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Anterior Lumbar Interbody Fusion (ALIF)

What is an ALIF?

ALIF stands for ‘anterior lumbar interbody fusion’. As the name suggests, it is a spinal fusion of the low back (lumbar area), where the operation is done from the front (anterior) rather than the back, and the fusion material is placed between the vertebrae (in the interbody region).

It was originally done by taking bone from the iliac crest (the ‘hip’ region) and putting it between the vertebrae. Often, screws would be placed at the back of the spine to help support the bone. There have been a number of improvements to this procedure since. Firstly, better techniques of anterior (through the belly) approaches including new retractors has meant that the operation is now more elegant. Secondly, cages have been developed to help hold the vertebrae in place. Thirdly, artificial bone graft replacements are now available, meaning that taking bone graft from the ‘hip’ (really the iliac crest of the pelvis) is no longer needed. Finally, small plates that are put on the front of the vertebrae have been designed to help hold the fusion in place, avoiding the need for screws from the back of the spine. Anterior procedures have the advantage of not interfering with the muscles at the back of the spine or the nerves in the spinal canal, meaning that recovery is quicker and nerve damage is infrequent.

When would an ALIF be done?

An ALIF is done when you want to do a fusion between the vertebrae (interbody fusion) and there is no need to open the spinal canal (as there is no nerve compression present). Sometimes it is not desirable to do the fusion from the front (through the abdomen), because

• it is too difficult (too many scars from previous surgery, or too much belly!)
• the surgeon is concerned about the risk of surgery from the front
• it is the surgeon’s preference, because of experience.

The main reason I do the operation is for severe low back pain with symptoms suggestive of discogenic pain (coming from the disc) but no neurogenic pain (coming from nerve compression), and we find a single (or occasionally two) degenerate disc(s) seen on MRI. Sometimes we need to do a discogram to prove that the abnormal-looking disc is the cause of the pain. This is a painful and invasive test where a needle is placed in the disc and dye is injected, to assess whether stimulating the suspect disc reproduces the usual pain.

What are the risks of an ALIF?

This is an elegant but technically difficult procedure because the abdominal contents need to be carefully moved out of the way to allow access to the spine. A complete list of risks is outlined elsewhere. The main specific risks of this procedure are

• Damage to the major blood vessels. In front of the spine run the aorta and vena cava, which travel from the heart, through the belly, and split to supply the legs. Tearing one of these vessels or their branches can lead to major bleeding.
• Retrograde ejaculation. A fine network of nerves run in front of the spine, and are responsible for a number of autonomic (subconscious) functions, such as sweating in the legs. Of importance is the function of ejaculation, meaning that if these nerves are damaged, men lose the ability to ejaculate (although the rest of sexual function including sensation and erection are unaffected), causing infertility.

How do i perform an ALIF?

What happens to you in hospital is outlined elsewhere. Once you are in hospital, in theatre and asleep lying on your back, this is how I do the operation.

Gaining access

A transverse (crossways) incision is made over the correct spot low in the abdomen, similar to the incision used for a caesarean. The rectus (six-pack) muscles are retracted aside, and the peritoneum containing the intestines is exposed. This is moved aside and held away with a special retractor. The blood vessels are then found and also moved aside and held with the retractor. Click here to see a picture of the retractor.

Disc removal

The disc is incised and completely removed. Click here to see a video of the disc being incised and removed.

Cage preparation and insertion

Artificial bone graft replacement (bone morphogenic protein-soaked collagen sponge called Infuse) is packed in the appropriate-sized cage. The cage is then inserted into the space. Click here to see a picture of the cage. Click here to see a video of the cage being inserted.

Supplementary plate

The plate is then attached to the front of the vertebrae to hold the cage in place until the artificial bone fuses. Click here to see an x-ray of the plate and cage in place.

Finishing the operation

The wound is then closed and a dressing is applied.