A new wearable device could one day help to show when patients recovering from a tendon injury are ready for action.
Developed by University of Wisconsin-Madison engineers, the non-invasive device measures tendon tension while a person is engaging in activities like walking or running.
According to the developers, the device could apply to a wide range of fields including orthopaedics, rehabilitation, ergonomics and sports. It could also provide new insights into the motor control and mechanics of human movement.
“Currently, wearables can measure our movement, but do not provide information on the muscle forces that generate the movement,” said UW-Madison mechanical engineering professor Darryl Thelen.
To overcome this challenge, Thelen and his team developed a simple device that can be easily mounted on the skin over a tendon. The device enables the researchers to assess tendon force by looking at how the vibrational characteristics of the tendon change when it undergoes loading, as it does during movement.
“We’ve found a way to measure the vibrational characteristics — in this case, the speed of a shear wave traveling along a tendon — and then we went further and determined how we can interpret this measurement to find the tensile stress within the tendon,” Thelen explained.
The new system is portable and relatively inexpensive, according to UW-Madison. It includes a mechanical device that lightly taps the tendon 50 times per second. Each tap initiates a wave in the tendon, and two miniature accelerometers determine how quickly it travels.
The researchers have used the device to measure forces on the Achilles tendon, as well as the patellar and hamstring tendons. They believe that, by measuring how muscles and tendons behave within the human body, the new system could eventually enable clinicians to plan more effective treatments for patients suffering from musculoskeletal diseases and injuries.
“We think the potential of this new technology is high, both from a basic science standpoint and for clinical applications,” Thelen said. “For example, tendon force measures could be used to guide treatments of individuals with gait disorders. It may also be useful to objectively assess when a repaired tendon is sufficiently healed to function normally and allow a person to return to activity.”
A paper on the new technology has been published in the journal Nature Communications.