31 Jul 2020

The intervertebral discs. The scapegoat of many a spinal dysfunction. I have heard many a patient, athlete, and fellow health professional refer to the infamous ‘slipped disc’, which to me always seemed misleading as, well, you cannot slip a vertebral disc. The implication that a vertebral disc can easily be slipped out of place has led to the popular misconception that they are easily mobile and fragile structures that are susceptible to injuries. This is simply not true. It is frustrating that an accurate idea of the anatomy, function and how these structures elicit pain is seemingly not yet entirely clear, or at least is not portrayed to patients. What is equally frustrating is the continued use of the term ‘slipped disc’ by health professionals who should know better, as this only adds to the problem and helps cement the inaccurate and wildly believed perception of intervertebral disks among the general public. Hopefully, I can quickly clear a few things up.

So, firstly, let us talk anatomy. The spinal column is typically divided into four main regions: The Cervical (Neck), the Thoracic (Upper Back), the Lumbar (Lower Back) and the Sacral (Sacrum) regions of the spine. Each region is made up of various joined segments known singularly as vertebra and plurally as vertebrae. Intervertebral discs, as suggested by their name, lie between each vertebra. Every vertebra in the spine (except for C1 and C2) has an intervertebral disc. Each disc is made up of an outer fibrous ring called the Anulus Fibrosis and an inner gel like centre called the Nucleus Pulposus. The annulus fibrosus consists of fibrocartilaginous layers, or laminae, made of both type I and type II collagen. The type I is concentrated towards the edge of the ring, providing it with greater strength. The Nucleus Pulposus is made up of loose fibres suspended in a mucoprotein gel. Together the Annulus Fibrosis and the Nucleus Pulposus form a fibrocartilaginous joint, known as a symphysis. Symphysis fusions are extremely strong and robust joints that can withstand enormous amounts of force.

Ok, so what do they do? The intervertebral discs separate the vertebrae, act as ligaments holding the vertebrae together and act as shock absorbers for the spine. How do they achieve this? Well, as discussed in the previous paragraph, the Nucleus Pulposus is made up of a mucoprotein gel. This allows for even distribution of pressure across the disc, preventing overly excessive forces on the vertebral endplates, while the endplates themselves hold the discs in place and provide an anchorage for the Annulus Fibrosis. Meanwhile, the stiff laminae allow for increased ability to withstand compressive forces. Combining all of this makes it PRACTICALLY IMPOSSIBLE for the disc to just “slip” out of place like a bar of soap! This does not mean however, that it is impossible to injure a disc!

So, intervertebral discs do get injured? Of course. If they do will they heal? 100%. Ok, but why is it called a ‘slipped’ disk if you cannot slip a disk? For that I have no answer, the bottom line is, it shouldn’t. Well what should it be called? When medical professionals refer to a slipped disk, they are likely referring to a HERNIATED disk. This is not a herniation of the entire disk, but of just a small section. Herniations can happen when unbalanced mechanical pressures substantially deform the Annulus Fibrosus, causing part of the Nucleus Pulposus to obtrude either laterally or posteriorly. This reduces local muscle groups’ ability to function properly, putting pressure on nearby nerves. So, the disc does not ‘slip’, it BULGES.

Such injuries can occur due to trauma through physical activity, mainly caused by shearing forces, or chronic deterioration typically accompanied with poor posture and can elicit symptoms typical of nerve root entrapment. Such symptoms include: Paraesthesia, numbness, acute or chronic pain, decreased muscle tone and decreased functional performance. These symptoms can occur either locally or anywhere along the dermatome served by the entrapped nerve. Therefore, we sometimes feel the referral of symptoms in other areas of the body such as our legs.

Well then, there we have it. A summary of why you do not, nor ever will, have a ‘slipped’ disk. For any members of the public reading this, I hope I have helped you understand intervertebral discs a little better. For any fellow health professionals, I implore you, please, ban the term ‘slipped disc’ from your vocabulary. Continuing the use of inaccurate terms when describing pathologies only furthers misinformation. As we know, the language we use is proven to have lasting effects on patients. Therefore, it is our duty to paint accurate pictures of these lesions to our patients, who are less enlightened on the inner workings of the human body. 

If you are suffering from a herniated disc, any other spinal problems or non specific lower back pain, then come and visit the MY Sports Injury Clinic in Manchester. We have many health professionals including Sports Injury Specialists, Strength and Conditioning Coaches and Massage Therapists to help answer your questions and provide specialist treatment to improve way of life!

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