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Posterior Lumbar Interbody Fusion (PLIF)

What is a PLIF?

PLIF stands for 'posterior 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 back (posterior) rather than the front, and the fusion material is placed between the vertebrae (in the interbody region).

It was popularised in the 1950's and 1960's by a surgeon called Cloward. It was originally done by taking bone from the posterior iliac crest (the 'hip' region) and putting it between the vertebrae. It lost popularity because of the high complication rate and technical difficulty. In the 1980's, metal spacers filled with bone ('cages') were designed to be used between the vertebrae. These cages have been heavily marketed and have led to a resurgence in the PLIF procedure. It is my opinion that the operation may be done too often at present. Hopefully in the future, it will become more clear when the PLIF operation should be done.

When would a PLIF be done?

A PLIF is done when you want to do a fusion between the vertebrae (interbody fusion) and either

  • the surgeon needs to open the spinal canal where the nerves are and so the surgery is done from the back. This would be the case where there was compression of the nerves that needed to be released, such as from a disc protrusion or bony narrowing (stenosis). Therefore it is preferable to do the fusion from the same approach, ie. from the back ,or
  • 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 (the main one being infertility from retrograde ejaculation in young males)
  • it is the surgeon's preference, because of experience.

The main reason I do the operation is if there is compression of nerves between two vertebrae due to the fact that the disc has collapsed and spurs have grown. This is called foraminal stenosis. Release of the nerves requires both removal of excess bone (decompression) and restoration of the space between the vertebrae (interbody fusion). It seems the best way to do this is with a PLIF. Another common reason is where there has been a disc protrusion treated surgically with discectomy in the past, and back and leg pain have developed again because of further disc bulging and disc space collapse. Again, decompression and fusion with a PLIF appears to be a good approach for this problem.

The PLIF operation is sometimes done when other techniques would have worked equally well or better. I am generally not in favour of this because the PLIF procedure is a difficult, time-consuming operation with more risks than some other procedures.

PLIF is also not suitable in some cases. These include

  • Spinal deformity secondary to degeneration, such as scoliosis or significant spondylolisthesis
  • Multiple level degeneration, as this procedure can only be done at one and at the most two levels
  • Osteoporosis, as collapse can occur as the fusion sinks into the soft vertebral bodies
  • Upper lumbar fusions (L3-4 and above) as here the nerves are at greater risk of damage

What are the risks of a PLIF?

This is a technically difficult procedure that takes longer than most similar fusion operations. A complete list of risks is outlined elsewhere. The main specific risks of this procedure are

  • Nerve root damage during the procedure. During removal of the disc and insertion of the cages, the nerves can be stretched, squashed or cut. This can cause leg pain, numbness and weakness.
  • Scarring after the procedure. Because the nerves are being extensively handled and manipulated and bleeding occurs in the region, there is an increased chance of scarring around the nerve sheath (epidural fibrosis) and even within the sheath (arachnoiditis). This can cause burning leg pain in the future.
  • Movement of the cages. The cages can move backwards and push on the nerves, causing leg pain, numbness or weakness. They can sink into the vertebrae, and the effectiveness of the operation is lost.

How do i perform a PLIF?

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

Gaining access

An incision is made over the correct spot, and the muscles are peeled back from the bone to expose the vertebrae. A special retractor is used to hold the muscles out of the way. Click here to see a drawing of the position you are in. Click here to see a video of the exposure and retractor.

Pedicle screws

The supplementary screws are inserted into the vertebrae. If for example, an L5-S1 fusion is being done, screws are inserted into the L5 and S1 vertebrae. Click here to see a picture of the screws.

Decompression

Bone is removed to free the compressed nerves. This is called a laminectomy. The nerves are then carefully retracted out of the way and the disc is then removed and the surfaces of the vertebrae are cleared. Click here to see a video of the disc removal.

Cage preparation and insertion

Bone is taken from the posterior iliac crest (the 'hip' region). Click here for a video of the bone graft harvesting. It is then packed into the cages. Click here to see a picture of the cages. The cages are then inserted into the space. Click here to see a video of the cages being inserted.

Pedicle device

The pedicle screws are then connected with rods. Click here to see a picture of the pedicle device.

Finishing the operation

The wound is then closed and a dressing is applied.