System of instruments for vitrectomy surgery comprising sharp trochar, cannula and canula valve cap and method for its use

Abstract

A system of instruments is provided for vitrectomy surgery, comprising a sharp trochar, a cannula and a cannula valve cap. The sharp trochar provided also has applicability to other fields of surgery. The sharp trochar has a hollow-ground blade that reduces the force necessary for insertion and upon removal leaves a wound with improved healing characteristics. The trochar is selectably insertable in a cannula, and in a preferred embodiment the cannula and the trochar are adapted with mutually tapered exterior surfaces to as to define a smooth transition in diameter to further facilitate insertion. A sealing valve cap is also provided for the cannula, designed to provide sealing while reducing the force required in for inserting instruments into the cannula. A method for angled insertion of this assembly is also disclosed.

1 . A surgical trochar comprising:
 a) a shaft;   b) a tapered blade section at the distal end of said shaft;   c) said blade section starting at a first point situated between the proximal and distal ends of said shaft, following a tapered contour from said first point and coming to a sharp tip at said distal end;   d) wherein said contour forms an acute angle, at said tip, with respect to the exterior of said shaft;   e) wherein said acute angle, measured at said tip, is no greater than about 5 degrees; and   f) wherein said blade section, measured from said tip to said first point is about 3-4 mm. in length.   
     
     
         2 . The trochar of  claim 1  wherein said contour has a concave curved shape with respect to a linear line extending from said first point to said tip. 
     
     
         3 . The trochar of  claim 1  wherein the length of the blade section is about 3.5 mm. 
     
     
         4 . The trochar of  claim 1  wherein said blade section comprises a first subsection and a second subsection, said first subsection having a linear contour and being situated at the distal end of said blade section, and said second subsection section being proximal of first subsection, adjoining said first subsection, and generally disposed at an angle less acute with respect to the exterior of said shaft than that of said first subsection. 
     
     
         5 . The trochar of  claim 4  wherein said second subsection also comprises a linear blade subsection so as to provide a biplanar blade section. 
     
     
         6 . The trochar of  claim 1 , wherein the exterior sides of said shaft distal of said first point, opposite said contour, and laterally disposed with respect to the longitudinally oriented plane normal to said contour, are recessed so as to reduce the cross-sectional area of said tapered blade section as viewed axially with respect to said shaft. 
     
     
         7 . The trochar of  claim 1 , wherein said shaft is adapted to be selectively insertable through the tubular sleeve of a cannula, wherein said distal end of said shaft is extended beyond the distal end of said tubular sleeve. 
     
     
         8 . The trochar of  claim 1 , wherein said shaft is made of metal. 
     
     
         9 . The trochar of  claim 8 , wherein said metal is selected from the group comprising stainless steel and titanium. 
     
     
         10 . A cannula having a proximal end adapted for insertion into biological tissue and a distal end which remains exterior to said tissue upon such insertion, comprising:
 a) a tubular sleeve having an axial passage therethrough; and   b) a top structure attached to the proximal end of said tubular sleeve, said top structure having a larger radial dimension than said tubular sleeve, having therethrough a continuation of the axial passage of said tubular sleeve, said top structure being shaped to receive at its proximal end an elastic removable cap;   
       wherein the exterior surface of said tubular sleeve is tapered at the distal end thereof. 
     
     
         11 . A cannula in accordance with  claim 10  wherein the distal portion of the external surface of said tubular sleeve is polished. 
     
     
         12 . A cannula in accordance with  claim 10  further comprising a roughened surface treatment on the exterior of the proximal portion of said tubular sleeve. 
     
     
         13 . A surgical assembly comprising:
 a) a cannula in accordance with  claim 10 ; and   b) a surgical trochar comprising a shaft, a tapered blade section at the distal end of said shaft, said blade section starting at a first point situated between the proximal and distal ends of said shaft, following a tapered contour from said first point and coming to a sharp tip at said distal end;   
       wherein said shaft is adapted to be selectively insertable through the tubular sleeve of said cannula, wherein said distal end of said shaft is extended through and beyond said distal end of said tubular sleeve; and 
       wherein said cannula and said trochar are adapted such that the junction formed between said shaft and said tubular sleeve, at the point where said shaft extends beyond said tubular sleeve, defines a smooth approximately continuous increase in diameter from said shaft to said sleeve by reason of the tapered exterior surface of said cannula, so as to facilitate the insertion of said assembly into biological tissue. 
     
     
         14 . The surgical assembly of  claim 13 , wherein said shaft further comprises a second tapered section starting at a point adjacent to where said distal end of said shaft extends beyond said distal end of said tubular sleeve and continuing toward said first point defining the proximal end of said blade portion, said second tapered section being adapted to further smooth the transition from the outer surface of said shaft to the outer surface of said tubular sleeve, so as to further facilitate said insertion of said assembly into biological tissue. 
     
