Abstract:
Methods and cannulae for providing access to a surgical location within a patient are described. A cannula ( 10 ) receives surgical instruments ( 120 ) for performing a surgical procedure on a body ( 130 ). The cannula ( 10 ) comprises a tube structure ( 12 ) defining a passage ( 16 ) through which the surgical instruments ( 120 ) are inserted into the body ( 130 ). The tube structure ( 12 ) has a proximal end ( 20 ) and a distal end ( 62 ). The tube structure ( 12 ) includes an expandable portion ( 40 ) for enabling an increase in the cross-sectional area of the passage ( 16 ) at the distal end ( 62 ). The expandable portion ( 40 ) of the tube structure ( 12 ), when expanded, has a conical configuration.

Description:
PRIORITY INFORMATION 
     This application is a continuation of U.S. application Ser. No. 09/772,605, filed Jan. 30, 2001, now U.S. Pat. No. 6,800,084 which is a continuation-in-part of U.S. application Ser. No. 09/137,335, filed Aug. 20, 1998, now U.S. Pat. No. 6,187,000. 
    
    
     TECHNICAL FIELD 
     The present invention is directed to a cannula for receiving surgical instruments for performing a surgical procedure on a body. 
     BACKGROUND OF THE INVENTION 
     Endoscopic surgical techniques allow a surgical procedure to be performed on a patient&#39;s body through a relatively small incision in the body and with a limited amount of body tissue disruption. Endoscopic surgery typically utilizes a tubular structure known as a cannula which is inserted into a small incision in the body. The cannula holds the incision open and serves as a conduit extending between the exterior of the body and the local area inside the body where the surgery is to be performed. 
     Due to the relatively small size of the passage into the body which is defined by the cannula, certain surgical procedures, such as posterior discectomies and procedures using steerable surgical instruments, have been difficult to perform using endoscopic techniques. 
     SUMMARY OF THE INVENTION 
     The present invention is a cannula for receiving surgical instruments for performing a surgical procedure on a body. In one embodiement, the cannula comprises a tube structure defining a passage through which the surgical instruments are inserted into the body. The tube structure has a proximal end and a distal end. The tube structure includes an expandable portion for enabling an increase in the cross-sectional area of the passage at least at the distal end. 
     The expandable portion of the tube structure, when expanded, has a conical configuration. The expandable portion of the tube structure includes an arcuate slot and a guide pin disposed in the arcuate slot. The guide pin is movable from a terminal end of the slot to a second terminal end of the slot to enable the cross-sectional area of the passage at the distal end to increase. 
     The tube structure includes first and second tubular portions attached to one another. The second tubular portion comprises the expandable portion. The first tubular portion comprises a length of stainless steel tubing and the second tubular portion comprises an arcuate segment of stainless steel sheet stock rolled into a tubular shape. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features of the present invention will becomes apparent to one skilled in the art to which the present invention relates upon consideration of the following description of the invention with reference to the accompanying drawings, wherein: 
         FIG. 1  is an exploded perspective view of a surgical cannula constructed in accordance with the present invention, the cannula being shown in an expanded condition; 
         FIG. 2  is a perspective view of the cannula of  FIG. 1  with parts removed for clarity, the cannula being shown in a contracted condition; 
         FIG. 3  is a schematic end view showing the cannula of  FIG. 1  in the expanded position; 
         FIG. 4  is a roll out view of a part of the cannula of  FIG. 1 ; and 
         FIG. 5  is a schematic sectional view of the cannula of  FIG. 1  during a surgical procedure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention is directed to a cannula for receiving surgical instruments for performing a surgical procedure on the body of a patient. The present invention is applicable to a variety of surgical procedures in which endoscopic surgical techniques are used. 
       FIG. 1  illustrates a cannula  10  constructed according to the present invention. The cannula  10  is a tubular structure  12  centered on an axis  14 . The tubular structure  12  defines a passage  16  through the cannula  10 . Surgical instruments are inserted into the body during endoscopic surgery through the passage  16 . 
