A method closely related to the one referred to above is described in the international application WO-A-97/16122. In this previous method, the various relatively movable assemblies, viz. the anvil assembly, the clamping assembly and the stapling assembly, extended circumferentially all the way around the internal space in the instrument accommodating the first vessel or graft vessel, for which reason it was necessary when removing the instrument from the anastomosis having been established to move it along the graft vessel to the latter's free end or to pull the graft vessel out of the instrument.
This means, of course, that the instrument of said application WO-A-97/16122 can only be used with totally free graft vessels leaving one free end after anastomosis, making it possible to use the instrument for establishing anastomoses at both ends of an originally free graft vessel--or at the only free end of a closely situated anatomical artery (typically, but not exclusively the Internal Mammarian Artery--the socalled IMA vessel), such as may be required in coronary surgery.
U.S. Pat. No. 3,519,187 and U.S. Pat. No. 4,076,162 disclose methods comprising the use of instruments for connecting an end region of a first vessel to the side of a second vessel by carrying out an end-to-side anastomosis, in which the anvil assemblies can be split lengthwise. This is not, however, sufficient to overcome the limitation explained above, as other active assemblies necessitate having a free end on the graft vessel to enable them to be removed.