This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Osteomyelitis, Subject name: Orthopaedics
[{'content': 'Non-healing sinus is a common clinical feature is chronic osteomyelitis. The most common frequent cause for this presentation is: \nSelect and explain. \nA. Resistant organisms, B. Retained foreign body, C. Presence of sequestrum, D. Intraosseous cavities', 'role': 'user'}, {'content': 'Answer: C \nExplanation: (C)- Due to necrosis pieces of dead bone separate as sequestra varying in size from spicule to large segment. It is lighter than live bone and normal pattern of bone is lost. It acts as nidus and is most common cause of non healing sinus in chronic osteomyelitis.', 'role': 'assistant'}]