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Aospine Thoracolumbar Spine Injury Classification System: Fracture Description, Neurological Status, and Key Modifiers.

·Spine·2013·881 citations·Spine
DOI·PubMed
SummaryAbstract on PubMed →

This international consensus study introduces the AOSpine thoracolumbar injury classification. It asks whether a simple, CT-based morphologic scheme can describe these fractures reliably while adding neurological status and clinical modifiers. Forty cases were graded twice by 9 spine surgeons to measure agreement.

Study Snapshot

Key Findings

  • The system sorts every thoracolumbar injury by mode of column failure into three types:
    –Type A: compression, anterior failure with intact tension band
    –Type B: tension band disruption (posterior or anterior) without translation
    –Type C: translation or displacement in any plane, or a completely disrupted hinge
  • Type A is subdivided into five subtypes by endplate and posterior wall involvement:
    –A0: minor (transverse/spinous process)
    –A1: wedge/impaction, single endplate
    –A2: split/pincer, both endplates
    –A3: incomplete burst, single endplate with posterior wall
    –A4: complete burst, both endplates with posterior wall
  • This matters because A3/A4 distinguish incomplete from complete burst, and posterior wall involvement defines the burst pattern.
  • Interobserver reliability for the main type was substantial at kappa = 0.72. Type A scored 0.72, type C 0.70, and type B the lowest at 0.58. This beats prior Magerl figures of 0.33 to 0.62 for main injury type.
  • The weakest links were B2 (kappa = 0.34) and B3 (kappa = 0.41), because separating a ligamentous from a bony tension band injury and judging an intact versus disrupted posterior hinge is genuinely hard on imaging.
  • A burst fracture with PLC disruption on MRI is coded as a B2 injury plus the A3 or A4 body fracture. A pure burst with an intact posterior tension band stays type A, even with retropulsion into the canal.
  • Neurological status uses a 5-grade descriptor:
    –N0: intact
    –N1: transient deficit, resolved
    –N2: radiculopathy
    –N3: incomplete cord or cauda equina injury
    –N4: complete cord injury (ASIA A)
    –NX: cannot be examined
  • Two modifiers flag the borderline surgical cases:
    –M1: indeterminate tension band injury on imaging or exam
    –M2: patient comorbidity such as ankylosing spondylitis, DISH, or osteoporosis
  • The scheme is built around CT because MRI identification of PLC injury is unreliable, with specificity as low as 52% and kappa values around 0.37 to 0.58 in prior work.
Board PearlAOSpine thoracolumbar fractures sort into three types by column failure: A compression, B tension band, C translation, with morphology graded reliably on CT.

Clinical Relevance

When you read a thoracolumbar CT, anchor on the column that failed. Anterior compression with an intact posterior tension band is type A. Add a tension band injury and it becomes type B. Add translation and it is type C.

The practical pivot is the posterior wall and the tension band. An A1 wedge is stable. An A3 or A4 burst involves the posterior wall but keeps the tension band intact. The moment the PLC is disrupted, the same burst becomes a B2 and the surgical conversation changes.

This system was designed to replace Denis and the more complex Magerl scheme as the modern common language for spine trauma. It deliberately runs on CT so it works at any trauma center, reserving MRI and the M1 modifier for when PLC integrity is genuinely uncertain.

For boards, memorize the A0-A4, B1-B3, C structure, the N0-NX neurological grades, and the M1/M2 modifiers. Note that this paper validated reliability only and explicitly did not finalize a surgical scoring threshold.

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Aospine Thoracolumbar Spine Injury Classification System: Fracture Description, Neurological Status, and Key Modifiers.

·Spine·2013·881 citations·Spine
DOI·PubMed
SummaryAbstract on PubMed →

This international consensus study introduces the AOSpine thoracolumbar injury classification. It asks whether a simple, CT-based morphologic scheme can describe these fractures reliably while adding neurological status and clinical modifiers. Forty cases were graded twice by 9 spine surgeons to measure agreement.

Study Snapshot

Key Findings

  • The system sorts every thoracolumbar injury by mode of column failure into three types:
    –Type A: compression, anterior failure with intact tension band
    –Type B: tension band disruption (posterior or anterior) without translation
    –Type C: translation or displacement in any plane, or a completely disrupted hinge
  • Type A is subdivided into five subtypes by endplate and posterior wall involvement:
    –A0: minor (transverse/spinous process)
    –A1: wedge/impaction, single endplate
    –A2: split/pincer, both endplates
    –A3: incomplete burst, single endplate with posterior wall
    –A4: complete burst, both endplates with posterior wall
  • This matters because A3/A4 distinguish incomplete from complete burst, and posterior wall involvement defines the burst pattern.
  • Interobserver reliability for the main type was substantial at kappa = 0.72. Type A scored 0.72, type C 0.70, and type B the lowest at 0.58. This beats prior Magerl figures of 0.33 to 0.62 for main injury type.
  • The weakest links were B2 (kappa = 0.34) and B3 (kappa = 0.41), because separating a ligamentous from a bony tension band injury and judging an intact versus disrupted posterior hinge is genuinely hard on imaging.
  • A burst fracture with PLC disruption on MRI is coded as a B2 injury plus the A3 or A4 body fracture. A pure burst with an intact posterior tension band stays type A, even with retropulsion into the canal.
  • Neurological status uses a 5-grade descriptor:
    –N0: intact
    –N1: transient deficit, resolved
    –N2: radiculopathy
    –N3: incomplete cord or cauda equina injury
    –N4: complete cord injury (ASIA A)
    –NX: cannot be examined
  • Two modifiers flag the borderline surgical cases:
    –M1: indeterminate tension band injury on imaging or exam
    –M2: patient comorbidity such as ankylosing spondylitis, DISH, or osteoporosis
  • The scheme is built around CT because MRI identification of PLC injury is unreliable, with specificity as low as 52% and kappa values around 0.37 to 0.58 in prior work.
Board PearlAOSpine thoracolumbar fractures sort into three types by column failure: A compression, B tension band, C translation, with morphology graded reliably on CT.

Clinical Relevance

When you read a thoracolumbar CT, anchor on the column that failed. Anterior compression with an intact posterior tension band is type A. Add a tension band injury and it becomes type B. Add translation and it is type C.

The practical pivot is the posterior wall and the tension band. An A1 wedge is stable. An A3 or A4 burst involves the posterior wall but keeps the tension band intact. The moment the PLC is disrupted, the same burst becomes a B2 and the surgical conversation changes.

This system was designed to replace Denis and the more complex Magerl scheme as the modern common language for spine trauma. It deliberately runs on CT so it works at any trauma center, reserving MRI and the M1 modifier for when PLC integrity is genuinely uncertain.

For boards, memorize the A0-A4, B1-B3, C structure, the N0-NX neurological grades, and the M1/M2 modifiers. Note that this paper validated reliability only and explicitly did not finalize a surgical scoring threshold.

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