Cervical Zygapophyseal Joint Pain- Is Whiplash Injury a Myth?

Bogduk in his textbook explains that no studies have identified the difference of response to the same treatment between patients with subacute neck pain from acute or chronic neck pain¹.

Manchikanti L. et al. nicely elucidated in his paper the difference between somatic and radicular pain patterns³. He stresses that there has been an increase in the demand of cervical facet joint injections and neurolysis³. In Australia, Medicare claims have increased tremendously over the last 10 years raising the eyebrows of stakeholders, insurance companies and policy-makers³. Currently, there is Level II evidence of radiofrequency neurotomy and facet joint injections³. Complications from facet joint injections and medial branch of the dorsal rami are exceedingly rare. Some of the reported complications are soft tissue infection, nerve damage, vasovagal syncope, haematoma formation, vertebral artery transection, and spinal cord infarction secondary to emboli³. A systematic review carried out by Engel A. et al. stipulates that for safety reasons cervical medial branch radiofrequency neurotomy should be done under local anesthesia and not under general anesthesia to allow early recognition of potential complications⁴. A fully wake patient will be able to report any unusual sensations due to incorrect electrode placement⁴.

Dwyer et al. was one of the first to look at somatic referred pain mapping in the cervical spine⁵. He constructed pain maps perceived by normal healthy volunteers when their cervical zygapophyseal joints were injected intraarticularly with contrast medium⁵. The study showed noxious stimulation of cervical zygapophyseal joints produced pain patterns that radiated into the upper arm and scapula¹. This study formed prima facie the acknowledging cervical zygapophyseal joint pain. Nevertheless, the validity and reliability of this study are questionable. This sparked other researchers in the later years to look at reproducing zygapophyseal joint pain. In 2007, Cooper G. and colleagues derived pain maps by relieving pain using local anaesthetic controlled blocks such as Lidocaine 2% (short acting) and Bupivacaine (long acting)⁶. Only a small amount of 0.3 mL local anaesthetic was used to anesthetize the medical branches of the dorsal rami to prevent bathing other anatomical structures that might confound the result. Since patients do not report neat patterns, grid densities were used to calculate the probability of pain reported in a particular area that might be attributed to a zygapophyseal joint⁶. C2-3 and C5-6 were the most commonly symptomatic zygapophyseal joints⁶. The conclusion from this paper was pain relieved by controlled blocks provide a more representative guide to the recognition of segmental origin of cervical zygapophyseal joint pain⁶.

Some emphasis is placed on the mechanism of whiplash associated injury. Bogduk in his textbook explains the step wise process of a whiplash injury¹. Contrary to the traditional belief, he refutes the idea of whiplash being a flexion-extension injury. He describes the stepwise process of what happens during a typical rear-end motor vehicle accident¹. The lower cervical spine flexes followed by an extension¹. The centre of gravity shifts as the trunk moves upwards and shearing the facet joints. This can lead to injury of the following structures: bone, intervertebral disc, muscles, ligaments, nerves, vessels and most importantly the facet joints. Unfortunately, in this era of modern radiographic imaging, imaging such as Magnetic Resonance Imaging (MRI) are unable to detect small lesions such as rim lesions, haemarthrosis or capsular tear of facet joints². James Taylor showed in his autopsy of 109 patients that most injuries were in fact non osseous and not demonstrable on imaging².  More than 90% of post mortem radiographic imaging missed minor lesion such as rim lesions, capsular tears and haemarthrosis². He stresses that soft tissue and ligamentous injury tend to heal quickly but articular cartilage damage is avascular and often leads to a pathological “degenerative sequelae”².

There is a general misconception among patients that an MRI will pinpoint the exact source of pain. MRI might be good at showing other abnormalities e.g. normal age related degenerative changes, but this in itself might not be the source of pain¹. To date, plain X-ray, Computed Tomography (CT) and MRI imaging have not been able to provide a valid diagnosis for a painful cervical facet joint⁴. MRI is good at excluding red flags for both the patient and clinician but often does not help tell the source of pain⁴.

One useful treatment option for chronic facet joint pain with good evidence backing it is cervical radiofrequency neurotomy. This involves using radiofrequency heat energy to coagulate the nerve fibres supplying the symptomatic facet joint, i.e. neuroablation⁷. Each cervical facet joint get its innervation from the medical branch of the dorsal rami, one each from above and below¹. Hence, a successful block requires both nerves to be denervated to block nociceptive input⁷.