     The tubular structure  12  comprises a first tubular portion  20  and a second tubular portion  40  attached to the first tubular portion. The first tubular portion  20  is preferably made of a length of stainless steel tubing, but could alternatively be made of another suitable material. The first tubular portion  20  has a proximal end  22  and a distal end  24 . Parallel cylindrical inner and outer surfaces  26  and  28 , respectively, extend between the ends  22 ,  24  of the first tubular portion  20 . The inner surface  26  defines a first passage portion  30  of the passage  16  through the cannula  10 . The first passage portion  30  has a diameter D 1  which is preferably in the range from 10 mm to 20 mm. 
     The second tubular portion  40  of the tubular structure  12  is attached to the distal end  24  of the first tubular portion  20 . The second tubular portion is preferably made from stainless steel, but could alternatively be made from another suitable material. 
     As best seen in the rollout view of  FIG. 4 , the second tubular portion  40  comprises an arcuate segment  42  of sheet stock. The arcuate segment  42  includes first and second arcuate edges  44  and  46 , respectively, and first and second planar edges  48  and  50 , respectively. The first and second planar edges  48  and  50  are rolled in an overlapping manner to form the tubular configuration of the second tubular portion  40 . 
     When the second tubular portion  40  has been rolled into its tubular configuration, the first and second arcuate edges  44  and  46  define oppositely disposed first and second ends  60  and  62  ( FIGS. 1 and 2 ), respectively, of the second tubular portion. The first and second ends  60  and  62  are connected by a central portion  64 . The first end  60  of the second tubular portion  40  is attached to the distal end  24  of the first tubular portion  20  by a single fastener, such as a rivet  66 . The rivet  66  extends through two aligned apertures  68  ( FIG. 4 ) at the first end  60  of the second tubular portion  40 . The first end  60  of the second tubular portion  40  is pivotable about the rivet  66 . 
     The second tubular portion  40  includes parallel inner and outer surfaces  70  and  72  ( FIGS. 1 and 2 ), respectively, extending between the first and second ends  60  and  62 . The inner surface  70  defines a second passage portion  74  of the passage  16  through the cannula  10  which extends as a continuation of the first passage portion  30  in the first tubular portion  20 . 
     An arcuate slot  80  is formed in the second tubular portion  40  and extends between the inner and outer surfaces  70  and  72  of the second tubular portion. The arcuate slot  80  extends along a curvilinear path in the central portion  64  of the second tubular portion  40  toward the second end  60  of the second tubular portion. The arcuate slot  80  has a first terminal end  82  located in the central portion  64  of the second tubular portion  40 . A second terminal end  84  of the arcuate slot  80  is located adjacent the intersection of the second arcuate edge  46  and the first planar edge  48  of the arcuate segment  42 . 
     A guide pin  90  is attached to the inner surface  70  of the second tubular portion  40  adjacent the intersection of the second arcuate edge  46  and the second planar edge  50 . In the tubular configuration of the second tubular portion  40 , the guide pin  90  is located in the arcuate slot  80  and is movable along the curvilinear path of the arcuate slot. A washer  92  is secured to an inner end of the guide pin  90  to retain the guide pin in the arcuate slot  80 . 
     The second tubular portion  40  of the tubular structure  12  is expandable from a contracted condition shown in  FIG. 2  to an expanded condition shown in  FIG. 1 . In the contracted condition, the guide pin  90  is located in the first terminal end  82  of the arcuate slot  80  in the second tubular portion  40  and the second passage portion  74  defined by the second tubular portion is cylindrical in shape. The second passage  74  has a generally constant diameter D 2  ( FIGS. 2 and 3 ) which is approximately equal to the diameter D 1  of the first tubular portion  20 . Thus, the cross-sectional area of the second passage portion  74  at the second end  62  of the second tubular portion  40 , which is a function of the diameter D 2 , is approximately the same as the cross-sectional area at the first end  60  of the second tubular portion and is approximately the same as the cross-sectional area of the first passage portion  30  in the first tubular portion  20 . 
