Risks of Surgery
The risk of death is low, it is difficult to quantify and is probably less than one death per 700 operations for sciatica. It would be from unexpected events such as blood clots in the legs passing to the lungs (pulmonary embolus), or catastrophic blood loss from major blood vessels. The risk will vary according to patient factors such as heart disease, high blood pressure, smoking, and specific age related risks. The risk of death from decompression surgery for stenosis is higher (possibly one per 350) than for disc surgery as the patients are usually older and less fit.
The risk of paralysis, which means loss of use of the legs, loss of sensation and loss of control of bowels and bladder is low. Probably occurring less than one per 300 operations. It could occur through bleeding into the spinal canal after surgery (an extradural spinal haematoma). The risk of paralysis is higher if patients are taking blood thinning medication (warfarin) or if there is an incidental durotomy (leak of spinal fluid). If an adverse event of this nature was to occur every effort would be made to reverse the situation. Sometimes paralysis can occur as a result of damage to the blood supply of the nerves or spinal cord, and this is not reversible.
Superficial wound infections are not rare and may occur in between 2% and 4% of spinal operations. Risks of infection are increased in diabetic patients, patients on steroids or those with lowered resistance to infection.
Deep spinal infections are much more serious but less common. A deep spinal infection occurs in less than 1% of cases. To reduce the risks of infection antibiotics are often given and the surgery is often performed in ultra clean air flow theatres. If a deep infection occurs it can require repeat operations to washout the spine and a prolonged and extensive course of antibiotics.
This is where an opening occurs in the dura which is the lining of the spinal canal. The spinal fluid within the spinal canal will drain out of the hole. It may occur deliberately if the surgeon intends to do it as part of the operation. It may occur as a result of the disc or bone being very stuck to the lining of the spinal canal. In primary sciatica surgery it occurs in 3% of cases. In decompression surgery it is more common , happening in 8% of cases.
If there has been a previous spinal operation it is even more common because of scarring. Repeat or revision operations have a higher risk of complications than first time operations.
Sometimes the hole in the spinal lining (the dura) can be repaired with stitches or a patch. Sometimes it is safer to leave it to heal. Sometimes the surgeon will insert a drain to divert the fluid. Usually the leak of fluid dries up within a few days and there is no long term effect. Sometimes despite precautions spinal fluid will leak through the wound. This represents a risk of infection and meningitis and further surgery might be required to correct the situation.
Damage to spinal nerves
The spinal nerve causing the pain may be already damaged by the disease process. The disc prolapse can cause scarring with in the nerve such that it is unable to recover despite technically successful surgery. The nerve can be stretched in trying to remove the disc lying under the nerve. The nerve can also be damaged by direct surgical trauma or by pressure effects necessary to control bleeding.
Damage to blood vessels
This can result in significant bleeding which can be life threatening. Damage to the main blood vessels at the front of the spine (the aorta) has been known to occur. The main blood vessels to the legs can also be damaged which could result in loss of limb. Events of this nature are rare, occurring in less than 1 per 10000 operations. Damage to vital organs: The liver, kidneys and bowel are in front of the discs and are theoretically at risk of injury. This again would be life threatening but rare.
The wrong operation
The spine has many discs and vertebra. During the operation the surgeon will commonly carry out x-rays to check that he is operating at the correct place in the spine. Many safety checks occur to make sure that the patient has the correct procedure. Occasionally the x-rays will show that the wrong disc space has been opened, in which case the correct level will then be approached. Intra-operative checking like this is essential to avoid wrong level or wrong site surgery