Smart implants are increasingly recognised for use in surgical procedures on patients. Typically, a smart implant (which may be, for example, an orthopaedic implant used to replace or support damaged tissue or bone) includes sensors for sensing the environment surrounding the implant and a transmitter for wirelessly transmitting data reporting on the environment to an external receiver located outside the body. Using the wireless link, the implant can send data out at certain intervals or provide real-time feedback, such that a medical practitioner is able to monitor the status of the implant and/or conditions within the patient's body.
The wireless link between the implant and the external receiver may be difficult to secure due to the fact that electromagnetic waves quickly attenuate as they propagate through human tissue. Depending on the depth of the implant within the body, the signal strength may be quite weak by the time the waves reach the skin. In order to address this problem, relay devices have been developed that are designed to be worn on the outside of the patient's body, or carried close thereto, and which can detect the signals emanating from the implant and relay those signals over the distance from the patient's body to the external receiver. Such “on-body relay devices” may comprise one or more antennas for relaying the signals between the implant and the external receiver.
There is a continuing need to improve on-body relay devices for relaying signals from a smart implant to an external receiver located outside the patient's body.