Thoracolumbar Burst Fracture¶
Definition¶
A burst fracture is a fracture of a vertebral body in which axial loading causes failure of both the anterior and middle columns, resulting in comminution of the vertebral body with retropulsion of bone fragments into the spinal canal. Burst fractures are distinguished from simple compression fractures by involvement of the posterior vertebral body wall (middle column) and the potential for spinal canal compromise and neurological injury.
Mechanism of Injury¶
Burst fractures result from high-energy axial compression, typically from:
- Falls from height (landing on the feet or buttocks)
- Motor vehicle collisions
- Diving injuries
The thoracolumbar junction (T11–L2) is the most common location because it represents the transition from the rigid, kyphotic thoracic spine to the mobile, lordotic lumbar spine, concentrating mechanical forces at this region.
Classification¶
Denis Classification¶
In the Denis system, burst fractures involve failure of both the anterior and middle columns. Denis described five subtypes based on the pattern of endplate involvement and the degree of comminution.
AO Spine Classification¶
- A3 — Incomplete burst — Posterior wall involvement with a single endplate fracture
- A4 — Complete burst — Posterior wall and both endplates involved
The distinction is important because A4 fractures are generally more unstable than A3 fractures.
Imaging Findings¶
CT¶
CT is the primary modality for characterizing burst fractures:
- Sagittal images — Comminution of the vertebral body, loss of vertebral body height, retropulsion of the posterior wall into the spinal canal, kyphotic deformity
- Axial images — Sagittal (vertical) fracture line through the vertebral body (characteristic of burst mechanism), retropulsed fragments in the canal, widened interpedicular distance
- Coronal images — Widened interpedicular distance (a hallmark of burst fractures), lateral displacement of pedicles
Radiography¶
- Loss of vertebral body height (both anterior and posterior)
- Widened interpedicular distance on AP view (an important distinguishing feature from compression fractures)
- Retropulsed fragment may be visible on lateral view as a step-off of the posterior vertebral body line
MRI¶
- Degree of spinal canal compromise and cord/cauda equina compression
- Bone marrow edema on STIR (confirms acuity)
- Posterior ligamentous complex integrity — critical for determining stability and guiding management
- Epidural hematoma
- Conus medullaris or cauda equina injury
Clinical Pearl
The widened interpedicular distance on AP view is a key finding that distinguishes burst fractures from compression fractures. On CT, look for the sagittal (vertical) fracture line through the vertebral body on axial images — this is characteristic of the axial loading mechanism and indicates that the vertebral body has been "split" by the compressive force.
Stability Assessment¶
Burst fractures exist on a spectrum of stability:
Stable burst fracture — No neurological deficit, intact posterior ligamentous complex, minimal kyphosis, canal compromise <50%.
Unstable burst fracture — Neurological deficit, disrupted posterior ligamentous complex, progressive kyphosis >30°, significant canal compromise, or associated posterior element fractures indicating three-column involvement.
Management¶
- Stable burst fractures without neurological deficit — Conservative management with thoracolumbar orthosis (TLSO brace) for 8–12 weeks, serial imaging to monitor for progressive kyphosis
- Unstable burst fractures — Surgical decompression and stabilization (posterior pedicle screw fixation is the most common approach, with or without anterior column reconstruction)
Key Points¶
- Burst fractures involve failure of the anterior and middle columns with retropulsion of bone into the canal
- Widened interpedicular distance on AP view and a sagittal fracture line on axial CT are hallmark findings
- The thoracolumbar junction (T11–L2) is the most common location
- MRI is essential for assessing PLC integrity, which determines stability
- Stable burst fractures may be treated conservatively; unstable fractures require surgery
- AO Spine classification: A3 (incomplete burst) and A4 (complete burst)
References¶
- Zhang A, Chauvin BJ. Denis Classification. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; last updated 2023. https://www.ncbi.nlm.nih.gov/books/NBK544310/
- Aebi M. Classification of thoracolumbar fractures and dislocations. Eur Spine J. 2010;19(Suppl 1):S2–S7. https://pmc.ncbi.nlm.nih.gov/articles/PMC2899723/
- Lee JY, Vaccaro AR, Lim MR, et al. Thoracolumbar injury classification and severity score: a new paradigm for the treatment of thoracolumbar spine trauma. J Orthop Sci. 2005;10(6):671–675. https://pmc.ncbi.nlm.nih.gov/articles/PMC2779435/
- Jiménez-Almonte JH, King JD, Luo TD, Cassidy RC, Aneja A. Classifications in Brief: Thoracolumbar Injury Classification and Injury Severity Score System. Clin Orthop Relat Res. 2018;476(6):1352–1358. https://pmc.ncbi.nlm.nih.gov/articles/PMC6263590/
- Kweh BTS, Tee JW, Dandurand C, Vaccaro AR, et al. The AO Spine Thoracolumbar Injury Classification System and Treatment Algorithm in Decision Making for Thoracolumbar Burst Fractures Without Neurologic Deficit. Global Spine J. 2024. https://pmc.ncbi.nlm.nih.gov/articles/PMC10867534/
- Muijs SPJ, Foppen W, Smithuis F, Smithuis R. AO Spine Classification of Thoracolumbar Fractures. The Radiology Assistant. 2024. https://radiologyassistant.nl/musculoskeletal/spine/ao-classification
- AO Spine classification of thoracolumbar injuries. Radiopaedia. https://radiopaedia.org/articles/ao-spine-classification-of-thoracolumbar-injuries-1