We have smartphones, smart watches, smart TVs… Now, the next innovation that could transform people’s lives is the smart knee implant.
A team of researchers at Binghamton University, State University of New York carried out a study, supported by the National Institutes of Health, which examined what could be done to address an increasingly common dilemma in knee implant surgery.
The problem for active patients
Knee replacement surgery is one of the most common of all joint replacement operations. Many of the surgical procedures are carried out to replace an older implant that has started to wear out. The problem is that knee replacement surgery is increasingly being performed on younger, more active patients who are keen to continue with their physically active lifestyles.
In terms of physical health and mental wellbeing, this is a positive benefit however too much physical activity can place the new implant under strain and cause it to wear more quickly than would normally be expected. Often, doctors don’t know if patients are overexerting themselves and damaging the implant until they start to develop symptoms and by then it is too late to do anything about it.
This means patients either face the prospect of undergoing revision knee replacement surgery usually after about 10 years, or they have to try and guess at the right level of physical activity to maintain their fitness levels without damaging the implant. It is a tricky balance.
Smart implant technology
Researchers set out to explore whether it was possible to create a smart knee implant that could monitor any negative impacts of exercise and flag up potential problems before they arose. They began developing an implant with built-in sensors that could monitor the amount of pressure the implant was being subjected to. They succeeded in creating a sensor that would alert patients when certain movements were too much for the implant so they could adjust what they were doing to potentially prevent any excessive implant damage.
However, the next problem was how to power the sensors. Batteries would be impractical as they would need to be replaced, so the researchers began exploring the possibility of using the knee’s own natural movement to harvest energy.
They developed a prototype mechanism that could harvest triboelectric energy, which is a form of energy that is collected from friction. The motion of walking brings micro-surfaces into contact with each other, which creates energy that is used to power load sensors. The research team estimated that 4.6 microwatts of power would be needed to power the sensors. Preliminary testing showed that the average person’s walk produces six microwatts of power so it was more than adequate.
Increasingly sophisticated joint replacement surgery
Smart knee implants are not yet a reality but it is hoped that they will be available in the future, once they have been adequately tested and refined, and orthopaedic surgeons may be able to offer them to younger, more active patients who require surgery.
In the meantime, implant surgery is becoming increasingly sophisticated, which is helping to improve the outcomes for a whole range of patients.
Here at Carrothers Orthopaedics, we use the latest Mako robotic-arm assisted technology to help us provide the most accurate and effective knee replacement surgery. Laboratory studies have shown that surgeons who use this technology can execute their surgical plans more accurately. Their patients report lower levels of pain and there is less chance of damage to soft tissues and ligaments. Six months after surgery, patient satisfaction levels seem to be higher than for people who undergo conventional knee replacement surgery.
For more information about Mako-assisted knee replacement, watch this short video featuring consultant orthopaedic surgeon, Andrew Carrothers. 
