Realising this clinical vision requires solutions to a host of engineering challenges. In the case of a strain-sensing intramedullary nail, TTP provided integrated engineering solutions for implant electronics, reliable through-tissue communication, and life-time implantation following bone healing – with the mechanical strength equivalent to the existing intramedullary nail.
We considered both analogue and digital implant electronics, and the digital design was selected for superior suitability for a medical product. We further developed a robust, error-checking communications protocol to ensure that accurate strain data was read-out from the nail, reflecting fracture healing.
Most importantly, smart implants need to be suitable for lifetime implantation. To eliminate batteries, and the associated risk of leaks, we developed a novel reader device that, when held to the patient, inductively powered the implant and simultaneously acted as the antenna for communications.
Completing the smart implant, the whole payload consisting of strain sensor, electronics and coils for radio signal generation was hermetically sealed in biocompatible titanium and embedded within the implant without creating structural weaknesses in the nail – ready for in vivo studies.