The Operation

How long does the surgery take?

The operation usually takes two to three hours but this will depend upon whether other procedures such as a wider decompression of the nerves in the spinal canal are being undertaken at the same time and also on the number of levels being fused.

Where is the incision made?

In the standard technique the patient is positioned face down and a midline incision is made over the levels to be fused. This will be relatively long, about 10 to 12 cm for a single level operation. The reason for this is that a longer incision is actually kinder to the spinal muscles, allowing more gentle and less damaging retraction.
If an image guided, minimally invasive technique is to be used two incisions will be made over the muscles about 3cms in length.

What happens during the procedure?

After making the incision and moving the muscles sufficiently to reach the insertion point for the screws these are placed down the pedicle into the vertebrae of the levels concerned. The placement of the screws is checked very carefully using feller gauges and x-ray control. Any additional procedures required, such as decompression, are undertaken next. Microsurgical instruments are then used to move the nerve roots slightly to either side, to protect them and to remove the central disc material and the cartilage from the endplates of the vertebrae. Special instruments are used to determine the appropriate size for the cages.

Bone graft is required for the fusion procedure. Sometimes sufficient graft is obtained from bone removed during the procedure. Otherwise bone graft will be obtained from shavings from the pelvis. This can usually be done through the same incision.

The cages are packed with bone graft and then positioned in the space left after removal of the disc material. Additional bone graft is also packed to either side of the cages. The outer surface of the back parts of the vertebrae are also removed together with the joint surfaces from the facet joints. This creates a raw bony surface ideal for fusion. Further bone graft is packed into the facet joints and over the raw bony surfaces.

The rods are positioned into the locking mechanisms of the pedicle screws and any adjustments made to achieve proper alignment of the vertebrae. The rods are then locked firmly in place.

An alternative but similar technique may be used in certain situations. In this procedure, called a Transforaminal Lumbar Interbody Fusion, the disc clearance and cage insertion is undertaken from one side.

About Spinal Stenosis

An epidural catheter is placed to help with any post-operative pain relief. The nerve roots and the exposed dura are covered with a barrier gel (Adcon-L) to reduce the risk of scarring. The wound is then closed with a small wound drain being inserted. Small clips are used to close the skin edges.

Posterior Lumbar Interbody Fusion

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