How does a spine become unstable?

Displaced vertebra

So-called spinal instability due to a displaced vertebra is an automatic indication for surgery. Such instability may be caused on the one hand by a congenital reduction defect of a vertebral arch, which is preventing the facet joints of a vertebra from being properly aligned. This generally happens in the lower part of the spine, and may result in the displacement of a vertebra at a relatively young age.

Symptoms caused by ageing

In addition, spinal instability may be caused by degeneration due to ageing. In a way, these are symptoms of old age, which some people will experience at a younger age than others. Symptoms include increasing inelasticity of the intervertebral disc, enlarged joints between the vertebral arches (facet joints) and thickening of the bands (ligaments) between the vertebral arches. All these things cause narrowing of the spinal canal, as well as increased mobility between the vertebrae. As a result, vertebrae may be displaced vis-à-vis each other.

Degenerative Disc Disease (DDD)

What the discussion is really about, is the question as to whether such increased mobility without any vertebrae actually having been displaced must be considered spinal instability, and whether this is causing the symptoms. This situation is known among doctors as degenerative disc disease. Opinion is divided on the subject, but research is increasingly proving that degenerative disc disease is a separate disorder (1).

Scientists are increasingly convinced that backache may be caused by degeneration of the intervertebral disc, which may lead to ‘micro movements’ even though X-ray images show no clear signs of displacement. This minimally increased mobility results in both pain and ongoing degeneration, thus creating a vicious circle.

Causes of spinal instability

Failed Back Syndrome

Even after several hernia operations all tackling the same spot (in the event that the hernia relapses), the quality of the intervertebral disc will decrease, as will its ability to absorb shock. As a result, while a patient’s leg may be less sore after each follow-up operation, the quality and functioning of the intervertebral disc will increasingly deteriorate, and the patient will increasingly suffer deep backache.

*1. Ann Rheum Dis. 2013 Jul; Novel genetic variants associated with lumbar disc degeneration in northern Europeans: a meta-analysis of 4600 subjects.

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