New smart knee implants could monitor changes in activity as they happen

The smart knee implants could soon become a reality thanks to research conducted by a team including professors from Binghamton University of the State University of New York.

Knee replacement surgery is the most common joint replacement procedure, the number of surgeries increasing each year. Many of these surgeries are performed to replace an older or worn implant. More and more, this operation is practiced in younger patients, more active and confronted with a dilemma. When they undergo the operation, they are expected to remain physically active for their overall health, but this activity may also carry the new implant. Often, doctors do not know if patients are overworking until they begin to develop symptoms. At this point, the damage to the implant has already been caused. For a young patient, undergo knee replacement surgery every five or ten years is a daunting task, but find the perfect balance between levels of activity to maintain the integrity of the knee. implant has also been.

The researchers decided that it was time to create smarter knee implants, able to monitor the changes in activity as they occurred. Assistant Professor Sherry Towfighian of the University of Binghamton was the principal investigator of the study, funded by the National Institutes of Health (NIH).

"We are working on a knee implant with built-in sensors that can control the pressure on the implant so that doctors can more clearly understand how the activity negatively affects the implant," he said. Towfighian.

The sensors allow doctors to tell patients when a certain movement has become too important for the implant so that patients can adapt quickly and avoid further damage to the implant. This helps them find the ideal activity point for each patient.

Although the sensors solved one problem, they brought another. The researchers did not want to power the sensors with a battery that might have to be replaced periodically and thus compromise the purpose of a smart implant. Instead, they worked on an energy recovery mechanism able to power the knee implant from motion. Wathiq Ibrahim, a Towfighian group postdoc, developed a prototype energy harvesting machine and tested it with a mechanical test machine to test its performance under equivalent loads.

They used triboelectric energy, a type of energy collected by friction. Once somebody walks, the friction of micro-surfaces coming into contact with each other can be used to power load sensors.

Associate Professor Emre Salman of Stony Brook University designed the circuit and determined that he would need 4.6 microwatts. Preliminary tests showed that the average step would produce six microwatts of power, more than enough to power the sensors. This part of the research was completed by Assistant Professor Ryan Willing of the University of Western Ontario, who worked on the design of the implant and on the sensor package.

These smart implants will not only give feedback to physicians, but will also help researchers to develop future implants. "The sensors will tell us more about the requirements for implants, and with that knowledge, researchers can begin to improve them even more," said Towfighian.

Towfighian hopes that the combination of activity sensors and a self-powered system will increase the life of knee implants and reduce the need for follow-up surgeries. For young patients who are considering the possibility of knee replacement surgery, this evolution could change their lives.