This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Orthopaedics
[{'content': 'Radiologically, the earliest sign of osteomyelitis is - \nSelect and explain. \nA. Loss of muscle and fat planes, B. Presence of sequestrum, C. Callus formation, D. Periosteal reaction', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Osteomyelitis is the infection of bone by microorganisms. It can be acute or chronic. \nAcute osteomyelitis: This can be primary (haematogenous)or secondary(following open fracture or bone operation). Staphylococcus aureus is the commonest causative organism. C/f: Child presents with an acute onset of pain and swelling at end of a bone, associated with systemic features of infection like a fever. \nInvestigations: Blood- polymorphonuclear leucocytosis and an elevated ESR. X-rays - The earliest sign to appear in X-ray is a periosteal new bone deposition at metaphysics. This is called periosteal reaction. It takes about 7-10 days to appear. Bone scan- bone scan using Tc 99 may show increased uptake by bone in the metaphysis.', 'role': 'assistant'}]