Id imagine thered be alot of variables that would contribute to this.
Time of year, track surface, track circumference, the dog itself, bad luck, sometimes training aswell etc.
Example would be auckland. March-may every year, this track is a killer.
Its worth noting the large majority of injuries are never picked up by the vet post racing so real data would be alot harder to make any real conclusions on, especially muscle injuries which may only start appearring after 6 or so hours