Abstract:
An introducer needle for an infusion set or the like includes a solid tip portion with a plurality of intersecting wedge surfaces that converge toward a common insertion point. Preferably, the common insertion point is coincident with a central axis of the introducer needle. The tip portion also includes a plurality of cutting edges formed at intersections of the wedge surfaces. The cutting edges converge toward the common insertion point so that insertion of the introducer needle into the membrane causes even cutting and separation of the membrane around the introducer needle.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to medical devices, and more particularly to an introducer needle arranged to facilitate membrane penetration and installation of a cannula or catheter within the membrane.  
           [0002]    The delivery of medication or other fluids is often accomplished through a cannula or catheter that is typically placed either subcutaneously or intravenously. For subcutaneous delivery of fluids, the use of an infusion set or injection port reduces the need to constantly puncture the skin and provides a method of temporarily detaching the fluid line for activities such as dressing or bathing. Infusion sets typically include a cannula and an introducer needle that extends through the cannula. A self-adhesive pad is often used to secure the cannula against movement once installed. A manual inserter is often used to install the fusion set. The manual inserter typically includes a housing and a spring-loaded sliding mechanism located in the housing to which the infusion set is temporarily connected. In use, the user typically grasps the inserter housing with one hand while pinching a fold of skin between the thumb and forefinger of the other hand. The sliding mechanism is then released to force the introducer needle and the outer end of the cannula into the fold of skin. The introducer needle is then removed, leaving the cannula installed in the subcutaneous layer. The cannula can then be secured against movement. A tubing from a fluid supply source, such as an insulin pump, can be connected to the cannula housing to deliver insulin or other substances to the subcutaneous layer through the cannula.  
           [0003]    The introducer needle is typically constructed of a hollow, metallic tube with one end ground at an angle to form a cutting tip that is offset from a central axis of the tube. Insertion of the introducer needle into the skin typically requires a relatively high insertion force, due at least in part to the offset nature of the cutting tip. The combination of relatively high insertion force and the offset nature of the tip may create a bending moment about the introducer needle during insertion. When the bending moment is relieved, such as when the introducer needle pierces the skin, the surrounding tissue may be damaged and discomfort may be increased as the introducer needle attempts to spring back to its original shape.  
           [0004]    In addition, burr formation is often prevalent during manufacture of the angle ground hollow introducer needle. The removal of such burrs can be time consuming and difficult.  
           [0005]    Furthermore, during assembly of an infusion set, the offset cutting tip of the introducer needle can contact and damage the inner side wall of the cannula. Thus, great care is needed to ensure that the introducer needle and cannula are properly aligned during insertion of the introducer needle through the cannula.  
         BRIEF SUMMARY OF THE INVENTION  
         [0006]    According to one aspect of the invention, an introducer needle for penetrating a membrane comprises a solid body portion having a central axis and a tip portion extending from the solid body portion. The tip portion includes a plurality of intersecting wedge surfaces that converge toward a common insertion point from the solid body portion. Preferably, the common insertion point is coincident with the central axis of the solid body portion. The tip portion also includes a plurality of cutting edges formed at intersections of the wedge surfaces. The cutting edges converge toward the common insertion point from the solid body portion. With this arrangement, insertion of the introducer needle into the membrane causes even cutting and separation of the membrane around the introducer needle.  
           [0007]    According to a further aspect of the invention, an infusion set comprises a cannula housing, a cannula extending from the housing, and an introducer needle extending through at least a portion of the cannula. The introducer needle comprises a solid body portion having a central axis and a tip portion extending from the solid body portion. The tip portion has a plurality of intersecting wedge surfaces that converge toward a common insertion point from the solid body portion and a plurality of cutting edges formed at intersections of the wedge surfaces, with the cutting edges converging toward the common insertion point from the solid body portion. Preferably, the common insertion point is coincident with the central axis of the solid body portion. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0008]    The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:  
         [0009]    [0009]FIG. 1 is a front perspective view of an inserter assembly incorporating an infusion set with an introducer needle in accordance with the present invention;  
         [0010]    [0010]FIG. 2 is an enlarged perspective view of a portion of the introducer needle and cannula;  
         [0011]    [0011]FIG. 3 is a side elevational view of a portion of the introducer needle;  
         [0012]    [0012]FIG. 4 is a front elevational view of the introducer needle; and  
         [0013]    [0013]FIG. 5 is a front elevational view of an introducer needle in accordance with a further embodiment of the invention. 
     
    
       [0014]    It is noted that the drawings are intended to represent only typical embodiments of the invention and therefore should not be construed as limiting the scope thereof. The invention will now be described in greater detail with reference to the drawings, wherein like parts throughout the drawing figures are represented by like numerals.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    Certain terminology may be used in the following description for convenience only and is not limiting. The words “left,” “right,” “upper,” and “lower” designate directions in the drawings to which reference is made. The words “inwardly” and “outwardly” refer to directions toward and away from, respectively, the geometric center of the needle and designated parts thereof. The terminology includes the words above specifically mentioned, derivatives thereof, and words of similar import.  
         [0016]    Referring now to the drawings, and to FIG. 1 in particular, an infusion set  10  in accordance with the present invention is shown temporarily positioned on an inserter assembly  12  for installation in the subcutaneous skin layer of a user.  
