Lumbar Spinal Fusion
Spinal Fusion is an operation to stabilise an area of the spine. It is done by a variety of techniques depending upon the pathology to be treated and the state of the spine that is being treated. Generally the idea of a spinal fusion is to weld two vertebrae together to prevent painful movement. It essentially is a mechanical treatment for a mechanical problem. That is to say it is used to treat areas of the spine where there has been a failure of a disc shock absorber and this failure being painful. It is sometimes also associated with a spinal decompression to relieve nerve entrapment at the same time as creating a stable spine afterwards. Spinal fusions are specifically used to treat bony problems such as scoliosis, spondylolisthesis, fracture and so on.
Generally spinal fusion is achieved by the use of bone graft between two areas of the spine which have been made raw. The idea is to make the body feel that there has been a fracture which it then unites by joining up the raw area of bone and the bone graft thus creating a link between two or more vertebrae. This fusion is enhanced often by the use of instrumentation. This instrumentation falls into two main types. The first type is the use of screws which are connected by rods, creating a framework to hold the area of spine which is being fused together allowing the bone graft to heal without excessive movement in the area which is being fused. This essentially is a form of internal scaffold. The other type of instrumentation used is cages which are inserted between the vertebrae where the discs have been removed either through the front, abdomen, or via an incision in the back. These cages are packed with bone graft to allow a fusion to occur between two vertebrae. The cases essentially act as a form of protection for the bone graft and hold it where it should be placed, at the same time it provides some form of support between the vertebrae.
This sort of surgery takes between 1 and a half and 3 hours to perform, depending upon the complexity and the number of levels being operated upon. It is done under a general anaesthetic and the usual hospitalisation time is approximately 7 days. It will take around 6 weeks to get over the general effects of the operation, including the wound ache.
The risks and complications of such surgery are the anaesthetic itself. There is a small risk of neurological injury either from the position of the screws, if they are too close too a nerve, or from moving a nerve out of the way whilst cages are inserted. There is a small risk of injury to a blood vessel particularly if the surgery is carried out anteriorly or via the abdomen. There is also a risk of infection or deep vein thrombosis; these are guarded against by the use of antibiotics and TED stockings.
This sort of fusion surgery is controversial and is therefore used in cases where there is intractable back pain which has not been resolved by non-operative means over a prolonged period of time. By fusing an area of the spine, there is a possibility of increased stress and strain being placed upon the area above and below the fusion and therefore a possibility of premature degeneration of this area of the spine. This may not however be the cause of major symptoms.
For the L5/S1 disc, the lowest disc in the lumbar spine, there is a novel technique which is currently used at SpineWorks. This allows the operation to be done through a small incision around the coccyx passing tubes up in front of the sacrum under x ray control to allow a drill to be passed through the bottom end of the sacrum into the L5/S1 disc space. This disc can then be removed from a drill hole within it rather like removing the inner tube of a tyre. This gap is then filled with bone graft and the disc held together by a bolt passed through the hole in the sacrum through the disc containing bone graft and into the L5 vertebra.
The advantages of the technique are the fact that it can be done through a very small incision and the approach avoids major blood vessels and nerves. There is a potential small risk to the bowel.
To assist fusion with this procedure screws would also be placed in the back but these can now be achieved through small incisions again.
In summary the total procedure length is quicker than a standard fusion and the hospital stay is reduced.