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: Unknown
[{'content': "A patient on colles cast present after two weeks with the inability to extend his thumb, the most likely reason is: \nSelect and explain. \nA. Rupture of extensor pollicis longus tendon, B. Compartment syndrome, C. Carpal tunnel syndrome, D. Sudek's osteodystrophy", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans: A (Rupture of extensor pollicis longus tendon) Ref: Apleys System of Orthopaedics and Fractures, 9th edition, p 774Explanation:Rupture of extensor pollicis longus occasionally occurs a few- weeks after an apparently trivial undisplaced fracture of the lower radius.The patient should be warned of the possibility and told that operative treatment is available.', 'role': 'assistant'}]