Spine Injections- Part 4- Facet-Directed Cervical Injections

In Part 1 we discussed lumbar epidural steroid injections (ESI). Part 2 covered facet-directed lumbar injections and their purpose. The significance of cervical epidural injections and what they are was explained in Part 3. In Part 4 below, we will be discussing facet-directed cervical injections.

One may assume that cervical and lumbar facet injections should be discussed in the same blog. However the cervical spine is very different than the lumbar.

The cervical disc is structurally configured distinct of the lumbar spine, as the cervical spine only supports the head and has a larger role in preserving mobility. The lumbar spine primarily serves in weight-bearing. There is a proportionally larger nucleus pulposus in the cervical region, and it maintains a fairly constant amount of collagen throughout life, in comparison to a decline in collagen after 10 years of age in the lumbar spine. The cervical annular fibers are about 30% thicker in the anterior aspect compared to the posterior, while the lumbar anulus fibrosus has a more consistent cross-sectional thickness. The cervical spine has uncovertebral joints supporting the disc, unlike the lumbar. The cervical facets are more coronally oriented, with a greater inclination angle and planar articular surfaces to facilitate a greater range of motion in axial rotation and lateral bending compared to the lumbar spine. The lumbar facets are larger and more sagittal oriented (although L5-S1 has some coronal orientation) to resist axial rotation but enable more flexion. The cervical synovium is very fibrous, preventing synovial fluid from escaping. Cervical synovial cysts are quite rare. The lumbar synovium is weaker, owing to lumbar synovial cysts not being infrequent.

Neck pain is the primary indication for cervical facet-directed therapies. Cervical facet pain can radiate, in fairly well known patterns, but rarely far into the arms. Radicular signs, or symptoms into the arms, tends to predict a poor response to cervical facet interventions.

The diagnosis of cervical facet joint pain relies on the combination of symptomatology, physical examination, sometimes imaging, and diagnostic block.

The C2-3 and C5-6 joints are the most common clinically implicated in neck pain, while C2-3, C3-4 and C4-5 are most likely to display radiographic degeneration. The indication for facet injections is neck pain, usually >4 out of 10, for at least 6 weeks (appropriate-use guidelines recommend 3 months) in the absence of neurological findings. Palpation of the facet joint may instigate symptoms in the known distribution, to help guide therapy. Possibly more so than the lumbar spine, manual spinal examination with palpation and extension-rotation can reliably identify the cervical facet as a principle source of pain.

 

While this blog will not delve into the complex literature on “whiplash”, some “whiplash” symptoms may be attributable to the facets. Several studies have found that the likelihood of developing chronic symptoms after “whiplash” depends on the country from which the data is collected. For example, studies in countries like Greece seem to show that nearly 100% of “whiplash” patients return to their preinjury state within about 6 months of injury and no cases of chronic disability occur. However studies in the United States or Great Britain differ. It appears that cultural differences in patient expectations, and the prevalence of accident litigation, directly impacts patient expectation and recovery.

On imaging, abnormal cervical facets may suggest a pain generator. When planning for a procedure, correlation with imaging may be helpful. However not all facet pain shows imaging changes, and imaging alone cannot predict pain 100% of the time.

When facetogenic pain is suspected, just as with radicular (arm) pain, conservative management is still the initial option. Physical therapy, chiropractic care, acupuncture, massage therapy and cognitive-behavioral therapy are recommended. Anti-inflammatories may be beneficial.

However with failure of conservative options, facet-mediated interventions may be considered.

Just as in the lumbar spine, intra-articular (IA) injections are primarily reserved for the presence of a synovial cyst, and as discussed, cervical synovial cysts are rare.

Diagnostic medial branch blocks (MBB) are the primary plan on a path to radiofrequency ablation (RFA).

Just as in the lumbar spine, a MBB is usually best performed in two separate stages, called dual-comparative-blocks. An initial injection is performed with a local anesthetic, and then pain response is followed. Steroids should not be used in a MBB.

Cervical facets are only present in C2-3 and below. C1-2 articulates using a different type of joint structure. Each cervical facet joint is innervated by two different medial branches, usually being the branch from the level above and the target level. C2-3 is a bit different in that it is innervated by the third occipital nerve.

