Spondylolysis/Pars Defect

Spondylolysis or Pars Fracture

Before we talk about what is Spondylolysis or Pars Fracture,
we need to understand what is normal.


So, what is normal
vertebral anatomy?

As you below in the two drawings the vertebra of 3 parts:
the vertebral body (which is in the front), the posterior elements (in the back;
red circles), and the pedicles (which connect the vertebral bodies in the front
to the posterior elements in the back.

The spinal cord and nerve roots run in the blue areas below:

Notice the 3 parts of the vertebra create a full bony ring
around the spinal cord and nerve roots (below):

What is a pars
A pars fracture/spondylolysis (red lines, below) is
a break in this bony ring at the area called the pars interarticularis.

This means the back area is not attached, is loose and can
wiggle back and forth with back motion.

What does
spondylolysis mean?
If you break down the word into its Latin roots,
spondylo- means “vertebra” and –lysis means “break”.  So the red lines are the place where the
break in in the posterior elements.

Is there a difference
between pars fracture and spondylolysis?
No, they mean the same thing.  I believe the main the phrase “pars fracture”
is more commonly utilized is due to the difficulty in pronouncing
“spondylolysis”, and its similarity of “spondylolysis” to the phrase
“spondylolisthesis”, which is a more advanced/severe stage.

Can you be born with
There have been no reports of spondylolysis being present at
birth, so they develop over time.

Why does it happen?
Most likely all those pars that break did not develop normally. The pars area
is very narrow and with motion gets stressed, then a crack develops.  If this problem was simply due to sports or a
particular activity, we would see this much more commonly.

The area then cracks…

We will continue to present this topic over the next several

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