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': 'Patellar tendon bearing P.O.P. cast is indicated in the following fracture - \nSelect and explain. \nA. Patella, B. Tibia, C. Medial malleolus, D. Femur', 'role': 'user'}, {'content': "Answer: B \nExplanation: Sarmiento's total contact below knee cast/PTB cast\n\nSarmiento PTB (patellar tendon bearing) plaster, is a carefully moulded patellar tendon bearing below knee plaster which is used in fractures of shaft of tibia in the later stages of conservative treatment when the fracture is more stable (& sticky) and requires the stimulus of direct weight bearing.\n\n\n\nIt is firmly moulded over-anterior tibial surface, lateral peroneal mass and posterior gastrocnemius mass in order to achieve a triangular shape which will prevent rotation and angulation of fragments. And a hydraulic environment provided by soft tissue is responsible for returning of the fracture to its preload state on the release of pressure (i.g., weight bearing).\nPatellar moulding is done in 45° extension (flexion). Most of the pressure is taken over gastrocnemius mass rather than over the bony prominences. 80% of weight is still taken through the leg. That's why it is not recommended for unstable early fractures.", 'role': 'assistant'}]