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. Facet joints are a specific anatomical structures with clear “edges,”1 so 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?
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.
This practice is supported as a diagnostic tool by scanty, conflicting scientific evidence. Some authors call it “fair” evidence, but probably shouldn’t have.3 The evidence is similar for the thoracic4 and lumbar5 spine.
Many other factors tend to confuse this method of diagnosis, which is probably why it hasn’t been valifated by research. For example:
Researchers found that the amount of relief the low back pain patients got from facet joint injections could be predicted by psychological factors.6 So much for a simple equation. Why would that be? Numbing might provide strong enough temporary relief to create an overconfident “eureka!” And that confidence might itself deliver some pain relief, further clouding the issue, and adding up to a false positive: a misleading result that puts a spotlight on the facet joint that is actually innocent, or only part of the problem. Fortunately, the evidence suggests that this kind of confusion is probably rare, and clear relief probably means what it seems to mean.
An MBB should be considered as a diagnostic tool for stubborn neck or back pain. But nothing is ever as simple as it seems.
And then there’s treatment. Numbing might be diagnostic, maybe, but can it be therapeutic?
Once again, the science is scanty and conflicting. The journal Pain Physician has published a few articles in recent years analyzing facet joint treatments for the cervical and lumbar spine (both cited above), and the thoracic spine spine.7 The only major review was published by Spine,8 which was the most discouraging: “There is insufficient evidence to support the use of injection therapy in subacute and chronic low-back pain,” although the benefits of some types of injection therapy for certain patients “cannot be ruled out.” The others were more positive, but also not based on much actual data. So what do the more specific reviews in Pain Physician have to say?
A treatment does not have to be perfect to be worthwhile, and there is probably some good being done with these procedures. But not a lot, or the evidence wouldn’t be so thin.
Much of what’s positive in these reviews comes from a 2008 experiment in which researchers gave medial branch nerve blocks to 120 chronic neck pain patients, and found that they produced “significant relief and functional improvement” in “over 83% of patients.”9
This study has been widely cited as near proof that nerve blocks “work,” and it is the main source of enthusiasm about needles for neck pain in recent history. I think it is pretty decent evidence, and so MBB is 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 …
I can see at least 6 reasons why the Manchikanti et al paper is not exactly a slam dunk, and MBBs are no miracle cure:
I am a science writer, former massage therapist, and I was the assistant editor at ScienceBasedMedicine.org for several years. I have had my share of injuries and pain challenges as a runner and ultimate player. My wife and I live in downtown Vancouver, Canada. See my full bio and qualifications, or my blog, Writerly. You might run into me on Facebook or Twitter.
— Change in position. After reviewing the same scientific papers previously cited more carefully, I decided that they were much less promising than I originally thought. The article has switched from optimism to pessimism about nerve blocks without a single change in what’s actually cited, just a change in the level of diligence in interpreting the science.
— Science update, additional references supporting the diagnostic utility of medial branch blocks, and an additional caveat about how they can fail.
— Updated with reference to Thackeray.
This small 2012 review concluded that the “evidence for cervical medial branch blocks is fair.” Unfortunately, “fair” is a ridiculous word to use when summing up a “body” of evidence based on one trial (no matter how good) and one prospective evaluation. They also granted “fair” evidence for radiofrequency neurotomy based on just one randomized controlled trial (and a few almost meaningless observational studies).
Evidence for two other cervical joint interventions was “limited” by comparison! Indeed.
In my opinion, they did not find enough of any kind of evidence about anything to draw any conclusions whatsoever.
This paper is very similar to Manchikanti et al, regarding the thoracic spine (again involving some of the same researchers).BACK TO TEXT
A review of barely adequate scientific literature on thoracic spinal joint interventions, but some of what they found was promising: good (Level I or II-1) for both diagnostic and therapeutic nerve blocks. But the number of papers on this topic really is extremely small: even years later, Manchikanti 2012 only reviewed a handful. The optimistic conclusion here is not resting on much.BACK TO TEXT
This review of diagnosis and treatment of lumbar facet joints found very little, a “paucity of published literature,” but what they did find seemed to be positive: good evidence for diagnostic nerve blocks, and fair when using them for treatment. Notably, Staal concluded that the literature was too scanty to conclude anything.BACK TO TEXT
This tiny review was based on extremely limited evidence: just four studies (three non-randomized), and “The only positive studies were of medial branch blocks performed by the same group of authors” (e.g. Manchikanti 2008) … who also happen to be the authors of this review. That doesn’t mean they are wrong, of course, but it’s an important caveat. The word they chose to describe this level of evidence was “fair.” I’m not sure that’s fair! They are mostly just re-reporting the positive results of their own trials.
They also concluded there wasn’t enough evidence about intraarticular injections and radiofrequency neurotomy. They probably should have concluded the same about medial branch blocks!
This paper is very similar to Falco et al, regarding the cervical spine (again involving some of the same researchers).BACK TO TEXT
A review of all kinds of injection therapies for the low back and finding “no strong evidence for or against the use of any type of injection therapy,” which is not as optimistic as Datta 2009.BACK TO TEXT