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Lumbar discs - introduction

The lumbar intervertebral discs (IVDs) are large structures which separate the lumbar vertebrae.

They are named with reference to the vertebra above and below.

The disc between the first and second lumbar vertebrae is known as the L1/L2 disc (ell one ell two disc), and this is the typical way you may have heard your own problems described.

Lumbar levels

The commonest levels to be affected in back pain syndromes are the L4/L5 and the L5/S1 (ell five ess one) levels, so you are likely to have this said by orthopaedic types. Oh yes, each disc is also referred to as a “level” (the L4/L5 level..), a way of finding our way round someone’s back so that others can understand what we mean.

Lumbar segments

And another thing before we zoom off into the insides of disc. Us orthopaedic types often refer to a “segment” when we talk about the lumbar levels. A segment includes the disc and the vertebra above and below. It acts as a unit in the lumbar spine, bending, arching and rotating as appropriate to the person’s activities.

Segmental failure

When a disc suffers from injury, heavy work and age, it may function less well and the resulting problems are often referred to as “segmental failure”, although scientific backing for the usefulness of this description is lacking.

What are discs for?

The main function of the IVDs is to transfer weight evenly from one vertebra to another, allowing small amounts of movement between them. People often think of them as shock absorbers, but apparently they are too stiff to be really good at that.

The discs separate the lumbar vertebrae enough so that the spine can do bending movements, and the discs need to be flexible to allow these changes. However, they also need to be strong and resistant to the loads which will be put on them.

Let’s go on now to look at disc structure as this is essential to understand what goes on in the spine and how pain, in some cases, is generated.


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