**Question:** A 38-year old lady presents with h/o backache. X-ray and MRI spine reveal collapse of D12 vertebrae with normal intervertebral disc space. The LEAST likely diagnosis is:

A. Spondylolisthesis
B. Spinal stenosis
C. Scoliosis
D. Spondylosis

**Correct Answer:** D. Spondylosis

**Core Concept:** Spondylosis, also known as degenerative disc disease, is a process characterized by the degeneration of intervertebral discs and surrounding structures. It is often associated with aging, leading to pain, inflammation, and reduced mobility. However, the collapse of a vertebrae (as seen in the given case) is not a typical presentation of spondylosis.

**Why the Correct Answer is Right:** In this case, the patient's symptoms and imaging findings indicate a problem with the D12 vertebrae, which is not typical of spondylosis. Spondylosis typically causes low back pain, radicular pain, and spinal stenosis, but not vertebral collapse.

**Why Each Wrong Option is Incorrect:**

A. Spondylolisthesis: This refers to the forward displacement of one vertebra over another, often due to ligamentum flavum hypertrophy or pars interarticularis fracture. Spondylolisthesis is more likely to cause low back pain, leg pain, and radicular symptoms.

B. Spinal stenosis: This refers to the narrowing of the spinal canal and/or nerve root canals, typically caused by disc degeneration, ligamentum hypertrophy, or osteophytes. Spinal stenosis is more likely to cause neurogenic claudication, radicular symptoms, and/or myelopathy.

C. Scoliosis: This refers to a lateral curvature of the spine, typically caused by musculoskeletal imbalances or vertebral alignment issues. Scoliosis is not directly related to the collapse of D12 vertebrae.

D. Spondylosis: As explained earlier, spondylosis is a general term for degenerative changes in the spine, not directly related to vertebral collapse. While spondylosis can cause low back pain and radicular symptoms, it is not the least likely diagnosis in this case.

**Clinical Pearl:**

Understanding the anatomy and pathology of the spine is crucial in making an accurate diagnosis. In this case, the collapse of the D12 vertebrae suggests a rarer cause, making spondylosis less likely. However, it is essential to consider the specific mechanism of the vertebral collapse and its potential consequences, such as spinal stenosis or nerve root compression, rather than just focusing on the broader term "spondylosis."