The vertebral endplates are the thin cartilaginous interfaces between the discs and the vertebrae above and below. The VEPs are dotted with fine pores that blood vessels in the rich capillary bed in the vertebral bodies butt up to, in order to harvest nutrients to be carried into the heart of the disc. The pores are more densely concentrated in the centre of the disc, over the nucleus, making the endplate weaker here. This means that fractures of the vertebral endplate are most common over the central zone of the vertebral body.
Schmorls nodes are extremely common in everybody's X-rays
The vertebral endplates are the weakest component part of the spine. They can easily suffer minute fracture with traumatic forces transmitted up through the spine. This can be done in any number of ways by traumatic forces within physiological range, such as sitting down hard on the bottom, or even pulling at something, such as a pulling a rope in a tug'o war, or a stubborn root in the garden. Young men in the Forces have more than their fair share of VEP fractures: pilot ejection seats and military exercises that involve jumping off ladder ropes with heavy backpacks can cause this sort of trouble.
An innocuous spinal compression mishap may sometimes start the steady decline of the disc, ending in prolapse of segmental instability
At the time of the incident, patients often say they heard a small popping sound, ping or crack from their back. Although it doesn't cause undue pain and alarm at the time, people often relate their back was 'never quite the same afterwards'. In the aftermath of VEP fracture the vertebra develops typical scoop-shaped indentations in the surface of the vertebral body called Schmorl's nodes. These can be seen on the scans and any radiologist will tell you these phenomena are extremely common, giving some indication to how often we pop a vent in the VEP with never knowing it.
Because they disturb nutrient pathways, fractures of this kind can however, fastrack the breakdown of the intervertebral disc. As a legacy of the healing process, the small pores in the cartilage of the endplate are occluded. At the same time, the bone immediately behind the endplate can become tougher and harder (sclerotic) and this too impedes the nutrient traffic in and out of the disc. The impairment in nutrient exchange can tip the borderline metabolic balance of the disc and speed disc breakdown. Once again, it is not the fracture of the vertebral endplate in-and-of-itself that causes the mischief, but the aftermath effects in the ensuing years.
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