To truly be accurate, 100% pain relief should be observed for the duration of the anesthetic, however some suggest at least an 80% improvement is sufficient. However using anything but a 100% cut-off may raise uncertainty of placebo response or another unidentified pain source. The pain relief really needs to be concordant, meaning the exact type of pain of which the patient originally was complaining. This will be short-lived. Lidocaine only really works for about 1 ½ to 2 hours. Bupivacaine should last a bit longer, closer to 2 ½ to 3 hours. If the pain relief lasts longer than the known duration of anesthetic, this should be considered a failure and likely placebo-response. Some patients think that when the pain returns after a couple hours, the injection failed… however that is exactly what was supposed to happen. If a positive response occurred with the initial injection, a 2nd injection may be performed on a different day using a different duration anesthetic, but in the exact same location. If the pain response is again concordant, and in-line with this different duration, then the trial is thought to be positive and the pain may be from that facet joint.

Diagnostic MBBs should be performed at no more than two bilateral levels or three unilateral levels per session. That equates to injections covering no more than two spinal levels.

The next consideration following a dual-comparative-block is radiofrequency ablation (RFA). In the exact same spot as the dual MBBs, an electrode “burns’ those small medial branch nerves. (Patients with pacemakers cannot undergo the procedure due to the interaction of the radiofrequency signal and their cardiac device.)

This can provide a more long-lasting interruption of sensory transmission from that cervical facet. Unfortunately the medial branch can regrow, so the procedure may need to be repeated in 6 months if at least 50% pain improvement was achieved. Again, a successful RFA is thought to improve pain by just 50%. This raises the question of exactly what a MBB or RFA is really doing. Why two MBBs, ideally achieving 100% pain relief could result in a RFA just alleviating 50% of the pain, is perplexing. If the MBB trial was accurate, and correctly diagnosed the facet as the pain generator, then one would think the RFA also should also nearly guarantee 100% relief. But this is the problem with pain injections, and why there is such controversy. Pain is subjective and the placebo-response is powerful. Just as with the lumbar spine, cervical RFA without the use of MBB, or just one MBB, has been advocated by some from a cost consideration. For accuracy in diagnosis, the two MBB option is preferred.

One issue with repeating RFA involves the other function of the medial branch nerve… providing some motor innervation to the cervical paraspinal muscles. Therefore the risk of RFA, and greater likelihood following numerous RFAs, is weakening of the paraspinal muscles leading to more pain and loss of structural integrity. There has been literature showing RFAs causing so much muscle injury that the patient could not hold their head upright (chin-on-chest deformity), necessitating cervical fusion surgery.

Therefore young patients who are athletes may wish to avoid any RFA. However in any patient, at some point, repeat RFAs should be abandoned if more permanent relief is not achieved. Of course, if despite repeat RFAs, the pain continues to recur, the patient should consider different options either for more permanent fix or exploration of a different pain generator.

Of interest, the prevalence of cervical facet pain, supported by successful dual MBBs, is higher than the prevalence of lumbar facet pain in those patients with chronic low back pain. This may be due to the greater mobility of the neck, possibly higher density of pain receptions, and increased relative size of the cervical facet joints to the discs.

The effectiveness of cervical RFA has been less studied than in the lumbar spine.

Failure of cervical facet interventions may not indicate neck surgery is necessary. Cervical fusion for purely facetogenic pain may not be the best indication.

 

Conclusion

Cervical MBB on a path to RFA is a reasonable option for axial neck pain with the combination of symptomatology, physical examination, and sometimes imaging, indicating facetogenic pain.

Some providers attempt to suggest no symptom, exam or imaging finding can predict the facet as a source of pain. This is ridiculous. If any provider offers any intervention, whether medication, injection, surgery, etc… without any reason to think it will work, then a second opinion is probably warranted.

Understanding the steps in diagnosing facetogenic pain is important, since the initial diagnostic injections are not expected to last more than a couple hours. Even RFA is not known to be permanent.

However facetogenic interventions may be helpful for the carefully selected patient.

Failure of a facet-directed injection does not necessarily mean surgery is indicated. Failure of these injections may just mean the pain generators is not yet identified and a more prudent analysis is warranted.