Cryogenic surgical instrument and method of manufacturing the same

A method of manufacturing a cryogenic probe having a distal closed tip probe shaft portion and proximal connection means to a supply of cryogenic fluid, the method comprising:

• a) providing a first sub-assembly comprising a cryogenic fluid return tube and a connector tube in linear arrangement and vacuum brazing said first sub-assembly whereby the proximal end of said connector tube is joined to the distal end of said cryogenic fluid return tube,
• b) telescopically positioning an elongated tubular tip having a closed distal end and an open proximal end with apertures adjacent said proximal end over said first sub-assembly whereby said connector tube is fully contained within said tubular tip and the proximal end of said cryogenic fluid return tube extends from the proximal end of said tubular tip and vacuum brazing said tubular tip to said first sub-assembly whereby a second sub-assembly is formed,
• c) aligning a cryogenic fluid return assembly comprising (1) a substantially cup shaped cryogen chamber having an open proximal end and an apertured base and (2) an extension tube extending axially from the aperture in said base and connectable to the proximal end of said cryogenic fluid return tube of said first sub-assembly with the longitudinal axis of said second sub-assembly and vacuum brazing said cryogen chamber to said extension tube and said extension tube to said cryogenic fluid return tube whereby a third sub-assembly is formed,
• d) forming a fourth sub-assembly comprising (1) an end cap adapted to engage and seal the open end of said substantially cup shaped cryogen chamber, said end cap having an inner and an outer surface, a central supply aperture extending from said inner surface to said outer surface and a radially offset return aperture extending from said inner surface to said outer surface, and (2) a cryogenic fluid supply tube extending perpendicularly from said central supply aperture on said inner surface of said cap by vacuum brazing said cap and said supply tube together, and
• e) conducting final assembly of said cryogenic probe by (i) inserting said third sub-assembly into a tubular handle body having a thermally activatable valve in a wall thereof whereby the distal end of said third sub-assembly extends through and beyond the distal end of said handle body with said apertures adjacent to the proximal end of said elongated tip being located within said handle body whereby the area within said handle body communicates with the area within said probe portion and whereby the proximal end of said handle body engages the base of said cryogen chamber, (ii) inserting said fourth sub-assembly into said third sub-assembly whereby said cryogenic fluid supply tube extends telescopically into said cryogenic fluid return tube and said end cap engages and closes the proximal end of said cryogen chamber, and vacuum brazing said cryogenic probe to join said third and fourth sub-assemblies to said handle body;
• whereby during vacuum brazing in step e) the handle body and the probe portion are evacuated via said thermally activatable valve, and said valve is thermally activated and sealed whereby a vacuum drawn in said handle body and said probe portion is maintained upon and following completion of brazing.

A method of manufacturing a cryogenic probe having an elongated probe shaft portion extending longitudinally from an elongated handle portion and having concentric cryogenic fluid supply and return conduits passing through said handle portion into said probe shaft portion, whereby said supply conduit is within and terminates distally of said return conduit and said handle portion and said probe shaft portion are simultaneously evacuated and sealed, the method comprising:

• a) providing said probe shaft portion comprising a first sub-assembly comprising an elongated tubular probe shaft having a closed distal end and an open proximal end and an elongated cryogenic fluid return tube extending telescopically within said probe tip and vacuum brazing said first sub-assembly,
• b) providing a second sub-assembly comprising said first sub-assembly and a return tube extension connected to the proximal end of said return tube in axial alignment with said first sub-assembly and vacuum brazing said return tube extension to said return tube,
• c) providing a third sub-assembly comprising a cryogenic fluid supply tube, a supply tube extension connected to the proximal end of said supply tube in axial alignment therewith and an end cap connected to the proximal end of said supply tube extension and vacuum brazing said third sub-assembly,
• d) providing an elongated tubular handle body and assembling said handle body and said sub-assemblies into a final assembly by inserting said second sub-assembly into said handle body whereby said probe portion extends from a distal end of said handle body and said return tube extension is confined within said handle body, inserting said third sub-assembly into said second sub-assembly whereby said cryogenic fluid supply tube extends telescopically into said return tube, said supply tube extension is confined within said return tube extension and said end cap closes the proximal end of said return tube extension and the proximal end of said handle body, and vacuum brazing said final assembly whereby said handle body and said probe portion are evacuated and the distal end of said handle body is fused to said probe shaft portion and said end cap is fused to said proximal ends of said return tube extension and said housing body thereby sealing said probe to maintain a vacuum therein.

A cryogenic surgical probe comprising a probe shaft portion and a handle portion, said probe portion comprising, in concentric arrangement, an inner elongated cryogenic fluid supply tube, an intermediate elongated cryogenic fluid return tube and an outer elongated probe shaft wherein said probe shaft has a closed distal end and an open proximal end, said cryogenic fluid return tube terminates proximally of the closed distal end of the probe shaft and said cryogenic fluid supply tube terminates intermediate the distal ends of said return tube and said probe shaft, said handle portion having a diameter greater than said probe portion and comprising, in concentric arrangement, an inner supply tube extension, an intermediate return tube extension and an outer handle body;

• wherein said handle portion is in longitudinal alignment with said probe shaft portion, said supply tube extension connects to the proximal end of said cryogenic fluid supply tube, said return tube extension connects to the proximal end of said cryogenic fluid return tube and said handle body connects to the proximal end of said probe shaft and wherein the proximal end of said handle portion is closed by an end plate having first and second cryogenic fluid connection tubes extending therethrough whereby said probe is connectable to a source of cryogenic fluid, said first connection tube connecting to said supply tube extension and said second connection tube connecting to said return tube extension, and wherein all of said connections are fused by vacuum brazing.