Finite element modeling of electromagnetic-coils targeting system for locating distal screw-hole in intramedullary interlocking-nail surgery

In this paper, we report a finite element modeling of an electromagnetic-coils targeting system to locate a distal screw-hole in intramedullary interlocking-nail surgery. The system consists of an internal coil, external coil, and control/measurement electronics. The internal coil is embedded in a distal screw-hole of the nail inserted into the bone. A current is applied to the internal coil to produce a directional magnetic flux penetrating the nail/bone. Thus, the external coil scans different regions of the nail/bone will receive different amount of magnetic flux, and thereby produces different voltage outputs due to the electromagnetic induction. By analyzing the voltage outputs, the distal screw-hole is targeted. However, to precisely apply this system to many different nails for people in different regions, modification and optimization of the system are needed. For rapid modification and optimization, we implement finite element method to model the targeting system. Because the modeling results are qualitatively consistent to experimental results, the modeling is successfully validated to be able to qualitatively predict experimental trends and thereby can be used for rapid system modification and optimization.