A nonradiographic strategy to real-time monitor the position of three-dimensional-printed medical orthopedic implants by embedding superparamagnetic Fe3O4 particles

Monitoring the position of orthopedic implants in vivo is paramount for enhancing postoperative rehabilitation. Traditional radiographic methods, although effective, pose inconveniences to patients in terms of specialized equipment requirements and delays in rehabilitation adjustment. Here, a nonradiographic design concept for real-time and precisely monitoring the position of in vivo orthopedic implants is presented. The monitoring system encompasses an external magnetic field, a three-dimensional (3D)-printed superparamagnetic intervertebral body fusion cage (SIBFC), and a magnetometer. The SIBFC with a polyetheretherketone framework and a superparamagnetic Fe₃O₄ component was integrally fabricated by the high-temperature selective laser sintering technology. Owing to the superparamagnetic component, the minor migration of SIBFC within the spine would cause the distribution change of the magnetic induction intensities, which can be monitored in real-time by the magnetometer no matter in the static states or dynamic bending motions. Besides horizontal migration, occurrences of intervertebral subsidence in the vertical plane of the vertebrae can also be effectively distinguished based on the obtained characteristic variations of magnetic induction intensities. This strategy exemplifies the potential of superparamagnetic Fe₃O₄ particles in equipping 3D-printed orthopedic implants with wireless monitoring capabilities, holding promise for aiding patients' rehabilitation.