The Best Valgus Angle of Hip Joint for the Treatment of Nonunion in Femoral Neck Fracture by Computational Simulation

Introduction & Femoral neck fracture is one of the most complicated fractures in orthopedic diseases, and its common complication is nonunion. If the head of femur is alive, one of treatments of nonunion is to alter the fracture line angle and the conversion of displacing force to pressure force at the site of fracture, and this leads to union. On the other hand, it changes the biomechanic of hip and disposes it early destruction that will affect patient’s life adverse. Our aim in this study was to achieve an angle that accelerates union and on the other hand does not lead to Arthrosis and joint destruction. With biomechanical analysis and using computational simulation, we assessed the displacing force of femur neck fracture and the pressure force on the head of femur at different angles of valgus. Considering individual geometrical and biological factores and producing graphs to be able to determine the proper angle for valgus osteotomy. It must be able to produce proper pressure force for union at the fracture site, not leading at the destruction of femur head, and not exceeding the physiological limits. To produce fracture in femur and Blade modeling we used solid work software, and then located the blade at the proper place for osteotomy. Geometry was used in the software to perform simulation. We offered values of stress intensity for fracture angles 30 to 70 and correction angles 0 to 40, and obtained from simulations suitable angles for osteotomy, based on the minimum of shear stress. Furthermore, at the angles 50 and 55 there was no significant change in the shear stress. According to the results of this study, we offered stress intensity suggested through simulations and recommended angles for osteotomy, based on the minimum of shear stress. Changing the fracture line between 0 to 40 degree had no obvious effect on the force on the head of the femur.