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What is "Bone within bone" appearance is classically seen in and explain in detail?
Ans. (b) OsteopetrosisRef: Sutton 7th/1339,1355, 1365DiseaseRadiological featureOsteoporosis* Cod fish vertebrae* Pencilling-in-vertebrae (loss of density of vertebral body with radiodense end plates)Osteomalacia* Looser's zone /Pseudo fracture is the Hallmark feature (B/L radiolucent band of uncalcified osteoid due to pressure of pulsating artery)* Cod Fish (marked biconcave) vertebrae* Pencilling in vertebraeOsteopetrosis/ Marble Bone disease/Alberg Schowenberg disease* Bone within Bone appearance* Erlenmeyer flask deformity of long bone disease ends (flask shaped metaphysis)* Rugger jersey spine* Increased density of bones