Cervical facet joint injections can provide some pain relief in patients with chronic neck pain emanating from the facet joints. However it is important to note that in some cases injection treatment may not provide the desired results or the pain relief may not be sustained. Overall the current recommendations favour diagnostic cervical facet joint nerve blocks (medial branch blocks), followed by radiofrequency denervation, rather than intra articular facet injections.
In 1933, Ghormley coined the term facet syndrome to describe a constellation of symptoms associated with degenerative changes of the lumbar spine. Relatively recently, the term cervical facet syndrome has appeared in the literature and implies axial pain presumably secondary to involvement of the posterior elements of the cervical spine. Many pain generators are located in the cervical spine, including the intervertebral discs, facet joints, ligaments, muscles, and nerve roots. The facet joints have been found to be a possible source of neck pain, and the diagnosis of cervical facet syndrome is often one of exclusion or not considered at all.
The cervical spine is composed of 7 cervical vertebrae, intervertebral discs, zygapophyseal or facet joints, ligaments, muscles and fascia and neural structures. There are 7 pairs or 14 facet joints in the cervical spine. They are true synovial joints and are composed of a fibrous capsule lined with synovium and hyaline cartilage between the bony structures. The capsule is richly innervated by nociceptors and mechanoreceptors that help with cervical spine proprioception.
The orientation of the facet joint provides resistance to anterior translation and assists in weight-bearing. They are at a 45-degree angle, allowing flexion, extension, rotation, and limited translation. The atlanto- occipital and atlanto-axial joints (C1 and C2) do not have facet joints. The C2/3 joint is innervated by the medial branch of the C2 dorsal rami and the medial branch of the C3 dorsal rami (the third occipital nerve). C3/4 to C7/T1 cervical joints are innervated by the medial branches of the cervical dorsal rami located above and below the joint.
The facet joint is richly innervated with nociceptors and mechanoreceptors; these nerves can be adversely affected by facet capsular strain. Inflammation of the facet joint can sensitize nociceptive neurons and lower the firing threshold, causing pain during ‘normal’ motion, or peripheral sensitization. Similarly, disruption of mechanoreceptors can cause subtle proprioceptive disturbances and result in spinal instability or uncoordinated, painful cervical muscle contraction and guarding.
Signs of cervical spondylosis, narrowing of the intervertebral foramina, osteophytes, and other degenerative changes are equally prevalent in people with and without neck pain. Hence imaging may not necessarily be helpful in management of cervical facet syndrome.
Patients with cervical facet joint syndrome often present with complaints of neck pain, headaches, and limited range of motion (ROM). The pain is described as a dull, aching discomfort in the posterior neck that sometimes radiates to the shoulder or mid back regions. Patients also may report a history of a previous whiplash injury to the neck. Clinical features that are often associated with cervical facet pain include tenderness to palpation over the facet joints or paraspinal muscles, pain with cervical extension or rotation, and absent neurologic abnormalities.
In patients with facet joint syndrome, distension of the joint with saline or contrast will reproduce the pain, and injection of a local anaesthetic agent will relieve the pain. This response pattern is the current gold standard for diagnosing the facet syndrome.
The diagnostic injection permits testing of the hypothesis that the target structure (facet joint) is the source of a patient’s pain. Clinical signs are generally unsuitable for making a diagnosis, but may be of value in selecting patients for the diagnostic block of the facet joint.
The primary indication is to confirm the clinical suspicion of the facet syndrome.
Injections are generally avoided in patients with systemic infection or skin infection over puncture site, bleeding disorders or coagulopathy, allergy to local anaesthetics or any of the medications to be administered.
The procedure is usually done on an outpatient basis. The procedure is performed under fluoroscopic guidance to ensure accuracy of needle placement. Patients need to be aware that the outcome of the procedure is variable and they may not receive the desired benefits. Similarly, they must be aware of the transient nature of the therapeutic benefits and that they may need repeated injections.
Generally a mixture of local anaesthetic and steroid is injected. The local anaesthetic agent within the injectate may act on the nociceptive fibres in the synovium, whereas intracapsular corticosteroids may reduce inflammation of the synovium. The anaesthetic is probably responsible for immediate pain relief, whereas steroids are believed to be responsible for pain relief 2–6 days after their administration. For a diagnostic block, a short-acting anaesthetic alone is sufficient. The role of steroids is controversial, with some studies showing no advantage from the addition of steroids to the injectate.
Complications are rare, particularly if the facet joint injections are performed using a precise needle-positioning technique. Possible complications include spondylodiscitis, septic arthritis, and reaction to the injectates. Septic arthritis can be avoided with appropriate aseptic precautions. Severe allergic reactions to local anaesthetics are uncommon. Steroid injections may produce local reactions, occurring most often immediately after injection. These local reactions last for 24 to 48 hours, and are relieved by application of ice packs. Post-procedural pain flare-up may occasionally occur, and may be treated with pain killers. Neurological complications including paraesthesias, numbness and paralysis have been described but are extremely rare. Infections including epidural abscess and chemical meningitis can occur but the incidence is very low as the procedure is performed under strict aseptic conditions.
When performed under fluoroscopic visualisation, cervical facet joint injections are accurate and clinically useful in the diagnosis and therapeutic management of chronic spinal pain. The diagnostic accuracy of facet joint blocks is strong for cervical and lumbar facet joints, and moderate for thoracic facet joints. In contrast to clinical evaluation and imaging techniques, diagnostic injections can identify facet joint pain with a higher level of certainty. However, the diagnostic value is limited by the high false-positive rates seen with single blocks (without control). False-positive rates with single blocks are 17%- 47% in the lumbar spine. There is limited literature on the therapeutic efficacy as most of the available data is based on non-controlled and observational studies. There are only few exhaustive randomised control trials available on this subject and they mostly pertain to the lumbar spine. For intra-articular injection of local anaesthetics and steroids, there is moderate evidence of short-term relief and limited evidence of long-term relief of chronic neck and low back pain.
Overall the current recommendations favour diagnostic cervical facet joint nerve blocks (medial branch blocks), followed by radiofrequency denervation, rather than intra articular facet injections.