1. Classification of Thoracolumbar Spine Injuries
Jim A. Youssef, MD
Original Authors: Christopher Bono, MD and Mitch Harris, MD; March 2004
New Author: Jim A. Youssef, MD; Revised January 2006

2. Historical Classification Systems
Summary
Comments
Nicoll
Differentiates stable from unstable fractures
Serves as a foundation for subsequent classification systems
Holdsworth
Modifies previous classification systems to include the mechanisms of injury and two-column theory
Fails to appreciate some burst fracture instabilities
Kelly & Whitesides
Refines the two-column model
Classification guides treatment of neurologic deficit
Denis
Development of the three-column model
The middle column is the primary determinant of mechanical stability.
Gertzbein et al.
Suggests a posterior component, anterior component and body component
Involves the vertebral body as it
relates to kyphosis.

3. More Commonly Used Classification Systems
Summary
Comments
McAfee
Based on CT appearance; classifies injuries into 6 categories
Easily communicated type of injury with patients
Ferguson and Allen
Combines work done by Denis and McAfee; mechanistic classification to clarify patterns of thoracolumbar injury
Cumbersome, nonspecific for everyday use
Gaines
Developed in response to poor patient outcomes; grades injury based on amount of damage to vertebral body, the spread of fragments in fracture site and amount of corrected kyphosis
Strong inter-observer reliability AO
Classifies types of fractures into A, B, or C and into subcategories subsequently
Moderate inter-observer reliability

4. Denis: Three-column model
Anterior column- formed by the anterior longitudinal ligament, the anterior annulus, and the anterior portion of the vertebral body
Middle osteoligamentous- the critical feature. Very important to spinal stability; consists of posterior longitudinal ligament, the posterior portion of the annulus, and the posterior aspect of the vertebral body
Posterior column- includes the neural arch, facet joints and capsules, ligamentum flavum, and remaining ligamentious complex
Denis F. Clin Orthop Relat Res. 1984

5. Denis: Middle-column concept
Developed to define burst fracture
Middle column has limited value for biomechanical stability modeling

6. History- Denis
Studies have supported the three-column theory and found that the middle column is the primary determinant of mechanical stability of the thoracolumbar region of the spine.
Panjabi, MM. Spine, 1995.

7. History- Gertzbein
Other classification systems developed concurrently, most focusing on flexion-distraction injuries
Gertzbein et al. suggests classification into three separate portions:
Posterior component
Anterior component
Body component
Gertzbein SD, Court-Brown CM: Flexion-Distraction Injuries of the Lumbar Spine. Clin Orth 1988

8. History- Gertzbein
The relative proportion of disc and ligamentous involvement compared to bony involvement predicts the probability that the injury will heal without surgical involvement
Involvement of the vertebrae is important as it might relate to bony collapse and thus kyphosis
Gertzbein SD, Court-Brown CM: Flexion-Distraction Injuries of the Lumbar Spine. Clin Orth 1988

9. McAfee and Associates Based on the CT scan appearance of 100 fractures
Six injury patterns:
Wedge-compression fracture
Stable burst
Unstable burst
Chance
Flexion-distraction
Translational
McAfee PC, Yuan HA, et al. The value of CT in thoracolumbar fractures. JBJS 1993

10. Classification Compression Fracture
McAfee PC, Yuan HA, et al. The value of CT in thoracolumbar fractures. JBJS 1993

11. Classification Stable Burst Fracture Minimal Kyphosis
< 50% Ht. Loss
Moderate CC
No Neuro Deficit
No Posterior Inj.
McAfee PC, Yuan HA, et al. The value of CT in thoracolumbar fractures. JBJS 1993

12. Classification Unstable Burst Fracture Posterior element disruption
Progressive neurological deficit
Kyphosis of greater than 20º-30º
Anterior height loss > 50%
Canal compromise > 50%
McAfee PC, Yuan HA, et al. The value of CT in thoracolumbar fractures. JBJS 1993

13. Classification Flexion - Distraction Injury
McAfee PC, Yuan HA, et al. The value of CT in thoracolumbar fractures. JBJS 1993

