The number and placement of the biosensors, treatment reservoirs and telemetry unit(s) is far from established. Additionally, the communication between the multiple biosensors and among the several types of units must be developed and fitted with an intelligent decision-making algorithm that can determine if a signal likely is a false alarm. Moreover, the operating system must be capable of deciding between a local release from a single reservoir and a global release from all reservoirs. Because of the size of the implants, it is thought that multiple biosensors should be used, providing as broad an area of coverage for the prosthesis as possible. It may not be possible, however, to place the sensors on the articulating surfaces and we don’t know if it will be efficacious or even possible to position biosensors on the parts of the implants which are seated directly in existing bone. One model has part of the prosthesis hollowed out for reservoirs, but mechanical engineering constraints may mandate the use of auxiliary reservoirs that would have to be placed with the implant. Two other major challenges that must be overcome are (1) designing a system that will be stable and functional for an extended period of time in situ at 37 °C; and (2) resetting the biosensor to baseline after exogenous signal is no longer present. It is understood that these and other major developmental hurdles will be have to be overcome at all levels and stages of this project.