Whether someone is recovering from a tendon injury, or they have an abnormality that makes walking difficult, it can be useful for their doctor to know how much tension their tendons experience when placed under load. A new non-invasive device is designed to provide that information.

Developed by a University of Wisconsin-Madison team led by Prof. Darryl Thelen and grad student Jack Martin, the inexpensive computer-connected device is adhered to the patient's skin over one of their tendons. It's so far been tested on the Achilles, hamstring and patellar (knee) tendons, with good results. It's then left in place as they perform activities such as walking or running, within a clinical setting.

As they do so, a mechanism within the device lightly taps on the tendon (through the skin) 50 times a second. This causes vibrational waves to travel through the tendon, sort of like a plucked guitar string. Two accelerometers in the device measure how long each wave takes to travel between them – the faster the wave travels, the tighter the tendon.

In this way, tensile stress values can be established for different activities, regarding the tendon in question. It's also possible to see how modifying the gait affects those values.

"We think the potential of this new technology is high, both from a basic science standpoint and for clinical applications," says Thelen. "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 research was recently published in the journal Nature Communications.

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