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Imaging - The Vertebral Column

Imaging - The Vertebral Column

Radiography


Survey radiography serves as a valuable initial method for assessing bone and, to a lesser degree, soft tissue. Spinal radiographs can detect fractures and luxations, discospondylitis, certain vertebral

tumors, congenital anomalies, and degenerative changes, and can offer indirect evidence of disc herniation. Bone lesions seen on survey radiographs can be more precisely defined using CT.


Technique Tips


  • Radiographs need to be made under sedation or general anaesthesia in order to achieve

adequate patient positioning.

  • If spinal instability is suspected, as may arise from atlantoaxial subluxation or a vertebral

fracture, only lateral views should be acquired initially in order to avoid iatrogenic neural injury

that may occur when positioning the patient for ventrodorsal (VD) views. Based on the findings

from the lateral views:

  • The examination can be terminated if the diagnosis is obvious (e.g. atlantoaxial subluxation)

  • Conventional VD views can be acquired

  • VD views can be obtained using a horizontal X-ray beam.

  • To interpret spinal radiographs accurately, it is important that the vertebral column is not rotated. Padding, ties and troughs should be used to achieve this.

  • It is important to avoid radiographic distortion of the vertebrae and intervertebral disc spaces due to the divergence of the X-ray beam. To minimize distortion, multiple radiographs are required so that more vertebrae and disc spaces can be imaged with the center of the X-ray beam.


Interpretation

To accurately interpret spinal radiographs, one needs high-quality images and an understanding of the spine's normal radiographic anatomy.


Normal anatomy of a canine vertebra

Radiographs should be evaluated for the following:


  • Basic anatomy, including the number of vertebrae and the presence of processes and ribs. There should be 7 cervical, 13 thoracic, 7 lumbar, and 3 fused sacral vertebrae in both dogs and cats.

  • Alignment of the vertebrae in two planes.

  • Width of the intervertebral disc space. Each space should be compared with the disc space immediately cranial and caudal. Only if the disc space being evaluated is not as wide as both

    adjacent disc spaces should it be considered narrow.

  • Shape and opacity of the intervertebral foramina.

  • Integrity of the vertebral endplates. They should be examined for lysis and sclerosis which may indicate infection

  • Evidence of vertebral neoplasia in the form of lysis, sclerosis, and distortion of the bone outline. It should be noted that a large amount of cancellous bone (up to 50%) must be lost from the vertebral body before bone lysis can be detected radiographically.

  • Degenerative changes of the vertebrae (e.g. spondylosis deformans) or articular processes

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