Electromagnetic coil/inductance-based nondestructive methods for locating distal screw-holes of an intramedullary interlocking-nail

We report an electromagnetic inductance/coil-based non-destructive method to target distal screw-holes in an intramedullary interlocking-nail surgical operation for fixing a long-bone fracture. The method is a radiation-free approach addressing the over-exposure issue of radioactivity caused by the typical X-ray-imaging approach. According to the method, we fabricate a targeting-system consisting of an internal inductance, external coil, guiding-mechanism, and driving/measurement electronics. When a voltage is applied to the internal inductance embedded in one of the distal screw-holes of a nail inserted in a bone, a directional magnetic flux is generated by the internal inductance due to the electromagnetic induction. Subsequently, the directional magnetic flux penetrates the nail and bone. When the external coil outside the bone scans along the axial and angular directions of the nail/bone, different amount of the generated magnetic flux is detected by the coil and consequently corresponding voltage response is induced in the coil due to the electromagnetic induction. In contrast to the magnetic flux generated and detected by the inductance and coil, respectively, we also investigate the reverse physics-behavior of the flux transmission (i.e., flux generated and detected by the coil and inductance) in order to improve the approach. Finally, by correlating the induced-voltage responses with the scanned axial-locations along the nail/bone, correlation curves are plotted. Through analyzing the curves, a criterion for predicting the location of the screw-holes of the nail is established. When compared the predicted location with the actual location of the screw-hole, the maximum targeting error is 2 mm for locating a screw-hole with a diameter of 5 mm. The result shows the targeting-method is accurate, fast, and easy for the surgeons and significantly simplifies the existed interlocking-nail surgical procedures.