FACET JOINT ARTHROPATHY
Facet joints are found in the cervical, thoracic, and lumbar spine. They are the articular connection between the superior articular process and the inferior articular process of two vertebrae (1). The facet joint is also known as the zygapophyseal or z-joint (11). Like other joints in the body, the facet joint is surrounded by a fibrous capsule with an inner lining of synovial membrane, articular cartilage, and meniscus (1). Within cervical facet joints there are synovial folds that contain fibrous and adipose tissue and are responsible for handling mechanical stress (1). The facet joints are located posterolateral to the vertebral body (11). The role of the facet joint is to prevent excess spinal motion (11).
A) Medial branch of the dorsal rami
B) Lateral branch of the dorsal rami
C) Cervical nerve root at level of the lateral recess
D) Cervical nerve root at the level of the neuro-foramina
The innervation of the cervical facet joints are through the medial branches of the cervical dorsal rami from the level above and below the joint (1,11). The innervation of the lumbar facet joints are also innervated by the medial branches of the dorsal rami found at the same level as the facet joint (5,11).
In the lumbar spine, facet joint degeneration is typically found with disc degeneration (4). Lumbar facet joint pain has also been found to be the source of 15% of pain for patients with chronic axial low back pain. The purpose of this review is to look at degenerative changes that occur through the facet joint.
Patients with facet arthropathy will typically have pain that is axial and will present similarly to other causes of back pain, including muscular strain and spinal stenosis (1). However, what makes the clinical diagnosis difficult is that lumbar facet joints can also cause “pseudoradicular” pain similar to disc herniations (3). Facet arthropathy in the cervical spine can also cause radiating pain into both the head and shoulders (7). The incidence will increase in older age, so it should be included on the differential in our older patients (11). Evidence does not find that any specific activity, such as twisting, walking or sitting, is found more often in facet arthropathy (11).
There is limited evidence in physical exam maneuvers to provoke symptoms of facet arthropathy (11). Many providers will use diagnostic blocks to help narrow down the differential of facet arthropathy (11).
Diagnosis of facet arthropathy can be made with standard radiographs, CT, or MRI. CT scans have been found to be sensitive for facet joint pain but not specific (3).
A normal facet joint on CT or MRI shows no joint space narrowing, no osteophyte formation or hypertrophy, no joint erosions, and no subchondral cysts (10). Severe facet arthropathy will show subchondral cyst formation and severe osteophyte formation with erosions (10).
A study published in the NEJM looked at MRI findings of the lumbosacral spine in asymptomatic patients to see the prevalence of abnormalities in patients with no symptoms (2). The study population average age was 42 years old and they found that 8% of the patient population had asymptomatic facet arthropathy (2). With this in mind, all providers must order imaging cautiously and try to correlate their physical exam findings with the MRI findings.
First line treatment for facet arthropathy is typically conservative and includes use of anti inflammatories and physical therapy (1).
If patients fail first line measures, they can consider intra-articular injection. Under fluoroscopic guidance, patients can receive a corticosteroid injection into the synovial joint or a nerve block of the affected joint (1). However, there is a lack of clinical data supporting benefit with facet joint corticosteroid injection for low back pain (3). Studies have found that patients only have short term improvement with these injections.
The best evidence for treatment options for facet arthropathy are for medial branch neurotomy (3). Radiofrequency ablation can be performed in the cervical and lumbar spine. Under fluoroscopic guidance, providers insert a radiofrequency probe to the affected nerve and at temperatures around 80 degrees, use heat to ablate the nerve (7). Thermal radiofrequency ablation at temperatures of 80 to 85 degrees C can cause neuritis (1).
There is also pulse radiofrequency that uses periods of stimulation to the target nerves without heat (7). The pulse radiofrequency causes an electric field that is possibly able to affect the neuronal membrane to affect the nerve signaling ability (12).
The challenge in evaluating the literature for radiofrequency ablation is the lack of homogeneity in the studies. For example, identifying what a positive response is has led to different levels of evidence for radiofrequency ablation. Several studies require resolution of pain and some report a positive test as a 50% improvement of pain. Another challenge with radiofrequency ablation is that the procedure is not curative and lasts for up to one year because the nerve cell body is not affected and can lead to axonal regeneration (12).
Facet arthropathy is a common source of pain in the cervical and lumbar spine. Facet joints in both areas can cause “pseudoradicular” features, making diagnosis difficult. Imaging with radiographs, CT, and MRI can aid in diagnosis. Gold standard treatment is nerve ablation with either radiofrequency or pulsed frequency. However, future studies should continue looking at longer lasting and more effective treatments for facet arthropathy.
By Gregory Rubin, DO
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