of Spine Trauma

Fig. 1

Diagram according to Denis classification showing anterior, middle and posterior columns

In 1994, Magerl described a new system based on the AO fracture classification used in the extremities [13]. Injuries were divided into three categories: A = compression, B = distraction, C = translation (Fig. 2). These three categories were further subdivided into three groups, each of which contained three subgroups. The higher the grade in all of these categories, the more severe the injury. This extremely comprehensive system is commonly used by surgeons, but its high degree of complexity limits its usefulness in daily practice and has contributed to poor reproducibility in several studies.

Fig. 2

Basic categories of the AO spine trauma classification system

The Thoracolumbar Injury Classification and Severity Score (TLICS) was proposed in 2005 in an attempt to provide a more clear construct that would also better help guide treatment decisions [14]. The three components of the system are: (1) injury morphology; (2) status of the posterior ligamentous complex (PLC- ligamentum flavum, facet joint capsules, interspinous and supraspinous ligaments; and (3) neurologic status of the patient. Injury morphologies include (from least to most severe): compression/burst, rotation/translation and distraction injuries (Fig. 3). The PLC is described as intact, indeterminate or disrupted based primarily on imaging findings. Point values are assigned to each category and the total is then used to direct therapy. A similar system has been developed for the cervical spine: the Subaxial Cervical Spine Injury Classification System (SLIC) [15].

Fig. 3

Basic categories of the TLICS classification system (a) compression/burst (b) rotation/translation and (c) distraction

Cervical Spine

Introduction

Cervical spine injuries are common and fractures of the C1-C2 complex account for about 25% of these injuries with nearly two thirds of these involving odontoid fractures [16, 17].

Cervical spine trauma is often associated with cord and nerve root injury that can be catastrophic if not diagnosed early or if missed. Cervical spine trauma incurs huge health care costs, estimated to be two-fold over an equivalent fracture in the thoracic and lumbar spine [18].

C1-C2 Region

Atlanto-axial dissociations are usually fatal. The diagnosis is made on lateral radiographic findings of displacement and increased distance between the basion and dens.

Occipital condyle fractures are best demonstrated on coronal reformatted CT images. An alar ligament avulsion fracture is the most common type in this region.

At C1, bilateral fractures through the neural arch are most common and result from hyperextension of the head which compresses the neural arch of C1 between the occipital condyles and arch of C2.

A comminuted burst fracture of C1 (Jefferson fracture) is usually due to an axial load to the vertex of the head.

C1-C2 atlantoaxial dissociation may be seen after traumatic rupture of the transverse ligament or in patients with rheumatoid arthritis or Downs syndrome. Imaging reveals an increase in the width of the predental space. Rotary atlantoaxial deformities may result from trauma or torticolis subluxation in children or adolescents. Radiographs show asymmetry of the C1-dens distance, and rotation of the spinous processes may be observed.

The C2 hangman’s fracture refers to bilateral fractures of the pars interarticularis, usually due to a hyperextension injury or to hyperflexion and axial compression in some cases. These fractures are not usually associated with cord compression or injury due to the favorable size of the canal at this level and also because the bilateral fractures decompress the cord. Hangman’s fracture classification proposed by Effendi consists of three types. Type 1 (commonest form) is a hairline fracture of the C2 ring without displacement. Type 2 is characterized by displacement of the anterior segment with an abnormal C2-3 disc appearance. Type 3 involves anterior displacement of the C2 body in flexion position with disruption of the facet joints.

Fractures of the dens can be difficult to detect, and if missed are associated with high morbidity and mortality. The Anderson and D’Alonzo dens classification describes three types. Type 1 is an oblique fracture through the tip of dens. Type 2 (Figs. 1 and 4) is a transverse fracture through its base that is unstable with the potential for motion and associated complications. Non-union and poorer outcomes have been reported to range as high as 35–40%, especially in the subgroup with atlantoaxial subluxation [19, 20]. Vertebral artery involvement may also occur [17, 21]. A type 3 dens fracture is an oblique fracture extending into the body of the dens and is considered to be a stable lesion with good potential for healing.

Fig. 4

Lateral radiograph of an 80 year old female patient after a minor fall and feeling “not quite right,” shows type 2 dens fracture

Of note, more C1-2 fractures are being documented in the elderly [22]. These are associated with higher morbidity (often associated with non-union) and mortality compared to other fractures. Accurate diagnosis may be compromised by the coexistence of extensive degenerative change and associated deformities. Comorbidities in this frail group also affect survival [17, 19, 20].

Subaxial Cervical Spine

A hyperextension tear drop fracture typically involves C2 resulting in a triangular fragment, though it may involve more than one level and occur in the lower cervical spine. This type of injury often occurs in the elderly with osteoporosis.

