Ribbed Cannula Structure
Methods and apparatus for direct visual rhizotomy using an elongated tubular sheath. The sheath includes: a proximal end configured to removably receive a cannula; a distal end; a horizontal shaft having a longitudinal axis extending between the proximal end and the distal end; a first cut-away generally defining a first plane at the distal end, the first cut-away characterized by a first angle relative to a vertical plane; and a second cut-away generally defining a second plane at the distal end, the second cut-away characterized by a second angle relative to a horizontal plane. The sheath further includes an endoscope camera disposed at the distal end, the camera having a line of sight substantially orthogonal to the first plane.
1 . A cannula for use in an endoscopic surgical apparatus of the type including a tubular sheath having an inner wall through which the cannula is slidably inserted, the cannula comprising:
a first channel configured to receive an endoscope shaft;
a second channel configured to receive an elongated cutter;
a third channel configured for fluid ingress to the surgical site without the use of a separate lumen within the third channel;
a fourth channel configured for fluid egress from the surgical site without the use of a separate lumen within the fourth channel; and
a longitudinal fluid seal disposed between the third and fourth channels, the fluid seal comprising an arcuate segment of the cannula adjacent the inner wall and configured to hydraulically isolate the third channel from the fourth channel;
wherein a portion of each of the first, second, third, and fourth channels is bounded by both: i) a portion of the cannula; and ii) a portion of the inner wall; and
wherein the third channel is configured such that ingress fluid contacts the inner wall, and the fourth channel is configured such that egress fluid contacts the inner wall.
2 . The cannula of claim 1 , wherein the cross sectional area of the fourth channel is greater than the cross sectional area of the third channel.
3 . The cannula of claim 1 , wherein the second channel is configured to receive an electrode-type cutter.
4 . The cannula of claim 1 , wherein at least one of the fluid ingress channel and the fluid egress channel is configured to be bounded by an internal arc segment of the sheath.
5 . The cannula of claim 1 , wherein at least one of the fluid ingress and fluid egress channels comprise a non-circular cross section.
6 . The cannula of claim 1 , wherein the first and second channels partially intersect.
7 . (canceled)
8 . (canceled)
9 . A surgical apparatus including a cannula configured to be slidably inserted into a surrounding sheath having an internal perimeter wall, the cannula comprising a first lobe, a second lobe, a third lobe, a fourth lobe, a fluid ingress channel, and a fluid egress channel;
wherein:
the fluid egress channel is configured for connection to an external fluid source without the use of a separate lumen and bounded by the first lobe, the second lobe, and a first portion of the internal perimeter wall such that egress fluid contacts the first lobe, the second lobe, and the first portion of the internal perimeter wall;
the internal perimeter wall further includes a first arc segment and a second arc segment;
the first lobe includes a first distal convex segment and the second lobe includes a second distal convex segment;
the first arc segment is configured to form a first fluid seal with the first distal convex segment;
the second arc segment is configured to form a second fluid seal with the second distal convex segment; and
the fluid ingress channel is connected to an external fluid drain without the use of a separate lumen and bounded by the third lobe, the fourth lobe, and a second portion of the internal perimeter wall.
10 . The apparatus of claim 9 , wherein at least one of the fluid ingress and fluid egress channels has a non-circular cross-section.
11 . The apparatus of claim 9 , wherein the fluid egress cross sectional area is greater than the fluid ingress cross sectional area.
12 . The apparatus of claim 9 , wherein:
the internal perimeter wall further includes a third arc segment and a fourth arc segment;
the third lobe includes a third distal convex segment and the fourth lobe includes a fourth distal convex segment;
the third arc segment is configured to form a fluid seal with the third distal convex segment; and
the fourth arc segment is configured to form a fluid seal with the fourth distal convex segment.
13 . The apparatus of claim 9 , wherein the sheath internal perimeter wall comprises a circular cross section.
14 . The apparatus of claim 9 , further comprising an electrode channel at least partially bounded by the first and third lobes, and an endoscope channel at least partially bounded by the second and fourth lobes.
15 . (canceled)
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20 . (canceled)