Discectomy is a surgical procedure designed to removed a fragment of disc to give relief of pain in the leg caused by irritation of a nerve. The disc is mostly simply thought of as a cushion that sits between individual vertebra. In reality it is a much more complex structure. It acts as a strong ligament between the vertebral bodies allowing movement in the spine. With age, a gradual change of proteins within the disc occurs (this protein change is probably determined by our genes more than anything else) and the new protein is weaker. When combined with mechanical forces on the spine a portion of disc can push out into the space where the nerves run through the spine. In some people this can cause pain, numbness or weakness of the effected nerve running into the leg ( sciatica).
The natural history of disc protrusion is generally favourable. The majority of people will substantially improve over a eight to twelve week period. There are many studies that show limited differences in the symptoms in patients two years after onset of symptoms when comparing people treated with surgery and those people who persisted with non operative management. However if after six to eight weeks of pain in the leg and they are unhappy to tolerate the symptoms any further it is reasonable to proceed with surgery to remove the fragment of disc which is usually an excellent procedure for relieving pain in the leg.
The operation is carried out under a general anaesthetic. A catheter is placed into the bladder once you are asleep and in most cases removed before you wake up. You are then positioned on your stomach on a special operating table. A small (2-3cm) incision is made in the middle of the back over the affected disc space. The muscles are taken off the side of the spine on the side of the pain. A marker is placed on the spine and an x-ray taken to make sure that the right level has been selected. A burr is then used to remove some bone and release the ligament running between the bones in the back of the spine (called the lamina). At this stage a small retractor is used to push the nerves towards the middle of the spine exposing the back margin of the disc and the spinal canal. Usually the disc protrusion will be visible. In some cases it can be hidden in parts of the spinal canal which are a little more difficult to access and can take some more effort to find. The fragment of disc is then removed. The spinal canal and hole where the nerve exits are probed to make sure there is no residual pressure. The wound is then closed with stitches and a dressing applied. You are then placed back on your bed and the anaesthetic reversed and taken to recovery.
WHAT TO EXPECT POST SURGERY
Post operatively you should notice the pain in the leg feels alot better. You will have a drip in your arm hooked up to a pump which you will be giving you some pain relief. After the procedure itself I am happy for you to get up and walk around as soon as you are able. The pain relief can make some people a little dizzy, you will need to do this with a member of the nursing staff until your drip is removed. This usually occurs on the morning following surgery. Unless there is a reason not to, you will be given an injection of an anti inflammatory drug which in most cases works well for the surgical part. I will also prescribe some tablets for pain relief. The physiotherapist will review you and demonstrate some simple stretching exercises. If you are mobile and comfortable you will be able to go home. Approximately half of patients go home on the first post operative day. The remainder go home on the second post operative day.
At home, I encourage you to walk regularly for exercise and do the stretches the physiotherapist has demonstrated to you. The stitches are beneath the skin and do not require removal. The dressing that is on the wound should be left on for three to four days. It then can be removed. You can get your wound wet but just make sure you dry it. I usually ask you to make an appointment around four weeks following your surgery for review.
RISKS / COMPLICATIONS
As with any surgical procedure there are a number of possible complications which can happen. Fortunately these are unusual. The more common ones are listed below:
The infection rate from surgical discectomy is pleasingly low (around half of one percent). Signs of infection would be redness and discharge from the wound, increasing pain in the back or leg, temperature, fevers or chills. If you develop such symptoms please contact the rooms. If you do develop an infection in the wound the treatment ranges from simply needing some antibiotics through to at times having to have further surgery to clean out the infection.
One of the ways blood gets back to the heart from the legs is through veins in the spine. In rare cases there can be substantial bleeding which could necessitate blood transfusion.
CAUDA EQUINA SYNDROME
The cauda equina is the name given to the nerves coming off the end of the spinal cord running through the spinal canal. Cauda equina is latin for “horses tail”. The nerves here go to the legs but also the bladder and bowel. Cauda equina syndrome is were a lump develops which squashes these nerves and causes compression of them causing loss of function of bladder and bowel. Following surgery this could be due to a blood clot or an abscess. The symptoms of cauda equina syndrome are numbness in the groin and around the genitals and anus, inability to pass urine with dribbling and incontinence of faeces. If this occurs, it is an emergency that the pressure is relieved with further surgery otherwise the pressure can cause permanent loss of bladder or bowel function. The incidence of developing such a problem after surgery and it being permanent despite surgical drainage is in the region of one in eight or nine thousand.
NERVE ROOT INJURY
The surgery involves retraction of the nerve root to expose the space where the disc protrusion is sitting. This could involve stretching of the nerve. Less commonly the nerve can be partially cut or torn using instruments to remove the piece of disc. This can cause either pain, numbness or weakness ( or any combination of these) in the distribution of a particular nerve in the leg.
The dura is the sac lining the nerves and contains spinal fluid. This can be torn by instruments resulting in leakage of spinal fluid. Often this is simply repaired with a stitch. Some patients develop a headache for a few days, this would usually resolve. On rare occasions the leakage will continue and lead to a clear fluid discharge from the wound. If this occurs, further surgery to seal the leak may be required. In vary rare cases there has been reported that some patients (usually elderly) have developed an unusual type of stroke after having had some leakage of spinal fluid. The mechanism for this is very poorly understood but in its simplest form is said to be due to pressure changes in the brain caused by loss of spinal fluid leading to shearing for some of the smaller blood vessels around the brain. Fortunately as above this is an exceptionally rare complication.
RECURRENT DISC PROTRUSION
In between 4-8% of cases another fragment of disc can push out causing recurrence of the sciatica. This is because the underlying protein abnormality still exist within the disc and further fragments can loosen and push into the spinal canal. If recurrence does occur, in the majority of cases it again usually settles with non operative treatment. Should it not settle, the procedure can be repeated. The chance of further recurrence is again then 5-8%. If the surgery is required a third time, my recommendation would be to fuse the disc space preventing further recurrence. It is unusual for a third recurrence to occur.
There are a variety of medical complications which can occur with major surgical procedures. The likelihood that these will occur to some extent is determined by your health before surgery and past medical history. Fortunately with modern anaesthesia and peroperative care, medical risks involved in elective surgery are comparatively low. Common surgical complications such as deep venous thrombosis, pulmonary embolism, pneumonia, urinary tract infection and skin pressure areas are best avoided with early mobilisation.
Generally discectomy is a reliable procedure for treating pain in your leg. Whilst there are a number of potential complications fortunately they are reasonably rare.
If you have any further questions regarding your procedure, please don’t hesitate to ask.
Rob Kuru, Spinal Surgeon