This type is seen in patients who had previously undergone spinal surgery either for scoliosis or for degenerative low back conditions. A number of things can happen:
1. Post-Laminectomy Scoliosis or Kyphosis
In rare instances, the spine will develop scoliosis (front curve) or kyphosis (forward bend) after a common procedure used to treat spinal stenosis (pinched nerves) in adults – especially if many levels are decompressed.
2. Post-surgical Instability or Failed Fusion
At times, especially after extensive low back surgery, the spine will lose its ability to support itself in a normal position. This is similar to adjacent-level disease, but may occur within the operated levels themselves. Also, every fusion procedure has a small chance that the bones will not join together. This is called “pseudarthrosis” (false joint) and may lead to further collapse of the spine.
(Figure 1 C&D)
3. Adjacent-Level Disease
When a spinal segment is fused together, additional stress is placed on the neighboring segments. This can contribute to accelerated arthritis. Depending on the body’s response, the body may lean to the side or forward. Most of the time significant spinal deformity does not occur. However, symptomatic curves can develop.
4. “Flat-back Syndrome”
Patients with this condition are unable to stand upright and are usually “pitched forward” where the lower back has lost its normal inward curvature or lordosis.
5. Traumatic Dcoliosis or Kyphosis
When a vertebra is deformed from trauma (fractures), the adjacent levels typically try to straighten out the spine. When the spine is unsuccessful, or the degree of deformity is too high, scoliosis or kyphosis can occur.
(Figure 1 G&H)
For more information about Fixed Sagittal Imbalance
(inability to stand up straight), click here.