An anvil assembly comprising: an anvil center rod assembly defining a longitudinal axis；a head assembly pivotally secured to the anvil center rod assembly and movable from a first tilted position, through an operative position to a second tilted position； and a sleeve member disposed about the anvil center rod assembly, the sleeve member being movable from a distal position to a proximal position as the head assembly moves from the first tilted position, through the operative position to the second tilted position.
