one vertebrae over another which may result in pain. There are
two types of spinal instability: macro instability such as in dynamic
spondylolisthesis and microinstability such as slight movement of
one vertebral body over another which may not be detectable on
MRI or CT scan. While there are many definitions of instability, the
most commonly used is: "
"4 mm of translation or >10° of angular motion between adjacent
end plates on lateral flexion and extension radiographs are the
most widely used criteria for lumbar hypermobility.
Segmental motion was studied by Boden and Wiesel in the
lumbosacral spines of 40 healthy individuals in an attempt to further
elucidate radiographic instability patterns. On flexion and extension
films, 42% of normal individuals had at least one level with a static
listhesis >3 mm. However, when measuring dynamic translation (ie,
the change in amount of slip between flexion and extension films),
the number of normal individuals with a dynamic slip >3 mm was
only 5%. The authors concluded that using dynamic lateral
radiographs should decrease the rate of false-positive diagnoses of
instability approximately eightfold."
This means that low grade spondylolisthesis is not in and of itself
necessarily a problem because it is stable, and does not move with
flexion or extension of the spine. For that reason, many surgeons
will not attempt to reduce the degree of slippage and may not
operate at all if there are no significant symptoms and the spine is
dynamically stable.
TWO TYPES OF SPONDYLOLISTHESIS:
Degenerative (most common) and Isthmic
Degenerative spondylolisthesis often occurs with advancing age and
is due to a reduced disc height with development of a "wobbly"
spine, facet joint enlargement and deformation, and laxity of the
supporting ligaments of the spine. This type of spondylolisthesis
may cause pain through the facet joints, by compression of the
nerves in the central spinal canal, and by foraminal stenosis.
Therefore, this type of spondylolisthesis may result in symptoms of
neurogenic claudication as seen in spinal stenosis, "pinched nerves"
with pain radiating to the foot, and facet syndrome.
Isthmic spondylolisthesis is accompanied by fracturing of the pars
interarticularis which allows the slippage to occur. Usually the
fracture (spondylolysis) occurs between ages 5 and 7, and is only
rarely due to overt trauma. Injections of these pars defects can
help to diagnosis painful fractures.
Treatment of spondylolisthesis is depend on the symptoms seen.
Often the treatment consists of surgery to target the specific
pathology caused by the spondylolisthesis.
