Normal Wedge Compression Fracture Size on Radiography & CT
A vertebral wedge compression fracture occurs when compressive forces cause the anterior vertebral body to collapse relative to the posterior cortex, producing a characteristic wedge-shaped deformity on lateral imaging. Accurate measurement of the anterior-to-posterior height difference is essential for distinguishing physiological vertebral wedging from a true compression fracture. This distinction directly guides clinical decision-making regarding bracing, activity restriction, and surgical referral.
Normal Reference Values
| Orientation | Location | Measurement |
|---|---|---|
| Lateral | Difference Between Posterior And Anterior Vertebral Height | <3 mm |
Clinical Significance
In the normal lumbosacral spine, the difference between posterior and anterior vertebral body height should be less than 3 mm on lateral projection. A difference exceeding this threshold raises concern for a pathological wedge compression fracture, which may indicate acute trauma, osteoporotic collapse, or underlying bone disease. In the paediatric population, physiological anterior wedging can mimic fracture; correlation with clinical history and mechanism of injury is therefore critical.
When the anterior-posterior height difference surpasses 3 mm, the following conditions should be considered:
- Acute traumatic compression fracture (e.g., axial loading or flexion injury)
- Osteoporotic vertebral collapse in older patients
- Pathological fracture secondary to metastatic disease or primary bone tumour
- Scheuermann’s disease (multiple-level anterior wedging in adolescents)
- Langerhans cell histiocytosis (vertebra plana in children)
Key pitfalls include parallax error on non-true lateral radiographs, overlapping posterior elements obscuring end-plate detail, and failure to account for normal developmental wedging at the thoracolumbar junction in children and adolescents.
Reference: Benson M, Fixsen J. Children’s Orthopaedics and Fractures. Springer Verlag. (2010).
Imaging Notes
On lateral radiography, measure the anterior vertebral body height from the superior to inferior end-plate at the anterior cortical margin and compare this to the posterior vertebral body height measured along the posterior cortex. Ensure a true lateral projection to avoid rotational artefact that can artificially increase the apparent height difference. On CT, sagittal reformats in bone window allow precise measurement of both heights at the mid-sagittal plane; multiplanar reformatting also helps identify subtle end-plate impaction and posterior element involvement not visible on plain films. Both modalities should be assessed for cortical disruption, retropulsion of bony fragments into the spinal canal, and involvement of the posterior vertebral wall, which would upgrade the injury classification.