskeletal Review Group criteria as utilized for interventional techniques for randomized trials.
    LEVEL OF EVIDENCE: The level of evidence was defined as Level I, II, or III based on the quality of evidence developed by the U.S. Preventive Services Task Force (USPSTF).
    OUTCOME MEASURES: For diagnostic interventions, studies must have been performed utilizing controlled local anesthetic blocks which achieve at minimum 80% relief of pain and the ability to perform previously painful movements. For therapeutic interventions, the primary outcome measure was pain relief (short-term relief up to 6 months and long-term relief greater than 6 months) with secondary outcome measures of improvement in functional status, psychological status, return to work, and reduction in opioid intake.
    RESULTS: Based on the utilization of controlled comparative local anesthetic blocks, the evidence for the diagnosis of cervical facet joint pain is Level I or II-1. The indicated evidence for therapeutic cervical medial branch blocks is Level II-1. The indicated evidence for radiofrequency neurotomy in the cervical spine is Level II-1 or II-2, whereas the evidence is lacking for intraarticular injections.
    LIMITATIONS: A systematic review of cervical facet joint interventions is hindered by the paucity of published literature and lack of literature for intraarticular cervical facet joint injections.
    CONCLUSIONS: The evidence for diagnosis of cervical facet joint pain with controlled comparative local anesthetic blocks is Level I or II-1. The indicated evidence for therapeutic facet joint interventions is Level II-1 for medial branch blocks, and Level II-1 or II-2 for radiofrequency neurotomy.
    BACK TO TEXT
  7. Datta et al. Systematic assessment of diagnostic accuracy and therapeutic utility of lumbar facet joint interventions. Pain Physician. 2009. PubMed #19305489. Abstract:
    BACKGROUND: Lumbar facet joints are a well recognized source of low back pain and referred pain in the lower extremity in patients with chronic low back pain. Conventional clinical features and other non-invasive diagnostic modalities are unreliable in diagnosing lumbar zygapophysial joint pain. Controlled diagnostic studies have shown the prevalence of lumbar facet joint pain in 27% to 40% of the patients with chronic low back pain without disc displacement or radiculitis, with a false-positive rate of 27% to 47% with a single diagnostic block.
    STUDY DESIGN: A systematic review of diagnostic and therapeutic lumbar facet joint interventions.
    OBJECTIVE: To determine the clinical utility of diagnostic and therapeutic lumbar facet joint interventions in managing chronic low back pain of facet joint origin.
    METHODS: Review of the literature for clinical studies on efficacy and utility of facet joint interventions in diagnosing and managing facet joint pain was performed according to the Agency for Healthcare Research and Quality (AHRQ) criteria for diagnostic studies and observational studies and the Cochrane Musculoskeletal Review Group criteria as utilized for interventional techniques for randomized trials. Data sources included relevant literature of the English language identified through searches of Medline and EMBASE from 1966 to December 2008 and manual searches of bibliographies of known primary and review articles. Analysis results were performed for diagnostic and therapeutic interventions separately.
    LEVEL OF EVIDENCE: The level of evidence was defined as Level I, II, or III with 3 subcategories in Level II based on the quality of evidence developed by the U.S. Preventive Services Task Force (USPSTF) for therapeutic interventions.
    OUTCOME MEASURES: For diagnostic interventions, studies must have been performed utilizing controlled local anesthetic blocks. Pain relief was categorized as at least 80% pain relief from baseline pain and ability to perform previously painful movements. For therapeutic interventions, the primary outcome measure was pain relief with secondary outcome measures of improvement in functional status, psychological status, return to work, and reduction in opioid intake. For therapeutic interventions, short-term pain relief was defined as relief lasting 6 months or less and long-term relief as longer than 6 months.
    RESULTS: Based on USPSTF criteria, evidence showed Level I or II-1 for diagnostic facet joint nerve blocks. Based on the review of included therapeutic studies, Level II-1 to II-2 evidence was indicated for lumbar facet joint nerve blocks with indicated level of evidence of Level II-2 to II-3 for lumbar radiofrequency neurotomy.
