This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anatomy of Bone & Fracture Healing, Subject name: Orthopaedics
[{'content': 'Fallen fragment sign is a feature of - \nSelect and explain. \nA. Simple bone cyst, B. Aneurysmal bone cyst, C. Giant cell tumor, D. Fibrous dysplasia', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Simple bone cyst Simple bone cvst (Soliterv/Unicameral bone cyst)o Simple bone cyst occurs before the age of 20 yearso The most common site is proximal humerus (50%)followed by Proximal femur (25-30%).o Radiological features are : -ConcentricMetaphysealExpansile lucent (lytic)Well defined border with sclerotic marginFallen Fragment sign : - Cortical fragment ofpathological fracture settles in the most dependent portion.Hinged fragment sign : - Sometimes fractured fragment does not separate from adjacent cortex.", 'role': 'assistant'}]