The intervertebral discs make up one fourth of the spinal column’s length. There are no discs between the Atlas (C1), Axis (C2), and Coccyx. Discs are not vascular and therefore depend on the end plates to diffuse needed nutrients. The cartilaginous layers of the end plates anchor the discs in place.
The intervertebral discs are fibrocartilaginous cushions serving as the spine’s shock absorbing system, which protect the vertebrae, brain, and other structures (i.e. nerves). The discs allow some vertebral motion: extension and flexion. Individual disc movement is very limited – however considerable motion is possible when several discs combine forces.
Annulus Fibrosus and Nucleus Pulposus Intervertebral discs are composed of an annulus fibrosus and a nucleus pulposus.
The annulus fibrosus is a strong radial tire–like structure made up of lamellae; concentric sheets of collagen fibers connected to the vertebral end plates. The sheets are orientated at various angles. The annulus fibrosus encloses the nucleus pulposus.
Although both the annulus fibrosus and nucleus pulposus are composed of water, collagen, and proteoglycans (PGs), the amount of fluid (water and PGs) is greatest in the nucleus pulposus. PG molecules are important because they attract and retain water. The nucleus pulposus contains a hydrated gel–like matter that resists compression. The amount of water in the nucleus varies throughout the day depending on activity.
Slipped Disc or Disc Prolapse
The inter-vertebral discs are protective cushion-like shock-absorbing pads between the two bones of the spine called vertebrae. These discs are soft gel filled pads bounded by few layers of membrane called lamella.
These discs do not actually “slip,” they may split or rupture. Following this rupture, the gel escape into the surrounding tissue. The leaking jellylike substance can produce pressure on the spinal cord or on a single nerve root and cause pain either around the damaged disc or anywhere along the area controlled by that nerve. This condition is also known as a herniated disc, ruptured disc, prolapsed disc, or, more commonly, slipped disc.
The most frequently affected area is the low back, but any disc can rupture, including those in the neck. When the discs of low back are ruptured there will be pain in low back that will radiate to the legs. Similarly in case of neck there will be pain in neck that will be radiating to the hands.
The nature of the pain is frequently electric shock-like pain or burning pain. This pain may be associated with some numbness, tingling sensations and sometime some muscle weakness. As there are so many discs in the spine, the exact area of pain depends on the nerve root involved and that again depends on the disc that is involved.
Sciatica is a frequently used term both by doctors and by patients. It is a symptom and not a disease. Sciatica is defined as any pain that is starting in the low back and is going towards the legs. Sciatica is a non-specific term like fever. Like many diseases may produce fever, many diseases may be the cause of sciatica. Slipped disc is one of the most common cause of sciatica.
Since disc prolapse was first diagnosed by Dandy and subsequently by Mixter and Barr it has been implicated as one of the important cause of low back & neck pain radiating to legs & hands. Apart from conservative therapy all other forms of treatment aim at decompressing the nerve roots.
These can be done by taking the disc out by surgery or by decompressing the foramen and disc by different interventions. The various treatment options have confused clinicians due to significant failure rate associated with different kinds of surgeries as well as with different interventions.
Outcome studies of lumber disc surgeries document a success rate between 49% to 95% and re-operation after lumber disc surgeries ranging from 4% to 15%.
Reasons for this failure are:
- Dural Fibrosis,
- Arachnoidal Adhesions,
- Muscle & Fascial Fibrosis
- Mechanical instability resulting from the partial removal of bony and ligamentous structures required for surgical exposure and decompression
- Presence of neuropathy.
There has been surge of interest in search of safer alternative nonoperative treatment of slipped disc to decompress the nerve roots maintaining the structural stability. Epidural steroid injection, transforaminal epidural decompressions has a high success rate (up to 85%) but chances of recurrences are there specially if these interventions are done at later stage.
Chemonucleolysis using chymopapain has also high success rate (80%) with low recurrences but not popular owing to the chances of anaphylaxis following intradiscal chymopapain injection.
Injection of ozone for slipped disc or discogenic radiculopathy (low back pain with radiation to legs) has developed as a nonoperative treatment of slipped disc which is an alternative to chemonucleolysis and disc surgery. Owing to its high success rate, less invasiveness, fewer chances of recurrences and remarkably fewer side effects, it is becoming popular day by day in the whole world. This is called ozone nucleolysis or ozone discectomy.
Automated percutaneous lumbar discetomy(APLD)is another less invasive nonoperative treatment of slipped disc where disc material is taken out with neucleotome.(see recent advances)
These nonoperative treatment of slipped disc have revolutionized the treatment of slipped disc. There is quick recovery, less hospital stay, more economical, very little chance of side effects, and no chance of failed back surgery syndrome- the most fearsome complication of open surgery