Minimally Invasive Surgery

The success rate for posterior fusion in the treatment of refractory discogenic back pain is only 60-70%. The selection of the appropriate patient for this surgery has been blamed for the relatively poor results. Other possible causes of poor results are that the actual pain-causer, the disc, is not addressed. Studies have shown continued significant movement of the disc despite solid posterior fusion. One study showed that patients with continued back pain after solid posterior fusion were improved after anterior fusion of the disc space.





image

This image shows a side view of an instrumented spine. The arrow shows the force of gravity which is diverted from the disc to the posterior instrumentation. One can imagine how the disc space could continue to have motion despite solid posterior fusion.



In an attempt to improve the results of fusion surgery, fusion of the disc has been performed to directly address the most common source of pain. Unlike the posterolateral gutter fusion, the PLIF achieves spinal fusion by inserting bone graft and possibly instrumentation directly into the disc space. The disc excision and fusion can be performed anteriorly, or through a posterior approach. When the posterior approach is used to remove and fuse the disc, this is called a PLIF, Posterior Lumbar Interbody Fusion.


An alternative approach is used to minimize retraction of the dura. By resecting the facet joint, a farther lateral approach can be used to remove the disc. This approach, with removal of the facet, is called a TLIF - Transforaminal Lumbar Interbody Fusion.

THE GENERAL PROCEDURE:

image image

1. First, the spine is approached through a three-inch to six-inch long incision in the midline of the back and the left and right back muscles (erector spinae) are stripped off the lamina on both sides and at multiple levels.


2. After the spine is approached, to perform the PLIF procedure (shown below), the lamina is removed (laminectomy) which allows visualization of the nerve roots. The facet joints, which are directly over the nerve roots, are usually undercut to give the nerve roots more room and more room for performing the fusion and/or instrumentation. For the TLIF procedure (shwon below), the entire facet joint is removed.


3. The nerve roots are then retracted to one side and the disc space is cleaned of the disc material. Bone graft is then inserted into the disc space with or without interbody cages. For a standard PLIF procedure, the bone graft and/or instrumentation is performed on both sides. For the TLIF procedure, the disc space is accessed from one side, reaching over to remove and replace the disc on the other side.
The TLIF approach is shown below, with removal of the disc. Bone graft, bone from the bone bank, or instrumentation in the form of a cage can be placed through this approach.                                 

AFTER SURGERY

Risks include:

  • Nerve Injury
  • Adjacent disc disease
  • Infection
  • Bleeding
  • Non-union


The PLIF and TLIF approach has an advantage over the posterolateral gutter fusion in that the large spinal muscles do not need to be dissected off the transverse processes, so there is less scarring of the muscle and associated pain for the patient. The major advantage of PLIF and TLIF is that there is significantly more surface area for fusion in the disc space as compared to the posterolateral gutter.


However, the PLIF requires substantial retraction of the nerve roots to gain access to the disc space. Significant traction can injure the nerve root and has the potential to result in chronic leg pain and back pain. The pain associated with this type of nerve root injury can be severe, and there are no effective options for treatment. The TLIF requires less retraction of the dural sac, but nerve injury can occur at the level of the nerve cell bodies (dorsal root ganglion). Pain associated with manipulation of the DRG can also be very severe and debilitating. Fortunately, these complications are rare with meticulous care of the nerves.


There are numerous veins (epidural veins) over the disc space, and surgery in this area creates the potential for excessive blood loss during the surgery.


Recurrent pain after a successful spinal fusion procedure is more likely due to a “transfer” lesion at the motion segment above or below the fusion, because stress is transferred to the next level and may cause that vertebral segment to degenerate and breakdown.


Nonunion rates of between 0% and 20% have been quoted in the medical literature. Nonunion rates are higher for patients who have had prior surgery, patients who smoke or are obese, patients who have multiple level fusion surgery, and for patients who have been treated with radiation for cancer.


Other than nonunion, the risks of a spinal fusion surgery include infection or bleeding. These complications are fairly uncommon (approximately 1% to 3% occurrence).

Possible Risks/Complications

Risks include:

  • Nerve Injury
  • Adjacent disc disease
  • Infection
  • Bleeding
  • Non-union

The PLIF and TLIF approach has an advantage over the posterolateral gutter fusion in that the large spinal muscles do not need to be dissected off the transverse processes, so there is less scarring of the muscle and associated pain for the patient. The major advantage of PLIF and TLIF is that there is significantly more surface area for fusion in the disc space as compared to the posterolateral gutter.


However, the PLIF requires substantial retraction of the nerve roots to gain access to the disc space. Significant traction can injure the nerve root and has the potential to result in chronic leg pain and back pain. The pain associated with this type of nerve root injury can be severe, and there are no effective options for treatment. The TLIF requires less retraction of the dural sac, but nerve injury can occur at the level of the nerve cell bodies (dorsal root ganglion). Pain associated with manipulation of the DRG can also be very severe and debilitating. Fortunately, these complications are rare with meticulous care of the nerves.


There are numerous veins (epidural veins) over the disc space, and surgery in this area creates the potential for excessive blood loss during the surgery.


Recurrent pain after a successful spinal fusion procedure is more likely due to a “transfer” lesion at the motion segment above or below the fusion, because stress is transferred to the next level and may cause that vertebral segment to degenerate and breakdown.


Nonunion rates of between 0% and 20% have been quoted in the medical literature. Nonunion rates are higher for patients who have had prior surgery, patients who smoke or are obese, patients who have multiple level fusion surgery, and for patients who have been treated with radiation for cancer.


Other than nonunion, the risks of a spinal surgery include infection or bleeding. These complications are fairly uncommon (approximately 1% to 3% occurrence).