The facet joints (or zygapophysial joints, zygapophyseal, apophyseal, or Z-joints) are a set of synovial, plane joints between the articular processes of two adjacent

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristi ...

e. There are two facet joints in each spinal motion segment and each facet joint is innervated by the recurrent meningeal nerves.

Innervation

Innervation to the facet joints vary between segments of the spinal, but they are generally innervated by medial branch nerves that come off the dorsal rami. It is thought that these nerves are for primary sensory input, though there is some evidence that they have some motor input local musculature. Within the cervical spine, most joints are innervated by the medial branch nerve (a branch of the

dorsal rami The dorsal ramus of spinal nerve (or posterior ramus of spinal nerve, or posterior primary division) is the posterior division of a spinal nerve. The dorsal ramus (Latin for branch, plural ''rami'' ) is the dorsal branch of a spinal nerve that form ...

) from the same levels. In other words, the facet joint between C4 and C5 vertebral segments is innervated by the C4 and C5 medial branch nerves. However, there are two exceptions: # The facet joint between C2 and C3 is innervated by the third occipital nerve and the C3 medial branch nerve. # The facet joint between C7 and T1 is innervated by the C7 and C8 medial branch nerves. In the thoracic and lumbar spine, the facet joints are innervated by the medial branch nerves from the vertebral segment above the upper segment and the upper segment. For example, the facet joint between T1 and T2 is innervated by C8 and T1 medial branch nerves. Facet joint between L1 and L2; the T12 and L1 medial branch nerves. However, the L5 and S1 facet joint is innervated by the L4 medial branch nerve and the L5 dorsal ramus. In this case, there is no L5 medial branch to innervate the facet joint.

Function

The biomechanical function of each pair of facet joints is to guide and limit movement of the spinal motion segment. In the

lumbar spine The lumbar vertebrae are, in human anatomy, the five vertebrae between the rib cage and the pelvis. They are the largest segments of the vertebral column and are characterized by the absence of the foramen transversarium within the transverse p ...

, for example, the facet joints function to protect the motion segment from anterior shear forces, excessive rotation and flexion. Facet joints appear to have little influence on the range of side bending (lateral flexion). These functions can be disrupted by degeneration,

dislocation In materials science, a dislocation or Taylor's dislocation is a linear crystallographic defect or irregularity within a crystal structure that contains an abrupt change in the arrangement of atoms. The movement of dislocations allow atoms to s ...

, fracture, injury,

instability In numerous fields of study, the component of instability within a system is generally characterized by some of the outputs or internal states growing without bounds. Not all systems that are not stable are unstable; systems can also be mar ...

from trauma,

osteoarthritis Osteoarthritis (OA) is a type of degenerative joint disease that results from breakdown of joint cartilage and underlying bone which affects 1 in 7 adults in the United States. It is believed to be the fourth leading cause of disability in the w ...

, and surgery. In the thoracic spine the facet joints function to restrain the amount of flexion and anterior translation of the corresponding vertebral segment and function to facilitate rotation. Cavitation of the synovial fluid within the facet joints is responsible for the popping sound (

crepitus Crepitus is "a grating sound or sensation produced by friction between bone and cartilage or the fractured parts of a bone". Various types of crepitus that can be heard in joint pathologies are: *Bone crepitus: This can be heard when two fragme ...

) associated with manual spinal manipulation, commonly referred to as "cracking the back." The facet joints, both superior and inferior, are aligned in a way to allow flexion and extension, and to limit rotation. This is especially true in the lumbar spine.

Facet joint arthritis

In large part due to the mechanical nature of their function, all joints undergo degenerative changes with the wear and tear of age. This is particularly true for joints in the spine, and the facet joint in particular. This is commonly known as '' facet joint arthritis'' or ''facet arthropathy''. As with any arthritis, the joint can become enlarged due to the degenerative process. Even small changes to the facet joint can narrow the

intervertebral foramen The intervertebral foramen (also called neural foramen, and often abbreviated as IV foramen or IVF) is a foramen between two spinal vertebrae. Cervical, thoracic, and lumbar vertebrae all have intervertebral foramina. The foramina, or openi ...

