Fracture neck femur cause of non-union-
Ans. is 'a' i.e., Injury to blood supply with shearing stresso 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 synovial fluid which inhibit the callus formation.Lack of hematoma.Washing away and dilution of osteogenic factors.