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: Surgery
[{'content': 'Fracture neck femur cause of non-union? \nSelect and explain. \nA. Injury to blood supply with shearing stress, B. Poor nutrition of the patient, C. Smoking, D. Old age and osteoporosis', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Injury to blood supply with shearing stress Causes of non-union in fracture neck of femur are :? Fracture morphology - high fracture angle and increased shear. Displaced fracture grade 3/4. Fracture comminution. Inadequate reduction and stability of fixation. Poor bone quality. Injury to vascularity- direct and tamponade effect. Absence of cambium layer in periosteum. Factors in synol fluid which inhibit the callus formation. Lack of hematoma. Washing away and dilution of osteogenic factors.", 'role': 'assistant'}]