- Slipped discs
- This is a term that is still often used. It probably derives from the fact that the intervertebral disc is comprised of 2 parts:
- An outer strong fibrous casing called the annulus fibrosis
- An inner gel like substance called the nucleus pulposus
- Under extreme loading the outer casing can break down allowing the gel like nucleus to protrude – and this is the slip
As we age – from our late 20’s on, the inner gel like substance begins to dehydrate (dry up). This causes the outer part to flatten a little and bulge at it edges. The disc becomes stiffer and shorter. It is quite common for the outer annulus to develop cracks as we age. Disc damage can vary and may have different causes, eg injuries, repetitive loading
Terms that are commonly used for disc injuries include:
- Disc bulge – this is when the disc bulges outwards but is intact – this is often seen in the aging disc and is normal.
- Disc protusion – this is when some of the outer fibres are damaged – there may be inflammation and or pressure of the annulus against the weakened area.
- Disc extrusion – this is an extended bulge.
- Disc sequestration – a fragment of disc breaks off.
- It’s normal for the spine to degenerate as we age.
- Degeneration is simply wear and tear and in the spine affects the discs that dehydrate and stiffen. The joints may lose their smooth surface (articular cartilage) and roughen up, bony spurs may grow at the edges of the joints and the ligaments around the joints and within the spinal canal may also thicken up.
- If there has been a previous injury when younger that area will tend to degenerate more quickly.
Depending on what structure of the spine including the nerves has been affected a person may experience a variety of pain syndromes.
- Local pain is when pain arises directly from the irritation of local tissues in the spine and is felt in that specific area.
- Referred pain is a little more complicated and is due to a phenomenon termed convergence which causes the brain to perceive pain from other areas than those directly affected. This means that pain from the lumbar spine can be felt in various parts f the lower limb.
- Radicular pain is a lot more severe than referred pain and is often described as lancinating, electric or pain that “shoots” down the limb in a narrow band. This type of pain is caused by direct inflammation of a nerve exiting from the spine.
MRI and CAT scans
- MRI scans give more information about soft tissues with water content and CAT scans are better at imaging bony and calcified areas
- Some studies have shown that as many as 60% of people without back symptoms have disc bulges and protrusions on MRI.
- This is not surprising as it can be regarded as part of the normal degenerative process.
- It can also mean that the clinical presentation of back pain may not correlate with what is found on imaging studies.
- Clinical findings can be more valid – ie what the patient reports and what the clinical examination reveals such as movement and neurological tests. However scans can confirm, identify and clarify clinical findings and assist in planning appropriate management.