Disc Herniation Types

How a Disc Nucleus Migrates

Herniated Disc-Prolapse
Herniated Disc. Adam

A healthy interaction between your discs and the nearby spinal nerve root is key for keeping back pain away. But when a part (or parts) of a damaged disc herniates, it may press on a nerve.  Symptoms of a herniated disc include pain, tingling, numbness, weakness and/or electrical feelings that go down one leg.

Related: Nerve Pain

While it's true that pain is pain, according to David J. Magee in his book Orthopedic Physical Assessment, there are 4 types of herniated disc.

All 4 types may cause these symptoms, he says.

Disc anatomy is such that a soft, jelly like substance located in the center is contained by tough fibers located on the outside. This outer covering is called the annulus fibrosis. Over time, the annulus can wear down and/or tear, leaving the nucleus and the spinal nerve root vulnerable to an injury (i.e. an unhealthy interaction between the two takes place, which generally causes pain and/or nerve symptoms.)

Related:  Nucleus Pulposus

With each type of disc disruption listed below, the central nucleus is in a different stage of migration towards the outside of annulus.

Related:  Annulus Fibrosis

Disc Protrusion

A disc protrusion occurs when the disc nucleus bulges but does not rupture. The nucleus remains contained within the disc structure.

Disc Prolapse

When a disc prolapse occurs, the nucleus is still contained within the annulus but only by the outermost fibers.

(The annulus is made up of several layers of fibers oriented on the diagonal. Each layer lies at an approximately 90 degree angle to the layer above - or below; this design provides scaffolding and support to the whole structure.)

Disc Extrusion

With disc extrusion, the soft material comprising the nucleus escapes from the disc structure to the nearby epidural space.

This is possible due to tears in the annular fibers that leave an opening from which the soft material can flow.

Sequestered Disc

In the case of a sequestred disc, fragments from both the annulus and the nucleus make it outside the disc proper. The most common problem resulting from a sequestered disc is an irritated spinal nerve root. Other problems that arise from sequestered discs include myelopathy and/or cauda equina syndrome. According to Magee, the degree of pressure placed on nerve structures by the freed fragments is what determines the severity of symptoms.

By the way, it is not always the disc injury alone that creates the pressure on nerve structures; it can be a combination of the injury with the resultant inflammation.

Body Positioning and Your Disc Health

Your body position may determine how much pressure is put on your discs. This is called intradiscal pressure. Generally speaking, the L5-S1 (last lumbar vertebra and top of the sacrum bone interconnection) gets the most pressure.

This is because much of the weight of you body is transfered through this area.

A 1970 Swedish study done by Nachemson and Elfstrom measured intradiscal pressure in in the lumbar spine (low back) from various positions. The study started with the premise that when a disc is healthy, pressure tends to be distributed evenly across the entire surface. The researchers then undertook to measure and compare pressure differences between standing (which then served as the comparison value) and a variety of movements, maneuvers and positions.

They found that walking resulted in less stress than side bending and/or twisting, and side bending and twisting resulted in less stress than jumping, coughing and laughing.

But the biggest culprit they identified was bending forward, which resulted in very high degrees of intradiscal pressure. The researchers commented that this finding supports what they called "ergonomic advice," i.e. the oft-repeated "bend with your knees and not with your back when you lift something heavy or bulky."

The only type of maneuver that the researchers found resulting in less pressure than standing was lying down. They found that being in a supine position (lying on your back) resulted in 50% less intradiscal pressure than the reference value of standing.

Sources

Magee, David, J. Orthopedic Physical Assessment. 4th Edition. Saunders Elsevier. St. Louis, MO. 2006.

Fishman, L. and Ardman, C., Back Pain: How to Relieve Back Pain and Sciatica. W. W. Norton and Company, New York, London. 1997

Nachemson, A. and Elfstrom, G. Intravital Dynamic Pressure Measurements in Discs. Almqvist & Wiksell. 1970. Stockholm. Accessed Jan 2015. http://www.energycenter.com/grav_f/studies_nachemson.pdf

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