Arbitrary axis to rotate a mesh

Collaborations

Hi, I have a pair of bones, a radius and an ulna, to be rotates one over the other but the rotation axis should go across a specific point of one aspect of the radius and the other in another specific point on the surface of the ulna.  Now I move the model to align it to one of the axis... Is there a way to tell the mesh to rotate over an axis that can be drawn without moving the objet?

...or setting an empty parent, choosing the axis of the empty...  like creating a line between two points through one of the axis of that empty