Intervertebral disc

Back problems are a widespread disease that everyone will probably get to know in the course of their lives. Often, however, it is not the bony components of the spine that cause problems, but the Band washers, also called disci intervertebrales.

What are the intervertebral discs?

A simplified definition of the Band washers could be that they are water pillows that act as natural shock absorbers to absorb the vibrations when walking. The intervertebral discs are thus fiber-cartilaginous, flexible connections between the individual vertebral elements.

The human spine contains 23 intervertebral discs. They lie between the vertebral bodies and contribute to mobility and resilience. The intervertebral discs take up about 25% of the total length of the spine.

Anatomy & structure

A basic understanding of the anatomy and structure of the Band washers is important to explain their usefulness. They contain two different types of tissue: In the middle there is a gelatinous core made of cell-poor tissue, the so-called nucleus pulposus, which is surrounded on the outside by a fibrous ring, the annulus fibrosus.

The annulus fibrosus consists of fibrous cartilage, i.e. H. a tight collagenous connective tissue with embedded cartilage cells. The collagen fibers are arranged in concentrically running lamellae and result in a cross-over, opposing pattern, which is used for optimal power transmission.

The outer lamellae radiate into the marginal ridges of the vertebral bodies, the inner ones are connected to the cartilage-covered cover plates of the vertebrae. Towards the middle, the fiber cartilage merges into the gelatinous substance of the nucleus pulposus. This consists largely of glycosaminoglycans and has a high water-binding capacity. It develops a swelling pressure to the outside, as a result of which the fiber ring tightens.

Under the weight of the upper body while standing and sitting, water is pressed out of the gelatinous core during the day, and the height of the intervertebral discs decreases. As a result, the height in the evening can be up to 2.5 cm less than in the morning. When lying down, the gelatinous core absorbs water again. This inflow and outflow of fluid simultaneously nourishes the intervertebral disc, which contains very few blood vessels.

Functions & tasks

Function and tasks of Band washers can be best illustrated if you look at the pressure conditions in the spine.

It bears the weight of the upper body, i.e. H. the intervertebral discs are exposed to vertical pressure, which they distribute evenly on the cover plates of the adjacent vertebral bodies. During the bumps that occur when walking, the water-rich gelatinous core cannot be compressed, so it expands laterally in the direction of the fiber ring and puts it under tension.

However, fiber cartilage is not a very elastic tissue, so that the effect of this "shock absorber" is minimal. In addition to cushioning impacts, the intervertebral discs have the task of limiting the movements of neighboring vertebrae. They provide stability in the spine by restricting rotational movements and forward, backward or sideways tilting movements between the vertebrae.

Diseases

Many diseases and ailments related to the Band washers occur due to non-physiological stress. However, genetic causes or signs of wear and tear can also impair the function of the intervertebral discs in the course of life.

In the cell-poor gelatinous nucleus, the very low metabolic rate causes molecular changes that reduce the water-binding capacity as early as the third decade of life. The swelling pressure in the core is reduced, the fiber ring is no longer tense. As a result, the intervertebral disc is less able to cushion vibrations and limit sliding movements between the vertebrae. In addition, it remains permanently flat, which puts excessive strain on the vertebral arch joints.

This can result in spondylarthrosis, i.e. H. the joint cartilage is abraded and new bone tissue proliferates. A herniated disc (disc prolapse) is also a well-known symptom. Abnormal loads cause cracks in the fibrous ring and parts of the gelatinous nucleus emerge. This tissue often penetrates the vertebral canal and presses the spinal nerve running there against the vertebral arch joint.

In addition to pain, this can also result in sensory or motor deficits. The transition between the cervical and thoracic spine and between the lumbar spine and sacrum are particularly vulnerable. There the spinal nerves that innervate the leg via the sciatic nerve are stimulated. The back muscles often cramp in order to widen the narrowed spinal canal or to immobilize the affected movement segment, which leads to painful "lumbago".

Typical & common diseases

• disc prolapse
• Intervertebral disc degeneration
• Scheuermann's disease (Scheuermann's disease)
• Hollow back (hyperlordosis)
• Failed back surgery syndrome (post-disectomy syndrome)