EMPA: Monitoring broken bones without wires

Development opportunity

Researchers from EMPA – the Swiss Federal Laboratories for Materials Testing and Research, part of the ETH system – have developed an electronics-free implant that could potentially be used by doctors to monitor broken bones as they heal. They are seeking an industrial partner to manufacture the sensors and integrate them into the implants.

Currently, doctors use expensive and complex electronic devices to measure the progress of broken bones as they heal. The new implant, developed by Felix Gattiker and colleagues at EMPA and the ETH-Zürich, contains a mechanical sensor that monitors the tensile and compressive forces it is subjected to. These data can be read with an ultrasound device and analysed by computer.

Information from such a device can help doctors decide if the healing process is normal, or if the fracture is overloaded. As this sensor is electronics-free, its manufacturing costs are lower than the electronic devices currently in use.

The sensor consists of a fluid reservoir and a small, hollow spiral that sits on the implant. When the implant is subject to compression or tension, the level of fluid in the spiral changes. This change is measured with an ultrasonic device, and the resulting data can be used to calculate the mechanical load on the implant. The ultrasonic image is too indistinct to allow the fluid level to be determined visually, but the EMPA researchers found that the weaker the ultrasonic echo measured, the higher the fill level, and therefore the greater the force acting on the sensor.

The researchers will now test the accuracy of the device using various animal tissues. They are also investigating the idea of making the sensor from biodegradable materials, so that it would not need removal from the body once the bones had healed.