Study On The Location Of Intramedullary Nail Based On Electromagnetic Navigation

Fracture is one of the most common medical diseases.The secondary injury of patients with fracture treated by intramedullary nail during orthopedic operation is small,It's a minimally invasive operation.Compared with other orthopedic operations,In the treatment of fractures,intramedullary nails need to be put into the bone marrow.orthopedics can't see the intramedullary nail in the bone marrow.Orthopedic doctors need advanced science and technology to find the location of the hole.In the field of positioning technology,the positioning technology often used by scientists includes mechanical positioning technology,ultrasonic positioning technology,optical positioning technology,electromagnetic positioning technology and so on.Among these positioning technologies,the accuracy of mechanical positioning technology is poor.Mechanical positioning technology can not achieve information feedback.Although the accuracy of optical positioning technology is relatively high,it is easy to be occluded by objects.Because the intramedullary nail is in the bone marrow,the optical localization technology is not feasible.Ultrasonic positioning technology is easy to be interfered by external noise,and its accuracy is very low.Compared with other positioning technologies,electromagnetic positioning technology has higher positioning accuracy and is not easy to be interfered by noise and not occluded by objects.Therefore,electromagnetic positioning technology is more suitable for intramedullary nail orthopedic surgery.In electromagnetic positioning technology,the model of magnetic dipole can be used to get the location and direction of the object.The location and direction of the target can be calculated by solving the nonlinear equations.Electromagnetic positioning technology includes signal generator,signal receiver and signal processing system.During electromagnetic positioning,coils are used to transmit and receive signals.The transmitting coil and the receiving coil will produce a coupling signal,which includes the position and direction of the receiving coil.Because the coupling signal is weak and contains many noises,it is necessary to filter and amplify the coupling signal.The signal after filtering and amplification is a useful signal.In this paper,electromagnetic positioning experiment and finite element simulation experiment are carried out.In the electromagnetic positioning experiment,the orthogonal receiving and transmitting coils are made,and the electromagnetic signal excitation circuit and the electromagnetic signal receiving and processing circuit are designed.In the process of electromagnetic signal processing,the least square method is used to fit the sine curve,and the amplitude and phase of the induction signal are calculated.The fitting curve of different signal-to-noise ratio is analyzed to verify its accuracy.The experimental platform of electromagnetic positioning is set up,and several points in the space are measured.The average position error of electromagnetic positioning experiment is close to millimeter level,and the average direction error is about 5 °.In the finite element simulation experiment,the geometrical models of the transmitting coil and the receiving coil are established,and the magnetic dipole model is simulated and verified.The solution error caused by LM algorithm under different equations is simulated.The electromagnetic positioning experiment is simulated and the average position error is in millimeter level,and the average square error is about 4 °.