Knee replacement surgery is the most common joint replacement surgery in the world, with the number of people going under the knife to improve their knee health and function increasing each year.
For many, the surgery is actually to replace older implants or ones that have worn out over the years. While people who receive a new knee are told to exercise and remain physically active for the benefit of their overall health, this kind of activity can cause an implant to wear down.
Unfortunately, doctors often can’t tell if a patient is working their new knee too hard until they begin showing symptoms. By this stage, damage to the implant is irreversible and a patient is usually required to undergo another replacement. This is particularly a problem for younger people who have undergone knee replacements, particularly because their lifestyle could mean they require surgery every five to 10 years.
In response, researchers from the Binghamton University have created smarter knee implants that have the potential to monitor changes in activity as they happen.
“We are working on a knee implant that has built-in sensors that can monitor how much pressure is being put on the implant so doctors can have a clearer understanding of how much activity is negatively affecting the implant,” Sherry Towfighian, Assistant Professor at Binghamton University, said in a statement.
These sensors allow health professionals to identify when certain movements become too much for the implant and relay the information to the patients. This will allow them to adjust their behaviour to avoid further damage to the implant and help patients tailor physical activity around their individual circumstances.
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While researchers acknowledged the sensors fix one problem, they quickly realised that if batteries were used to power the sensors, a patient may still need to undergo surgery to replace them. As a result, the research team worked on an energy harvesting mechanism that powers the knee implant from motion, rather than battery power.
Using energy collected from friction known as triboelectric energy, researchers tested their prototype under a mechanical testing machine to assess its output under equivalent body loads. For example, when someone walks, the friction of the micro-surfaces coming into contact with each other will be used to power the load sensors.
Researchers found the sensors would need 4.6 microwatts to work and the average person’s walk produces 6 microwatts of power, meaning there would be more than enough to power them. In addition to helping existing patients, the data will also assist researchers develop future implants.
“The sensors will tell us more about the demands that are placed on implants, and with that knowledge, researchers can start to improve the implants even more,” Towfighian said.
It is hoped that the combination of smart sensors with a self-powered system will increase the life span of knee replacements and reduce the need to further surgeries down the track. Researchers have even said the new technology could be “life-changing”.