While multilevel spinal fusions are a common and necessary procedure to treat many types of spinal pathology, such as scoliosis or other types of deformity, for treatment of low back pain from lumbar degenerative disc pathology this type of procedure remains controversial.
Figure 1: X-ray of two-level and three-level spine fusions, from the lateral view.
Representation modeled after x-ray data.
- Two-level fusion. In certain instances, a two level spinal fusion may be an effective treatment for debilitating low back pain from two degenerated lumbar discs.
- Three-level fusion. Lumbar fusion of three or more levels of the low back as a primary treatment for low back pain is rarely recommended, and many surgeons recommend against it in all cases of multilevel degenerative disc disease.
This article examines the potential risks and benefits of multilevel fusion for patients with low back pain from degenerative disc problems.
Fusion Overview
The lumbar spine (low back) has six mobile spinal levels, also known as motion segments, surrounding and in between the five lumbar vertebrae. A spinal level carries the name of the disc at that level, named by the vertebra above and below the disc. For example, the disc space or motion segment between the L4 and L5 vertebrae is known as the L4-5 disc or the L4-5 level.
The lowest spinal segment, between the L5 vertebra and the sacrum bone of the pelvis, is known as the L5-S1 level. At each spinal level, motion is controlled by the disc, located between the vertebral bodies, and the paired left and right facet joints, in the back of the spine, which allow flexion and extension motion in the lumbar spine and block rotation motion.
Fusion of only one motion segment of the spine (e.g. L5-S1) is referred to as a single level fusion. Multilevel spinal fusion refers to fusion of more than one spinal disc level (e.g. L3-L4 and L4-L5 fusions). When a multilevel spinal fusion is performed, it is almost always on contiguous spinal levels. The most common levels included in a multilevel spinal fusion are L4-5 and L5-S1.
Indications for Multilevel Fusions
Multilevel spinal fusion for treatment of low back pain is a controversial topic. In general, lumbar spine fusion has a relatively poor success rate for treatment of multi-level disc degeneration seen on MRI scans. A two-level fusion may be considered for patients with severe, disabling pain that occurs at two levels of the spine (e.g. L4-L5 and L5-S1) after extensive non-surgical and pain management approaches have been tried. However, three-level fusions for treatment of low back pain from lumbar degenerated discs are rarely advisable for three main reasons:
- Uncertain outcomes. With fusion at three or more levels of the spine, there is a significant risk that the surgery will not improve the patient’s pain.
- Too much rigidity. Three level fusions limit movement and flexibility in the patient’s back so much that this in and of itself is likely to cause pain.
- Adjacent level degeneration. Extensive fusion of the lumbar spine transfers stress to the next level of the spine and puts that level at risk for degeneration. For example, a fusion from L3 through S1 would put the L2-L3 level of the spine at risk for degeneration and causing future pain.
Because of the above, some physicians believe that lumbar degenerative disc disease at three or more levels of the spine means that fusion surgery is not an option. Instead, patients with severe pain and degeneration at three or more levels of the spine are often advised to enter a comprehensive pain management program.
In addition to treatment for severe low back pain, there are many different reasons that surgeons perform multilevel spinal fusions. One common indication is for the treatment of spinal deformity, including scoliosis (side curvature of the spine), kyphosis (forward bending of the spine), and spondylolisthesis (forward slippage of one vertebra on another). In addition, multilevel spinal fusions are often performed in the treatment of the less commonly seen fractures, tumors, and infections of the spine.
