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.

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.

Advantages:

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.