In Pott disease, the vertebral body is typically affected first. Which anatomical region of the vertebra is the initial site of tuberculous infection?

Explanation

## Anatomical Pathology of Pott Disease **Key Point:** Tuberculosis of the spine characteristically begins in the anterior metaphyseal region of the vertebral body, just beneath the endplate, due to the rich vascular supply in this area. ### Initial Site of Infection The infection typically starts in the **cancellous bone of the anterior vertebral body**, near the superior or inferior endplate. This is the region with the highest blood flow and oxygen tension, making it the most vulnerable to hematogenous seeding from a primary focus (usually pulmonary). ### Progression Pattern 1. **Early phase:** Anterior vertebral body involvement 2. **Progressive phase:** Spread to adjacent vertebrae (skip lesions are uncommon) 3. **Late phase:** Kyphotic deformity, paravertebral abscess formation, potential spinal cord compression **Clinical Pearl:** The anterior location explains why Pott disease classically causes kyphotic (gibbus) deformity rather than lordosis — the anterior vertebral body is progressively destroyed, leading to anterior column collapse. **High-Yield:** Unlike pyogenic spondylodiscitis, TB typically spares the intervertebral disc initially (though late disc involvement can occur). The posterior elements (lamina, spinous process) are involved only in advanced disease.