     
         15 . A cannula cap, formed from an elastic material, comprising:
 a) a generally cylindrical portion bottom shaped to receive the top structure of an insertion cannula;   b) a substantially flat upper surface member attached along its periphery to the top periphery of said generally cylindrical bottom portion, oriented normal to the axis of said axially oriented passage of said insertion cannula, and covering said axially oriented passage, said upper surface member having its minimum thickness at the approximate center thereof such that the profile of said surface member defines a progressively thinning cross section from said periphery to said center.   
     
     
         16 . The cannula cap of  claim 15 , wherein the interior surface of said generally cylindrical bottom portion has a flared edge around the distal end thereof. 
     
     
         17 . The cannula cap of  claim 15 , wherein said upper surface member further comprises at least one pre-formed slit completely cutting through said upper surface member, wherein the pattern formed by said at least one slit is of sufficient size that the diameter of the smallest imaginary circle on the proximal surface of said upper surface member that fully encloses said pattern is at greater than half the diameter of the axially oriented passage at the top of said insertion cannula. 
     
     
         18 . The cannula cap of  claim 17 , wherein said at least one slit is a single slit extending approximately through said center of said upper surface member, said single slit being part of a cut made through said upper surface member, the plane defined by said cut being inclined at a substantial angle from a direction perpendicular to said surface. 
     
     
         19 . The cannula cap of  claim 17 , wherein said at least one slit comprises three slits having a common end point approximately at said center of said upper surface member, each such slit creating an angle of about 120 degrees with the adjacent slit. 
     
     
         20 . The cannula cap of  claim 15 , wherein said elastic material is silicon rubber. 
     
     
         21 . An inserter for a cannula cap in accordance with  claim 15 , comprising:
 a) a shaft; and   b) an opening at the distal end of said shaft; said opening adapted to receive and hold the upper surface member said cannula cap.   
     
     
         22 . A surgical system, comprising:
 a) a cannula in accordance with  claim 12 ;   b) a cannula cap formed from an elastic material, comprising a generally cylindrical portion bottom shaped to receive the top structure of said cannula; and a substantially flat upper surface member attached along its periphery to top periphery of said generally cylindrical bottom portion, said surface being oriented normal to the axis of said axially oriented passage of said cannula and covering said axially oriented passage; and   c) A surgical trochar comprising a shaft; a tapered blade section at the distal end of said shaft; said blade section starting at a first point situated between the proximal and distal ends of said shaft, following a tapered contour from said first point and coming to a sharp tip at said distal end; wherein said contour forms an acute angle, at said tip, with respect to the exterior of said shaft; wherein said acute angle, measured at said tip, is no greater than about 5 degrees; and wherein said blade section, measured from said tip to said first point is about 3-4 mm. in length, wherein said shaft of said trochar is adapted to be selectively insertable through the tubular sleeve of said cannula;   
       wherein said distal end of said shaft is extended through and beyond said distal end of the tubular sleeve of said cannula; and 
       wherein said cannula and said trochar are adapted such that the junction formed between said shaft and said tubular sleeve, at the point where said shaft extends beyond said tubular sleeve, defines a smooth approximately continuous increase in diameter by reason of the tapered exterior surface of said cannula, so as to facilitate the insertion of said assembly into biological tissue. 
     
     
         24 . The surgical system of  claim 22 , wherein said shaft of said trochar further comprises a second tapered section starting at a point adjacent to where said distal end of said shaft extends beyond said distal end of said tubular sleeve and continuing toward said first point defining the proximal end of said blade portion, said second tapered section being adapted to further smooth the transition from the outer surface of said shaft to the outer surface of said tubular sleeve, so as to further facilitate said insertion of said assembly into biological tissue. 
     
     
         25 . A method of inserting an insertion cannula into the sclera during ophthalmic surgery, comprising
 a) sliding said insertion cannula onto the shaft of a trochar, said trochar having a proximal blade section;   b) positioning said trochar near the surface of the sclera, inclined at a substantial angle from a line normal to the sclera.   c) inserting said trochar at said angle into the sclera in a cutting motion, up to a depth greater than the length of said blade section but not deep enough to insert the distal portion of said cannula;   d) changing the angle of said trochar from said inclined angle to a second angle, so as to make the angle of insertion approximately normal to the surface of the sclera;   e) completing the insertion of said cannula at said angle approximately normal to the surface of the sclera; and   f) withdrawing said trochar from said cannula, leaving said cannula in place in the sclera.   
     
     
         26 . A method of using a cannula in vitrectomy surgery, said cannula having an opening at the proximal end thereof of a passage therethrough for the introduction of instruments, said method comprising applying an elastic cap to said cannula so as to cover said opening, after said cannula has been inserted into and seated in the sclera and does not have such a cap applied. 
     
     
         27 . A method of using a cannula in vitrectomy surgery, said cannula having an opening at the proximal end thereof of a passage therethrough for the introduction of instruments, wherein said cannula has been inserted and seated in the sclera after having been fitted with an elastic cap so as to cover said opening, said method comprising removing said cannula cap without disturbing said cannula. 
     
     
         28 . The method of  claim 26  further comprising using an inserter in accordance with  claim 21  to apply said cannula cap to said cannula.