CT lumbar spine (Sagittal view)
Description of Case No. 3:
Sagittal reformatted image derived from axial CT scans of the
lumbar spine shows degeneration at the L4/5, level with a
vacuum phenomenon. A grade II spondylolisthesis is seen at the
L4/5, level. L4/5, level disc spaces are narrowed.
The most frequently seen alignment abnormality is spondylolisthesis, which is defined as ventral slippage of
a vertebra relative to the vertebra below.
Spondylolisthesis is most frequently seen at L5/S1, level and to a lesser extent at L4/5, level.
A commonly used classification system defines spondylolisthesis as
- Type I (dysplastic/congenital): secondary to an abnormal neural arch.
- Type II (isthmic): secondary to the lesion of pars interarticularis.
- Type III (degenerative): due to chronic instability and intersegmental degenerative changes.
- Type IV (post-traumatic): fracture other than fracture of pars leading to slippage.
- Type V (pathological): may be due to diffuse or local pathology.
- Type VI (iatrogenic): due to unknown causes.
The two most common causes of spondylolisthesis relate to bilateral defects in the pars interarticularis (isthmic or spondylolytic spondylolisthesis) and facet disease (degenerative spondylolisthesis)