The newest device in this market is the MedEl Bonebridge. A receiver is surgically implanted in the mastoid cavity, and attached to bone. An external processor /transmitter is held on with a magnet, and sound signals are transmitted across the skin. Sound energy however is generated by the implanted receiver.
No percutaneous fixture, so no daily cleaning required
The signal, not sound energy, is transmitted across the skin, so there is no attenuation.
The magnet only holds the processor in place, and is not involved in transmission of energy, so less pressure is required.
Disadvantages include the need for surgery, and the need for a large enough mastoid cavity.
Children: For children with growing skulls, the devices with two point fixation to the skull are unsuitable, but the BAHA is a widely used device for treatment of children, for example in cases of congenital ear atresia.