|
|
|
|
|
|
|
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
|
|
|
    |
|||||
|
|||||
|
Why the pars fractures is incompletely understood, but research has revealed some telling facts. Approximately 5-8% of the ambulatory (walking) population older than age 5 has pars fractures. Pars fractures interestingly have not been found in two populations of humans: fetuses and patients who have been paralyzed and non-ambulatory from birth. Moreover, pars fractures are found in increased frequency in athletes who hyperextend their spine such as gymnasts and football inside lineman. These facts taken together indicate that pars fractures are in fact stress fractures produced when the predisposed, weakened pars interarticulars is subjected to repetitive hyperextension forces. Why certain patients become variably symptomatic is unknown. The magnitude of symptoms caused by spondylolisthesis does correlate
with the degree of anteriolisthesis of the vertebra. A grading system
has been defined to characterize the degree of slip: the full front-back
Low back pain and nerve compression symptoms are found in patients with
isthmic spondylolisthesis. For the same reason that the vertebra translate
relative to each other, the pars fracture permits abnormal vertebral motion
creating low back pain. Chronic tearing and degeneration of the disc may
actually be the pain
Treatment is designed to stop either the progression of the slip or the abnormal motion which creates pain. As with most spinal problems, children are treated for different reasons than adults. In children, low back pain and associated nerve irritation causing leg pain and hamstring tightness can initially be treated by rest and cessation of athletic activity. In some cases, bracing may be attempted. Documented progression of the slip and pain refractory to conservative measures are indications for surgery. Adults should initially be treated with rest, anti-inflammatories, and physical therapy as symptoms subside. Slippage does not usually progress in adults. Studies have shown that subtle neurological deficits can exist in 18% of patients without surgery, but that severe neurological deficits are rare. It is for this reason that serial neurological examinations should be performed during the course of conservative treatment. Patients with symptoms refractory to conservative treatment may be candidates for surgery.
Last
updated: 9/20/02
|
Spondylolisthesis
refers to the relative translation of adjacent Vertebra in the spine.
Anteriorlisthesis means forward translation of the upper vertebra. Although
spondylolisthesis can be caused by various pathologic states in the spine,
Isthmic Spondylolisthesis is produced when bones (pars interarticularis)
connecting the facet joints in the posterior spine are fractured causing
anteriolisthesis of the vertebra. The pars serves as a checkrein for translation
movement of the vertebra and when fractured, the vertebra are allowed
to move past each other producing symptoms ranging from mild low back
ache to severe neurologic deficits. Although L5-S1 is most commonly affected,
isthmic spondylolisthesis has been found at every lumbar level. 
depth
of the vertebra is divided into fourths and a spondylolisthesis is graded
1-4 based on the quarter percentage of slip. For example, a grade 2 slip
is defined as the upper vertebra moving 50% on the lower vertebra. A grade
5 slip means that the vertebra has completely dislocated off the lower
vertebra. In general, grade 4 slips may present with more low back pain
and neurological problems than a grade 1 slip, although this rule does
have exceptions. One study has suggested that 2/3rds of grade 2 slips
could be treated non-operatively, while larger slips uniformly needed
treatment including surgery. In general though, approximately 50% of individuals
with Isthmic spondylolisthesis will seek treatment for low back pain at
sometime during their life.
generator,
but this has never been proven. This chronic abnormal motion (sometimes
referred to as instability) also creates a situation where the pars fracture
cannot heal. New bone forms around the fracture and may actually compress
the nerves which pass in proximity. This compression, plus the nerve stretch
caused by the forward motion of the vertebra, is responsible for the nerve
irritation and leg pain.
The
current state of the art is fusion surgery for isthmic spondylolisthesis.
How this fusion will be done depends on multiple factors. As the vertebra
translates, it also tilts producing the characteristic slip angle. The
slip angle produces kyphosis in the lumbar spine which may need to be
corrected if severe. It is generally held that if correction of the spondylolisthesis
is attempted, that it is more important to correct the slip angle than
translation. These factors might determine whether a fusion surgery can
be effectively done from the back only versus a front and back operation.
In my hands it is impossible to correct slip angle without a front operation.
The rate of fusion failure (pseudarthrosis) for posterior-only fusion
is 25% meaning that only 75 out of 100 patients will obtain a solid fusion
with this technique. In my practice, in approximately 300 patients with
front and back surgery for spondylolisthesis, none required revision surgery
for failure of fusion. Unequivocally, isthmic spondylolisthesis should
not be treated with decompression surgery only. Anterior-only surgery
for spondylolisthesis is risky because the potential instability created
by the pars fractures does not lend itself to correction by the placement
of dowel grafts or cages primarily. Each patient should be individualized
and a specific operative strategy implemented.