A surgical fixation apparatus, comprising: a handle assembly (12) adapted to actuate said surgical fixation apparatus； a central body portion (14) extending from the handle assembly； and a distal head portion (16) including an envelope assembly (27) and an anvil assembly (30), including the anvil assembly: an anvil head assembly (40) including an anvil head (42) defining an inner recess (42a) supporting an activation plate (48) having at least one lug (48e), a deformable member (46) located distally of the activation plate, and a fixing ring (50) located proximally to the activation plate and adapted to fix the activation plate； and a central anvil shank assembly (60) comprising a central anvil shank (62) defining a longitudinal axis (A) and being rotatably connected to the anvil head assembly about an axis of rotation (B) and including a plunger (64) and a piston spring (66) in mechanical communication with the anvil head (42), the piston being configured to come into contact with the anvil head assembly after an operation of the surgical fixation apparatus, defining the anvil central stem assembly a relief configured to inhibit the anvil head (42) against rotation around the axis (B), the relief being configured to be applied to the lug (48e) of the activation plate； wherein, after actuation of the surgical fixation apparatus, the deformable member (46) is configured to deform so that the activation plate (48) is advanced distally within the inner recess (42a) and de-applies the lug of the Anvil stem central relief relief plate (62) so that the anvil head (42) is free to rotate around the axis of rotation (B) under the piston preload (64) and the piston spring (66) , characterized in that the anvil head assembly includes a post (44) that extends proximally from the anvil head (42), the post including a tooth (44f) to be applied to the central anvil stem assembly, further comprising a sleeve (68) slidably disposed along an outer surface of the anvil rod (62), the s
