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Pars defects often lead to spondylolisthesis.
The final ancillary observation that may aid in the detection of spondylolysis is an abnormal wedging of the posterior aspect of the vertebral body at the level of the pars defect. This finding is a well-known radiographic finding that occurs at the level of spondylolisthesis. It is unclear if this finding is an effect of the spondylolisthesis, a predisposing condition, or a combination of both. On sagittal MR images, wedging of the posterior vertebral body is seen both in patients with spondylolisthesis and in those with spondylolysis and no significant subluxation.8 Therefore, such wedging may suggest the presence of pars defects (Figure 8).
A unilateral pars defect (spondylolysis) may not demonstrate any degree of slippage; thus, a patient may have spondylolysis without spondylolisthesis. The reverse is also true as in the degenerative-type slips described below.
development of the pars defects and spondylolisthesis.
Type I. Dysplastic: This type results from congenital abnormalities of the upper sacral facets or inferior facets of the fifth lumbar vertebra that allow slipping of L5 on S1. There is no pars interarticularis defect in this type. The sacrum is not strong enough to withstand the weight and stress. Thus, the pars and inferior facets of L5 are deformed. If the pars elongates, it is impossible to differentiate it by x-ray from the isthmic (type II b) Spondylolisthesis. If the pars separates, it becomes impossible to differentiate it by x-ray from the isthmic lytic (type II a) Spondylolisthesis. This type is also associated with sacral and neural arch deficiencies. It has a familial tendency.
Type II. Isthmic: This type results from a defect in the pars interarticularis that allows forward slipping of L5 on S1. Three types of isthmic spondylolistheses are recognized:
L5-S1 Spondylolisthesis, pars defect ..
The most frequent site of pars defect spondylolisthesis is L5 where 70% to 90% are found. (4,23) The next most common site is 4L where 25% are found. (4,23). L1 to L3 and C5 to C7 are the location of 2% to 3% each. (23) In the chiropractic office, isthmic spondylolisthesis is typically seen at L5 and degenerative spondylolisthesis at L4/L5. At times, one finds both a degenerative L4 and isthmic L5 spondylolistheses in the elderly patient.
There are various types of spondylolistheses. The primary types of interest to us are the isthmic and degenerative with pars interarticularis defect.
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Bilateral Pars Defect - neck and back
Spondylolisthesis refers to the forward slippage of one vertebral body with respect to the one beneath it. This most commonly occurs at the lumbosacral junction with L5 slipping over S1, but it can occur at higher levels as well. It is classified on the basis of etiology into the following five types :
07.06.2011 · Treatment for L5-S1 Spondylolisthesis
The term spondylolisthesis was coined by Killian in 1854 to describe gradual slippage of the L5 vertebra due to gravity and posture. In 1858, Lambi demonstrated the neural arch defect (absence or elongation of the pars interarticularis) in isthmic spondylolisthesis. Albee and Hibbs separately published their initial work on spinal fusion. Their methods were applied quickly to cases involving trauma, tumors, and, later, scoliosis. In the latter half of the 20th century, spinal fusion was used increasingly to treat degenerative disorders of the spine, including degenerative spondylolisthesis and degenerative scoliosis.
Spondylolysis (Pars Fractures) and Lytic Spondylolisthesis; ..
The pars interarticularis, or isthmus, resists significant forces during normal motion. The pars may be congenitally defective (isthmic spondylolisthesis as spondylolysis) or may undergo repeated stress under hyperflexion and rotation that results in microfractures. Lumbar lordosis, gravity, posture, high-intensity activities (eg, gymnastics), and genetic factors all play a role in slip development. If a fibrous nonunion forms from an ongoing insult, elongation of the pars and progressive listhesis results; this is observed in another subtype of type 2 (isthmic) spondylolisthesis. In persons with spondylolysis, 30-50% are believed to progress to spondylolisthesis. The most common location is at L5-S1.
(Pars Fractures) and Lytic Spondylolisthesis
The pars interarticularis, or isthmus, is the bone between the lamina, pedicle, articular facets, and the transverse process. This portion of the vertebra can resist significant forces during normal motion. The pars may be congenitally defective (eg, in spondylolytic subtype of isthmic spondylolisthesis) or undergo repeated stress under hyperextension and rotation, resulting in microfractures. If a fibrous nonunion forms from ongoing insult, elongation of the pars and progressive listhesis results. This occurs in the second and third subtypes of type 2 (isthmic) spondylolisthesis. These typically present in the teenage or early adulthood years and are most common at L5-S1.
at the site of the pars defect and no spondylolisthesis
Biomechanical factors are significant in the development of spondylolysis leading to spondylolisthesis. Gravitational and postural forces cause the greatest stress at the pars interarticularis. Both lumbar lordosis and rotational forces are also believed to play a role in the development of lytic pars defects and the fatigue of the pars in the young. An association exists between high levels of activity during childhood and the development of pars defects. Genetic factors also play a role.
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