ARCADIA, Calif. – Exercise rider Adrian Valenzuela underwent surgery to stabilize his spinal cord on Tuesday after suffering a devastating injury in a spill at Santa Anita on Saturday morning that left him partially paralyzed, according to his father, Martin Valenzuela. Martin Valenzuela said his son was scheduled to be taken out of intensive care at Huntington Memorial Hospital in Pasadena, Calif., on Wednesday but does not have a favorable long-term prognosis. “The operation went as good as it could go,” Martin Valenzuela said. “Right now, he has paralysis from mid-torso down. They said his chances of walking are pretty slim. “We’ll do what we can to get him the best treatment we can.” Adrian Valenzuela, 21, was injured when one of the bandages on the front legs of a horse he was working became unraveled, causing the horse to stumble and fall. Adrian Valenzuela has worked primarily as an exercise rider in recent years. He rode briefly at the Los Alamitos nighttime meeting in 2016, winning one race from eight mounts. Martin Valenzuela said his son will be transferred to a rehabilitation center in coming days. “He’ll start rehab fairly soon,” he said. “He’ll be in the rehab center for a month or two.”