A 32-year-old presents with back pain and gibbus deformity. MRI spine shows D7-D8 vertebral body destruction with large bilateral psoas abscess but preserved disc space initially. Which feature of spinal TB is being described by the PRESERVED disc space early in disease?

• A TB involves disc primarily via haematogenous spread to disc directly
• B TB lacks proteolytic enzymes to degrade cartilage, so disc destruction is a late feature ✓
• C The disc is protected by the posterior longitudinal ligament in thoracic spine
• D Disc involvement requires direct extension from paraspinal abscess

Explanation

Unlike pyogenic spondylodiscitis (which attacks the disc early due to bacterial proteases), Mycobacterium tuberculosis lacks proteolytic enzymes and does not degrade the avascular disc cartilage early. TB spine characteristically begins in the anterior vertebral body (subchondral) and spreads under the anterior longitudinal ligament, involving the disc only in later stages. This explains the classic 'preserved disc space early' feature. In contrast, pyogenic osteomyelitis shows early disc destruction. As TB progresses, endplate collapse and mechanical disc compression eventually cause disc space narrowing.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.