Accurately numbering vertebral segments is essential for reporting the exact location of radiographic abnormalities.
Normally there are five non-rib bearing lumbar type vertebral bodies.
Transitional lumbosacral and thoracolumbar anatomy is common and must be recognized to accurately identify and number vertebral segments.
There is a variety of anatomic variation, but most commonly you will encounter:
- Sacralization of L5
- Lumbarization of S1
- Hypoplastic/aplastic ribs at T12
Appropriate description often requires full axis imaging, especially if a surgical intervention is planned.
Lumbar spine radiographs obtained after trauma should evaluate for fracture and malalignment.
It is helpful to subdivide the vertebral column into 3 parts. Instability is present when 2 contiguous columns are affected:
- Anterior column: anterior longitudinal ligament and anterior 2/3 of vertebral body and intervertebral disc.
- Middle column: posterior 1/3 of vertebral body and disc and posterior longitudinal ligament.
- Posterior column: pedicles, facet joints, ligamentum flavum, interspinous ligaments
Each vertebral body should be similar in height to the adjacent vertebral body. Any degree of wedging and height loss may indicate compression fracture.
Other fractures may also appear as subtle lucency, cortical step-offs, or cortical buckling.
- Compression deformity of the superior endplate of L1 with fracture extending into the posterior spinous process concerning for 3 column fracture.
- Compression fracture of the Superior endplate of L2 with 15% estimated vertebral body height loss.
Some vertebral body fractures will demonstrate retropulsion which is term used to describe posterior displacement of a fracture fragment into the spinal canal, potentially causing stenosis or spinal cord injury.
The presence of asymmetric disc space, facet joint or interspinous widening is highly concerning for ligamentous injury, even in the absence of fracture. This warrants further assessment with cross sectional imaging.
- Comminuted fracture of T12 vertebral body with extension of fracture planes to anterior and posterior cortex with slight retropulsion.
- Focal kyphosis centered about T11-T12 with associated widening of the interspinous space posteriorly.
- Comminuted fracture of T12 associated retropulsion, focal kyphosis and interspinous widening, suggesting flexion-distraction mechanism of injury.
- Recommend CT and MRI for further assessment.
Visualization of some posterior element structures is limited and can only be achieved on certain views:
- Pars interarticularis- oblique projection; “Scottie dog sign”- fracture through neck
- Transverse process- AP projection
Example report negative for traumatic injury:
- There are 5 non-rib bearing vertebral bodies. Normal lumbar lordsosis. Vertebral body heights and alignment are maintained.
- No traumatic malalignment or compression deformity. Radiographic sensitivity for lumbar spine injury is limited. Recommend cross-sectional evaluation if suspicion for injury persists.
Traumatic Thoracolumbar Spine Injuries: What the Spine Surgeon Wants to Know Bharti Khurana, Scott E. Sheehan, Aaron Sodickson, Christopher M. Bono, and Mitchel B. Harris
RadioGraphics 2013 33:7, 2031-2046
Lumbosacral Transitional Vertebrae: Classification, Imaging Findings, and Clinical Relevance. G.P. Konin, D.M. Walz. American Journal of Neuroradiology Nov 2010, 31 (10) 1778-1786; DOI: 10.3174/ajnr.A2036