AO CLASSIFICATIONS THORACO-LUMBAR SPINAL INJURIES

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1 AO CLASSIFICATIONS THORACO-LUMBAR SPINAL INJURIES T H E A O / A S I F ( A R B E I T S G E M E I N S C H A F T F Ü R O S T E O S Y N T H E S E F R A G E N / A S S O C I A T I O N F O R T H E S T U D Y O F I N T E R N A L F I X A T I O N )

2 A classification of injuries is necessary in order to develop a common language for treatment indications and outcomes.

3 However, the most important classification of spinal injuries aims to differentiate between: 1) stable fractures 2) unstable fractures This concept was first introduced by Nicoll in 1949(the Orthopaedic and Accident Service of the Mansfield General Hospital ) However, this classification is insufficient to give detailed treatment recommendations. (THE JOURNAL OF BONE AND JOINT SURGERY.VOL. 31 B, NO. 3, AUGUST 1949

4 Definition of spinal column stability is given as abilityof the spine to maintain its integrity and correlations between vertebras under physiological load, so there is no initial or additional compromise to the spinal cord and other neural structures

5 Holdsworth (1963) proposed classifying spinal fractures by the mechanism of injury (MOI) of compression, flexion, extension, and flexionrotation. He divided the injuries involvement of the anterior weight bearing column and the posterior tension bearing column of facet joints and ligament complex.(holdsworth FW. Fractures, dislocations and fracture/dislocation of the spine. J Bone Joint Surg Br 1963;45:6-20 ) Fails to appreciate some burst fracture instabilities

6 Denis in 1983 used the term three column in the context of thoracolumbar injuries. Denis F (1983) The three column spine and its significance in the classification of acute thoracolumbar spinal injuries. Spine 8: The middle column is the primary determinant of mechanical stability. The problem of this classification system is that it is based on an assumption, which is anatomically unidentifiable: the socalled middle column.

7 IN THE 1990S, THE AO GROUP REVIEWED THE ISSUE OF CLASSIFICATION OF SPINE INJURIES AND CAME TO THE CONCLUSION THAT THERE WAS NO COMPREHENSIVE CLASSIFICATION SYSTEM AVAILABLE

8 The AO classification is based on the two column theory described byholdsworth and Kelly and Whitesides. The AO classification considers the spine to comprise two functionally separate supportive columns. The anterior column consists of the vertebral body and the intervertebral discs and is loaded in compression. The posterior column consists of the pedicles, the laminae, the facet joints, and the posterior ligamentous complex, and is loaded intension.

9 CLASSIFICATION INTRODUCED BY MAGERL ET AL. IN 1994 Therefore, the classification system of the AO Group is based on three basic functions of a stable spine according to Whitesides. A stable spine can resist three major forces: axial compression forces, axial distraction forces and torsional forces, respectively, rotation around the longitudinal axis

10 These mechanisms have more or less typical morphological patterns namely socalled compression injuries, distraction injuries and torsional injuries representing shortening, lengthening and rotation of the spine A comprehensive classification of thoracic and lumbar injuries. Magerl F, Aebi M, Gertzbein SD, Harms J, Nazarian S.Eur Spine J. 1994; 3(4):

11 FRACTURE VERTEBRAL BODY ANTERIOR COLUMN DISRUPTION OF THE DISC POSTERIOR COLUMN FRACTURE RUPTURECOF LIG. TYPE B3,1,1 SIGN OF ROTATION A B C

12 A Classification of injuries has to tell the user something about the severity and the prognosis of the injury. Therefore, in the AO classification, there is a basic principle concerning severity: increasing severity from a Type A, Type B to the Type C injury and from the Group 1 to Group 3.

13 The severity of the injury is determined by the amount of the bony, ligamentous lesions or the combination of both as well as the combination of neurodamage and mechanical instability. the most severe Type A injury may be more severe than their least severe B.

14 The AO classification has a prognostic value when taking into account the simple lesion types like A, B, C and analysing them with regard to the stability, the deformity and for potential of neurocompression. A-lesions do usually have a good stability, a minor deformity, however, specifically in the burst fractures, we may find a significant neurocompression by the fragments located in the spinal canal)

15 The important morphological criteria of instability according to the AO classification are injuries to the ligaments and discs. A graded classification is useful because there is a range from definitely stable to definitely unstable fractures. Fractures are considered stable if no injury to ligaments or discs is evident, e.g., pure impaction fractures (Type A1). Structural changes of the spine under physiologic loads are unlikely. Slightly unstable fractures reveal partial damage of ligaments and inter vertebral discs, but heal under functional treatment without gross deformity and without additional neurological deficit. This is the case in a frequent type (A3), the so-called incomplete superior burst fracture (A3.1.1). Highly unstable implicates a severe damage of the ligaments and inter vertebral discs, as it occurs in the fracture Types A3, B, and C.

