A 7-year-old boy with Legg-Calve-Perthes disease has a plain radiograph showing a subchondral lucent line in the anterosuperior femoral head with increased density of the epiphysis and apparent widening of the medial joint space. In which stage of the disease do these findings appear?

• A Reossification stage
• B Fragmentation stage
• C Initial (necrotic) stage ✓
• D Residual stage

Explanation

The crescent sign, a subchondral lucent line representing a subchondral stress fracture of the necrotic epiphysis, along with increased density of the ossified epiphysis and apparent medial joint space widening from cartilage hypertrophy, characterises the initial or necrotic stage of Perthes disease, lasting several months to a year. The fragmentation stage follows, marked by fragmentation and collapse of the epiphyseal ossific nucleus rather than the crescent sign.

Reference: Tachdjian's Pediatric Orthopaedics, 5th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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