An instrumented intramedullary implant to monitor strain in fracture healing

Tibia fractures are often treated by implanting an intramedullary nail, a thick-walled titanium metal tube that stabilizes the fracture during healing. We investigated instrumentation of an intramedullary nail with a wireless SAW strain sensor to follow the progress of bone healing by measuring strain. An insert was designed and instrumented with a LiNbO3 surface acoustic wave device. Testing of a prototype inser has been performed ex situ. Wireless measurements were used to observe changing strain on the insert as mounted into the nail. Monitoring fracture healing may facilitate early intervention when proper bone healing does not take place. The practicality of the design is assessed in view of the constraints imposed by the implantation procedure.