Anterior Lumbar Interbody Fusion

The great advantage of anterior lumbar interbody fusion is that there is no surgical approach through the back. The surgical incision is on the abdomen and the front of the disc is approached surgically behind the abdominal contents. The alternative to this procedure is sometimes disc replacement surgery.


This means that if the surgery is done for pain there is no interference with, or scarring of, the back muscles. A bone graft can also be placed between the vertebrae where it provides the best support for the body weight. It also allows for correction of disc space height and realignment of the spine. The disadvantage is that there are very large blood vessels in the way. The aorta is the main artery coming from the heart and taking blood to the legs and the venae cava is the main vein taking blood back to the heart from the legs. These vessels need to be shifted somewhat to gain access to the spine.

 

The procedure is performed under a general anaesthetic. An incision is made on the front of the abdomen and the spine is approached behing  the abdominal contents. To gain access to the L5/1 disc space the major vessels are dissected and shifted to one side and held in place with tempory retraction pins. The disc is the removed and a fusion cage is inserted into the disc space. Within the cage is an artificial bone graft material consisting of bone morphogenic protein. No bone graft is needed to be taken from the hip. The L4/5 disc space is more difficult to approach. It is managed by shifting both the main vessels to the right.


The implant is usually fixed in place with a titanium plate.

 

Post-operative course

It is usual to have a urinary catheter inserted for this procedure, there will also be a wound drain and an intravenous fluid drip. It is important to limit oral intake of fluid and food for at least the first day. As with any operation around the bowel, there is the risk of developing a paralytic ileus. This occurs when the bowel contraction temporarily 'goes to sleep'. The condition is worsened if fluid and food is taken orally. For this reason fluids should be given intravenously until the bowel is working (until flatus is passed). After this happens oral intake of food and fluid is commenced. Pain from the wound is controlled usually with a patient controlled analgesic device. Compression stockings are worn for the first few days to reduce the risk of deep venous thrombosis (DVT). The risk of this occuring in this operation is higher because of the need to surgically 'shift' the position of the large veins and this temporarily occludes the blood flow from the legs.

Patients are usually mobile in 2-3 days and are discharged by day 5.

 

Complications

  • Wound infection
  • Major vessel damage causes bleeding. The largest blood vessels in the body need to mobilized in this procedure and they are therfore at risk of tearing (particularily the venae cava). This situation is rare, though if it occurs there is the potential for major heamorrhage. This may necessitate further emergency surgical procedures such as the extension of the wound to a much larger one and the need to call for the assistance of a skilled vascular surgeon. Usually small tears in the major vein can be controlled reasonably simply, though there remains the very small risk of catastrophic bleeding that could, in extremely rare circumstances, lead to death.
  • Non union - the bone graft doesn't 'take'. This is not common. If it occurs another operation may be required.