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': 'Hallux valgus is associated with all except - \nSelect and explain. \nA. An exostosis on the medial side of the head of the first metatarsal, B. A bunion, C. Osteoarthritis of the metatarsophalangeal joint, D. Over- riding or under- riding of the second toe by the third', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Hallux valgus \n\nHallux valgus is lateral (outward) deviation of great toe at the metatarsophalangeal joint.\nIt is the commonest foot deformity.\nIt is common in women past middle age and is not infrequent even in young women.\nCommon causes are :\n\n\nRheumatoid arthritis\nWearing pointed shoes with high heels\nHereditary factors\nIdiopathic\n\nPathology\n\nOutward deviation of the great toe.\nMedially deviated head of the first metatarsal, causing an unduly wide gap between 1st & 2nd metatarsal heads (metatarsus primus varus).\nAfter several years two secondary changes occur:-\n\n\nFormation of a thick-walled bursa (bunion) over the medial prominence of 1" metatarsal head.\nOsteoarthritis of the metatarsophalangeal joint.\n\n\nIt is worth noting that medial prominence over metatarsal head looks like an exostosis, but there is no true\xa0exostosis.\xa0(Apley\'s 9th/e 603)\nLateral deviation of great toe causes overcrowding of lateral toes and sometimes overriding of adjacent toes.', 'role': 'assistant'}]