Answer:
Dear
Matthew,
Disc
bulge or protrusion results when the disc bulges out from between
two vertebrae without rupturing its surrounding envelope, the annulus
fibrosis.
The causes
of a bulging disc include:
Age
Arthritis
Injury
Lifting
Overweight
Posture
Spondylolisthesis
can be caused by:
- a birth
defect
- fractures
- spondylolysis (a defect or fracture in the pars interarticularis)
- degeneration due to age or overuse
- tumors
- surgery
There
are different types of spondylolisthesis. It all depends on the original
cause: what made your vertebra slip forward.
Spondylolisthesis
Type II also called isthmic, is the most common kind of spondylolisthesis.
With type II spondylolisthesis, there's a problem with the pars interarticularis,
a particular region of your vertebra.
In Spondylolisthesis
Type II A, gymnasts, weight lifters, and football linemen are especially
prone to this kind of spondylolisthesis. It's caused by multiple micro-fractures
on the pars interarticularis-micro-fractures that occur because of
hyperextension (overarching) and overuse. The pars interarticularis
fractures completely in type II A.
Pseudodisc
bulging without disc herniation is the most common type in isthmic
spondylolisthesis.
However,
in cases of disc herniation, extreme lateral disc herniation occasionally
occurs; therefore, every isthmic spondylolisthesis patient should
be examined carefully for extreme lateral disc herniation with thin-cut
axial CT or MRI, especially when the patients complain of lateralizing
symptom.
Normally
the facet joints in the back of the spine protect the disc from shear
as they act to limit the shear force.
When
there is a pars interarticularis fracture the facet joints cannot
limit shear.
Discs
work well as a shock absorber but they are susceptible to being damaged
if they have to resist shear.
When
a disc is damaged, it may bulge.
Degenerative
spondylolisthesis is an acquired condition related to chronic degenerative
disc disease and the associated changes that may lead to segmental
instability. The pars interarticularis is not affected in degenerative
spondylolisthesis.
The degeneration
of intervertebral discs (degenerative disc disease) results in narrowing
of the disc space, which allows the supporting structures to become
lax and can lead to segmental instability, most common at L4-L5.
Bulging
of the discs is possible for degenerative disc disease
