A lifter assembly includes first and second lifter segments movably attached to one another and defining a lifting channel having an expandable bladder contained therein. Each lifter segment has an arm extending away from a base of the lifter segment and a travel stop at a distal end of the arm. Each lifter segment further has a keyway opening. The keyway opening of the first lifter segment receives the arm of the second lifter segment and the keyway opening of the second lifter segment receives the arm the first lifter segment.