Pott Disease — Spinal Tuberculosis

A 28-year-old man from a TB-endemic region presents with 4 months of progressive mid-dorsal back pain, night sweats, weight loss, and recent-onset bilateral lower-limb weakness with urinary hesitancy. Examination reveals a sharp angular kyphosis at T8 with spastic paraparesis and a cold abscess in the right iliac fossa. Lateral thoracic spine X-ray shows the classic features of Pott's disease. The structure marked **A** (collapsed vertebral body) demonstrates the characteristic WEDGE COLLAPSE with destruction of anterior vertebral elements in a paradiscal pattern. Which of the following BEST explains why the intervertebral disc space is relatively preserved in this patient's presentation, distinguishing it from pyogenic spondylodiscitis?