16 Type A: vertebral body compression A 1 I M PA C T I O N F R A C T U R E S A 2 S P L I T F R A C T U R E S A 3 BU R S T F R A C T U R E S

17 B1 Predominantly Lig.injury B2 predominantly osseous Chance # B3Anterior disruption throughthe disc (hyperextension shear injury) Type B: anterior and posterior element injury with distraction

18 C1 Type A injuries with rotation C2 Type B injuries with rotation C3 Rotational-shear injuries Type C: anterior and posterior element injury with rotation

19 Types Groups Subgroups Specificastions A1.1 A1 impaction A1.3 A1.2.1, A1.2.2, A1.2.3 A1.3 A2.1 A compression A2 split A2.2 A2.3 A3.1 A3.1.1, A3.1.2, A3.1.3 A3 burst A3.2 A3.2.1, A3.2.2, A3.2.3 A3.3 A3.3.1, A3.3.2, A3.3.3 B1.1 B1.1.1, B1.1.2, B1.1.3 B1 post ligamentous B1.2 B1.2.1, B1.2.2, B1.2.3 B2.1 B distraction B2 post osseous B2.2 B2.2.1, B2.2.2 B2.3 B2.3.1, B2.3.2 B3.1 B3.1.1, B3.1.2 B3 anterior B3.2 B3.3 C1.1 C1 A with rotation C1.2 C1.2.1, C1.2.2, C1.2.3, C1.2.4 C2.1 C2.1.1, C2.1.2, C2.1.3, C2.1.4 B rotation C2 B with rotation C2.2 C2.2.1, C2.2.2, C2.2.3 C2.3 C2.3.1, C2.3.2, C2.3.3 C3 shear C3.1 C3.2

20 A1. Impaction fractures A1.1. Endplate impaction A1.2. Wedge impaction fractures A Superior wedge impaction fracture A Lateral wedge impaction fracture A Inferior wedge impaction Fracture A2. Split fractures A2.1. Sagittal split fracture A2.2. Coronal split fracture A2.3. Pincer fracture A3. Burst fractures A3.1. Incomplete burst fracture A Superior incomplete burst fracture A Lateral incomplete burst fracture A Inferior incomplete burst fracture A3.2. Burst-split fracture A Superior burst-split fracture A Lateral burst-split fracture A Inferior burst-split fracture A3.3. Complete burst fracture A Pincer burst fracture A Complete flexion burst fracture A Complete axial burst fracture B1. Posterior disruption predominantly ligamentous (flexion-distraction injury) B1.1. With transverse disruption of the disc B Flexion-subluxation B Anterior dislocation B Flexion-subluxation/anterior dislocation with fracture of the articular processes B1.2. With Type A fracture of the vertebral body B Flexion-subluxation + Type A fracture B Anterior dislocation + Type A fracture B Flexion-subluxation/anterior dislocation with fracture of the articular processes + Type A fracture B2. Posterior disruption predominantly osseous (flexiondistraction injury) B2.1. Transverse bicolumn fracture B2.2. With transverse disruption of the disc B Disruption through the pedicle and disc B Disruption through the pars interarticularis and disc (flexion-spondylolysis) B2.3. With Type A fracture of the vertebral body B Fracture throughthepedicle + Type A fracture B Fracture through the pars interarticularis (flexion-spondylolysis) + Type A fracture B3. Anterior disruption through the disc (hyperextensionshear injury) B3.1. Hyperextensionsubluxations B Without injury of the posterior column B With injury of the posterior column B3.2. Hyperextensionspondylolysis C1. Type A injuries with rotation (compression injuries with rotation) C1.1. Rotational wedge fracture C1.2. Rotational split fractures C Rotational sagittal split fracture C Rotational coronal split fracture C Rotational pincer fracture C Vertebral body separation C1.3. Rotational burst fractures C Incomplete rotational burst fractures C Rotational burst-split fracture C Complete rotational burst fracture C2. Type B injuries with rotation C2.1. B1 injuries with rotation (flexiondistraction injuries with rotation) C Rotational flexion subluxation C Rotational flexion subluxation with unilateral articular process fracture C Unilateral dislocation C Rotational anterior dislocation without/ with fracture of articular processes C Rotational flexion subluxation without/ with unilateral articular process + Type A fracture C Unilateral dislocation + Type A fracture C Rotational anterior dislocation without/ with fracture of articular processes + Type A fracture C2.2. B2 injuries with rotation (flexion distraction injuries with rotation) C Rotational transverse bicolumn fracture C Unilateral flexion spondylolysis with disruption of the disc C Unilateral flexion spondylolysis + Type A fracture C2.3. B3 injuries with rotation (hyperextensionshear injuries with rotation) C Rotational hyperextension-subluxation without/with fracture of posterior vertebral elements C Unilateral hyperextension-spondylolysis C Posterior dislocation with rotation C3. Rotational-shear injuries C3.1. Slice fracture C3.2. Oblique fracturetypes

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25 THE MODERN CLASSIFICATION FRACTURE PATTERN,MECHANISM OF INJURY AND FRACTURE BIOMECHANICS STABILITY DEGREEN OF NEUROLOGIC INJURY GUIDLINE FOR TREATMENT: COSERVATIVE V. OPERATIVE PROGNOSTIC INFORMATION.