Radiography of the Dog
Atlas cranial aspect
Atlas lateral aspect
Atlas caudal aspect
Axis cranial aspect
axis lateral aspect
Axis caudal aspect
The other cervical vertebrae
The thoracic vertabrae
The other Lumbar vertebrae
The Cervical Region
Yorkshire Terrier cervical spine: Lateral view, neutral position. In small and toy breeds of dogs the vertebral canal is relatively wider than in large breeds. This lateral radiograph of a Yorkshire terrier shows the wide gap between the vertebral bodies and the corresponding dorsal laminae, which are projected dorsal to the articular facets. C1 looks tall and narrow compared with its appearance in large breed dogs.
Yorkshire Terrier cervical spine: Lateral view, flexed position. Another radiograph of the same Yorkshire terrier made with the head ventroflexed shows that flexion occurs at the occipitoatlantal joint (“yes” joint) but not at the atlantoaxial joint (“no” joint). This appearance is normal. In dogs suspected of having atlantoaxial subluxation, abnormal displacement of C1 may occur when the neck is manipulated, typically producing a widened gap between C1 and C2 in a ventroflexed lateral radiograph like this.
Puppy cervical spine: Lateral view. Just as in the limb bones, open physes are normally visible in the vertebral bodies in dogs less than 9 months old. Each vertebral body (except C1) has two physes.
Cervical spine survey: Lateral view. This lateral radiograph of the cervical spine shows the normal features of the 7 cervical vertebrae. C2 (axis) is the easiest to recognise because of its large dorsal spine. Immediately cranial to it is the spineless dorsal lamina of C1 (atlas). The wings of the atlas are superimposed over the cranial aspect of the body of C2. The cervical vertebrae are well aligned and the intervertebral spaces are regular in width. C6 is recognisable because of the large bent transverse processes, which project ventral to the vertebral body in a lateral radiograph.
Cervical myelogram: Lateral view. Injection of contrast medium into the subarachnoid space of the same dog as in the cervical spine survey image outlines the spinal cord, which is now visible as a lucent space between the two thin contrast lines. The ventral contrast line bends slightly dorsal above the intervertebral spaces, most noticeable at C2-3 and C6-7; this appearance is normal.
The Thoracic region
Thoraco-lumbar myelogram: Lateral view, large dog. The thoracolumbar region (T11-L2) is a frequent site of disc prolapse in dogs. This radiograph show the normal appearance of a thoracolumbar myelogram in a large breed dog. The contrast lines are regular and gently curved, with no sign of deviation over the intervertebral spaces. It is normal for the dorsal contrast line to be thicker than the ventral. This radiograph is slightly oblique - as you can see from the lack of superimposition of the ribs (ribs on one side projected dorsal to contralateral ribs) - but this is not a major problem; in a perfect lateral both sets of ribs may be superimposed over the myelogram, making it hard to see clearly. It is sometimes easier to see the myelogram in a slightly oblique radiograph like this.
Thoraco-lumbar spondylosis: Lateral view. In middle aged or old dogs (and cats), exostoses are frequently observed arising from the ventral and lateral aspects of the vertebral bodies adjacent to the end-plates. These exostoses can be quite large and pointed and extend ventral to the intervertebral space, sometimes bridging the space with solid bone. This condition is called spondylosis deformans. It is not a cause of clinical signs.
The Lumbar Region
Lumbar spine: Lateral view. This lateral radiograph of the lumbar spine shows the normal features of the 7 lumbar vertebrae, which are well aligned and the intervertebral spaces are regular in width. L7 is often a bit shorter than the others, although that is not very noticeable in this dog.
Lumbar myelogram: Lateral view. This lumbar myelogram shows the very regular, almost straight, contrast lines that we see in large breed dogs. Note that the ventral contrast line goes over each intervertebral space (i.e. over each disc) without any dorsal deviation. Also note the gradually tapered thecal sac, which contains the cauda equina. In this dog it terminates at the cranial aspect of the sacrum.
Lumbar epidurogram: Lateral view. A myelogram is a radiograph made after contrast medium has been injected into the subarachnoid space. To do this a needle is inserted through the dura, the thick outer layer of the meninges. Sometimes it is difficult to place the needle accurately, and if the tip fails to penetrate the dura there is the possibility that injected contrast will be deposited in the tissues around the dura instead (i.e. in the epidural space). This lateral radiograph of the lumbar spine shows epidural deposition of contrast medium. Compared to a myelogram, the contrast has an uneven wavy appearance with focal accumulations at each of the intervertebral foramina because epidural contrast ends to spread along the spinal nerves. An epidurogram is not as satisfactory for diagnosis as a myelogram.
Thecal sac myelogram: VD view, normal appearance. This is a ventrodorsal radiograph of the lumbosacral region of a dog after a total Hip prosthesis
Thecal sac myelogram: Lateral view, normal appearance. In large breed dogs, the thecal sac is frequently wide in the lumbosacral region period. In this instance it has a blunted termination well within the sacrum. This is a normal anatomical variation.
Lumbosacral joint: Lateral view. This lateral radiograph shows the lumbosacral joint in a large dog. Note that in a lateral radiograph the lumbosacral joint and L7 must be viewed through the wings of the ilium This is a common site of disc disease. This dog has spondylosis at the lumbosacral joint.
The Coccygeal vertebrae
“Screw-tail”: Lateral view. Congenital anomalies affecting the vertebrae are common in brachycephalic breeds such as the bulldog and pug. This lateral radiograph shows a short, bent tail in an English bulldog. This malformation is known as a screw tail.
Tail: Lateral view. This lateral radiograph of the pelvis includes the sacrum and first few caudal vertebrae. The remainder of the tail is thin and hence overexposed in this radiograph. The vertebral canal through the lumbar vertebrae, sacrum and tail is fairly straight.