Abstract:
A cannula including an inner structure, an outer structure, and a flexible portion. The outer structure is disposed about the inner structure and movable with respect to the inner structure. The flexible portion is attached to the inner structure at an end thereof and attached to the outer structure at an end thereof. The flexible portion is adapted to be stretched from a first smaller diameter when the outer structure is in a first position to a larger diameter when the outer structure is in a second position.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is related to cannulas. More particularly, the present invention relates to an improved cannula with a retractable anchoring system. 
       BACKGROUND OF THE INVENTION 
       [0002]    Endoscopic techniques allow surgical procedures to be performed in a minimally invasive manner, thereby avoiding many of the complications associated with traditional, or open, surgery. Typically, a small puncture is made in the skin and one or more instruments are inserted by way of cannulas for access to the area of interest. Cannula devices are typically tubular in shape and can be of various sizes. 
         [0003]    A problem inherent in the use of surgical cannulas is the risk of dislodgement from the body cavity opening. In addition, soft tissue can obscure vision or interfere with the passage or use of instruments. A surgical cannula may be dislodged by manipulation of surgical instruments through the cannula during use. When a cannula becomes dislodged, it must be re-inserted. A common problem is that of having to re-insert the device back through the previously made tract through the soft tissues to regain access to the body cavity. This becomes increasingly difficult with each dislodgement episode. Dislodgement of a cannula results in increased operative time and increased surgical trauma with the necessity of re-inserting the cannula. There are several cannula devices available that attempt to decrease the risk of dislodgement. Complex devices preclude their common employment as a result of 1) their prohibitive price and 2) the increased risk of malfunction inherent in their more complex construction. Cannulas incorporating additional stabilizing elements are often inadequate and are not commonly employed. 
         [0004]    Previous designs suffer a number of deficiencies. For example, U.S. Pat. No. 4,608,965 describes an endoscope having a single soft plastic cylindrical tube with one end being formed having a smaller end diameter which is forced over the probe portion of an endoscope, and a portion of the soft plastic cylindrical tube adjacent the end having the smaller diameter is formed having longitudinal slits forming flexible strips. U.S. Pat. No. 5,197,971 describes a retractor having a complex mechanical expanding portion for expanding against sub-surface tissues when the retractor is in use, and describes a fluid-operated expanding portion. 
         [0005]    Other devices are provided with serrations, protuberances or threads at their tips, in order to stabilize them in an anatomical cavity. For example, U.S. Pat. No. 7,125,411 provides a flexible coil to be secured to the cannula device after being inserted through the puncture opening. Similarly, U.S. Pat. No. 6,808,494 describes an accordion-like tube which expands against and grips the side walls of an incision. Another example is U.S. Pat. No. 6,542,283 which utilizes a balloon anchor for stabilization of the cannula device. U.S. Pat. No. 5,637,097 to Yoon describes a penetrating instrument having an expandable anchoring portion having a membrane, wherein the expandable portion is biased in the expanded position by means of forming the expandable portion of a resilient spring material or a material having shape memory. Other related art includes U.S. Pat. No. 5,002,557, and U.S. Pat. No. 5,882,340. The teachings of these patents are hereby incorporated by reference. 
         [0006]    None of the available designs, however, are effective in maintaining the cannula in proper position while providing a simple two-tube device for deploying and retracting an anchoring flange. For example, Yoon provides a bias means for employing the expandable portion which is ineffective for preventing the retraction of the device while using the cannula to manipulate the cavity. A surgeon may use the cannula to expand the cavity for operation by pulling the cannula, which would cause the cannula taught by Yoon to retract—a problem which is overcome by the present invention. 
         [0007]    In addition, none of the available designs provide the above benefits while preventing fluid and/or tissue from entering the expandable portion of the cannula cavity, and becoming caught by portions of these devices. Furthermore, none of the available designs provide the above benefits while providing a tool for manipulating the operation cavity. Also, none of the available designs provide the above benefits while providing an outer flange limiting the entry distance of the distal portion of the cannula into the cavity. Furthermore, none of the available designs provide the above benefits while providing a simple mechanism for deploying the stabilizing portion of the cannula in a fixed position. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention provides a cannula comprising an inner structure, an outer structure, and a flexible portion. The outer structure is disposed about the inner structure and movable with respect to the inner structure. The flexible portion is attached to the inner structure at an end thereof and attached to the outer structure at an end thereof. The flexible portion is adapted to be stretched from a first smaller diameter when the outer structure is in a first position to a larger diameter when the outer structure is in a second position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of a cannula in a first position according to an embodiment of the present invention; 
           [0010]      FIG. 2  is a perspective view of a cannula in a second position according to an embodiment of the present invention; 
           [0011]      FIGS. 3-6  illustrate the use of a cannula according to an embodiment of the present invention; 
           [0012]      FIG. 7  is a partial section side view of a cannula lock according to an embodiment of the present invention; 
           [0013]      FIGS. 8A and 8B  are a partial section side view and a top view of a cannula lock according to an embodiment of the present invention; and 
           [0014]      FIG. 9  is a perspective view of a cannula having an external limiter according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated. 
         [0016]    The preferred embodiment, described below, relates to a cannula having an improved anchoring system. The improved cannula is simple to operate and inexpensive to manufacture. The cannula further has the ability to remain in position while a surgical procedure is performed to prevent waste of time from having to reinsert the cannula and to prevent unnecessary damage to the patient&#39;s tissue due to unnecessary movement and reinsertion of the cannula. 
