What is a microdiscectomy?
This operation is done to remove a prolapsed portion of a disc that is compressing a nerve and causing sciatica. When a tear occurs in the outer fibres of a disc (annulus), part of the central disc (nucleus) may squeeze out through the tear and press on the nerve. Although this gradually resolves in most cases, in some people it persists and requires surgical treatment. The aim of the operation is to remove this part of the disc that is pressing on the nerve and take the pressure off the nerve. Any loose parts of nucleus within the disc are also removed but the whole disc is not (and can not) be removed. The outer portion (annulus) consists of fibres holding the bones together and this is left intact. Within this there may be small pieces of nucleus that remain attached and can later break off and prolapse. This explains the small (4% or 5%) risk of recurrent disc prolapse after a microdiscectomy.
How is it done?
You will be admitted on the morning of surgery and the operation will be done under general anaesthetic. You will be placed face down in a kneeling position on the operating table as this reduces the pressure on the chest and abdomen. An x-ray is taken to mark the correct level and then a small two centimetre incision is made in the midline of the back. The muscle is stripped from the bone on the side of the disc prolapse and a small, tube-like retractor is inserted. The rest of the operation is done through this tube using an operating microscope and small instruments. The fibres between the vertebra (ligamentum flavum) are removed and in most cases no bone removal is necessary as the approach is between the bones, as shown by the blue arrow.
The nerve is then identified and gently retracted away from the disc prolapse. A grasping instrument is used to pull out the fragments of disc that have prolapsed out of the disc space and there will usually be a visible hole through the annulus into the disc space. The grasping instrument is then placed through that hole and any loose pieces of disc removed. Once the disc has been cleared an analgesic (Fentanyl) and sometimes a steroid (Celestone) are injected into the space around the nerves and the retractor is removed and the wound closed. A dissolving stitch is used under the skin so that no stitches need to be removed later.
What to expect post-operatively
In most cases you will notice an immediate improvement in your leg pain. Any weakness or numbness is likely to improve gradually and may take a few months. Numbness is usually the last thing to get better and depending on how much damage has been done to the nerve by the pressure from the disc prolapse it may never go away completely.
Postoperatively you will be able to lie in any position that you find comfortable and the physiotherapist will get you up out of bed the following morning. You will be encouraged to walk or lie down but not to sit for prolonged periods as this is likely to make your back muscles sore. You will have some aching and tenderness in the back but this will improve fairly quickly. Most people are able to go home after two or three days. The length of time that you need to take off work will depend on what you do. If you work in a sedentary occupation and are able to return on reduced hours with no lifting or bending or prolonged sitting without a break, you will probably only need three or four weeks off work. On the other hand if you work in a heavy manual job you may need up to three months off work. In most cases it is best to avoid any lifting for six weeks and then to gradually increase activities over the following six weeks. The physiotherapist will give you a booklet explaining what exercises to do. You will be given an appointment to see me in my rooms in 4 to 6 weeks.
Are there risks involved?
There are risks involved with anything in life and surgery is no different. Some of these risks are common to most or all operations and some are specific to the particular procedure.
The following are the most common or most serious complications. Other problems may occur rarely and it is impossible to list every one of them. Just try to list all of the possible things that could happen on your drive to work-a car crash is obvious; an aeroplane crashing onto the road in front of you is also possible but extremely unlikely and would not normally be considered common enough to affect your decision to drive. If there is anything in particular that you are concerned about, please ask me.
General risks of any operation
Anaesthetic complications such as heart attack, drug allergy or even death are possible but very rare.
Blood clots in the leg (DVT) or lung (pulmonary embolus) may occur unexpectedly but are very uncommon in otherwise healthy people.
Infections such as pneumonia, wound infection or urinary tract infection may occur after any operation.
Bleeding may occur especially in people taking aspirin. It is therefore recommended to cease aspirin (also called Cartia or Disprin) two weeks before elective surgery.
Lumbar microdiscectomy successfully relieves leg pain in approximately 90% of patients. This means that 10% will not get relief of their pain despite an otherwise apparently successful procedure. In most cases the reasons for this will be unknown.
The aim of the operation is to relieve leg pain due to pressure on a nerve. Back pain is usually due to the fact that the disc is damaged and this will not be helped by surgery. If most of your pain is back pain rather than leg pain surgery would not normally be recommended.
The spinal cord finishes at L1 in most cases and the majority of disc prolapses occur well below this level. In this area are the nerves going to the legs, bladder and bowels. These nerves are more resistant to damage than the spinal cord but can still be injured and at the very worst this can result in paraplegia. This would be an extremely rare complication of microdiscectomy.
The single nerve that is being compressed by the disc prolapse can be injured by the disc itself, by surgical manipulation or by subsequent scarring. All of these can result in numbness or weakness in the distribution of that nerve as well as pain and pins-and-needles. When this occurs as a complication of surgery, which is unusual, it would usually improve over two to three months. Permanent nerve damage however can occur rarely.
Infection is uncommon and you will be given an antibiotic during the operation. With this, the risk of infection in the disc space is less than 1%. Infection in the wound itself may occur and will usually respond to antibiotics.
Bleeding is unusual except in patients taking Aspirin or other anti-clotting medications. It is therefore recommended to cease Aspirin (Disprin, Cartia) for two weeks before surgery.
As the entire disc is not removed there is a risk of recurrent disc prolapse which is approximately 4%.
On the other side of the disc space is the abdomen and on very rare occasions abdominal organs or blood vessels may be injured. The risk of this is extremely small.
Coming into hospital for surgery
These days, most operations are done on the same day as admission. You will need to come to the hospital admissions area at the advised time. If you have not already sent in the hospital admission forms, bring them with you.
You will need to fast for 6 hours which means nothing to eat or drink after the time notified.
You will usually be able to take your normal tablets but medications that affect your bleeding will usually be stopped preoperatively. Aspirin, (also called Disprin or Cartia),and Plavix (also called clopidogrel) should be stopped for two weeks if possible before an elective operation. Fish oil should be stopped for a week. Anti-inflammatories should be stopped for 48 hours. Warfarin will need to be discussed with me and your GP.
Make sure you bring your Xrays as these will be essential for most operations. If you cannot find them please let me know early so that they can be repeated if necessary.
If you would like to have a private room that should be indicated on the hospital admission forms. There are only a finite number of single rooms and sometimes it will not be possible to go straight into one, but if you indicate your preference every effort will be made to move you into a private room as soon as possible. (I do not have any say in this except in cases of medical need eg infections).
I will see you in hospital before you go to the operating room and the anaesthetist will also see you preoperatively and will want to know about your general health and any medications you are on. Please bring your usual tablets with you.