Spinal Injuries: Biomechanics & Classification
Understanding spinal trauma requires distinguishing between Stable and Unstable injuries. Stability determines whether a patient needs a simple brace or emergency fixation to prevent paralysis.
1. The Denis Three Column Concept
Francis Denis divided the spine into three columns to assess stability:
- Anterior Column: ALL (Anterior Longitudinal Ligament) + Anterior 2/3 of the vertebral body/disc.
- Middle Column (The Key): PLL (Posterior Longitudinal Ligament) + Posterior 1/3 of the vertebral body/disc.
- Posterior Column: Everything behind the PLL (Pedicles, Lamina, Facets, Spinous process, Interspinous ligaments).
Rule of Thumb: If 2 or more columns are damaged, the spine is UNSTABLE. (Note: Damage to the Middle Column usually implies instability).
2. Common Fracture Patterns
- Wedge Compression Fracture: Only Anterior column fails. Usually Stable.
- Burst Fracture: Anterior + Middle columns fail. Axial loading injury. Usually Unstable (retropulsed fragment hits cord).
- Chance Fracture (Seatbelt Injury): Distraction injury tearing all 3 columns horizontally. Unstable.
- Fracture-Dislocation: All 3 columns fail with translation. Highly Unstable.
3. Specific Cervical Injuries
- Jefferson Fracture (C1): Burst fracture of Atlas ring.
- Hangman's Fracture (C2): Traumatic spondylolisthesis of Axis (pars interarticularis fracture).
- Odontoid Fractures: Fracture of the Dens.
25 Practice MCQs
Q1. According to Denis, the Middle Column consists of:
Answer: B). This is the pivot point for stability.
Q2. A Burst fracture typically involves failure of:
Answer: B). Caused by axial loading (e.g., falling on feet/buttocks).
Q3. A Chance Fracture is caused by:
Answer: B). The spine is literally pulled apart horizontally.
Q4. Jefferson Fracture involves:
Answer: A). Often caused by a blow to the top of the head (diving).
Q5. Hangman's Fracture is a fracture of:
Answer: B). Caused by hyperextension-distraction.
Q6. Which Odontoid fracture type is most unstable and prone to non-union?
Answer: B). The watershed area of blood supply is at the base.
Q7. Clay Shoveler's fracture affects:
Answer: A). Avulsion by supraspinous ligament; usually stable.
Q8. According to Denis, if the Middle Column is intact, the injury is likely:
Answer: A). e.g., Wedge compression fractures.
Q9. "Jumped Facets" (locked facets) occur in the cervical spine due to:
Answer: A). The inferior facet jumps over the superior facet below it.
Q10. Whiplash injury involves:
Answer: A). Soft tissue injury to ALL (extension phase) and posterior ligaments (flexion phase).
Q11. The "Retropulsed fragment" in a burst fracture enters the:
Answer: A). Compressing the spinal cord/cauda equina.
Q12. Which view is best to visualize C1-C2?
Answer: B). Moves the teeth out of the way to see the dens.
Q13. Spondyloptosis refers to:
Answer: A). Total dislocation.
Q14. Halo Vest is used for:
Answer: A). Screws go into the skull.
Q15. The thoracolumbar junction (T12-L1) is the most common site of injury because:
Answer: A). Mechanical stress concentration.
Q16. Compression fractures typically result in:
Answer: A). Loss of anterior height causes forward bending.
Q17. Teardrop fracture of the cervical spine is:
Answer: A). Associated with anterior cord syndrome.
Q18. The Swimmer's View is used to visualize:
Answer: A). Because the shoulders often obscure this area on lateral X-ray.
Q19. Log-rolling is used to:
Answer: A). Maintains alignment.
Q20. Is paralysis inevitable in a burst fracture?
Answer: B). Many burst fractures are neurologically intact.
Q21. Posterior column failure involves the:
Answer: A). Also facets and neural arch.
Q22. Seatbelt injuries often cause injury to:
Answer: A). Associated bowel injury is common.
Q23. Vertebroplasty involves:
Answer: A). For painful osteoporotic compression fractures.
Q24. Kummell's Disease is:
Answer: A). Vertebra collapses months after minor trauma.
Q25. What is the most common cause of spinal cord injury?
Answer: A). Followed closely by falls (especially in elderly).
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