Paget's disease of bone causes characteristic 'flame-shaped' ('V-shaped' or blade-of-grass) lytic lesion advancing through the tibial cortex. This represents:

• A Osteosarcomatous transformation occurring in 30% of cases
• B Stress fracture occurring in the anterior tibial cortex from bowing
• C Metastatic deposit from prostatic carcinoma
• D The advancing lytic phase of Paget's disease (phase 1) — osteoclast-mediated osteoporosis circumscripta progressing along the diaphysis ✓

Explanation

The flame/blade-of-grass lytic lesion in the tibia represents the advancing front of osteoclastic resorption (Phase 1/lytic phase) of Paget's disease — also called 'osteoporosis circumscripta' when seen in the skull. In the tibia, osteoclasts advance from the proximal to distal end creating a V-shaped lytic area. Osteosarcomatous transformation occurs in only 1% of Paget's disease (not 30%). Stress fractures in pagetic bone produce 'banana fractures' (transverse cortical fissures on the convex surface).

Reference: Maheshwari Essential Orthopaedics, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.