There are many reasons why we would consider surgery but it is generally kept as a last resort, once conservative measures of treatment have been exhausted.
Fusion surgery is not usually done for back pain alone as the results for this are poor. Low back fusion surgery is usually done where there is nerve compression (resulting in leg pain) from a structural deformity. This includes spondylolisthesis (instability with slip of one bone on the other), scoliosis (abnormal spinal curvature) and disc degeneration (loss of the shock absorber between the bones).
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Procedure
A spinal fusion is a surgical procedure that is done to stabilise two or more vertebrae of the spine. This involves using metalwork and bone graft (either from your body or synthetic bone). The goal is to allow the body to build bony bridges across those segments and eventually stop movement and hence pain generated by this part of the spine.
There are three main approaches used in low back fusion surgery:
- Anterior, where the surgical cut is made through your abdomen
- Posterior, where the surgical cut is made on your back
- Lateral, where the surgical cut is made on your side
Surgery involves inserting metal screws and rods into the vertebrae of the spine. Sometimes we use cages to replace the disc material that is taken out. The screws and rods act as a scaffold and allow the body to build new bone between the vertebrae.
After the operation you will feel some pain and discomfort, which will be helped by medication. You may have the following:
- Small drainage tubes coming from your wound
- A drip to replace lost fluids
- Patient Controlled Analgesia (PCA) Device
- An oxygen mask
- A urinary catheter
These will be removed as soon as possible following the surgery.
You are likely to stay in the hospital for two to three days if your surgery involves only one approach. However, the length of stay can be longer with more complex operations.
There is a possibility that you will be required to wear a brace or a soft corset following surgery. The surgical team decides on this. You will be guided by the therapists on the ward as to when you need to wear the corset or brace, and for how long.
The aim of a spinal fusion is to relieve leg pain and hopefully back pain. It is difficult to anticipate how much your symptoms will improve following this procedure. However more than 50% of patients experience improvement of their back pain and 50 – 80% of patients will experience improvement of their leg pain.
All operations involve risks and potential complications. Broadly speaking, risks attached to spinal surgery are divided into the risks of the general anaesthetic and the risks of the procedure itself. The anaesthetic risks will be discussed with you by the anaesthetist on your admission.
General risks applicable to all spinal surgery
Infection: it is mostly superficial. Deep infection affecting the metalwork can be a devastating complication with long-term effects. Thankfully it is rare.
Blood clot in your legs or lungs (DVT/PE): several precautions will be taken to reduce the risk of deep vein thrombosis, most importantly moving feet and legs in bed and mobilising as soon as possible. Very rarely, the clot passes to the chest and can be life threatening.
Nerve injury and paralysis: Around one in every 20-100 people who have lumbar surgery will develop new numbness or weakness in part of one or both legs as a result of the operation. Paralysis is an uncommon but serious complication that can occur as a result of lumbar surgery (this can be temporary or permanent). It is estimated to occur in less than one in every 300 operations.
Dural tear and leakage of cerebrospinal fluid: During lumbar surgery, there is a risk of accidental damage to spinal nerve lining (dura), which can lead to the leakage of cerebrospinal fluid (CSF). If this is discovered during the operation it will be patched and repaired at the time with no serious problems but you will have to lie flat for 24-48 hours after the operation. However, small leaks can sometimes only become apparent after the operation, causing problems such as a headache and leaking from the wound. In some of these cases, further surgery to repair this may be required.
Bleeding: on rare occasions you will require blood transfusion.
Increased leg or back pain: despite a successful procedure, there is a chance that your pain might not resolve or can even get worse. This is particularly so if you are having revision surgery.
Death: As with all types of surgery, there is a risk of dying during or following lumbar surgery, although this is rare.
Specific risks applicable to the posterior approach
Facial sores and blindness: As you are positioned face down for posterior lumbar surgery, you will be resting on your forehead and chin while the operation is performed. The anaesthetist will regularly check to make sure this isn’t causing any problems, but many people will wake up with a slightly puffed up face which varies in severity. In some cases, a red sore can develop over the forehead or chin which could last several days. In extremely rare circumstances (about one in every 30,000 cases), patients can slip during the operation and rest on their eye balls rather than forehead and chin, which could affect circulation to the eyes leading to partial or even complete, permanent blindness.
Specific risks applicable to the anterior approach
Vessel/Bowel/Visceral injury: if the spine is reached through the abdomen, there is a small risk of injuring the vessels or bowel. Also the nerves controlling temperature can be injured hence one leg can feel cooler than the other. The kidney and ureters can also rarely be damaged during the anterior or lateral approach.
Abdominal wall hernia – during anterior and lateral surgery the muscles of the abdominal wall are dissected and subsequently repaired. Occasionally this repair fails and a hernia develops where contents of the abdominal cavity bulge out of their usual cavity. It this occurs you may need to have this repaired.
Retrograde ejaculation: In men there is a risk of injuring the nerves that control ejaculation; however this does not cause impotence. With retrograde ejaculation, the sensation of ejaculating is largely the same, but it makes conception very difficult (special harvesting techniques can be utilized). This complication does not result in impotence as these nerves do not control erection.
Specific risks applicable to the lateral approach
Thigh pain and weakness: If your surgery involves a lateral (side of abdomen) approach to your spine, the muscle supplying your hip and thigh is dissected to enable access to the spinal column. It is common to wake up and find that it is difficult to move your hip (pain and weakness) and that the sensation over the thigh is numb. Usually these symptoms are temporary and can take several months to improve but occasionally it can be permanent. The skin over the thigh can also feel strange (dysaesthesia) and this can also be either temporary or permanent. If the cause of your pain is a blood clot in the hip muscle (psoas muscle) then it is possible you may need an operation to release this.
Damage to the lumbar plexus: there are many nerves running through the side of the abdomen and the psoas (hip) muscle which need to be dissected. Occasionally they are inadvertently damaged due to retraction or due to stretch from correction of the deformity. This can result in damage to nerves such as the femoral nerve which leads to weakness in leg movements, in particular knee extension.
Specific risks applicable to any spinal fusion surgery
Failure of fusion & Metalwork failure: sometimes the bones fail to knit together (failure of biology) and hence the metalwork can back out or fracture. This will require further procedure to enhance the bone to fuse. The chance of a non-union is twice as high if you are a smoker – if you have not given up smoking prior to a fusion procedure your operation will be cancelled. Non-union is also higher in obese patients.
Implant malposition: screws are introduced via a small channel of bone in your spine called a pedicle. This channel of bone is only a few millimeters bigger than the screw (sometimes it is the same size or even smaller). Occasionally a screw is malpositioned and if this occurs it can cause nerve damage and pain. If this happens and the screws is causing pain then you may have to undergo another operation to change or remove the screw. Cages can also be inadvertently malpositioned and require revision.
Adjacent segment disease: fusing one segment increases the load on the adjacent segments and accelerates the process of degeneration. This may lead to the fusion being extended.
Fortunately most of the listed risks are rare however, it is crucial that you consider the decision to embark upon such procedure carefully. Please therefore discuss the procedure thoroughly with your surgeon before having surgery.
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