In TB of the hip joint, the classical clinical finding is 'Rose thorn sign'. What does this refer to?

• A A periosteal reaction along the femoral neck on X-ray
• B Lateral femoral cortical erosion on plain X-ray suggesting periarticular erosion by TB granuloma ✓
• C On fluoroscopy, the contrast-filled acetabulum shows a pointed spur of bone at the acetabular margin from erosion
• D Subchondral crescent sign in the femoral head indicating early avascular necrosis

Explanation

The 'rose thorn sign' in hip joint TB refers to small periosteal spurs (trabecular radiolucencies or erosions) at the lateral cortex of the femoral neck, produced by penetration of granulomatous tissue through the thin cortical bone. This is an early radiological sign of periarticular TB osteitis. The Phemister triad (juxta-articular osteoporosis, peripheral osseous erosions, and gradual joint space narrowing) is the more comprehensive radiological description of TB arthritis. Crescent sign is associated with avascular necrosis. Rose thorn is distinct from the acetabular sign.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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