Nonunion

After a traumatic radius ulna break is it custom to leave the little bone to heal by itself with no support.  Bone was initally plated, but screws broke 8 months later after his first run.  Xray shows there has been no attempt at healing on the bone in 9 months.  The plan now is to take the plate off and leave it.  Is that normal?

That sounds extremely frustrating - poor you and your dog!  Fractures certainly do recurr or fail to heal at times.  I read a stat of just under 5% for failure of fractures to close as expected in dogs.  Sometimes a plate proves too rigid to withstand the forces on the bone; sometimes infection may be present;  sometimes the age of the dog / biological activity of the bone / blood supply to the area / loading on the fracture / nutritional factors as so on compromise healing; sometimes the leg is subjected to a sudden, unexpected force of a nature that the implant cannot withstand.  If a plate or frame has failed to fix a fracture once, a surgeon would have to have a good reason why the same technique would work differently a second time, in a potentially weaker bone.  Resorting to a different, less perfect / less precise method of healing may be understandable.  As I'm sure you'll be aware, I know insufficient to pass judgement on this particular case; I am unaware how  comfortable / stable this bone is as present, for example.  Furthermore, it is beyond the scope of the service to give second opinions.  Obviously some vets' knowledge and experience of orthopaedics greatly surpasses others and even the most experienced do come across fractures that fail to heal as they expected.  If they would like a second opinion on the subject, your vet may ask to acquire one - and certainly as a vet, if a client has asked me for a second opinion on something, I have always been happy to send them to a more experienced expert in the hope that either I may be proved to be correct, or that I might learn something.   I hope that something here is useful.