This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bone Tumour, Subject name: Orthopaedics
[{'content': 'Shepherd crook deformity is seen in? \nSelect and explain. \nA. Fibrous dysplasia, B. Non ossifying fibroma, C. Adamantinoma, D. Fibrous cortical defect', 'role': 'user'}, {'content': "Answer: A \nExplanation: ANSWER: (A) Fibrous dysplasiaREF: Sutton's 7th ed p. 1131Fibrous dysplasia in the femur, deformity due to softening, expansion and fracture gives an appearance likened to a 'shepherd's crook' and discrepancies in limb length result. Lesions are well defined and may be expanded with well-defined margins. These may be lucent, dense or a mixture of the two, with small flecks of density due to ossification", 'role': 'assistant'}]