Patients undergoing spinal fusion will usually have been given a general anaesthetic and rolled onto their front during preparation for surgery. Depending on the specific spinal fusion procedure to be performed, the surgeon will make an incision in the back or neck over the area where there are problems with segmental motion. In an open procedure the surgeon will use retractors to move and hold the muscles and tissues aside to allow access to the spine itself. Some muscles may be scraped away from the bone to achieve this, and spinal ligaments may also be severed during an open procedure.
In a minimally invasive spine surgery procedure the surgeon will make a smaller incision either in the back, abdomen, or side, and insert a series of dilators with increasing diameters to gradually push the tissues aside and allow access to the segment in question. This tube also allows the surgeon to insert an endoscope (a small camera on a length of tubing) which projects a video image onto a monitor in the operating theater. The surgeon can then use a number of small, specialized instruments inserted into the tubular retractor to conduct the surgery whilst maintaining visual access via the endoscope. In some cases a number of small (half-inch) incisions may be used in order to reach the spine, maintain a visual connection, and insert instruments to conduct the fusion.
If a discectomy, laminectomy, or other procedure is to be performed then spinal fusion will occur after that part of the operation. Patients having an autograft placed will have a small incision made in their hip in order to excise a small amount of bone from the back of the pelvis. Bony material removed during the surgery from the spine may also be ground and used to fill the center of an allograft from the bone bank in order to improve fusion rates. Metal cages may be used to contain the bone graft, with screws and metal plates also used in spinal fusion procedures to attach the bone to the vertebrae and prevent movement of the spinal segment until the bone graft has fully healed and fused solidly. Spinal fusion surgery takes approximately three or four hours and is considered a major operation. After the graft has been put in place the retractors and instrumentation will be removed and the muscles and ligaments eased back into place, with suturing as necessary. The surgeon will close the incision and apply a dressing before the patient is taken to recovery for monitoring as they come round from the anaesthetic.