What is spinal instability? The term is certainly a mouthful, and definitely can be confusing.
If we break it down, “spinal” means spine, and “instability” means it is not stable.
As we have described in other videos, the spine is composed of bones and a disc. Among the functions of the disc, is to provide a strong structure between the vertebrae that’s soft enough to move, but firm enough to prevent bones from dislocating on top of each other.
In prior videos, I also explained the concept of spondylolisthesis. Which is a slippage of one vertebrae on top of the other. To prevent that slippage, the bones must be secured to one another by ligamentous structures, including the discs in the front of the spine, and the various ligaments in the back of the spine that holds the bone to one another. Because these ligaments provide some movement, but it’s controlled, the bones cannot dislocate. The bones cannot move too far forward of one another to cause compression or pinching of what’s encased within the vertebrae. Which is either the spinal cord, and sometimes including the nerves. The control of how far the bones can twist, and turn, and bend is this concept of spinal stability.
With spinal instability, in other words, with excessive movements of bones on top of each other, there’s potential for damage, pain, and very bad things such as paralysis or permanent muscle weakness; because the nerve signals are compromised or no longer transmitted.
As doctors and scientists, we know that certain medical studies such as x-rays can give us information that demonstrates spinal stability or instability. In the neck, if one vertebral bone slips forward more than 3.5 millimeters on flexion and extension views, that is considered unstable.
In the neck, if the angle of one bone in relationship to the other is greater than 11 degrees, comparing the flexion and extension views, that is a sign of instability.
The same instability signs are also used for the lower back. In addition, with the development of more recent diagnostic tools, scientists and doctors are working on other concepts of defining instability; including rotational instability, and dynamic instability based on weight bearing.
In the end, the reason doctors and scientists try to better define this concept of instability is that certain people may have pain to the spine and weakness and numbness secondary to instability. If instability is identified, doctors may recommend treatments that can include possible surgery to prevent the instability from causing further complaints, and to prevent potential permanent injuries from this condition.
I hope I simplified this concept, instead of making it more confusing. Thank you for listening.
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Last modified: February 17, 2020