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RFID tags for orthopaedic instruments

2019-10-08 14:20:08

The research team of the University of Pittsburgh has completed the development and testing of special orthopaedic labels and RFID system, which reads passive labels through radio frequency signals and has passed patent registration.


Researchers at the University of Pittsburgh in the United States have developed an orthopaedic labeling system, which attaches RFID tags with embedded sensors to orthopaedic instruments, so as to enable implanted human labels to track the use of devices in the body. Signals emitted by labels in the human body are transmitted through skin tissues to readers outside the skin. The system can not only track the implantation environment of human body, but also have certain anti-counterfeiting property for orthopaedic instruments themselves.


The solution was tested in university laboratories by Professor Marlin Mickle of the School of Engineering, who is also chairman of the Scientific and Technological Advisory Board of Orthopaedic Labeling Company. The company mainly supplies specific labels for orthopaedic equipment manufacturers, as well as hand-held label readers (which are specially developed for such labels to collect data for doctors).


This special label was invented by orthopaedic surgeon Lee Berger and patented in early 2008. It has been effective in helping patients and doctors track the healing status of implants. Berger envisages developing a system that uses sensors to measure the physical pressure of implanted devices, as well as the chemical balance and temperature around them, to determine whether they cause infection, and then to decide whether to replace the original device. Doctors use hand-held readers to receive unique ID numbers and sensing data sent by RFID chips. Berger first built a prototype with passive ultra-high frequency (UHF) EPC Gen 2 RFID tag, which needs further testing and improvement before it can be extended to the market.


Started working with Berger in 2008. The University of Pittsburgh School of Engineering has developed a contact probe that can be used to read tags attached to metals and to test radio waves propagating through the human body. In May 2010, he identified funding available to further improve the orthopaedic labeling system using existing contact probe testing in universities.


Thereafter, researchers constructed a contact probe system based on a flexible dual RFID tag antenna. These improved antennas can transmit data across the human body, which can be carried by ultra-high frequency (UHF) or high frequency (HF) signals. The solution consists of a label with multiple sensors and a touch probe connected to a handheld reader. The size of the label on sale remains to be determined, but it is about 5 mm * 10 mm (0.2 inches to 0.4 inches) used in the test. Engineering departments are also developing software to analyze tag data received through touch probes. In order to read the label information accurately, the contact probe should be inserted nearest to the label. This is also to ensure the security of data, in order to prevent others from obtaining the ID number of the label and sensor data.


Orthopaedic labeling will provide patients and doctors with the following benefits: First, it will help track infection. Sensors measure the pH of the tissue in which the label is located, and then pass these sensor readings to reading devices, such as labels implanted in the knee. Sensors are powered by on-board supercapacitors, which are similar to rechargeable batteries, charged by a piezoelectric transducer built in the label, or powered by radio frequency signals emitted by contact probes. In addition, the sensor can be directly powered by the radio frequency signal emitted by the contact probe. Contact probes display captured ID and sensor data (elevated pH may indicate, for example, infection) on the screen of a handheld device, or transmit detailed information to the background system via a Wi-Fi connection or a USB port. In this way, doctors can do a good job of prevention before the symptoms of infection appear.


In addition, the sensor can also be used to obtain the motion frequency of the implanted joint, which provides a basis for better use of the joint. If the results of label transfer indicate that joints are rarely used, doctors can solve this problem by arranging suitable physiotherapists for patients and further examining diseases that hinder joint movement.


Labels also have other functions, such as determining whether implanted joints should be recalled. Because the implanted product is difficult to maintain for a long time, it needs to be replaced regularly. With this system, users can capture the ID of the label, which is linked to the back-end database, so that they can find the manufacturer of the implanted device, production date and shelf life. Through this information, we can determine whether the joints implanted into human body are real or not, and prevent counterfeit products more effectively.


Researchers at the University tested the system, including the following steps: first, using high-frequency structure simulator software that can simulate electromagnetic field to test; and then, reading labels through salt solution (simulated human tissue environment). Thirdly, using pigskin to simulate human body. Mickle said that the next step might be to use human cadavers for experiments, but that has not been approved by the test leader.


The team is looking for silicon chips that can withstand gamma radiation. Because the label is sterilized by gamma ray before implantation. Mickle said that researchers are testing Tego chips, which may have larger memory (currently tested mainly in the range of 8 to 64 kilobits), can store more data and have stronger radiation resistance.


Mickle did not specify when the product would be commercialized. Because it is not easy to put products into the market in batches, there are several stages to go through, for example, the cooperation of equipment manufacturers, and the approval of FDA in the United States. A system has been developed for embedding passive high frequency (13.56 MHz) labels or EPC Gen 2 ultra-high frequency (UHF) labels that meet the ISO 18000-3 standard into credit cards to store implant information and serial numbers of manufacturers, production dates and products. Patients can put their cards in their wallets, Mickle said, noting that the system will be on the market within a year.

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