Surgical snare
Embodiments of the invention provide a surgical snare structure in which the material used for the snare and the deployment mechanism of the snare are configured to improve the cutting efficacy of the snare. In particular, the surgical snare structure of the invention may omit the kink or nib present in the loop of known surgical snares and/or may provide a reaction surface against which the cutting action of the snare is effective. The surgical snare of the invention may be a cold, i.e. mechanical-only effect, snare, or may be used in conjunction with radiofrequency (RF) and/or microwave energy to enhance a cutting or coagulation effect.
1. A surgical snare comprising: a flexible actuator shaft comprising an outer sleeve and an inner push rod mounted within and slidable relative to the outer sleeve; an end cap mounted at a distal end of the outer sleeve; a nibless loop of wire connected to a distal end of the inner push rod, and configured to capture biological tissue, wherein the end cap includes a passageway for receiving the nibless loop of wire, whereby the inner push rod is operable to retract the nibless loop of wire into the end cap, and wherein the end cap includes a reaction surface at its distal end against which the nibless loop of wire is configured to cut biological tissue captured within the nibless bop of wire when fully retracted into the end cap such that the nibless loop of wire bears against the reaction surface resulting in the nibless loop of wire and the reaction surface cutting the biological tissue.
2. A surgical snare according to claim 1 , wherein the reaction surface is a flat or concave distal face of the end cap.
3. A surgical snare according to claim 1 , wherein the reaction surface includes a groove for receiving the nibless loop of wire when fully retracted into the end cap.
4. A surgical snare according to claim 1 , comprising a catheter, wherein the flexible actuator shaft is slidably mounted in the catheter to deploy the end cap at a distal end thereof.
5. A surgical snare according to claim 4 , wherein the catheter has a tip section that narrows towards a distal end of the catheter.
6. A surgical snare according to claim 4 , wherein there is a fluid flow path around the catheter to permit a suction force to be applied beyond the distal end of the catheter.
7. A surgical snare according to claim 1 , wherein the outer sleeve forms a catheter that is slidably receivable in an instrument channel of a surgical scoping device.
8. A surgical snare according to claim 1 , wherein the nibless loop of wire comprises a fixed circumference loop formed from a length of wire whose two ends are attached together.
9. A surgical snare according to claim 8 , wherein the nibless loop of wire is connected to the inner push rod at a junction between the two ends of the length of wire.
10. A surgical snare according to claim 8 , wherein the length of wire is a shape memory alloy trained to preferentially adopt a round shape.
11. A surgical snare according to claim 10 , wherein the round shape is a circle having a diameter of 10 mm or less.
12. A surgical snare according to claim 8 , wherein the length of wire is made from nitinol.
13. A surgical snare according to claim 8 , wherein the inner surface of the fixed circumference loop is roughened to facilitate cutting.
14. A surgical snare according to claim 1 , wherein the end cap and nibless loop of wire are detachably mounted on the flexible actuator shaft.