What is Adjacent Segment Disease and Why is it Important?

Between the vertebrae are discs that act as shock absorbers and allow your neck to move freely side to side and forward and backward. Over time, or after an injury, these discs can break down, lose their height and have less of a cushioning effect. They can also rupture or herniate where the soft nucleus of the disc breaks through the disc wall to pressure nerve roots coming off the spinal cord. A herniated disc in the neck can cause serious symptoms like numbness, weakness or radiating pain down an arm or hand. A herniated disc in the low back can cause radiating pain, numbness or weakness into a leg or foot. It is important to understand, that the most serious symptom of a herniated disc is not radiating pain into a leg or arm, but rather numbness or weakness especially when it reaches the hand or foot. If numbness or weakness is not addressed promptly with a few days, there can be permanent neurological damage which causes the numbness to become permanent. Sometimes a spinal injection can resolve this symptom.   But if non-surgical treatment like injections and specialized physical therapy are not able to address the problem, surgery will likely be the next step.

In the past, your only surgical choice was a spinal fusion. During a spinal fusion, the damaged disc is removed and replaced with a bone graft — either from a bone bank or harvested from your own body. The vertebrae above and below the bone graft are then fixed in place using a metal plate and screws. This provides the necessary stability while your body’s natural healing process fuses to the new bone graft, creating one solid vertebral segment.

Because this new fused segment does not retain the natural bending and turning motion of the original spine, additional stress is exerted on the vertebral segments above and below the fusion. This can lead to a condition called adjacent segment disease.

Adjacent segment disease can be very problematic as the stress from everyday activities places increased stress on the nearby discs, leading to degeneration and damage of the once healthy surround discs. Ultimately this can lead to the need for additional fusions, creating a larger locked vertebral segment and perpetuating a domino effect of stress on the healthy remaining discs.

Artificial Disc Replacement Reduces the Likelihood of Adjacent Segment Disease

Artificial Disc replacement surgery is a minimally invasive procedure in which the problematic disc is replaced by an artificial disc.

Unlike a fusion in which the vertebrae are locked into place with a bone graft and plate, an artificial disc is designed and engineered to mimic the natural rotation and side-to-side bending and turning of the natural spine. The major advantage of the motion preservation is that it decreases the stress placed on the discs above and below the treated level, reducing the likelihood of adjacent segment disease.

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