Posterior Lumbar Interbody Fusion (PLIF)

Posterior lumbar interbody fusion is a fusion procedure that is performed from the back (posterior) through an incision in the low back. Most of the disc is removed and an implant and bone graft is inserted in the disc space - in other words between the vertebral bodies (interbody).

The main benefit of a PLIF is that it allows the alignment of one vertebrae to another to be changed (as in spondylolisthesis and degenerative scoliosis) and for a collapsed disc space to be restored to its normal height. Correction of the deformity and restoration of disc height relieve pressure on the spinal nerve (leg pain). The wedge shaped implant used also restores the correct lumbar lordosis (low back curve).

 


The procedure is performed under a general anaesthetic . An incision is made in the middle of the back. Pedicle screws are inserted. A partial or complete laminectomy is performed to get access to the spinal canal. Part of the disc is removed and a specially shaped instrument is inserted into the disc space.

This instrument is flat when viewed from one side, though when rotated through 90 degrees it appears wedge shaped. The instrument is rotated in the disc space and the space is opened up and a better curvature of the spine is achieved. This tends to correct disc space narrowing and usually also corrects small to moderate slips of one vertebrae on another (spondylolisthesis).

A series of different shaped instruments is used to achieve the correct alignment. By restoring the correct alignment of one vertebrae to the next most problems with nerve compression are resolved. Importantly the vertebrae can no longer deform under loads, such as standing or bending, that might otherwise produce more compression of the nerves in  this position.

Titanium rods are now connected to the pedicle screws and the instrument between the vertebrae is removed and replaced with high strength plastic implants (R90 spacers). One spacer is inserted on each side of the spinal cord (cauda equina) and a bone graft substitute is place between the spacers and the sides of the spacers.
 
 
Post operative course

The average hospital stay is 5 days. Some patients need longer. Without appropriate care, the first 48 hours after the surgery can be very painful. Modern post-operative pain relief, however, is  very effective and patients are usually quite comfortable with the use of an epidural infusion or a patient controlled analgesia device (PCA). A wound drain is inserted at the time of surgery and this is removed on the day after surgery.  A urinary catheter is inserted at the time of surgery and this is usually removed once the patient is mobile.
 
The epidural cather is normally removed on day 3.  Compression stockings are worn on both legs to reduce the risk of deep venous thrombosis (blood clots) and these are removed once the patient is independantly mobile.
 
Physiotherapy is commenced with gentle exercises by day 3 or day 4. At the time of discharge patients are normally independantly mobile, though slow and still sore.
 
 
After discharge exercises provided by the physiotherapist should continue. Most recovery occurs over a 6 week period though it may take another two months to recover fully.

 

Possible complications

This type of surgery is complex and its potential benefits need to be balanced against the potential for complications. Generally, as with any surgery, these are:
  1. Superficial wound infection
  2. Risk of clots (deep venous thrombosis) - possible causing pulmonary embolism (the clot travelling to the lungs with occasional fatal consequences)
  3. Deep wound infection
  4. Risk of precipitating age-related medical problems in individuals prone to the problem such as heart attack or stroke (rare)
  5. Drug allergy to anaesthetic agents - occasionally very serious.

 

For this surgery in particular these complications are:
  • Nerve damage - causing either weakness in some muscles in one or both legs (uncommon) or partial or complete loss of bowel or bladder control (very rare).
  • Excessive bleeding requiring blood transfusion.
  • Post-operative bleeding around spinal cord (epidural heamatoma) causing compression and the need for further surgery.
  • Pedicle screw malplacement requiring a return to the operating theatre to re-position the screws.
  • Displacement of the screws or implants - usually due to soft bone (osteoporosis).
  • Fracture or failure of implants (very rare)