Spinal abnormalities rarely cause back problems
Spine surgeons and radiologists (who both may read
and interpret MRI scans) sometimes differ in their
method of labeling a particular spinal segment. This
creates confusion—among both patients and insurance
companies—triggering the question: “Where
is the problem?”
A sixth lumbar vertebra
One of the reasons for the confusion is that some people,
approximately 10% of adults, have a congenital anomaly
in their lower back. One of the most common anomalies
is the presence of a sixth lumbar vertebra. Having
one extra lumbar vertebra provides no advantage or
disadvantage to the individual and is rarely a cause
of back problems, but it can create some confusion.
For example:
-
Radiologists commonly count down from the last
rib when numbering the lumbar vertebral bodies.
-
Surgeons on the other hand, count up from the
sacrum when numbering the lumbar vertebrae.
Neither method of labeling lumbar vertebrae is incorrect,
but obviously it can create confusion. For an individual
with 5 vertebral bodies, they would be in agreement
when labeling the L4-L5 level. If the individual
has 6 lumbar vertebrae, however, the radiologist would
typically refer to the lowest level as L6-S1 and the
level above that L5-L6, which in the surgeon’s
mind, would be correctly labeled L4-L5.
It is obviously
very important to clearly identify the location of
lumbosacral anomalies in order to avoid injection or
surgical exposure of the incorrect level. This becomes
particularly important for minimally invasive procedures.
A physical exam and complementary imaging studies,
such as an MRI scan and x-ray, can help improve the
accuracy and the communication of the diagnosis.
When spinal anomalies cause back problems
Patients are sometimes told that a spinal anomaly—such
as a sixth lumbar vertebrae or an extra sacral bone—has
been found on an x-ray and is causing their back
problems. However, anomalies such as these in the
lumbar spine and sacral spine are simply variants
of normal bony architecture and are typically of
no consequence. In other words, it would be very
rare for an abnormality such as a sixth lumbar vertebra
or extra bone in the sacrum to cause back problems.
The one exception to
this general guideline is in cases where the last transverse
process (a bony protrusion near the vertebra) is partially
attached to the sacrum, or “sacralized”.
If this bony protrusion is attached to the sacrum,
it can create a rudimentary joint (pseudoarticulation)
where there shouldn’t
be one. The resulting motion in this section of the
spine can sometimes be a cause of localized low back
pain. This condition can usually be successfully
treated without surgery. For instance, an injection
of steroid medication at the pseudoarticulation of
the transverse process and the sacrum can often be
both diagnostic and therapeutic.
By: Pamela E. Verkuilen, APNP
November 18, 2005
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