The timeline for major spine classification systems is summerized below:
Böhler proposed the earliest classification system for TL spine fractures.
Based on both anatomic appearance and mechanisms of injury,
TL injuries were divided into compression fractures,
flexion-distraction injuries,
extension fractures,
shear fractures,
and rotational injuries.
Yet,
he did not attempt to define instability patterns.
Later on Watson-Jones & Nicoll recognized the importance of recognizing unstable fractures in order to avoid long-term neurological sequel as well as skeletal deformities.
Watson-Jones described fractures according to their anatomic appearance with emphasis on ligamentous integrity as one of the key determinants of stability in various injury subtypes. Nicoll afterwards identified four anatomical structures (vertebral bodies,
facet joints,
posterior ligaments,
discs) involved in any injury pattern and divided fractures into stable fractures and unstable fractures based on posterior ligamentous injury.
Holdsworth was the first to introduce the concept of column classification into TL fractures.
He divided the spine into anterior column consisting of vertebral bodies and inter-vertebral discs and posterior column consisting of facet joints and the posterior ligamentous complex.
Fractures categories include anterior compression fractures,
fracture-dislocation,
rotation fracture-dislocation,
extension injuries,
burst fractures,
and shear injuries. The main drawback of this classification system is that it it oversimplified the biomechanics of injury in TL fractures e.g. unstable burst fractures based on their natural history were falsely categorized as “stable”.
To overcome this, Denis later on came with the concept of three columns, anterior column including anterior longitudinal ligament to the anterior two-thirds of the vertebral body,
middle column including the posterior one-third of the vertebral body and posterior longitudinal ligament,
and posterior column,
which includes all structures posterior to the posterior longitudinal ligament.
Four types of fractures emerged: compression fractures,
burst fractures,
fracture-dislocations,
and seatbelt injuries. Denis's original concept of instability has been oversimplified to designate any fracture with two columns' disruption as unstable ones.
This contradicts with Denis’ original emphasis on distinction of mechanical and neurologic instability.
In contrast to Denis's mechanical based classification, Mergel et al classified injuries based on the direction of injury force into three types; compression,
distraction and rotational.
As mentioned earlier,
this proposed system was criticized for its detail.
To address the drawbacks of the aforementioned classification schemes,
the revised AO classification for TL injuries was proposed.
It is divided into three categories:
• Type-A injuries: failure under axial compression of the anterior elements with intact posterior constraining elements (Fig.
1,2,3,4&5).
• Type-B injuries: failure of the posterior constraining elements (tension band or PLC injuries in case of TLspine) .
Unfortunately,
we didn't encouter fracture type B2 in our collection,
so only a diagram is provided (Fig 6,7&8).
• Type-C injuries: failure of anterior and posterior elements leading to displacement (Fig.
9).
N.B More than one type of injury can be descibed together for instance Type -A1 and type-B2 according to fracture morphological description.
Figure 10 presents a suggested simplified approach for morphological classifcation of TL injuries.
Posterior ligamentous complex the integrity and neurologic status of the patient in addition to the previously described morphologic classification of TL injuries are combined together to give thoracolumbar injury classification and severity score. This allows a more objective approach in determining the managment approach of a certain patient.
This score is illustrated in figure 11.