An electromagnetic-induction approach for screw-hole targeting in interlocking-nail surgery

We report a novel approach for targeting screw-holes of an intramedullary nail in a long-bone fracture surgery. The approach utilizes the electromagnetic induction to avoid over exposure of radioactivity which is the critical issue in conventional X-ray-imaging targeting method. Based on the approach, we fabricate a targeting system. The targeting system consists of a c-shaped electromagnet, detecting-coil, guiding-mechanism, and measurement electronics. When a voltage is applied to the electromagnet, magnetic flux is generated in the air gap of the electromagnet and subsequently detected by the coil. When the flux is detected by the coil, a voltage response is induced in the coil. When a nail in a bone is scanned through the air gap of the electromagnet, the flux is influenced due to a discrepancy of the permeability between the location with and without the hole of the nail. The influenced flux induces different voltage response in the coil. Through analyzing the voltage response, we establish a criterion for targeting the holes. By the criterion, the experimental result shows the maximum error of targeting a hole with a diameter of 5 mm is less than 2.5 mm.