Plain radiography
Plain radiography is frequently used as a screening test because it is readily accessible. However, radiographs of the lumbosacral
articulation are often difficult to interpret because of the complexity of the anatomy and overlying wings of the ilium bilaterally.
Furthermore, soft tissue structures, often the main structures involved in degenerative lumbosacral stenosis, are not seen
with plain radiography. As a result, false positive and false negative diagnoses are often reached based on radiographs alone.25
Figure 2: A lateral lumbosacral radiograph of a dog with a transitional vertebra. Note the sacralization of the L7 vertebra
(arrow). The craniocaudal length of the L7 vertebral body is shortened in comparison with the L6 vertebral body. The long
axis is in alignment with the sacrum rather than with the remaining lumbar vertebral column. The lumbosacral intervertebral
disk space is narrowed (arrowhead). The sacrum appears normal (asterisk); Figure 3: A ventrodorsal lumbosacral radiograph
of the dog in Figure 2. The left transverse process of the L7 vertebra is normal (long arrows). On the right side, the L7
vertebra is articulating with the wing of the ilium (small arrows). Normal sacroiliac articulation is seen on the left (asterisk).
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The real value of radiography lies in the ability to exclude other causes from consideration. Diseases such as diskospondylitis
and neoplasia and traumatic injury are often easily identified radiographically. Plain radiography is also useful in identifying
anatomical anomalies of the vertebrae such as transitional vertebrae, or vertebrae with anatomical features characteristic
of the two different regions of the vertebral column (Figures 2 & 3). In one study, dogs with a combination of degenerative changes and transitional vertebrae at the lumbosacral articulation
were significantly more likely to have degenerative lumbosacral stenosis then dogs with degenerative changes or transitional
vertebrae alone.26
Figure 4: A lateral lumbosacral radiograph of a dog. Note the sclerosis of the vertebral end plates of the L7 vertebra and
the sacrum with narrowing of the disk space as well as the ventral spondylosis. A slight ventral subluxation of the sacrum
is also present; Figure 5: A lateral radiograph of the lumbosacral vertebral column. Changes are similar to those noted in
Figure 4. Additionally, note the degenerative changes in the articular facets of the L7 vertebra and the sacrum, which are
difficult to appreciate given the superimposition of the wings of the ilium (arrow); Figure 6: A ventrodorsal lumbosacral
radiograph of the dog in Figure 4. Lateral spondylosis can be seen at the L7 sacral articulation (long arrow). Also note the
narrowing of the lumbosacral intervertebral disk space (two short arrows).
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Typical abnormalities associated with degenerative lumbosacral stenosis include spondylosis deformans, which can extend from
both the ventral and lateral aspects of the L7 and sacral vertebral bodies; narrowing of the L7-S1 intervertebral disk space;
sclerosis of the vertebral end plates; and ventral displacement of the sacrum in relation to the L7 vertebra (Figures 4-6).19,25,27,28
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