Lumbar Facet Arthropathy: The Commonest Cause of Low Back Pain

What Is the Function of the Lumbar Facet Joint?

The lumbar zygapophysial joint, also known as the facet joint, is one of the most common generators of lower back pain. The facet joint is a true synovial joint that contains a synovial membrane and hyaline cartilage surfaces and is surrounded by a fibrous joint capsule. The joint plays an important role in load transmission, aiding in posterior load-bearing, stabilizing the spine in flexion and extension, and restricting exaggerated axial rotation.

Who Is Susceptible to Lumbar Facet Arthropathy?

Lumbar facet arthropathy is seen in a wide range of prevalences, throughout history, from under five percent to over 90 percent of patients complaining of back pain. Studies have implicated the facet joint as a source of 15 to 45 percent of chronic lower back pain. Moderate to severe lumbar facet arthropathy is seen in 36 percent of adults below the age of 45 years, 67 percent of adults between 45 to 64 years, and 89 percent of adults over 65 years.

Computer tomography studies have found women over 50 years to be more susceptible to facet joint osteoarthritis than men. The study also concludes that Caucasians are more susceptible than African-Americans. BMI (body mass index) poses etiologic to lumbar facet arthropathy. BMI between 25 to 30 has three times the increased susceptibility and five times the risk for patients with BMI in the range of 30 to 35.

The condition is most prevalent in L4 and L5 vertebrae, followed by L3 and L4, and then L1 to L3 vertebrae.

What Causes Lumbar Facet Arthropathy?

Facet joint arthropathy is a degenerative condition that occurs secondary to age, inadequate body mechanics, excessive overuse, and microtrauma. Degeneration of the facet joint is caused due to degeneration of intervertebral discs, which is a precursor to facet joint arthrosis. These mechanical changes occur as a result of loading of the facet joints following intervertebral disk degeneration. The joint is more prone to degeneration when conditioned with a more sagittal orientation of the joint.

What Is the Pathophysiology of Lumbar Facet Arthropathy?

Degenerative changes that involve the facet joint begin with the degradation of the hyaline cartilage leading to the formation of erosion and joint space narrowing. These changes lead to sclerosis of the subchondral bone. Progressively, the posterior capsule of the joint capsule gets hypertrophied along with fibrocartilage proliferation and with a possibility of synovial cyst formation. Osteophytes arise at the entheses (attachment sites) where the fibrocartilage extends beyond the original joint space. The entire joint complex is richly innervated, which gives rise to facet-mediated pain.

Another hypothesis suggests facet intra-articular meniscoid entrapment and synovial impingement be the cause of facet-mediated pain.

What Are the Signs and Symptoms of Lumbar Facet Arthropathy?

• Unprovoked chronic lower back pain.

• Pain localized over the back.

• Non-dermatomal pain radiation pattern.

• Referred pain is around the buttock and thigh.

• Lumbar radiculopathy.

• Bowel dysfunction.

• Bladder dysfunction.

• Tenderness to palpation.

• Diminished lower extremity strength.

How to Diagnose Lumbar Facet Arthropathy?

The gold standard for lumbar facet arthropathy is an anesthetic block to the facet joint. Imaging studies can be undertaken to rule out other causes of facet arthropathy like disk herniation, spinal stenosis (narrowing of the spinal canal), spondylolisthesis (slip disc), ankylosing spondylitis (vertebral fusion), diffuse idiopathic skeletal hyperostosis (DISH - hardening of spinal ligaments at the site of attachment), infection, or neoplasm. Rarely, concomitant facet joint degeneration can be an alternative cause of lower back pain.

Radiographic Findings

Classic radiographic findings of facet arthropathy reveal both degenerative and proliferative changes.

• Radiographic imaging shows.

• Narrowing of the facet joint space.

• Subarticular bone erosions.

• Subchondral cysts.

• Osteophyte formation.

• Hypertrophy of the articular process.

Other Imaging Studies

MRI (magnetic resonance imaging) is useful in visualizing facet degeneration at the bony cortex margins. CT (computed tomography) scans are considered the preferred evaluation method for imaging due to a more precise demonstration of bony details. MRIs are preferred to rule out any non-facet-mediated pain. Bone scintigraphy shows synovial changes and degenerative remodeling.

Anesthetic Blocks of the Facet Joint

This is the gold standard for facet joint arthropathy, with two levels of evidence based on established criteria. Both intra-articular injections of the facet joint and medial branch blocks are equally effective. Both fluoroscopic-guided and ultrasound-guided injections have similar outcomes, although ultrasound is less accurate in obese patients.

