Dr. Patrick Kerr wants to save football’s neck. The Manhattan chiropractor designed a protective collar to insert between a player’s shoulder pads and jersey to reduce the force of blows endured during games and practices. The device rises to support the neck and head as a player prepares to make a tackle. The aim is to control neck movement, which could prevent a common injury called a stinger, a nerve condition that can vary in severity. “The neck is completely overlooked in football,” he said.