Development of a radiation-free magnetic guidance device for distal screw placement in intramedullary nails

This study developed a practical device for guiding distal interlocking screws during intramedullary nail fixation, aiming to address issues associated with the conventional free-hand approach using fluoroscopy. The objectives were to attain precision, reduce radiation exposure, and ease of operation. A small cylindrical magnet was embedded in the distal screw hole to emit signals for positioning. Due to the magnet's relatively weak magnetic force, especially in clinical settings with obese patients, the required long sensing distance is significant, making it susceptible to interference from the Earth's magnetic field. Therefore, three magnetic sensors were integrated to detect subtle magnetic changes: two sensors detect the position and tilt of the magnet, while the third sensor identifies the Earth's magnetic field. Consequently, this handheld device can freely rotate and tilt in three-dimensional space to accommodate the surgical site as required by the patient. Testing was conducted on porcine legs using a nonferromagnetic intramedullary nail and a magnet. Two validation methods were employed: passing a cotton rope through the drilled hole and using colored tape to assess drill bit accuracy. In tests, all targets of passing through the intramedullary nail hole were successfully achieved, with high accuracy rate (position accuracy of 91%-96%). Since this device is self-contained, sterilization can be achieved using an external plastic protective cover. The developed device offers a safe, accurate, and efficient radiation-free solution for distal screw placement, with strong clinical applicability and ease of use.