In broilers with suspected spondylolisthesis, a vertebral abscess is most commonly found around the thoracic vertebrae, especially the free thoracic vertebra. During the postmortem examination, you should look for both vertebral deformities and evidence of an abscess.

The location can easily be identified just behind the last rib and in front of the cranial lobes of the kidneys. A prominent bulge in the spine may be detected by palpation in the area between the lungs and kidneys.

Postmortem approach:

Position the bird dorsally and expose the vertebral column.
Carefully remove the skin and musculature over the thoracolumbar region.
Cut the vertebral bodies and joints longitudinally with a sharp knife.
Examine:
alignment of the vertebrae
evidence of abscess
spinal cord compression

In this video, a large abscess is revealed. For more information see the chapter "Spondylolisthesis" in the book.