The vast majority of patients with low back pain are successfully treated without surgery, but if the pain is so disabling that non-surgical care doesn’t work, then fusion is sometimes considered. The discs are the cartilage shock absorbers between the spine bones that function as pivot points for motion of the spine. Just like the cartilage in the knee or hip, disc cartilage can wear out over time. While degeneration of the discs can be caused by a specific injury, most cases result from normal aging or “wear and tear”. This condition is referred to as “degenerative disc disease.”
Indications For Spinal Fusion
Various techniques of spinal fusion have been developed to treat a variety of conditions such as spinal trauma, tumors or instability. In these situations, fusion is employed to decrease motion in a particular area of the spine in order to protect the spinal cord and nerves from damage due to abnormal movement of the spinal bones.
Some Examples of Spinal Fusion are:
This fracture of a lumbar verterba was compressing the spinal cord. The displaced bone that was surgically removed and replaced with a cylindrical “fusion cage”. Titanium screws were applied from the back to provide additional support.
Spondylolisthesis (a forward slippage a vertebra) can result from injury, a congenital defect in the bone, or degeneration due to age. This case was corrected and stabilized using screws and rods.
X-rays of an adolescent girl with a 65 degree curvature of the spine. The curve was corrected and stabilized using screws and rods.
DEGENERATIVE DISC DISEASE:
Left image: Degenerative disc disease of the lowest disc, L5-S1. Note the loss of disc height compared to the other normal discs. Right image: Degenerative disc disease affecting multiple discs.
TECHNIQUES FOR SPINAL FUSION
There are several techniques used to fuse the spine. One technique entails placing bone graft, usually obtained from the pelvis, along the sides of the vertebrae to be fused. The success of this technique is improved with the addition of screws and rods used to decrease motion between adjacent vertebrae.
The success of fusion can also be improved with the use of “fusion cages” which are inserted into the disc space. First the disc is removed, and then the fusion cage, filled with bone or a bone substitute, is inserted. Fusion cages increase the space between the vertebrae thereby taking pressure off of nerves.
In the lower back, interbody fusion cages can be inserted from various approaches—from the back (Posterior Lumbar Interbody Fusion or PLIF), from the front (Anterior Lumbar Interbody Fusion or ALIF), or from the side (Extereme Lateral Interbody Fusion or XLIF). The patient’s surgeon will take into consideration certain advantages and disadvantages of each approach in deciding which approach is most appropriate for that patient.
POSTERIOR LUMBAR INTERBODY FUSION (PLIF)
PLIF surgery is the preferred approach when there is severe compression of nerves due to bone spurs or disc protrusion that need to be addressed directly.
PLIF can be performed using minimally invasive techniques which decrease the damage to the back muscles, which hastens recovery.
ANTERIOR LUMBAR INTERBODY FUSION (ALIF)
The anterior approach allows a very thorough discectomy and elevation of the disc space, which indirectly increases the space available for the nerves. It can often be performed as a “stand alone” procedure using instrumention, thereby avoiding any damage to the back muscles.
The anterior approach requires retracting large blood vessels to allow access to the spine, so it is often performed by both a spine surgeon and a vascular surgeon working as a team.
EXTREME LATERAL INTERBODY FUSION (XLIF)
XLIF surgery provides many of the advantages of an anterior approach, while avoiding retraction of the large blood vessels in the abdomen. The procedure is performed using a tubular retractor so the incision is small and heals quickly.
XLIF can be very effective in correcting degenerative scoliosis when combined with posterior instrumentation. Because the pelvis blocks access to the lowest disc space, XLIF can only be utilized above L5-S1.
A slippage forward the lowest lumbar vertebra (spondylolisthesis), corrected using an interbody cage inserted anteriorly, and screws inserted posteriorly.
Next Section: Treatment Options for Herniated Discs
are a variety of treatments that should first be explored when
trying to treat this herniated disc pain, the final of which is herniated disc
surgery. Go to Treatment
Options for herniated discs.