         [0017]    In that regard and referring to  FIG. 1 , the inventive cannula  10  of the preferred embodiment comprises a hollow inner structure  12  and a hollow outer structure  14  that are preferably cylindrical. The outer structure  14  is disposed about the inner structure  12  and movable with respect to one another along a common central axis. The inner structure  12  may optionally comprise an enlarged end  16 . An opening of the enlarged end  16  may be covered with a diaphragm  18  through which surgical instruments may be inserted. Diaphragms  18  covering an end of a cannula are well known in the art and will not be further described herein. 
         [0018]    The outer structure  14 , as stated above, disposed about the inner structure  16  and is easily movable with respect to the inner structure  12 . Attached to the outer structure  14  is a flexible portion  20  that has the ability to resiliently stretch and deform. The flexible portion  20  is preferably made from a polymeric material. The flexible portion  20  comprises a first attachment portion  22 , second attachment portion  26  and a hinge point  24  between the attachment portions  22  and  26 . 
         [0019]    The first attachment portion  22  comprises the interface where the flexible portion  20  attaches to the outer structure  14 . The outer structure  14  may itself be made from the same flexible material or maybe made from a more rigid material and adhered to the flexible portion  20  by a solvent weld, friction weld or other suitable attachment method. 
         [0020]    The second attachment portion  26  attaches the inner structure  12  to the flexible portion  20 . Again, the flexible portion  20  and the inner structure  12  may be made from the same material or attached by a suitable attachment method. 
         [0021]    The hinge point  24  is a weakened circle around the circumference (if the flexible portion is cylindrical) along which greater flexibility in the flexible portion  20  is experienced causing the circle around the circumference to act as a living hinge, as further described below. The hinge point  24  may optionally be made by pre-stretching or pre-stressing a portion of the flexible portion  20  or by creating a score line in the flexible portion, for example. Regardless of the method chosen, which will be dependent upon the material chosen for the flexible portion  20 , the flexible portion  20  will have the ability to behave as a living hinge at the hinge point  24 . 
         [0022]    Referring to  FIG. 2 , when the outer structure  14  is moved toward the attachment portion  26 , the flexible portion  20  expands and folds at the hinge point  24  to create an enlarged flange having a diameter greater than the flexible portion  20  before movement of the outer structure  14 . Near the attachment points  22  and  26 , the flexible portion  20  also folds and acts as a living hinge to allow for the outward movement of the flexible portion  20 . 
         [0023]    The cannula  10  further provides a lock mechanism for locking the outer structure  14  with respect to the inner structure  12  in the position of  FIG. 2 . By means of example and not by limitation, several known lock structures may be used, such as in  FIG. 6  where a spring-loaded detent  28  rises when then outer structure  14  passes from above to prevent return of the outer structure  14  to the initial position. The detent  28  may optionally pass through a bore in the outer structure ( FIG. 9 ). Alternatively in  FIG. 7 , a resilient tab  30  formed from the inner structure  12  having a raised barb  32  could be implemented to form the lock mechanism. One of ordinary skill in the art would recognize a myriad of lock structures that could be used to maintain the inner structure  12  in a fixed position with respect to the outer structure  14 , and it is the concept the lock structure that is inventive and claimed below and not any specific lock structure unless a specific lock structure is explicitly claimed below. 
         [0024]    The cannula  10  is used as shown in  FIGS. 3-6 . In a first step ( FIG. 3 ) the cannula  10  is brought into position next to a patient&#39;s skin A. A puncture is made, commonly with a trocar (not shown), through the skin A by inserting the trocar through the cannula. In a second step ( FIG. 4 ), the cannula  10  is inserted through the puncture in the skin such that the flexible portion is within the patient&#39;s body. In a third step ( FIG. 5 ), the outer structure  14  is moved coaxially with the inner structure  12  to expand the flexible portion  20  to form a flange and lock the outer structure  14  with respect to the inner structure  12 . In a fourth step ( FIG. 6 ), the cannula  10  is secured within the body such that it will not accidentally become dislodged while the surgeon uses instruments B through the cannula  10  to perform the operation. To remove the cannula  10 , the surgeon merely disengages the lock mechanism to return the cannula  10  to the configuration of  FIG. 4  and removes the cannula  10  from the body. 
         [0025]    As shown in  FIG. 9 , the cannula  10  may include an external limiter  34  for limiting the entry distance of the cannula  10  into the opening in the patient&#39;s body. The external limiter  34  can also be used to provide further stability for the cannula  10  when the flexible portion  20  is in the large diameter state. Accordingly, the external limiter  34  can be connected to the outer structure in a fixed position. Alternatively, the external limiter  34  can movable with respect to the outer structure 
         [0026]    The cannula  10  may also optionally include a side port  36  for the introduction or removal of fluid, as is known in the art. 
         [0027]    The above examples show that the invention, as defined by the claims, has far ranging application and should not be limited merely to the embodiments shown and described in detail. Instead the invention should be limited only to the explicit words of the claims, and the claims should not be arbitrarily limited to embodiments shown in the specification. The scope of protection is only limited by the scope of the accompanying claims, and the Examiner should examine the claims on that basis.