Direct intra-articular anesthetic injection into the capsule (even 1 to 2 ml) is capable of rupturing the capsule and leaking the anesthesia into adjacent structures. The medial nerve branch involves one injection of local anesthetic at the medial branch divisions of the dorsal rami at the level of the facet joint and one above. A successful diagnosis is achieved with greater than 80 percent pain relief on injection.

Owing to the other innervations by the medial branch, the test is susceptible to 25 to 40 percent of false positives. Therefore, a double diagnostic block may be practiced for astute diagnosis, subject to the patient’s willingness.

How to Treat Lumbar Facet Arthropathy?

1. Conservative Treatment:

A conservative management approach can be considered even in the absence of a confirmatory diagnostic block. Physical therapy includes postural education, stretching, and exercises tailored to strengthen the core musculature are useful in a preliminary conservative approach. Pharmacotherapeutic approaches involved nonsteroidal anti-inflammatory drugs (NSAIDs) and Acetaminophen as the first line of treatment. Adjuvant medications in the form of antidepressants and muscle relaxants have demonstrated effectiveness.

2. Invasive Treatment:

In case of failed conservative management, more invasive treatments can be considered. Intra-articular steroid injections have shown evidentiary support in their favor. Other treatment approaches include radiofrequency neurotomy through continuous, high-temperature medial branch radiofrequency ablation. Due to axonal regeneration, recurrence may be expected within six months to one year. Other treatment options are pulsed radiofrequency ablation (use of radiofrequency for pain management), cryo-denervation (use of extreme cold temperature to destroy nerves that transmit pain), and phenol neurolysis (use of chemical agents to interfere with nerve conduction) but with limited success.

3. Surgical Intervention:

Facet-mediated pain rarely indicates surgical intervention, except in cases of traumatic dislocation. Due to facet arthropathy, osteophytes or large synovial cysts may impinge upon surrounding structures which may lead to stenosis, nerve root impingement, and radiculopathy, which may further warrant lumbar facetectomy, often in conjunction with laminectomy (space creation by removing bone spurs). In the case of lumbar fusion, complete facetectomy may be considered.

What Is the Prognosis of Lumbar Facet Arthropathy?

Facet arthropathy progresses with age. Conservative treatment with physical therapy is the first line of management, failure of which warrants diagnostic block and intensive therapy. Positively successful radiofrequency neurotomy has shown efficacy for 6 to 12 months, after which the procedure must be repeated. Owing to its nature of relapse, all outlooks of facet arthropathy exhibit a poor prognosis.

What Is the Differential Diagnosis of Lumbar Facet Arthropathy?

• Lumbar herniated disc (part of the lumbar disc bulge into the spinal canal).

• Discogenic pain syndrome (pain originating from a damaged vertebral disc).

• Lumbosacral radiculopathy (compression of nerve roots in the lower back).

• Piriformis syndrome (compression of the sciatic nerve by the piriformis muscle).

• Ligament strain (ligament stretch or tear).

• Lumbar spondylosis (degeneration of the lumbar vertebrae).

• Spondylolysis (fracture in the spine).

• Spondylolisthesis (slip disc).

• Rheumatoid arthritis (autoimmune inflammatory joint disorder).

• Seronegative spondyloarthritis (joint disorder with no detectable antibodies in the serum).

• Gout (arthritis due to uric acid accumulation).

• Pseudogout (arthritis due to calcium pyrophosphate deposition).

• Diffuse idiopathic skeletal hyperostosis (DISH-hardening of spinal ligaments at the site of attachment).

• Sacroiliac joint dysfunction (inflammation of the sacroiliac joint).

• Thoracolumbar fascia dysfunction (injury to the thoracolumbar fascia).

• Infection.

• Neoplasm (cancers).

• Fibromyalgia (widespread musculoskeletal pain).

What Are the Complications of Lumbar Facet Arthropathy?

• Metabolic side effects (affecting the metabolism).

• Endocrine side effects (affecting the hormonal balance).

• Elevated glucose levels (affecting the blood sugar levels).

• Suppression of the hypothalamic-pituitary-adrenal pathway (affects stress and other body processes).

• Septic arthritis (arthritis due to acquired infection).

• Epidural abscess (infection within the brain or spinal cord).

• Meningitis (inflammation of the neuron covering-meninges).

• Dural puncture (puncture of the dura during spinal anesthesia).

• Spinal anesthesia.

• Neuritis (inflammation of the optic nerve).

• Transient numbness (temporary lack of sensation).

• Dysesthesias (skin problems).

Conclusion

Chronic back pain is one of the leading causes of disability worldwide. Modifiable risk factors for facet arthropathy are best achieved by an interprofessional approach. Physical therapy, along with weight loss, exercise, nutrition, and bariatric surgery, may improve and dissuade the progression of symptoms. A psychological evaluation must be warranted for patients with a high association with back pain. AN interdepartmental approach is essential to improve the quality of life of patients.