Trocar assemblies

Abstract

A trocar assembly wherein a trocar with an elongated polygonal tube can receive either an obturator or a medical instrument of a dissimilar cross-sectional shape with the medical instrument of the different cross sectional shape maintable in a central condition therein to inhibit pressure losses to lateral flow to thereby permit use of a cannula having a smaller cross sectional area than a cylindrical cannula as well as inhibit trauma to an entry site around the cannula.

1 - 11 . (canceled) 
     
     
         12 . A trocar comprising:
 a housing;   a cannula having a polygonal cross sectional shape for axially receiving either an obturator or a cylindrical surgical instrument.   
     
     
         13 . The trocar of  claim 12  wherein the cannula comprises a transparent material with a surface finish thereon normally rendering the cannula opaque until moisture wets the surface finish. 
     
     
         14 . The trocar of  claim 12  wherein a minimum diameter of the cannula is greater than a maximum dimension of the surgical instrument so that placement of the surgical instrument within the cannula provides a set of triangular shaped peripheral fluid passages therepast and a set of web faces for centering the surgical instrument therein to inhibit failure of a trocar seal. 
     
     
         15 . The method of introducing a medical gas into a body cavity during a medical procedure while minimizing trauma comprising the steps of:
 forming an opening into a body cavity by inserting a trocar assembly comprising a trocar having a cannula with a polygonal shaped exterior surface through the body tissue of a patient by pushing an end of the cannula through the body tissue while allowing the body tissue to flow around an exterior surface of the polygonal shaped cannula;   removing an obturator from the cannula; and   inserting a surgical instrument into a polygonal lumen in the polygonal shaped cannula wherein the surgical instrument has a radial dimension from a center of the surgical instrument less than a radial dimension from the geometric center of the lumen to a web and the radial distance from the geometric center to an internal corner of the polygonal cannula is greater than the radial distance from the geometric center of the lumen to the web to thereby provide a set of peripheral fluid passages between the exterior surface surgical instrument and the interior surface of the polygonal shaped lumen.   
     
     
         16 . The method of  claim 15  including the step of placing the obturator in engagement with the webs of the polygonal tube to enable rotation of both the cannula and the obturator during the insertion of an end of the cannula into a body cavity of a patient. 
     
     
         17 . The method of  claim 16  including the step of removing the obturator and inserting a surgical instrument into the polygonal lumen in the cannula. 
     
     
         18 . The method of  claim 17  including the step of maintaining a surgical instrument in a central location within the polygonal shaped lumen through engagement with the internal webs of the polygonal tube. 
     
     
         19 . The method of  claim 17  including directing an insufflation gas through the fluid passages between an interior surface of the polygonal tube and an exterior surface of the surgical instrument. 
     
     
         20 . The method of  claim 19  including the step of expanding the step of unevenly expanding tissue around a port into the body cavity with the polygonal cannula to reduce trauma to a patient.