Facet arthrosis

The articular facets of the spine are the ones that articulate the posterior part of the vertebrae. The latter are connected inferiorly through the intervertebral disc, vertebral body, and facet joints of the posterior laminae.

The latter have degrees of mobility and harmoniously allow forward lumbar flexion, backward extension and lateralization. They also prevent excessive rotation of the vertebrae.

Each facet joint is contained within a capsule and reinforced by ligaments. When we lean backwards or sideways, the facet joint closes and compresses. If, on the contrary, we lean forward, the joints open and the ligaments are stretched.

The facet joints of the spine provide resistance by preventing rotation or anterior displacement of the vertebrae. It also has a supporting role with 10% of the axial load (weight supported by the spinal column), although the main volume (80%) is supported by the vertebral bodies and the intervertebral disc.

The progressive degenerative process of the spine is physiological. It usually begins in the second decade of life in the intervertebral disc, producing protrusions and herniations that cause a decrease in the intervertebral disc. This situation causes an increase in pressure on the facet joints that results in greater wear of their cartilage. Synovitis occurs in the joint and irritation of the capsule, causing facet pain.

Deterioration of the facet joint cartilage causes joint laxity and subluxation. This hypermobility causes osteophytes and joint sclerosis, producing facet hypertrophy. This instability exceeds physiological limits and pain appears.

Forced flexion and hyperextension postures, especially those related to weight manipulation, increase the load on the facet joints and can accelerate lumbar facet osteoarthritis.

Lumbar facet syndrome can be the origin of facet arthrosis, inflammation and back pain.

To understand the process of arthrosis in the facets of the spine, it is important to refer to the minor nerve branches that  are integrated into the different spinal nerves of each vertebral segment:

• Posterior branch: Innervates the facet joints, spinous ligaments, ligamentum flavum, lumbar muscles, and skin. 
• Sinuvertebral nerve of Luschka: supplies the most posterior and lateral area of the annulus fibrosus. 

The transmission of pain collected through the posterior branch can be perceived as local pain (low back pain) and/or referred pain. The inflammation or wear of the articular facets activates the nerves that transmit the stimuli to the joint and can trigger said discomfort. The action on the posterior ramus should block the conduction of pain information from the facet joint.

The main symptom of facet arthrosis is chronic low back pain. In most cases it is a deep, constant and difficult to locate ailment on the lumbar region. This pain can also affect the buttocks, inguinal region, hips or non-specifically, the lower extremities.

The patient's discomfort increases when walking or sitting for a long time with prolonged standing and/or sitting. Sometimes you have the feeling of "not being able to find a posture without pain" and, on a recurring basis, episodes of discomfort are exacerbated, with a decrease in lumbar mobility that especially affects lumbar extension and rotation.

Facet osteoarthritis can cause spinal canal stenosis due to deformation of the joint and hypertrophy of the facets. If the stenosis compresses a nerve structure or the spinal cord, the pain radiates down the legs with paresthesias, loss of strength, and limitation. In these cases, it is necessary to stop the march to experience relief.

The diagnosis of chronic low back pain of facet origin is fundamentally based on clinical examination, imaging studies and the response to facet block.

The characteristics of pain of facet origin are also common to other causes of low back pain, which is why it is difficult to associate these symptoms with facet arthrosis. The imaging studies used (X-rays, CT, MRI or scintigraphy) are capable of detecting facet and/or disc degenerative changes, but the accuracy of the diagnostic tests to identify the facets as the origin of chronic low back pain is limited diagnostic validity.

The facet or posterior ramus block with local anesthetic in a fluoroscopically guided injection does not offer a definitive diagnosis. In the case of positive response with this technique, the pain ceases or is reduced by at least 50%.

• Oblique radiograph showing the facet joint (scottydog). 
• Sagittal CT scan showing the normal posterior facet joints. 
• Axial CT scan showing normal posterior facet joints without degeneration.

Treatment of facet arthrosis should begin with analgesics or anti-inflammatories, and muscle relaxants may be added.

Physical rehabilitation as a symptomatic treatment must be accompanied by re-education of the back through exercise, lowering body weight, and correcting bad postural habits.

Facet infiltration with anesthetic and corticosteroid may have a calming effect with prolonged symptom relief and predict success with radiofrequency or rhizolysis surgical technique.

Percutaneous lumbar facet joint denervation by radiofrequency or rhizolysis is a minimally invasive technique for the symptomatic treatment of chronic low back pain of facet joint origin. This type of spinal microsurgery consists of damaging the nerve fibers that transmit stimuli to the pain-transmitting facet joints (posterior branch) in a controlled manner by means of punctiform heat. Being a spine surgery, the traumatologist specializing  in the spine is in charge of performing this operation.

Characteristics and advantages of Facet Rhizotom:

• The procedure must be performed in the operating room and with fluoroscopy to verify the correct placement of the electrodes in the vicinity of the posterior ramus at its exit, between the facet and the transverse process. 
• It can be performed at all lumbar levels with unilateral or bilateral facet arthrosis. 
• It is performed percutaneously without openings in the skin and the patient is discharged without hospitalization. 
• The patient is required to be awake to assist in the identification of pain. 
• The electrodes transmit the heat generated by radiofrequency and cause a lesion in the posterior branch that causes the cessation of the transmission of pain originating in its innervation territory. 
• Analgesic efficacy may decrease over the months, but the level of pain prior to rhizolysis is not usually reached. This technique is harmless, so it can be carried out on more occasions if the improvement was significant. 

Our spine specialists are traumatologists who are pioneers in minimally invasive spinal microsurgery operations in Madrid.