Thoracic spine fracture-dislocation
Thoracic spine fracture-dislocations are severe forms of spinal column injuries that occur secondary to high-energy trauma, in which there is vertebral fracture concomitant with dislocation of facet joints and/or the intervertebral disc space. They are mechanically unstable and are associated with a high risk of spinal cord injury.
A meta-analysis found that the rate of injury to the thoracolumbar spine was 6.9% in patients presenting to trauma centers secondary to blunt trauma, of which 14.2% were the fracture-dislocation type .
Patients usually present following high-energy trauma, the most common mechanism being motor vehicle accidents . These patients are mostly intubated at the scene and have a constellation of life-threatening injuries. Complete fracture-dislocation often results in severe neurological injury causing lower extremity weakness and/or decreased sensation in the lower body on presentation.
The thoracic spine is rigidly stabilized by anterior, middle, and posterior columns as well as the thoracic cage, which helps prevent horizontal displacement. Therefore, significant force is required for fracture-dislocation to occur, via a combination of compression, tension, rotation, and/or shear forces.
Fracture-dislocation of thoracic vertebrae without neurological compromise is rare. Those fracture-dislocations with preservation of neurological function tend to occur between T6 to T10 . This is due to the fact that spinous processes extend farther inferiorly in this region. Consequently, strong shear forces would be concentrated in the middle column leading to pedicle fractures and spontaneous spinal decompression (relieving deformities that narrow the spinal canal).
- flexion rotation
- flexion distraction
Under the Thoracolumbar Injury Classification and Severity Score (TLICS) classification, a spinal dislocation corresponds to one of two morphologies:
- translation/rotation (3 points)
- distraction (4 points)
Under the AOSpine classification of thoracolumbar injuries, a spinal dislocation is a type C (translation) injury.
CT with a sharp reconstruction kernel is usually the modality of choice for evaluation of suspected osseous spinal injuries. In fracture-dislocation, there is displacement of a vertebra relative to the one below with associated fractures of the vertebral body, pedicle, lamina, transverse process, or spinous process in the vast majority of the cases.
Vertebral body translation >3.5 mm is correlated with higher risk of injury to the posterior ligamentous complex and greater motor deficits .
MRI is useful in evaluating for additional significant nonosseous findings such as:
- posterior ligamentous complex injury
- traumatic spinal cord injury
- spinal cord compression
- spinal epidural hematoma
Treatment and prognosis
Maintaining spinal immobilization precautions is imperative in these patients. The main treatment goals are realignment and fixation of involved vertebrae to avoid any further neurological deficits . The neurologic prognosis depends on the initial neurologic evaluation (e.g. ASIA impairment scale for spinal injury) and early course in rehabilitation.