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

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.

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

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

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

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.

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

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

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

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

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

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

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

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

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 31:376-394, 1949

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 31:376-394, 1949

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

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

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

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.

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. 1994.

AO Classification Classification reflects progressive scale of morphological damage by which the degree of instability is determined Consists of a 3-3-3 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. 1994.

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. 1994.

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. 1994.

Examples of AO Classification

AO Classification Superior incomplete Burst fracture A3.1.1

AO Classification Flexion-subluxation B1.1.1

AO Classification Rotational shear injury C3.2

Determination of Thoracolumbar Instability

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

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. If you would like to volunteer as an author for the Resident Slide Project or recommend updates to any of the following slides, please send an e-mail to ota@aaos.org E-mail OTA about Questions/Comments Return to Spine Index