Expandable cannula

Abstract

Cannulas for surgical and medical use expand along their lengths. The cannulas are inserted through tissue when in an unexpanded condition and with a small diameter. The cannulas are then expanded radially outwardly to give a full-size instrument passage. Expansion of the cannulas occurs against the viscoelastic resistance of the surrounding tissue. The expandable cannulas do not require a full depth incision, or at most require only a needle-size entrance opening. In one embodiment of the invention, the cannula includes a number of arcuate plate segments movable with respect to each other for enabling an increase in cross-sectional area of the cannula lumen. In this embodiment, the cannula can be provided with a pointed end portion. The cannula may be expanded by inserting members or by fluid pressure. The cannula is advantageously utilized to expand a vessel, such as a blood vessel. An expandable chamber may be provided at the distal end of the cannula.

What is claimed is:  
     
         1 . An expandable cannula movable into body tissue for inserting medical instruments and the like into the body tissue, the cannula comprising: 
 a tubular member having proximal and distal ends, an outer surface for engaging the body tissue, and an inner surface, said inner surface defining a passage extending through the tubular member and through which the surgical instruments and the like are inserted, the passage having a first cross-sectional area between the proximal and distal ends in a non-expanded condition,    the tubular member including an expandable portion being comprised of a number of arcuate plate segments, the arcuate plate segments being movable with respect to each other for enabling an increase in cross-sectional area of the passage to a second cross-sectional area in an expanded condition, the second cross-sectional area greater than the first cross-sectional area.    
     
     
         2 . The cannula of  claim 1  wherein the tubular member is expandable under the influence of force applied against at least a portion of the inner surface of the passage.  
     
     
         3 . The cannula of  claim 2  wherein a trocar is insertable in the passage to apply the force against the at least a portion of the inner surface of the passage.  
     
     
         4 . The cannula of  claim 1  wherein portions of the arcuate plate segments overlap in the non-expanded condition.  
     
     
         5 . The cannula of  claim 1  wherein the arcuate plate segments extend along substantially the entire length of the tubular member.  
     
     
         6 . The cannula of  claim 5  wherein each of the arcuate plate segments includes a longitudinally extending portion and a widened proximal end portion, the widened proximal end portions together forming a handle portion of the cannula.  
     
     
         7 . The cannula of  claim 5  wherein a sheath covers the arcuate plate segments.  
     
     
         8 . The cannula of  claim 7  wherein the sheath is made of an elastic material and biases the expandable portion in the non-expanded condition.  
     
     
         9 . The cannula of  claim 8  wherein the arcuate plate segments are made of a polymer.  
     
     
         10 . The cannula of  claim 7  wherein the sheath is bonded to the arcuate plate segments.  
     
     
         11 . The cannula of  claim 5  wherein each of the arcuate plate segments has an inwardly tapering distal end for facilitating entrance through body tissue.  
     
     
         12 . The cannula of  claim 1  wherein the arcuate plate segments move outward away from each other for enabling the increase in cross-sectional area of the passage.  
     
     
         13 . The cannula of  claim 1  wherein the cannula has a pointed end portion for piercing body tissue.  
     
     
         14 . The cannula of  claim 1  wherein the arcuate plate segments have a common axis of curvature when the cannula is in the expanded condition.  
     
     
         15 . A cannula, at least expandable in part and movable into body tissue, said cannula comprising a tubular member having an outer surface for engaging the body tissue and an inner surface, said inner surface defining a passage extending through the tubular member and through which surgical instruments and the like are inserted, said tubular member having proximal and distal ends, said passage having a first cross-sectional area between said proximal end and said distal end, said tubular member being expandable under the influence of force applied against at least a portion of the inner surface of the passage, the distal end of the tubular member including an expandable portion being comprised of at least one arcuate plate member furled in a contracted state with portions of the at least one plate member overlapping in the contracted state, and wherein said one at least plate member defines the passage therethrough of said first cross-sectional area and wherein said at least one plate member enables an increase in the cross-sectional area of said passage at said distal end of said tubular member to a second cross-sectional area which is greater than said first cross-sectional area.  
     
     
         16 . The cannula of  claim 15  wherein a trocar is insertable in the passage to apply the force against the at least a portion of the inner surface of the passage.  
     
     
         17 . The cannula of  claim 15  wherein portions of the arcuate plate segments overlap in the non-expanded condition.  
     
     
         18 . The cannula of  claim 17  wherein a sheath covers the arcuate plate segments.  
     
     
         19 . The cannula of  claim 18  wherein the sheath is made of an elastic material and biases the expandable portion in the non-expanded condition.  
     
     
         20 . The cannula of  claim 19  wherein the arcuate plate segments are made of a polymer.  
     
     
         21 . The cannula of  claim 20  wherein the sheath is bonded to the arcuate plate segments.  
     
     
         22 . The cannula of  claim 15  wherein each of the arcuate plate segments has an inwardly tapering distal end for facilitating entrance through body tissue.  
     
     
         23 . The cannula of  claim 15  wherein the arcuate plate segments move outward away from each other for enabling the increase in cross-sectional area of the passage.