, possibly impinging on the spinal nerve roots within. More advanced cases can involve severe inflammatory responses in the Z-joint, not unlike a swollen arthritic knee.

Diagnosis

Facet joint arthritis does not always have any symptoms, but often manifests as a dull ache across the back. However like many deep organs of the body it can be experienced by the patient in a variety of referral pain patterns. The location of facet joints, deep in the back and covered with large tracts of paraspinal muscles, further complicate the diagnostic approach. Typically facet joint arthritis is diagnosed with specialized

physical examination In a physical examination, medical examination, or clinical examination, a medical practitioner examines a patient for any possible medical signs or symptoms of a medical condition. It generally consists of a series of questions about the pati ...

by specialist physicians. Stork test will be eligible to differentiate disorder either from facet joint or from isthmus (pars interarticularis). Bone scan with SPECT/CT hybrid imaging are easily to tell and make an exact diagnosis (Ref 9,10). Advanced imaging such as

MRI Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...

or CT may be necessary to rule out other conditions rather than making a diagnosis.

Treatment

Conservative treatment

Conservative treatment of facet joint arthritis involves physical therapy or

osteopathic medicine Osteopathy () is a type of alternative medicine that emphasizes physical manipulation of the body's muscle tissue and bones. Practitioners of osteopathy are referred to as osteopaths. Osteopathic manipulation is the core set of techniques in ...

, with muscle strengthening, correction of

posture Posture or posturing may refer to: Medicine * Human position ** Abnormal posturing, in neurotrauma ** Spinal posture ** List of human positions * Posturography Posturography is the technique used to quantify postural control in upright stance in ...

, and biomechanics being the key.

Corticosteroid injections

Corticosteroid injections into the joint space may provide temporary pain relief anywhere from days to several months. With repeated injections, sometimes the patient may experience a more permanent improvement in their symptoms. Steroid injections are typically performed under image guidance to ensure accuracy given the complex shape and deep location of the facet. Some patients do not benefit from corticosteriod injections.

Ablation

Radiofrequency ablation Radiofrequency ablation (RFA), also called fulguration, is a medical procedure in which part of the electrical conduction system of the heart, tumor or other dysfunctional tissue is ablated using the heat generated from medium frequency alternati ...

or lesioning, also known as rhizolysis, can be used to give longer lasting relief by destroying the nerves that supply the facet joint ( medial branch nerves).

Surgery

Surgery, in the form of a

facetectomy Facetectomy is a surgical procedure which involves decompression of a spinal nerve root. For example, it can be performed in severely resistant cases of cervical rhizalgia, where the cervical nerve roots within the intervertebral foramina ...

, can be performed in certain cases, particularly when the nerve root is affected.

Etymology

Ancient Greek: ' ("yoke") + ' ("out/from") + ' ("grow")

References

9. Shin-Tsu Chang, Chuan-Ching Liu, Wan-Hua Yang. Single-photon emission computed tomography/computed tomography (hybrid imaging) in the diagnosis of unilateral facet joint arthritis after internal fixation for atlas fracture. HSOA Journal of Medicine: Study & Research 2019; 2: 010. 10. Zhu Wei Lim, Shih-Chuan Tsai, Yi-Ching Lin, Yuan-Yang Cheng, Shin-Tsu Chang. A worthwhile measurement of early vigilance and therapeutic monitor in axial spondyloarthritis: a literature review of quantitative sacroiliac scintigraphy. European Medical Journal (EMJ) Rheumatology 2021 July 15; 8 129-139.

External links

Diagram at spineuniverse.com

Emedicine article on Lumbosacral Facet Syndrome
{{Authority control Bones of the vertebral column Joints Joints of the head and neck