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': 'The operative procedure is known as "microfracture" is done for the - \nSelect and explain. \nA. Delayed union of femur, B. Non union of tibia, C. Loose bodies of ankle joint, D. Osteochondral defect of femur', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Microfracture surgery\n\nMicrofracture surgery is one of the articular cartilage repair surgical techniques that works by creating tiny fractures in the underlying bone.\nThis cause new cartilage to develop a so-called super-clot.\nThe surgery is performed by arthroscopy and in the area of the osteochondral defect, tiny fractures are created in the subchondral bone.\nBlood and bone marrow (which contains stem cells) seep out of the fractures, creating a blood clot that releases cartilage-building cells.\n\nNote: Osteochondral defect means there is a loss of cartilage along with subchondral bone from a small area of a joint.', 'role': 'assistant'}]