Back in the 1970’s Swedish researchers at Sahlgrenska University Hospital and Chalmers University of Technology in Gothenburg developed the original bone anchored hearing aids (BAHA) that thousands of people with hearing loss use today. 
Designed for those with a healthy cochlea in the inner ear but with one of various conditions that prevent sound from reaching it, a bone anchored implant uses a small titanium screw implanted behind the ear to resonate bone and send sound waves to the cochlea.
The people behind the original BAHA decided that thanks to newly available technology, a novel approach involving a fully implanted component may overcome the downsides, such as infection and loose screws, of bone anchored devices. The new Bone Conduction Implant (BCI) is placed directly within the bone behind the ear, and using inductance receives signals from an external component that has a microphone. A tiny speaker on the implant placed close to the cochlea regenerates the sound heard by the microphone allowing the user to hear. The first patient to be implanted with the new device was outfitted last month in Sahlgrenska University Hospital and further clinical testing is in the works.
Press release: New implant replaces impaired middle ear
Flashbacks: Middle Ear Microphone Opens Possibilities For a Smaller, More Discreet Hearing Aid; Esteem Totally Implantable Hearing Device Under Consideration for Approval in US