A cartilaginous structure located between each vertebra of the spinal column in the lumbar, thoracic, and cervical regions is called Intervertebral disc me
The fibers that make up the intervertebral discs pass obliquely between the vertebral bodies, acting as connecting ligaments while allowing movement of the spine, albeit to a limited extent. It also cushions intervertebral pressure.
In the human body there are a total of 23 intervertebral discs . There is one between each pair of vertebrae, except at the junction between the atlas and the axis, the first two vertebrae of the spine whose articulation allows much larger movements of the neck than the movements of the rest of the spine.
intervertebral disc anatomy
The articular facets of the vertebral bodies and the intervertebral discs participate in the articulation between two vertebrae. Is a amphiarthrosis of type of cartilaginous joint (joint of very limited movement). Each disc consists of two main parts, the nucleus pulposus and the annulus fibrosus.
nucleus pulposus
The nucleus pulposus is located in the central part of the vertebral disc. Have gelatinous consistency and it is transparent. Its composition is 70 to 90% water with various substances in suspension, mainly collagen fibers and mucopolysaccharides . Fibrous compartment-forming septa enter from the periphery of the spinal disc. In the nucleus pulposus there is no innervation or blood supply and its main function is to absorb shock and give flexibility to the spine.
annulus fibrosus
Surrounding the nucleus pulposus is the so-called annulus fibrosus. It is made up of concentric helical layers of fiber. cartilage type I that intersect vertically and obliquely one above the other. They maintain the shape and protect the intervertebral disc and is attached to the vertebral body by the Sharpey’s fibers .
Size
Throughout the spinal column, the intervertebral discs vary in thickness. The thicker they are, the less movement they allow. . The discs between the cervical vertebrae have an average thickness of 3 mm and are the most mobile area of the entire spine. It is 5 mm thick in the dorsal region and 9 mm thick in the lumbar region, being the least flexible part of the spine (with the exception of the coccygeal region, which does not have intervertebral discs, and the sacral region, whose vertebrae lose their discs and fuse in the adult).
intervertebral disc function
The intervertebral disc functions to separate the vertebrae from each other and provides the surface for the cushioning gel of the nucleus pulposus. The nucleus pulposus of the disc functions to distribute hydraulic pressure in all directions within each intervertebral disc under compressive loads. The nucleus pulposus consists of large vacuolated notochord cells, small chondrocyte-like cells, collagen fibrils, and aggrecan, a proteoglycan that aggregates by binding to hyaluronan.
Attached to each aggrecan molecule are the chondroitin sulfate and glycosaminoglycan (GAG) chains of keratan sulfate. Increasing the amount of negatively charged aggrecan increases oncotic pressure, resulting in a shift of extracellular fluid from the outside to the inside of the nucleus pulposus.
Pathologies and medical considerations
There are numerous pathologies and medical problems related to the intervertebral discs, commonly known as discopathies . Among them, the most frequent are vertebral osteoarthritis, herniated discs, degenerative disc diseases and spinal canal stenosis.
disc herniation
A herniated disc is a disease characterized by displacement of the nucleus pulposus towards the nerve root of the spinal cord . This prolapse and deformation of the disc can put pressure on the nerve causing a variety of neuropathies, including severe pain, proprioceptive and sensory deficits, and paresis of varying degrees. Some cases of herniated discs can remain asymptomatic for a long time. The vast majority of disc herniations are located in the lumbar intervertebral discs L4-L5 and L5-S1. followed by cervical discs and, less frequently, thoracic disc herniations.
Disc herniations are mainly treated on two fronts: conservative methods and surgical methods. The most commonly used conservative methods are muscle augmentation, especially Selective Muscle Augmentation and passive treatments, such as massages, ultrasounds and various electrotherapy techniques . Conservative methods alone do not improve a herniated disc, but they do make the pain go away for most patients and improve their quality of life.
Surgical intervention is used only in cases that do not improve with conservative methods and whose symptoms progressively worsen. In any case, for the best long-term results, follow-up surgery is always done before and after selective muscle augmentation and other physical treatments.
spinal osteoarthritis
Spinal osteoarthritis is a disease caused by normal wear of the spinal discs overtime. From the age of 30 it is normal to observe the wear of the intervertebral discs in some area of the spine. Spinal canal stenosis occurs in advanced ages as a consequence of vertebral osteoarthritis. It is usually treated with analgesics by various routes, including infiltrations, and in some severe cases surgery may be used.
Degenerative disc diseases also occur as a consequence of age. As age advances, the intervertebral discs lose water and progressively dehydrate. This dehydration is usually asymptomatic, but in some cases the approach between two vertebrae can produce a spinal impact . Impacts manifest with severe pain, tingling in the extremities, weakness and/or difficulty moving.
