What is a slipped disc?
A Disc Herniation, sometimes called a Slipped Disc, is an injury which occurs in the neck or back where part of the intervertebral disc bulges out and presses on a nerve in the spine. One of the most common symptoms of a disc herniation is a shooting type of pain going down into the arms or legs. This type of pain is typically referred to as radicular pain.
In addition to the typical shooting pain, it is also possible to experience localized pain around the spine pain from the disc itself, muscle spasms, as well as active myofascial trigger points in the muscles around the affected area. Muscle weakness, loss of sensation or even muscle atrophy as a result of prolonged nerve root compression can also occur.
Things that typically aggravate a disc herniation can include: bending or leaning forward, standing, walking or sitting for long periods and pain while sneezing, coughing or straining while on the toilet.
Usually, a clinical examination will reveal positive nerve root tension tests and imaging studies such as CT or MRI will show that part of the intervertebral disc (IVD) is bulging out and pressing on a nerve root. We’ll specifically be looking at the lumbar spine as an example, but disc herniations can occur throughout the spine.
What are the potential causes of a disc herniation?
Disc herniations can occur from some of the following:
- Chronic/prolonged overloading of the disc, usually from activities that involve heavy lifting.
- A previous injury to the lower back
- Bad posture, muscle imbalances and congenital defects in the spine structure.
- Age-related degeneration
The above causes are also dependent on certain risk factors such as:
- Weight (obesity in particular)
- Systemic conditions (e.g. rheumatoid arthritis)
- Lack of exercise and weak core muscles
- An increased curve in the lumbar spine/hyperlordosis from an Anterior pelvic tilt.
Let’s explore the anatomy of the spine to help better understand how and why a disc herniation occurs. This is where my amazing drawing skills come into play ?
Each vertebra in the spine has an anatomical cushion or shock absorber between each vertebral body, the IVD. The size of the IVD corresponds to the vertebra it sits in-between; They start off fairly small in size at the top of the cervical spine and increase in size moving down through the thoracic spine and to the lumbar spine as the weight of the trunk increases.
The IVD is made up of 2 structures:
1.Annulus Fibrosis – An outer layer of fibrocartilage rings
2.Nucleus pulposus – An inner gel-like centre
The 2 parts of the IVD allow for even weight distribution at each vertebral level. This, however, changes when there is damage or degeneration in the IVD occurs.
Disc degeneration and the stages of disc herniations
Degeneration… Scary word right? ? Well, the truth is that osteoarthritis is a very common occurrence from years of wear and tear on the cartilage and joints. In the spine, the IVD’s can become dehydrated and start to thin out, which reduces its shock absorbing ability. There are some predisposing factors that will obviously speed up the process such as those mentioned earlier, but in general, the nucleus of the intervertebral disc becomes dehydrated as a normal part of aging just like any other cartilaginous joint in the body.
Degeneration in the spine usually involves narrowing or flattening of the IVD’s and wearing down of the cartilage in the facet joints. Over time these joint surfaces become rough and bumpy with additional bone growths such as osteophyte formation will occur.
Stage 1: Degeneration
The fibrocartilage rings of the annulus are susceptible to tearing as a result of an injury or age-related degeneration. These tears can occur in two directions: circumferentially or radially.
Circumferential tears are believed to be more common and indicate a separation of the layers of concentric fibrocartilage of the annulus.
Radial tears usually start from the inner part of the annulus (near the nucleus) and progress outwards.
Once the tearing has occurred, nerve endings within the annulus the become extremely sensitive to inflammation and pressure, which will result in a lot more pain sensation compared to other/healthy discs in the spine. One unfortunate trait of the IVD is that only the outer 1/3 of the annulus is innervated by nerves (in a healthy disc). So a patient could possibly have tearing in the inner annulus and not experience any painful symptoms until it becomes quite advanced. The irony of this is that once a disc has become damaged, more nerve receptors, specifically ones that detect pain, develop deeper into the layers of the annulus.
Stage 2: Prolapse
The nucleus then starts squeezing through the space in the annulus until it eventually starts to bulge outwards:
Stage 3: Extrusion
If the bulge progresses, it will eventually herniate out of the disc and can then put pressure onto a spinal nerve root.
At this point we can consider that a patient may be experiencing pain from one source or a combination of different sources:
- From the direct pressure of the nucleus onto a nerve root causing the typical shooting pain down the leg, also known as Sciatica,
- Pain arising from the disc,
- Pain due to irritation of the nerve roots as a result of the inflammation response to the nucleus protruding into the vertebral canal.
Stage 4: Sequestration
The next stage of disc degeneration doesn’t always occur but it is still a possibility and that is Sequestration of the herniating nucleus. Here part of the herniating nucleus will break off and cause all sorts of trouble as it’s a loose body within the spinal column:
It is also possible that the disc bulge can be larger, occur on the opposite side or centrally compressing the spinal cord:
Why does bending forward hurt so much?
Certain movements will cause a lot of pain if a person has a disc herniation, specifically leaning or bending forward into a flexed position. This occurs because of the biomechanics involved in this type of movement. Usually, when you flex forward, the top vertebra slides forward on top of the vertebra below. This causes compression and wedging of the IVD in the front, which in turn causes the nucleus to be pushed backward. In a healthy disc, the nucleus stays within the confinements of the disc, but if the annulus is torn from injury or degeneration, it will bulge out and compress the spinal cord and/or nerves. This emphasizes the importance of squatting down and using your legs to lift heavy objects.
So, how do you treat this?
Well there are 2 main options:
- Conservative treatment
- Surgery – laminectomy or disc replacement.
Chiropractors will usually treat disc herniations conservatively using the following treatment techniques:
- Spinal decompression in the form of flexion distraction or lumbar traction,
- Adjusting the lumbar spine
- Soft tissue therapy such as dry needling, massage, and fascial release
- Recommending exercises and stretches to help strengthen the core musculature and help to correct any postural imbalances that the patient may have.
- Better ergonomics, especially if you’re sitting at a desk all day
Can the IVD heal on its own over time?
The IVD is similar to cartilage, being that is has a very limited blood supply and this slows down the healing process quite a lot. A healthy IVD won’t spontaneously herniate so there must be something that is putting that disc under a lot of pressure that makes it susceptible to injury. This is why finding the underlying cause is a very important part of the treatment instead of just treating the symptoms.