In Legg-Calve-Perthes disease, which of the following radiographic findings is classified as a 'head at risk' sign indicating a poor prognosis?
- A Gage sign, a V-shaped osteoporotic defect in the lateral epiphysis and metaphysis ✓
- B Crescent sign, a subchondral lucent fracture line
- C Sagging rope sign across the femoral neck
- D Coxa magna with a broadened femoral neck
Correct answer: A. Gage sign, a V-shaped osteoporotic defect in the lateral epiphysis and metaphysis
Explanation
Catterall described five head-at-risk signs: Gage sign, lateral calcification adjacent to the epiphysis, metaphyseal cysts, lateral subluxation of the femoral head, and a horizontal growth plate. These predict residual deformity and indicate the need for containment. The crescent sign represents a subchondral fracture seen in the early stage and is not a prognostic at-risk marker. The sagging rope sign reflects old Perthes disease with widened femoral neck, and coxa magna is a residual deformity.
Reference: Tachdjian's Pediatric Orthopaedics, 5th ed.
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