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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
Jun 17, 2011Researchers at the University of Pittsburgh have developed a system, known as the Ortho-Tag, including an RFID tag that would be affixed to an orthopedic implant, thereby enabling sensors built into the tag to track the device's health and use within a patient's body. The tag would convey that information via RF signals transmitted through human tissue to a reader placed against a patient's skin. Not only would the system track conditions inside the body surrounding the implant, but it could also identify the device itself in the event of a recall. Moreover, it could help verify that the implants were authentic, and not counterfeit.

The solution was tested at one of the university's laboratories, under the leadership of Marlin Mickle, one of the school's engineering professors. Mickle is also the chairman of the scientific advisory board of Ortho-Tag Inc., the fledgling firm that will commercialize the technology. The company aims to provide the tags to an orthopedic device manufacturer, for attachment to implants as those devices are built. Ortho-Tag would then sell handheld interrogators developed specifically for reading the tags through human tissue, as well as software to manage read data, to physicians and hospitals.

An Ortho-Tag would be affixed to an orthopaedic implant and scanned via an RFID probe. A card (foreground) would be available to patients with an existing implant.
Orthopedic surgeon Lee Berger first developed and patented the tag in early 2008, with the goal of helping patients and physicians track the status of healing around the site of a new implant (see Surgeon Designs System to Monitor Orthopedic Implants and Promote Healing). Berger envisioned a system employing sensors that would measure the physical pressure on a device once it was implanted, as well as the surrounding chemical balance and temperature, in order to identify an infection, as well as determine if the implant had shifted. The sensors would be wired to an RFID chip that would transmit a unique ID number, along with the sensor data, to a handheld reader being used by a physician. Berger built a prototype using passive ultrahigh-frequency (UHF) EPC Gen 2 RFID tags, then began seeking partners to further develop and test the technology's ability to read through the body, prior to marketing it to implant vendors and distributors.

Mickle says he began working with Berger in 2008. The University of Pittsburgh's school of engineering had developed a touch probe that could be utilized to read tags attached to metal, and had also conducted work testing the ability to transmit radio waves through the human body. In May 2010, he says, he secured funding to test and further develop the Ortho-Tag system, using the university's existing touch probe.

Since then, researchers have built a system with modified dual antennas in the touch probe, as well as in the RFID tags. These modified antennas allow the transmission of data through a body, either via UHF or high-frequency (HF) signals. The solution consists of a tag with several built-in sensors, and a touch probe wired to a handheld reader. The size of the commercially available tag has yet to be determined, but the prototype measures approximately 10 millimeters by 5 millimeters (0.4 inch to 0.2 inch). The engineering department is also developing software to interpret tag data as it is received by the touch probe. To read the tag's information, the touch probe would need to be in contact with the patient's skin nearest the point at which a tagged implant is located. This is a benefit for the patient's data security as well, Mickle says, since it would be impossible for someone to read the tag's ID number and sensor data using a standard reader, or to read the tag with a touch probe if it were not pressed against the skin.

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