What is a “Slipped Disk”?
A “slipped disk” as it is commonly known, is correctly named as a “herniated disc” in the medical world. Before explaining this condition, it is best to firstly explain the anatomy of a disc.
What we are referring to here is a disc in between each of the vertebrae of the spine. These are called intervertebral discs and there are 23 of them in total, which act like shock absorbers to cushion and protect the spine. Six are in the cervical region (neck), twelve in the thoracic region (middle back) and 5 in the lumbar region (lower back).
The discs are made of a hard outer casing (annulus fibrosis) and a gel like inner structure (nucleus pulposus). The latter accounts for much of the spines’ strength and is 66% to 86% water and the remainder is made up of collagen.
A good analogy of a slipped disk is to think of a tube of toothpaste with the outer casing being your annulus fibrosis and the toothpaste inside being your nucleus pulposus. If you squeeze the toothpaste tube hard enough the toothpaste gel will come out of the top of the tube.
This is what happens when the pressure in the spine becomes more than discs can tolerate causing the inner gel to push through the outer casing. Sometimes this can press or touch an adjacent nerve root causing referred pain or either pins and needles, numbness and tingling. This is known as a slipped disk with nerve compression or radiculopathy.
The outer third of the casing is innervated by nerves but the rest is not. Therefore, it is not unusual for patients to not experience any symptoms at all unless there is a nerve that has been compressed. However, in some patients even without nerve compression they can experience symptoms. The most common discs to herniate are right at the bottom of the lower back at L4-5 or L5-S1 but they can occur anywhere in the spine.
You can see here then that nothing in the spine slips. There is a different condition called Spondylolisthesis which results in the vertebrae slipping off one another but essentially discs do not slip so the term “slipped disk” can be rather misleading and in my experience leads to more anxiety than is necessary.
It is most common in the younger population of whom are sporty, lift heavy weights, have a laborious job but it can occur in the older population also.
What does a slipped disk feel like?
This can differ depending on whether the disc is touching the nerve or not as previously mentioned. If it is and the lower two nerves in the lower back are being compressed you may get referred neurological pain (and/or pins and needles, numbness and tingling) in either or sometimes in both legs.
This could be in the buttock, groin, side of the legs, back of the legs, the calves and feet or a combination or could shoot down all of these structures. Sometimes you can experience weakness or sensory changes in these areas and a condition called “foot drop” where the foot points downwards causing the patient to trip up. Luckily the latter is rare, in my experience.
If you believe to have a slipped disk please do not panic. Many cases can be managed long term with conservative treatment and sensible lifestyle advice such as reducing the amount of load going through the spine. Exercise rehabilitation can also help and can be managed without surgery. However, in more severe cases surgery may be required but non-invasive treatment should be recommended to be attempted beforehand.