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Pittsburgh Researchers Develop Implantable RFID for Orthopedic Device

A University of Pittsburgh team has completed the testing and development of the Ortho-Tag, a patented RFID system to read a passive tag via RF transmissions passing through a patient's body.
By Claire Swedberg
According to Mickle, the Ortho-Tag would provide several benefits to patients and physicians. For one thing, it would help track infections. A sensor that measures the pH level in tissue around the tag could provide those sensor readings to the tag, which would then transmit the measurements to a reader placed against the skin nearest the implant, such as outside the knee for a knee implant. Sensors could be powered by an onboard supercapacitor—akin to a rechargeable battery, and charged either by a piezoelectric transducer built into the tag, or by the RF signals transmitted by the touch probe. Alternatively, the sensors could be powered directly by RF signals emitted by the touch probe at the time of a read event. The touch probe would capture that ID and sensor data (an elevated pH level might indicate an infection, for instance), and the handheld device could then display the results on its own screen, as well as send the details to a back-end system, either via a Wi-Fi connection or a USB port. In that way, physicians could be alerted to an infection before any visible symptoms emerged.

Another sensor could be used to track the frequency of the implanted joint's movement, thereby enabling physicians to determine how well the patient was using that joint. If, for example, the implant tag transmitted results indicating that the joint was rarely being used, physicians could address the problem, such as assigning a physical therapist to that individual, or learning more about how pain around the joint might be hindering his or her movement, for example.

Marlin Mickle
The tag could have other functions as well, such as assisting with identifying an implanted joint that has been recalled. Once a joint is implanted, it can often be difficult for patients or physicians to maintain a record of which particular product was inserted. With the Ortho-Tag, a user would capture the tag's ID, which would be linked with details regarding the joint in a back-end database.

Finally, if physicians read the tag before placing the joint within a patient, they could ensure that the product was not counterfeit, since the ID number would indicate that device's manufacturer, when it was built and its expiration date.

The university researchers began testing the system's ability to read through tissue using High-Frequency Structure Simulator (HFSS) software with an electromagnetic field simulation. The next test was conducted by reading tags through tanks of saline solution that mimic human tissue. The third test involved transmitting information through strips of pig skin, which also mimics human flesh. Further testing using human cadavers is a possibility, Mickle says, but that decision will be made in the future by Ortho-Tag's leadership.

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