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
'Shepherd's crook' deformity of the proximal femur seen in 
Select and explain. 
A. Fibrous dysplasia, B. Chondroblastoma, C. Osteochondroma, D. Aneurysmal bonecyst
A: Fibrous dysplasia
Answer: A: Fibrous dysplasia 
Explanation: (Fibrous dysplasia) (227-M) (174-75-Abley 8th)FIBROUS DYSPLASIA is a developmental disorder in which areas of trabecular bone are replaced by cellular Fibrous tissue containing flecks of osteoid and woven bone* ** Occasionally the bone disorders is associated with "cafe-au-lait " patches on the skin and (in girls) precocious sexual development (Albright's syndrome)* * Malignant transformation to fibrosarcoma occurs in 5-10% of patients with polystotic lesions, but only rarely in monostotic lesionsX ray shows radiolucent 'cystic ' areas in the metaphysis or shaft because they contain fibrous tissue with diffuse spots of immature bone, the lucent patches typically have a slightly hazy or 'ground glass' appearanceThe weight bearing bones may be bent and one of the classic features is the 'shepherd's crook' deformity of the proximal femur