Denis three column system
- Clinical relevance
- Only moderately reliable in determining clinical degree of stability
- Definitions
- Anterior column
- Anterior longitudinal ligament (ALL)
- Anterior 2/3 of vertebral body and annulus
- Middle column
- Posterior longitudinal ligament (PLL)
- Posterior 1/3 of vertebral body and annulus
- Posterior column
- Pedicles
- Lamina
- Facets
- Ligamentum flavum
- Spinous process
- Posterior ligament complex (PLC): consists of
- Supraspinous ligament
- Interspinous ligament
- Ligamentum flavum
- Facet capsule
- Instability defined by
- Injury to middle column
- As evidenced by widening of interpedicular distance on AP radiograph
- Loss of height of posterior cortex of vertebral body
- Disruption of posterior ligament complex combined with anterior and middle column involvement
Fracture classification
- See TL fracture
AO spine fracture classification
- AO spine injury score
- Score 0–3: Manage conservatively
- Score 4–5: Can be managed surgically or conservatively
- Score 6–13: Manage surgically
- Patients with burst fractures who are neurologically intact should have an MRI to assess the posterior ligamentous complex (PLC).
- On CT: PLC injury likely if > 50% loss of anterior vertebral height and > 25° of angulation causing focal kyphosis)
- If the PLC is intact, non- operative treatment is recommended. In patients with an indeterminate PLC, surgery might be considered.
- In cases where there is frank disruption of the PLC, the fracture should be reclassified as B2 and surgical treatment is recommended.
Fracture type | Score | Neurological | Score | Clinical modifiers | Score |
A0 | 0 | N0 | 0 | M1 | 1 |
A1 | 1 | N1 | 1 | M0 | 0 |
A2 | 2 | N2 | 2 | ㅤ | ㅤ |
A3 | 3 | N3 | 4 | ㅤ | ㅤ |
A4 | 5 | N4 | 4 | ㅤ | ㅤ |
B1 | 5 | NX | 3 | ㅤ | ㅤ |
B2 | 6 | ㅤ | ㅤ | ㅤ | ㅤ |
B3 | 7 | ㅤ | ㅤ | ㅤ | ㅤ |
C | 8 | ㅤ | ㅤ | ㅤ | ㅤ |
McCormack Load-sharing Classification
- Total score ranges from 3 to 9.
- Low scores (3-6) reflect less comminution and generally better suitability for posterior-only fixation.
- High scores (7-9) suggest greater anterior column damage and historically were thought to favour adding anterior reconstruction.
- Evidence
- Filgueira 2021
- Load-sharing scores up to 6 are 100% reliable, only requiring posterior instrumentation for stabilization.
- For scores >6, the risk of implant breakage and loss of kyphosis correction in posterior fixation alone is low
- Stam 2019
- Lost its value in predicting sagittal collapse and posterior instrumentation failure
Feature | 1 point | 2 points | 3 points |
Sagittal collapse / vertebral body involvement | 30% | 30–60% | >60% |
Fragment apposition / displacement | 1 mm | 2 mm | >2 mm |
Correction of kyphosis | 3 degrees | 4–9 degrees | 10 degrees |