A tool assembly includes a cartridge assembly, a shell, and an anvil assembly.The shell houses the cartridge assembly and defines a passage. The anvilassemblyincludes an anvil and a center rod extending from the anvil. The center roddefines alongitudinal rod axis and includes an alignment portion that is sized to passthroughthe passage. The alignment portion includes first and second splines that eachextendin a direction parallel to the rod axis. The first spline has a first leadingportion andthe second spline has a second leading portion. The first leading portion ispositionedalong the rod axis proximal of the second leading portion.
