Farriers and Equine Vets please help....

This is what the vet said was wrong with Sonny:

FIRST EMAIL
"Just wanted to let you know that I sent off Sunny's x-rays this weekend
(sorry, busy week at my other job). I should have an answer by the end of the week to see if there is anything we can do with shoeing for your
horse. I will pass along that info and the pictures of the x-rays then. I
did do a bit of reading and they call this an extensor process fracture of
the coffin bone. As you had mentioned, it can be due to an injury- either
from hyperextension of the coffin joint or excessive tension on the
extensor tendon- or it can be growth related if the bone doesn't form
properly in that area. Unfortunately there is some arthritis at the
coffin joint and that is likely the cause of the pain. I am not sure why
he would show toe pain- unless pressure there moves the coffin bone enough to stress the arthritic area. I will let you know what the experts say about it."

SECOND EMAIL
"I received a reply on your horse's x-rays. They confirmed the diagnosis. They also mentioned that injecting the coffin joint with depo (a kind of cortisone) could make that foot feel better. Let me know."

She also said he shouldn't have any pain except for the arthritis, and it will not get worse.

Long story short....The vet was not much help other than diagnosing Sonny. Does anyone know anything about his extensor process fracture of
the coffin bone problem? Any information, opinions, or recommendations would be appreciated. He gets quite sore at times, though he is known to bluff! We would like to get to the bottom of this, but the vets here aren't familiar with the problem and hundreds and thousands of dollars aren't an option. We've spent lots already on this problem.