Which anatomical structure indicates an incorrect positioning for a lateral thoracic spine projection?

In a lateral thoracic spine projection, the zygapophyseal joints are not the primary focus because this projection primarily visualizes the intervertebral foramen and the spinous processes. The zygapophyseal joints, or facet joints, are best demonstrated in an oblique projection rather than a lateral one, making it an indication of incorrect positioning if they are emphasized in a lateral view. This projection is intended to provide a clear image of the vertebral bodies and the relationship between adjacent vertebrae, which would be hindered by misaligning the zygapophyseal joints.

The costovertebral joints and intervertebral foramen, when positioned correctly, should be well visualized in a lateral projection, so they are not indicators of incorrect positioning. Similarly, spinous processes should be aligned and visible correctly in a lateral view to ensure accurate interpretation of spinal alignment and any potential pathologies.