**Core Concept**
The question is testing the understanding of the relationship between vertebral body collapse and intervertebral disc space in the context of spinal diseases.

**Why the Correct Answer is Right**
The maintenance of intervertebral disc space in the presence of vertebral body collapse is characteristic of osteoporotic compression fractures. In osteoporosis, the bone density is reduced, leading to a higher risk of vertebral body compression fractures. However, the intervertebral disc space is maintained because the disc is not directly affected by the osteoporosis. The collapse of the vertebral body is due to the loss of bone density, which increases the risk of fractures.

**Why Each Wrong Option is Incorrect**
* **Option A:** Osteoblastic metastasis would typically cause an increase in bone density, leading to a "Codman's triangle" or a "ivory vertebra" appearance on X-ray. This would not be associated with a maintained intervertebral disc space.
* **Option B:** Spondylosis deformans is a degenerative condition characterized by the formation of bone spurs, which would not typically cause vertebral body collapse.
* **Option C:** Pott's disease (tuberculous spondylitis) would likely cause destruction of the intervertebral disc space due to the infection.

**Clinical Pearl / High-Yield Fact**
Osteoporotic compression fractures are a common cause of vertebral body collapse, especially in postmenopausal women. It's essential to consider osteoporosis in the differential diagnosis of vertebral body collapse.

**Correct Answer: A. Osteoblastic metastasis.**