A hyperflexion tear drop fracture results from severe flexion and axial loading and produces a characteristic triangular fracture fragment at the anterior inferior margin of the affected vertebral body. It is commonly associated with cord injury producing an anterior cord syndrome or permanent quadriplegia. The anterior and posterior longitudinal ligaments and intervertebral disc are disrupted and there is associated subluxation or dislocation of the facet joints, with a focal kyphosis above the level of injury.

Anterior wedge compression fractures and occasional burst fractures may occur at the C6 or C7 levels. Burst fractures are associated with multiple often displaced fracture fragments that may impinge on the anterior cord. Vertebral widening or a split fracture line may be seen on a frontal radiograph. Vertical split fractures may occasionally occur due to compression in the sagittal plane and may involve more than two contiguous vertebral bodies.

Facet joint injury may result in fracture, subluxation, perching or locking. Bilateral facet dislocation is due to flexion trauma combined with distraction and rotation. Dislocation of the facet joints results in the superior vertebral body being displaced anteriorly by at least 50% over the vertebral body below. Anterior displacement of one vertebral body over another of 25% or 4–5 mm usually reflects a unilateral facet joint dislocation, resulting in the “bow-tie” sign or “messy roof tile” sign (Fig. 5). Dislocation is present when the inferior facet of the vertebra above is located anterior to the superior facet of the subjacent vertebra.

Fig. 5

30 year old male footballer sustained an acute injury during a tackle. CT bone reconstructed sagittal plane images shows (a) C4-5 fracture dislocation with (b) facet fracture dislocation on one side and (c) subluxated facet on the other side

Hyperflexion sprain of the cervical spine is due to disruption of all the posterior ligaments of two adjacent vertebral bodies, with the anterior longitudinal ligament remaining intact. Hyperkyphosis and widening of the posterior elements may be evident although these injuries can quite subtle and initially missed. These are unstable lesions and require surgical fixation.

Hyperextension sprain/dislocation, usually occurs in the elderly though may affect a younger patient as the result of a high speed motor vehicle accident. The anterior longitudinal ligament is disrupted and avulses the disc from the adjacent superior vertebral body at the level of injury. A thin sliver of an avulsed fragment may be seen which differentiates this from an extension tear drop fracture which is more triangular and larger in height. There may also be posterior longitudinal ligament stripping and the cord may be compressed resulting in associated hematomyelia and central cord syndrome. Extensive soft tissue swelling may be evident.

Posterior element fractures are common, occurring in some 20% of all patients with cervical spine fractures any may include fractures of a spinous process, pillar, facet, lamina or transverse process. An avulsion fracture of a spinous process in the lower cervical spine is called a clay shoveler’s fracture. Radiculopathy suggests pillar fracture. Laminar fractures usually occur in association with other fractures. Transverse process fractures may extend to the transverse foramen placing the adjacent nerve root and vertebral artery at risk (Fig. 6).

Fig. 6

25 year old male surfer who sustained a neck injury. (a) Sagittal CT reconstruction reveals left lateral mass fractures at C6 and C7. (b) Axial image demonstrates an additional left pedicle fracture extending into the left foramen transverse foramen raising concern for a vertebral artery injury, however a CT angiogram of the neck showed no arterial injury

Cervical spine trauma can be associated with whiplash injury. This remains a contentious subject although sub endplate fractures, ligamentous tears and facet fractures as well as soft tissue muscle injuries have been implicated.

SCIWORA, spinal cord injury without radiographic abnormality, may occur in young children without evidence of fracture or dislocation. Spinal cord injury occurs due to elasticity of the vertebral column in the young, with more spinal cord lesions being evident in children under 8 years. The prognosis is often very guarded.

Spinal cord injury may be evident early after trauma on MRI, with the presence of focal cord hematoma having poorer outcome than diffuse signal change or contusion. Delayed findings include intra or extramedullary cysts, syringomyelia, cord tethering or atrophy.

Common sources of diagnostic error relate to which imaging modality is used, the presence of normal variants such as ossicles and coexisting degenerative disease. The reported incidence of second level spinal fracture is dependent on the imaging modality used. These are reported to be 5–7% for radiographs, (with some reports as high as 20%) [16, 23, 24], 15–17% for CT, and 50% with MR. Normal variants can be a source of error [25]. Being aware of the common C1 and C2 variants (Fig. 7) is useful since these may mimic a fracture.

Fig. 7

25 year old patient after minor trauma and concern for fracture. CT sagittal bone window reconstruction shows os odontoideum, a normal C2 ossification variant and no fracture. Note also the congenital fusion of the C2 and C3 vertebral bodies

Thoracolumbar Spine

Most injuries in the thoracic and lumbar spine occur near the thoracolumbar junction. This is likely because it is the area of greatest motion in the thoracolumbar spine and the transition point besteen the first nine vertebrae, which are relatively stable because of the ribcage, and the more mobile lumbar and lower thoracic vertebrae (which have only “floating” ribs). Injuries above the thoracolumbar junction are less common, but are associated with a higher incidence of neurologic injury, probably because of the higher forces required to overcome the inherent stability of the ribcage in this region [26, 27].

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