I guess I'm just confused in that for a joint replacement, they sand down the socket and head off the bones and line them with titanium.

Something like that is going to pick up interference from the Earth's field like an antenna and rotate its broadcast vectors in all sorts of different directions everytime you even shift your sitting position. I mean, you turn over in your sleep and your arrangements are all discombobulated, and you won't even know about it until you wake up and assess the damage.

Aargh - what about hearing aids? Those don't run on solar power. Their little batteries are like a dynamo every time you move your jaw, no?