My taxidermist is an avid outdoorsman and bow hunter, raising 3 boys to follow in his footsteps, not to mention he gets to see several hundred racks a year. He's the one that clued me in on body injuries also resulting in abnormal rack growth, the year after the injury. Was the first I'd ever heard of it, I had always suspected genetics, and injury to the antler in velvet or injury to the pedicle as cause.