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': 'In some old fractures, cartilaginous tissue forms over the fractured bone end with a cavity in between containing clear fluid. This condition is called as - \nSelect and explain. \nA. Delayed union, B. Slow union, C. Nonunion, D. Pseudoarthrosis', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Pseudarthrosis develop after a fracture that has not united due to inadequate immobilization, i.e. Pseudarthrosis is a type of nonunion.\nInadequate immobilization permits constant movement at the fracture site which hampers the formation of normal callus, and fibroblast forms excessive fibrous tissue in this situation which results in non-union.\nIf the movement continues to occur at the non-union site, the fracture site develops features of a joint,i.e. Pseudarthrosis:-\nCovered by a cartilage (fibrocartilage)\nThere is synovial lining\nSpace is filled with synovial fluid like clear fluid\nMobility', 'role': 'assistant'}]