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: Surgery
[{'content': 'All of the following are types of avascular non-union except: \nSelect and explain. \nA. Comminuted, B. Elephant foot, C. Torsion wedge, D. Atrophic', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Classification of non-union:\n\xa0Hypervascular non-union:\n\nElephant foot (hypertrophic , rich in callus)\nHorse foot (mildly hypertrophic , poor in callus)\nOligotrophic (non-hypertrophic, no callus)\n\nAvascular non-union:\n\nTorsion wedge\nComminuted\nDefect\nAtrophic', 'role': 'assistant'}]