A Novel Magnetic High-Permeable Thin-Film Electroplated-On-Nail Approach for Electromagnetic Targeting in Intramedullary Interlocking-Nail Surgery

In this article, we report a novel magnetic high-permeable NiFe thin-film electroplated-on-nail approach for electromagnetic targeting in intramedullary interlocking-nail surgery. The electromagnetic targeting system consists of a specific nail (on which a magnetic high-permeable NiFe thin film is electroplated onto specific outer and inner surfaces of the nail), a C-shape electromagnet module (includes a C-shaped silicon steel core, emitting coil, and receiving coil), guiding mechanism, and measurement electronics. An ac input voltage is applied to the emitting coil to produce an ac magnetic flux/field in the air gap between the emitting coil and the receiving coil. Consequently, this induces a corresponding ac voltage in the receiving coil. When the C-shape electromagnet module with the producing constant magnetic field is used to scan the nail, the magnetic flux/field is influenced (concentrated) by the magnetic thin film on the outside and inside surfaces of the nail, and thus, the induced voltage of the receiving coil is changed. Through analyzing the changes in the induced voltage, the location and orientation of the thin film are obtained. Because the distance between the thin film and the screw hole is already known when electroplating thin film onto the specific regions of the nail, the location and orientation of the distal screw hole are also obtained. According to blind tests, our test results show that the maximum targeting error of the location- and orientation-targeting are 1.06 mm and 3.76°, respectively, with a success rate of 96%. Due to these results, our approach not only can achieve a decent targeting accuracy, but also does not necessitate any placement of any bulk components (such as sensors or coils) inside the nail, which is generally required by conventional approaches. The placement of bulk components generally causes a retrieving problem (difficult to retrieve the components from the inside of the nail to the outside of the bone/body) during the surgery and can be solved by our approach in this article.