**Core Concept:** Tuberculosis (TB) is a common infectious disease caused by the bacterium Mycobacterium tuberculosis. Spinal TB, or TB of the spine, can involve different spinal segments and has distinct clinical presentations based on the affected vertebrae.

**Why the Correct Answer is Right:** Spinal TB most commonly affects the thoracic spine (T1-T12), followed by the lumbar spine (L1-L5) and the cervical spine (C3-C7). The reason behind this pattern lies in the anatomy and the distribution of the blood supply to the vertebrae. The thoracic spine receives blood supply primarily from the intercostal arteries, while the lumbar spine receives blood supply from the lumbar arteries. The cervical spine gets blood supply from the subclavian arteries, which makes it less prone to TB infection.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because the lumbar spine receives blood supply from the lumbar arteries, making it less prone to TB infection compared to the thoracic and cervical spines.
B. This option is incorrect because the sacroiliac joints are not typically affected in spinal TB; the disease primarily affects the vertebrae.
C. This option is incorrect because the occipital bone is not involved in spinal TB; the disease primarily affects the vertebrae.
D. This option is incorrect because the pelvic bones are not involved in spinal TB; the disease primarily affects the vertebrae.

**Clinical Pearl:** A high index of suspicion is required when evaluating patients with back pain or spinal deformities, especially in endemic regions. Treatment typically involves a combination of anti-TB medications and surgical intervention in severe cases. Early diagnosis and treatment are crucial for optimal outcomes and prevention of complications like neurological deficits and deformities.