In order to understand what a disc protrusion of the lumbar spine (lumbar spine) is and why it causes which symptoms, one should briefly consider how the spine is structured. In our body, our spinal column forms the skeleton’s basic structure and consists of the cervical, thoracic and lumbar spine (lumbar spine). It also protects the spinal cord that lies within it.
It has essential functions for a stable stand and must withstand and distribute a large amount of force every day. Therefore it does not only consist of bony vertebrae but also has elastic intervertebral discs between the vertebrae. A total of 23 intervertebral discs ensure the mobility and elasticity of the spine, including the lumbar spine, and consist of an inner, gelatinous core (nucleus pulposus) surrounded by a stable fibrous ring (annulus fibrosus).
The spinal cord runs in the spinal canal directly behind the intervertebral discs and the vertebral bodies. Shortly after the beginning of the lumbar spine at the level of the lumbar vertebral bodies L1/L2, the spinal cord itself stops, but many large nerves still emerge from it and continue to run down the spinal canal (cauda equina). The disc protrusion of the lumbar spine now describes the condition in which one of the nuclei of a disc has bulged backwards and is pressing on parts of the spinal cord or central nerves. In contrast to a herniated disc, in which the outer fibrous ring of the disc is at least partially torn and the core has slipped relatively far back, in disc protrusion the fibrous ring is intact.
Causes of a disc protrusion
The reasons that lead to a disc protrusion of the lumbar spine are similar in many ways to those that also trigger a herniated disc in the lumbar spine. Most disc protrusions occur in the lumbar spine, which has its reasons. On the one hand, the lever forces and distribution of the load have the most unfavourable effect on the lumbar spine, especially when the load is incorrectly applied, for example when carrying heavy loads.
On the other hand, compared to other areas of the spine, the vertebral bodies are structurally more at risk of allowing disc protrusion in the lumbar spine area. Especially when the intervertebral discs are structurally already weakened, the risk is higher. The normal ability to bind water and thus keep the disc elastic decreases with increasing age.
In addition, the surrounding fibres become weaker and have to give way to the pressure of the core. The disc protrusion of the lumbar spine is almost always preceded by incorrect loading in the context of incorrect movements or excessive strain. The classic method is to carry a box of water from the back.
It is also possible to provoke a lumbar disc protrusion after a jump with an awkward landing. An unaccustomed, new strain, for example in the context of a new sport, can also trigger this. Besides the strain on the back, the training condition of the back muscles must also be considered.
If these are weakened or insufficiently trained, as is the case especially with taller people, even everyday movements such as getting up in the morning or leaving the shower can lead to disc protrusion in the lumbar spine. In addition, there are several other, but quite rare causes for a disc protrusion. These include congenital muscle weaknesses or structural defects of the spine.
Individual cases of disc protrusion are caused by an inflammation of the intervertebral discs. In the case of disc protrusion of the lumbar spine, the discs between the fourth and fifth vertebrae (L4/L5), but also between the fifth lumbar vertebra and the first vertebra of the sacrum (L5/S1) are particularly often affected. The lower lumbar region is also exposed to particular stress in everyday life, for example during sports, physical work and bending. Even before disc protrusions and prolapses occur, these vertebral regions are already particularly prone to pain.
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