How are pars interarticularis injuries classified?

Updated: Jan 22, 2019
  • Author: Gerard A Malanga, MD; Chief Editor: Craig C Young, MD  more...
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Spondylolysis is derived from the Greek word spondylo, which means vertebrae, and lysis, which means fracture. Spondylolysis is defined as a defect in the pars interarticularis of the vertebral arch. Often, it is described in association with spondylolisthesis, which can be found concurrently with spondylolysis. Spondylolisthesis is defined as the anterior or posterior displacement of a vertebral body on the one below it. These conditions are generally described according to the following classification of Wiltse, Newman, and Macnab [20] :

  • Type I (dysplastic): Congenital abnormalities of L5 or the upper sacrum allow anterior displacement of L5 on the sacrum, which can occur with the pars interarticularis remaining intact.

  • Type II (isthmic): A lesion in the pars interarticularis occurs. This type of spondylolysis is subclassified as a fatigue fracture (IIA), elongation (IIB), or acute fracture (IIC).

  • Type III (degenerative): This type of spondylolysis is associated with long-standing segmental instability and alterations in the articular processes with associated remodeling of the articular process.

  • Type IV (traumatic): Acute fractures of the vertebral arch occur in areas other than the pars.

  • Type V (pathologic): This type of spondylolysis is due to generalized or focal bone disease affecting the vertebral arch.

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