CHAPTER 9: Imaging the Thoracic Spine

1. INTRODUCTION: FAST THORACIC SPINE FACTS

❑ Traumatic Injuries

• The most commonly injured levels in the spine are the cervicothoracic (C6, C7, T1, T2) and thoracolumbar (T11, T12, L1, L2) vertebrae. These segments are predisposed to mechanical forces because they are the transitional areas between the relatively fixed (via the rib cage) thoracic spine and the more mobile cervical and lumbar spines.

• Compression fractures and fracture–dislocations occur with highest frequency at T12 and L1. Of these, 15% to 20% involve neurological injury.

• Anterior compression fractures of the vertebral bodies are the most common spinal injury detectable on radiographs in all age groups. The following are contributing factors:

  • ◗ The vertebral bodies are composed primarily of cancellous bone, which is structurally weaker than the cortical bone of the vertebral arches.

  • ◗ An axial force applied through the spinal column often converts to a flexion force, resulting in compression of the vertebral bodies, with sparing of the vertebral arches. This occurs in falls, whether landing on the feet from a height or landing on the buttocks in a ground-level fall.

  • ◗ The normal thoracic kyphosis always predisposes the thoracic spine toward more flexion.

❑ Pathologies

• Osteoporosis: Vertebral Body Compression Fractures

  • ◗ The four fractures seen most often as a sequelae of osteoporosis include the hip, distal radius, proximal humerus, and vertebral body. As discussed, these common spinal injuries increase with age owing to demineralization of bone, which renders the vertebral bodies even weaker, and the degenerative changes in the disks, which render them less shock absorbing, thereby transferring even more force directly to the bone.

• Scoliosis

  • ◗ The most common type of scoliosis is adolescent idiopathic scoliosis, appearing around age 10, with a 7:1 female to male ratio. Radiographs identify skeletal maturity or bone age to determine when to cease bracing, as the curve is less likely to progress after this point.

• Scheuermann's Disease

  • ◗ The second most common spinal disorder in adolescence after scoliosis is Scheuermann's disease. Backache and a thoracic kyphosis are manifestations of the osteochondrosis of the vertebral endplates. It is a benign condition without further progression after skeletal maturity. There is no gender prevalence.

• Spinal Tuberculosis (Pott's disease)

  • ◗ Osteomyelitis of the thoracic vertebrae most often results from the hematogenous spread of the tubercle bacilli (TB) infection from a pulmonary lesion. TB remains an ongoing public health concern, even in developed countries.

❑ The Imaging Choices

• Radiographs are the initial imaging study for thoracic spine problems, with the exception of high-risk trauma patients, who are evaluated by CT. However, if CT is not available, radiographs are indicated.

• Computed tomography (CT) is the initial imaging study for high-risk trauma patients. One scan can evaluate for multi-system trauma: the head CT for the brain, the thoracic-abdominal-pelvic (TAP) scan for the viscera, and finally, all images of the ...