14. Classification Translational Shear Injury
McAfee PC, Yuan HA, et al. The value of CT in thoracolumbar fractures. JBJS 1993

15. Ferguson and Allen Combines the work of Denis and McAfee and et al.
Uses a mechanistic classification to clarify the patterns of thoracolumbar spine injury
Hypothesizes that most injuries were the result of:
Compression
Tension
Torsion
Translational forces
Nicole EA: Fractures of the dorsolumbar spine. J Bone Joint Surg Br 31: , 1949

16. Ferguson and Allen
Treatment is linked to injury patterns and an attempt was made to match the type of instrumentation to the type of injury
System proved to be cumbersome and non-specific for everyday use
Nicole EA: Fractures of the dorsolumbar spine. J Bone Joint Surg Br 31: , 1949

17. Gaines: Load Sharing Classification
Created system in response to poor patient outcomes when the vertebral body sustained a disproportionately severe injury
Classification system grades:
Amount of damaged vertebral body
Spread of the fragments in the fracture sight
Amount of corrected kyphosis
McCormack et al. Spine, 1994

18. Gaines: Load Sharing Classification
Load-Sharing Classification: a straight-forward way to describe the amount of bony comminution in a spinal fracture
Can help the surgeon select short-segment pedicle-screw-based fixation using the posterior approach for less comminuted injuries and the anterior approach for those more comminuted injuries if the patient meets the following criteria:
Isolated spine fracture
Compliant with 3 to 4 months of spinal bracing
Parker et al, Spine, 2000

19. Gaines: Load Sharing Classification
System can be used pre-operatively to:
Predict screw breakage when short segment, posteriorly placed pedicle screw implants are being used
Describe any spinal injury for retrospective studies
Select spinal fractures for anterior reconstruction with strut graft
McCormack et al. Spine, 1994

20. Gaines: Load Sharing Classification
Inter-observer and intra-observer reliability of the Load Sharing system was evaluated by 5 observes on 2 occasions.
Analysis found high levels of agreement when Load Sharing Classification was used to assess thoracolumbar burst fractures.
Dai and Jin (2005) concluded that the system could be applied with excellent reliability.
Dai LY, Jin WJ. Spine, 2005.

21. AO Classification
Based on the review of 1445 consecutive thoracolumbar injuries
Primarily based on pathomorphological criteria
Categories based on:
Main mechanism of injury
Pathomorphological uniformity
Prognostic aspects regarding healing potential
Magerl et al. Eur Spine J

22. AO Classification
Classification reflects progressive scale of morphological damage by which the degree of instability is determined
Consists of a grid for sub-grouping injuries into three types:
A, B and C
Every type has three groups, each of which contains three subgroups with specifications
Magerl et al. Eur Spine J

23. AO Classification
Types have a fundamental injury pattern which is determined by the three most important mechanisms acting on the spine
Compression
Distraction
Axial torque
Magerl et al. Eur Spine J

24. AO Classification - A, B, C’s
Type A:
Vertebral body compression- injury patterns of the vertebral body
Type B:
Anterior and posterior element injuries with distraction, characterized by transverse disruption either anteriorly or posteriorly
Type C:
Anterior and posterior injuries with rotation, injury patters resulting from axial torque
Magerl et al. Eur Spine J

25. Examples of AO Classification

26. AO Classification
Superior incomplete
Burst fracture
A3.1.1

27. AO Classification
Flexion-subluxation
B1.1.1

28. AO Classification
Rotational shear injury
C3.2

29. Determination of Thoracolumbar Instability

30. Reproducibility studies
Blauth el al: Mean inter-observer reliability 67% when 22 hospitals evaluated 14 radiographs and CT scans
Wood, Vaccaro, et al: Only moderate reproducibility and repeatability among well-trained spine surgeons using AO and Denis classification systems
Orthopade, 1999; NASS, 2004

31. Summary
Currently no classification system that has achieved global clinical utility and acceptance
Few studies evaluating the effectiveness of the different systems; studies which have been conducted use small samples sizes
Gotzen L, et al. Unfallchirurg, 1994.
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