Question

Which of the following is a radiological sign in Perthes disease?

• A. Epiphyseal calcification
• B. Organized calcification
• C. Lateral subluxation of femoral head
• D. Restriction of abduction

Hint:

The necrotic head collapses and drifts out of the acetabulum on imaging.

Answer 1

The Correct Option is C

Step 1: Legg-Calve-Perthes disease is an idiopathic avascular necrosis of the femoral head epiphysis in children, typically between 4 and 8 years of age.

Step 2: As the femoral head undergoes necrosis, fragmentation and flattening, the head loses its normal containment within the acetabulum. This produces lateral displacement, that is, lateral subluxation of the femoral head, which is a recognised radiological sign.

Step 3: Other classic radiographic findings include the crescent sign (subchondral fracture), increased density and later fragmentation of the epiphysis, widening of the joint space, and a small or flattened (coxa plana) femoral head.

Step 4: Restriction of abduction is a clinical, not a radiological, finding. Epiphyseal calcification and organized calcification are not specific radiological signs of Perthes disease, so the correct radiological answer is lateral subluxation of the femoral head.