What is a disc?
The intervertebral disc is a ring of fibrous tissue that lies between the vertebral bodies in the spine. It consists of a tough outer ring with a jelly-like centre. The disc normally absorbs water and acts as a shock absorber as well as providing stability to the spinal column. With age the lowest lumbar discs degenerate and can become less effective at their job. The lack of support is thought to cause back pain by straining the surrounding joints, ligaments and muscles. The disc may cause leg pain by compressing or irritating the adjacent nerve.
What is a disc prolapse?
Also known as: slipped disc, prolapsed interverterbral disc, disc herniation
Sometimes the tough outer ring of the disc tears and this allows the softer centre escape. If this material travels backwards it can compress the nerve root and cause leg pain i.e. " sciatica". The pain is rarely due to physical compression alone and it is the chemicals released with this process that inflame the nerve root. This is why your doctor may prescribe anti-inflammatory medication. The pressure on the nerve may in addition to pain cause loss of function of the nerve i.e. numbness or weakness.
The majority of patients with disc prolapses will find that their pain will resolve spontaneously over a period of six weeks. They may require painkillers, anti-inflammatory medication or anti-inflammatory injections to help with their pain during this period. Numbness and weakness will also improve in the majority of cases but over a longer period of time. However, the recovery of numbness and weakness cannot be influenced by surgery.
What treatment is there?
Simple rest, painkillers and anti-inflammatories should be tried in the first six weeks. Try to keep mobile. The role of physiotherapy, chiropractic manipulation and osteopathy in the acute stages is controversial but may help.
If your symptoms have not improved after six weeks your doctor will refer you to a spinal specialist. Depending on your symptoms consideration will be given to performing an epidural injection. These injections can take 2 to 4 weeks to work.
If these non-operative treatments are failing or your symptoms are too severe to wait then surgery may be advised.
SURGERY IS INTENDED TO RELIEVE LEG PAIN ARISING FROM NERVE ROOT COMPRESSION.
THE EFFECT OF SURGERY ON BACK PAIN IS UNPREDICTABLE AND IS RARELY THE PRIMARY REASON FOR SURGERY.
What is a discectomy?
This is a commonly performed surgical procedure which is performed from the back with the patient lying on their front or side. The skin and underlying muscles are cut to expose the back of the spine. Small amounts of bone and ligament are removed until a big enough window is achieved to safely pull the nerve root to one side. The prolapsed material is then removed. Any loose fragments in the disc space are also removed. The amount of material usually represents about 20% of the disc. The rest of the disc is left in place. Nothing is placed in the disc to fill the space. The nerve is then replaced in its proper position.
The procedure is performed under general anaesthesia and generally takes about 1 hour. You will be in hospital between 1 to 3 days and will mobilse after surgery with the aid of a physiotherapist. The wound takes about 2 weeks to heal and you will need to be off work between 2 weeks and 2 months depending upon your activity and type of work.
What are the risks?
Studies would suggest that in the long-term (3 years) the end functional result following a disc prolapse is the same whether an operation has been performed or not. A successful operation is associated with an earlier achievement of this end result. There is, however, a small but definite risk of complications some of which can be very serious. Therefore, your surgeon will not usually recommend surgery without offering a non-operative alternative.
This procedure is performed under general anaesthesia and your anaesthetist will explain the risks to you.
There is a small risk of nerve damage during this procedure. This may leave you with permanent numbness, weakness or pain in the area of the leg supplied by the nerve. The risk is 1%.
The front of the disc lies adjacent to the major abdominal blood vessels and contents. There have been reported instances of fatal complications arising from damage to these structures. This is very rare.
Cauda Equina Syndrome
If there is significant post-operative bleeding then the central spinal canal can become included with severe loss of function of the bowel and bladder and lower limbs which can be permanent. This complication is rare.
Sometimes during surgery the lining of the nerve roots ( dura) can be torn. This leads to a fluid leak which can cause headaches and necessitate compulsory flat bed rest for 2 days. Usually the leak seals itself off and routine mobilisation can follow but occasionally the leak can persist and necessitate a return to theatre to have the leak closed. The risk is 1%.
Infection following discectomy surgery is less common than after other types of surgery but infection in the disc space can be very serious necessitating further major surgery and long term antibiotics. Infection carries the risk of nerve damage and meningitis.
Medium term risks
Recurrent disc prolapse
As the whole disc has not been removed further material can dislodge at a later date. This is fairly uncommon.
It is not unusual for some of the symptoms of sciatica to return a few weeks after the procedure. This is probably due to the swelling and bleeding around the nerve root following surgery. If this does not settle with anti-inflammatory medication an epidural injection may be required.
The cut muscles take some time to recover and the first two months following surgery may be associated with discomfort following prolonged activity and sitting.
Long term risks
Nerve root scarring
It is thought that the trauma of surgery may induce scarring around the nerve root following discectomy. This can cause the nerve root to become stuck down and cause pain. This is a very difficult problem to treat and may necessitate steroid injections or rarely further surgery to release the nerve.
This is not necessarily related to surgery. A damaged disc does not repair itself and will not function as normal. By building up the supporting muscles around the spine back pain can be prevented (core stability) but occasionally, despite this, back pain can be a problem. There is no way to predict this at the time of the discectomy with certainty but occasionally your surgeon may recommend additional procedures to try and prevent this problem occurring.