Development of a telemetry unit for bone strain monitoring

A telemetry unit designed to monitor strain in bones is presented. This unit allows studying the relationship between bone load and bone mass in small animals such as mice and rats. The unit measures 2.5 cm × 1.5 cm and consumes less than 20 mA of power while measurements are been transmitted. The telemetry unit was tested on an ex-vivo setting. The strain gage was attached to the ulna of a mouse and the readings were wirelessly transmitted to a remote computer at the rates of 76.7 kBaud. The low power consumption allows the unit to be powered by a small battery weighing less than 3 grams. Currently, strain gage data is collected by a bench top load instrument and a data acquisition unit. The current setup is accurate but is bulky and the subjects have to be sedated and immobilized to take accurate measurements. We present the readings from both setups and show that our telemetry unit is comparable in accuracy to the current setup and can easily replace it.