Is it a stress fracture or did he hit it? I saw some posts about a problem at the gate.
Not sure if it was related to the incident at the gate, where he broke out early in a false start. A broken back leg isn't really what I'd assume from busting out of the gate.
He slowed and looked fine, they led him back around and reloaded him in the gate, and he broke down in the first part of the race. The fracture to the cannon bone happened first, stress fracture I guess, and the pastern, below the fetlock came apart as the jockey tried to get him stopped he was running on it.