Prushansky T. and colleagues published a paper in 2006 studied 40 chronic whiplash-associated disorder patients and the outcome of radiofrequency neurotomy⁷. Although the paper has a few limitations, for example, the lack of control group and diagnostic blocks, the authors concluded that with a good history taking, examination and imaging, the outcomes for neurotomy is desirable at the one year mark⁷. This was further reinforced by other randomized controlled trials carried out in the latter years. As aforementioned, for a successful radiofrequency neurotomy, selecting the right patient population is essential. Lord SM. and colleagues looked at comparative local anaesthetic blocks and innocuous agent(normal saline) with placebo controlled⁸. The paradigm of two types of local anaesthetic blocks, i.e., short acting and long acting has been attractive for a long time. The conclusion drawn from the paper was placebo-controlled blocks are recommended from the medicolegal perspective or when surgery is being considered⁸.

The study by MacVicar and Borowczyk is an appropriate representation of this case study. Most of their patient cohort were trauma patients, with only around 5% of the subjects having degenerative related disease of the facet joint⁹. The study was rigorous with pre-set strict criteria, e.g., achieving almost 100% complete pain relief if the correct zygapophyseal joint was injected⁹. Although, we need to accept that there could be other sources of pain including the “culprit” zygapophyseal joint as the sole nociceptive pain generator, a stepwise approach of good clinical history and examination with radiographic imaging can usually help pinpoint the source of pain⁹. This is also backed up by a systematic review by Engel A. published in 2020 which emphasized the importance of stratifying the studies¹⁰. Statistically significant pain relief is achieved if patients are selected with complete relief from their index pain following comparative dual controlled blocks¹⁰. A negative study should not negate a positive study for RF neurotomy¹⁰. The selection criteria play a huge role in terms of determining the outcome of the study. If a study is poorly designed with laxed inclusion and/or exclusion criteria, it will lead to false study outcomes. Accepting poorly designed studies can lead to misconception in policy making.

Newer treatment options have cropped up with time. Pulsed radiofrequency neurotomy has attracted some attention by using full intensity radiofrequency but with cooling of needle tip with cold saline, or applying current in short pulses with rest intervals to allow cooling of surrounding tissues¹¹. With the advent of this new RF neurotomy, there is lower risks of complications and the efficacy is maintained¹¹. The time spent seems to be similar to traditional RF, i.e., 90 to 240 seconds¹¹.

Invariably, patients with chronic neck pain tend to have central neurosensitization features. These patients tend to have widespread sensory disturbances and heightened central reflex symptoms¹².  A paper published by Smith AD. et al. tries to proof “augmented central nociceptive processing”¹². The authors of the paper acknowledge that peripheral lesion might not be present on imaging, nevertheless, there is some source of peripheral nociception from the facet joint¹². Radiofrequency neurotomy abolishes this nociceptive pathway. The study showed that by abolishing the nociceptive pathways, patients had better neck range of motion, reduced widespread hypersensitivity and central hyperexcitability¹². This supports the notion of augmented central nociceptive processing¹². There has also been studies in animal models where stretching of facet joint capsule can lead to the release of a cocktail of inflammatory mediators, causing peripheral sensitization¹². The paper concluded that by reducing peripheral nociception causes changes in the central processing system, thus supporting radiofrequency neurotomy¹².

CONCLUSION

Some “centralist” believe that chronic pain is not amenable from the treating the peripheral lesion due to central sensitization which is irreversible⁴. Often a psychological approach is recommended, while medical therapy is downplayed. This vexatious belief makes it futile for the treating medical clinician to help the patient. It should be a clinician’s modus operandi to offer the patient any possible treatment options available. Cervical radiofrequency neurotomy has shown some promising results with chronic pain patients being completely pain-free and being able to participate in their normal life again. Although this may be plausible, some chronic pain patients do not benefit from neurotomy and never seem to be completely pain free. Nevertheless, they have been offered a possible treatment option which every patient deserves. It is imperative as a clinician to understand that in the “pain world”, compromise is necessary, and that not accepting complete pain relief as a marker of success.