    LIMITATIONS: The shortcoming of this systematic review of lumbar facet joint interventions is the paucity of published literature.
    CONCLUSION: The evidence for diagnosis of lumbar facet joint pain with controlled local anesthetic blocks is Level I or II-1. The indicated level of evidence for therapeutic lumbar facet joint interventions is Level II-1 or II-2 for lumbar facet joint nerve blocks, Level II-2 or II-3 evidence for radiofrequency neurotomy, and Level III (limited) evidence for intraarticular injections.
    BACK TO TEXT
  8. Atluri et al. Systematic review of diagnostic utility and therapeutic effectiveness of thoracic facet joint interventions. Pain Physician. 2008. PubMed #18850026. Abstract:
    BACKGROUND: Chronic mid back and upper back pain caused by thoracic facet joints has been reported in 34% to 48% of the patients based on the responses to controlled diagnostic blocks. Systematic reviews have established moderate evidence for controlled comparative local anesthetic blocks of thoracic facet joints in the diagnosis of mid back and upper back pain, moderate evidence for therapeutic thoracic medial branch blocks, and limited evidence for radiofrequency neurotomy of therapeutic facet joint nerves.
    OBJECTIVES: To determine the clinical utility of diagnostic and therapeutic thoracic facet joint interventions in diagnosing and managing chronic upper back and mid back pain.
    STUDY DESIGN: Systematic review of diagnostic and therapeutic thoracic facet joint interventions.
    METHODS: Review of the literature for utility of facet joint interventions in diagnosing and managing facet joint pain was performed according to the Agency for Healthcare Research and Quality (AHRQ) criteria for diagnostic studies and observational studies and the Cochrane Musculoskeletal Review Group criteria as utilized for interventional techniques for randomized trials. The level of evidence was classified as Level I, II, or III based on the quality of evidence developed by United States Preventive Services Task Force (USPSTF) for therapeutic interventions. Recommendations were based on the criteria developed by Guyatt et al. Data sources included relevant literature of the English language identified through searches of Medline and EMBASE from 1966 to July 2008 and manual searches of bibliographies of known primary and review articles. Results of the analysis were performed for diagnostic and therapeutic interventions separately.
    OUTCOME MEASURES: For diagnostic interventions, studies must have been performed utilizing controlled local anesthetic blocks. For therapeutic interventions, the primary outcome measure was pain relief (short-term relief = up to 6 months and long-term relief > 6 months) with secondary outcome measures of improvement in functional status, psychological status, return to work, and reduction in opioid intake.
    RESULTS: Based on the controlled comparative local anesthetic blocks, the evidence for the diagnosis of thoracic facet joint pain is Level I or II-1. The evidence for therapeutic thoracic medial branch blocks is Level I or II-1. The recommendation is IA or 1B/strong for diagnostic and therapeutic medial branch blocks.
    CONCLUSION: The evidence for the diagnosis of thoracic facet joint pain with controlled comparative local anesthetic blocks is Level I or II-1. The evidence for therapeutic facet joint interventions is Level I or II-1 for medial branch blocks. Recommendation is 1A or 1B/strong for diagnostic and therapeutic medial branch blocks.
    BACK TO TEXT
  9. Manchikanti et al. Cervical medial branch blocks for chronic cervical facet joint pain: a randomized, double-blind, controlled trial with one-year follow-up. Spine. 2008. PubMed #18670333. BACK TO TEXT
  10. For more detail, see another article on SaveYourself.ca, Does Acupuncture Work for Pain? A review of modern acupuncture evidence and myths, particularly with regards to treating low back pain and other common pain problems. BACK TO TEXT
  11. For more detail, see another article on SaveYourself.ca, Does Spinal Manipulative Therapy (SMT) Work? Adjustment, manipulation, and popping of the spinal joints and the subluxation theory of disease, back pain and neck pain. BACK TO TEXT