August 23, 2008

The First Step in Repairing Herniated Discs

In my previous post, we discussed my hypothesis that inactivity and compressive loading are the main culprits that lead to herniated discs.

Naturally, there may be other contributing factors such as age, smoking, poor diet, and external trauma that also play a role in the degenerative process, but I believe they are secondary causes at best.

In this post we’re going to continue the discussion by taking a close look at just how the disc is put together.

After all, in order to understand disc degeneration in general — and herniated discs in particular — we need to know a little bit about the object we’re dealing with. If we’re going to attempt to repair this problem, we first need to understand what it is we’re actually trying to fix.

Fortunately, for our purposes, we can keep things pretty simple and I promise to hold the medical speak to a minimum.

A Little Refresher Course

You’re probably already familiar with the anatomy of the spine but just in case things have gotten a little rusty here’s a quick rundown of the major players.

The Spine

The spine is made up of 24 segments of bone we call vertebrae. These bones are stacked one upon another like round blocks. Between each segment is an elastic membrane we call a disc. At the rear of the round blocks are two sets of joints known as facet joints.

The Facet Joints

The facet joints act as a hinge between the vertebrae above and below. It is this series of hinge points running the full length of the spine that allows us to bend in all directions.

The facet joints are of the ball and socket type and at the point where each ball is in contact with its socket is a layer of cartilage that acts as a bearing surface. These joints are enclosed in a membrane called a capsule, which is filled with a lubricating fluid called synovial fluid.

The Spinal Canal

A channel between the round blocks of the vertebrae and the facet joints contains what we commonly call the spinal cord.

In reality, the spinal cord only travels from the base of the skull down through the cervical and thoracic vertebra. Once it reaches the lumbar region, it branches into a multitude of nerve roots that resemble a horse’s tail.

The Ligaments

The entire structure of the spine is wrapped in a sheath of ligaments which run vertically, horizontally and crosswise totally enclosing the entire package like a suit of armor.

Our Old Friend the Disc

The intervertebral disc is basically made up of two parts and is often compared to a jelly donut. This donut-like structure is porous much like a sponge and (when healthy) is filled with fluid.

The center of this disc contains a jelly-like sack called the nucleus that — along with the fluid in the disc itself — acts like a hydraulic shock absorber.

The outer portion of the donut is called the annulus and is a series of concentric rings of fibrous connective tissue that surrounds the nucleus much like a ring of forts built one inside the other.

The top and bottom of the disc are capped with more of this fibrous connective tissue and these caps are called end plates. It should be noted that the end plates are strongly attached to the vertebrae above and below making it virtually impossible for the disc to slip.

Why Would a Disc Fail?

That’s a good question because in order for a disc to rupture, the nucleus has to break through all of those tough fibrous rings we just talked about. This soft squishy sack of jelly which has about as much penetrating power as well, a soft squishy sack of jelly, has to break through ring after ring of what should be some of the toughest ligament fibers in your entire body.

How is this possible?

In the next installment, we’ll answer that very question, so stay tuned. In the mean time, I’ll give you a little hint: it has to do with moisture. (Don’t you just love cliffhangers?)

Till then,
Dean

References:

1. Orthogate, Lumbar Disc Herniation (eOrthopod) Friday, 28 July 2006

2. Nelson, B. The Herniated Disc: New Concepts and Treatments. Physicians Neck & Back Clinics [2005]

3. McGill, S. Low Back Disorders, Evidence-Based Prevention and Rehabilitation, 2nd Edition. (p. 44-47) Human Kinetics (2007)

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