The purpose of this article is to emphasize the role of oblique views and an AP lumbosacral spot view in the detection of the subtle pars interarticularis defects; literally, the area between the articular processes.

Spondylolisthesis comes from the Greek spondylos, which means 'vertebra' and listhesis, which means to 'slip or slide'.

Types of Spondylolisthesis:

  1. Congenital - present at birth - abnormal vertebra development.
  2. Isthmic (pars defect) - most likely due to stress fractures weakening the bone in the pars region due to excessive hyperextension.
  3. Degenerative - with ageing, the discs lose water content and allow slippage of one vertebra upon another. Most commonly occurs at L4.

Less common types:

  1. Traumatic - due to an injury.
  2. Pathologic - a vertebra weakened by a disease process.
  3. Post Surgical - slippage becoming worse after spinal surgery.

In the typical chiropractic office, patients will commonly present with lower back pain associated with spondylolisthesis.


Figure 1 - Netter Diagram

Figure 2 - Pars Defect

Defect is indicated by double arrows.

Anterior slippage of the L5 vertebra on sacrum is indicated by arrow with base.

If the physician is concerned about subtle pars defect, an AP spot view or oblique views are warranted to evaluate the pars region optimally.

Figure 3 - AP Lumbosacral Spot View

Central ray is directed between umbilicus and symphysis pubis with ~25 degrees cephalic tube tilt.

C = Pedicle of vertebra. Pars region is immediately below the pedicle on the AP radiograph.


Single view will show both pars.

Less radiation exposure to patient.

Figure 4 - Oblique Views

Properly positioned (coned down) oblique view showing the pars region optimally.

2 views required to present both pars.


  1. Fig. 2 - 2005
  2. http:// mydlevelandclnic. Org/disorders/back/hic...spondylolisthesiis

Contact ACRRT

American Chiropractic Registry
Radiologic Technologists

52 W. Colfax Street
Palatine, Illinois

Telephone: 847.705.1178


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