     In the expanded condition, the guide pin  90  is located in the second terminal end  84  of the arcuate slot  80  in the second tubular portion  40  and the second tubular portion has a conical configuration. At the second end  62  of the second tubular portion  40 , the second passage portion  74  has a diameter D 3  ( FIG. 3 ) which is larger than the diameter D 2  of the second passage portion at the first end  60 . Preferably, the diameter D 3  of the second passage portion  74  at the second end  62  of the second tubular portion  40  is 40% to 80% greater than the diameter D 2  of the second passage portion at the first end  60 . Thus, in the expanded condition, the cross-sectional area of the second passage portion  74  at the second end  62  of the second tubular portion  40 , which is a function of the diameter D 3 , is 40% to 80% greater than the cross-sectional area of the second passage portion at the first end  60  of the second tubular portion. 
     The cannula  10  includes an outer layer  100  ( FIG. 1 ) for maintaining the second tubular portion  40  of the cannula in the contracted condition. It is contemplated that other suitable means for maintaining the second tubular portion  40  in the contracted condition could be employed. In accordance with a preferred embodiment of the present invention, the outer layer  100  comprises a section of plastic tubing  102  which is heat shrunk over both the first and second tubular portions  20  and  40  to hold the second tubular portion in the contracted condition. 
     In addition, a loop of nylon string  104  for tearing the heat shrink tubing  102  is wrapped around the heat shrink tubing so that it extends both underneath and on top of the tubing. An outer end  106  of the string  104  extends beyond the tubing  102 . 
     The cannula  10  further includes an actuatable device  110  for expanding the second tubular portion  40  from the contracted condition to the expanded condition. In accordance with a preferred embodiment of the present invention, the actuatable device  110  comprises a manually operated expansion tool  112 . The expansion tool  112  resembles a common pair of scissors and has a pair of legs  114  pivotally connected to one another. The expansion tool  112  includes a frustoconical end section  116  formed by a pair of frustoconical halves  118 . Each of the frustoconical halves  118  extends from a respective one of the legs  114  of the expansion tool  112 . It is contemplated that other suitable means for expanding the second tubular portion  40  toward the expanded condition could be employed, such as an inflatable balloon (not shown). 
     During an endoscopic surgical procedure, the cannula  10  is inserted in the contracted condition into the body of a patient. The outer end  106  of the string  104  is then manually pulled on by the surgeon. Pulling on the string  104  tears the heat shrink tubing  102  which is then removed from the cannula  10  by the surgeon. With the heat shrink tubing  102  removed, the second tubular portion  40  of the cannula  10  is thereby released for expansion toward the expanded condition. 
     Next, the expansion tool  112  is inserted into the passage  16  in the cannula  10  until the frustoconical end section  114  is located at the second end  62  of the second tubular portion  40 . The legs  118  of the expansion tool  112  are manually separated, causing the frustoconical halves  118  to separate also. As the halves  118  separate, a radially outwardly directed force is exerted on the inner surface  70  of the second tubular portion  40  by the halves  118 , causing the second tubular portion to expand toward the expanded condition. Under the force of the expanding expansion tool  112 , the guide pin  90  slides from the first terminal end  82  of the arcuate slot  80  to the second terminal end  84  of the arcuate slot to permit the expansion of the second tubular portion  40 . The expansion tool  112  can be rotated about the axis  14  to ensure that the second tubular portion  40  of the cannula  10  is completely expanded to the expanded condition. The expansion tool  112  is then collapsed and removed so that one or more surgical instruments (indicated schematically at  120  in  FIG. 5 ) and a viewing element can be received through the cannula  10  and inserted into a patient&#39;s body  130 . The expandable second tubular portion  40  of the cannula  10  provides a significantly larger working area for the surgeon inside the body  130  within the confines of the cannula. 
     The expandable second tubular portion  40  of the cannula  10  provides a significantly larger working area for the surgeon inside the body  130  within the confines of the cannula. As a result, the simultaneous use of a number of endoscopic surgical instruments, including but not limited to steerable instruments, shavers, dissectors, scissors, forceps, retractors, dilators, and video cameras, is made possible by the expandable cannula  10 . 
     It is contemplated that the cannula  10  described herein could be the centerpiece of a endoscopic surgical kit which would include an assortment of surgical instruments designed and/or selected for use with the cannula. 
     From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.