A back problem may have been responsible for Ten Most Wanted's disappointing performance in the Kentucky Derby (gr. I), according to trainer Wally Dollase.An examination by veterinarian Foster Northrum revealed that the colt "threw his back out" during the race, Dollase said on Monday. Ten Most Wanted has been treated by a chiropractor and will miss at least several days of training."It (the colt's back) was about a half an inch out of alignment," Dollase said. "We think he might have done it coming out of the gate."Sent off the third betting choice in the Derby, Ten Most Wanted finished ninth after being bumped by Scrimshaw at the start.