What are the four findings of osteoporosis on plain radiographs?

1. Picture framing: cortex is sharp, and trabeculae are decreased.
2. Empty box sign: relative increased density of vertebral end plates with resorption of central spongy bone.
3. Codfish vertebrae: biconcavity of the vertebral bodies owing to bulging of the structurally stronger disc.
4. Compression fractures of the vertebrae