         [0017]    The infusion set  10  includes a cannula  14  extending from a generally hollow cannula housing  16  and an introducer needle  18  extending through the cannula  14  and into the cannula housing  16 . The cannula  14  is preferably constructed of a fluoropolymer material, such as Teflon™, or other inert material. An adhesive-backed pad  20  is preferably attached to the cannula housing  16  with the adhesive layer (not shown) facing away from the cannula housing  16 . A portion of the pad  20  is shown broken away in FIG. 1 to more clearly illustrate the introducer needle  18  and cannula  14  extending underneath the housing. It will be understood that the infusion set  10  is not limited to the low-profile type, but may be arranged to insert the introducer needle  18  and cannula  14  at different angles, including perpendicular, to the skin surface.  
         [0018]    The inserter  12  includes an inserter housing  22  with an angled alignment guide  24  formed therewith so that the infusion set  10  can be inserted into the skin at a predetermined angle. The inserter  12  also includes a spring-loaded slide assembly  26  that is biased toward a forward position as shown, and is retractable to a rearward or cocked position. A locking mechanism  28  is adapted to hold the slide assembly  26  in the cocked position, and an actuating button  30  is operatively associated with the locking mechanism  28  for releasing the slide assembly  26 . A locking lever  32  can also be provided for preventing inadvertent depression of the actuating button  30 , and thus inadvertent release of the slide assembly  26 . Further details of the inserter assembly can be found in copending U.S. patent application Publication No. 2002/0077599 filed on Dec. 18, 2001, the disclosure of which is hereby incorporated by reference. It will be understood that the infusion set  10  can be used with inserters of different configurations, or can be used without an inserter.  
         [0019]    With reference now to FIGS.  2 - 4 , the introducer needle  18  includes a body portion  40  and a tip portion  42  that is integrally formed with, and extends from, the body portion  40 . Preferably, the body portion  40  and tip portion  42  are of solid construction. As shown, the body portion  40  is circular in cross section, but may be configured with other cross sectional shapes, such as triangular, square, oval, and so on.  
         [0020]    The tip portion  42  preferably includes a plurality of substantially planar wedge faces, such as first wedge face  46 , second wedge face  48  and third wedge face  50  that converge toward a common insertion point  52  from the body portion  40 . The common insertion point  52  is preferably coincident with a central axis  54  of the introducer needle  18 . Preferably, the wedge faces extend from the solid body portion  40  to the central axis  54  at an angle A in the range of approximately 5-30 degrees, and more preferably at an angle A of approximately 15 degrees. As shown, the first and second wedge faces  46  and  48  intersect to form a first cutting edge  60 , the first and third wedge faces  46  and  50  intersect to form a second cutting edge  62 , and the second and third wedge faces  48  and  50  intersect to form a third cutting edge  64 . The cutting edges  60 ,  62  and  64  preferably converge toward the common insertion point  52  from the solid body portion  40  and are preferably circumferentially spaced about the central axis  54  at an angle B of approximately 120 degrees. Since the cutting edges extend along the intersection of the wedge faces, they also extend or slope from the solid body portion  40  to the common insertion point or central axis  54  at an angle A in the range of approximately 5-30 degrees, and more preferably at an angle A of approximately 15 degrees. In this manner, the length of each cutting edge  60 ,  62  and  64  can be less than a cutting length of the prior art angle ground hollow needle to thereby reduce material costs.  
         [0021]    The introducer needle  18  is preferably constructed from a solid rod or bar of material, such as stainless steel, by cutting the rod or bar to a predetermined length, then grinding or otherwise forming one end of the rod or bar to form the tip portion  42 .  
         [0022]    Referring again to FIG. 1, in use, and by way of example, the infusion set  10  is loaded onto the slide assembly  26  of the inserter assembly  12 . The slide assembly  26  is then retracted to the cocked position and held in place by the locking mechanism  28 . The inserter assembly  12  is then positioned against the skin of a user and the button  30  is depressed to release the slide assembly  26 . The infusion set  10  moves together with the slide assembly under spring bias toward the skin until the introducer needle  18  and cannula  14  are positioned in the subcutaneous layer. The concentric location of the insertion point  52  together with the symmetrically spaced cutting edges  60 ,  62  and  64  facilitate insertion of the introducer needle  18  into the skin with a concentric coaxial force. This coaxial force has no bending component, as in the prior art angle ground hollow needles. The three cutting edges  60 ,  62  and  64  cooperate with the concentric insertion point  52  and the wedge faces  46 ,  48  and  50  to minimize skin displacement during needle insertion while assuring a clean cut through the tissue. In addition, the solid construction of the introducer needle  18  gives added strength over prior art hollow body constructions.  
         [0023]    Still another advantage of the above-described introducer needle  18  is less burr formation and easier burr removal during manufacturing than in the prior art angle grinding of hollow needles.  
         [0024]    Still further, the introducer needle  18  facilitates assembly of the infusion set  10 . When inserted through the cannula  14  during assembly, the introducer needle  18  glides through without touching or damaging the cannula  14  since the insertion point  52  is spaced away from the wall of the cannula.  
         [0025]    Referring now to FIG. 5, a front elevational view of an introducer needle  18   a  in accordance with a further embodiment of the invention is illustrated. The introducer needle  18   a  has a tip portion  42   a  with a plurality of substantially planar wedge faces, such as first wedge face  70 , second wedge face  72 , third wedge face  74 , and fourth wedge face  76  that converge toward a common insertion point  78  from the body portion  40 . The insertion point  78  is preferably coincident with a central axis of the introducer needle  18 A. Preferably, the wedge faces extend from the solid body portion  40  to the central axis  78  at an angle A in the range of approximately 5-30 degrees, and more preferably at an angle A of approximately 15 degrees. As shown, the first and second wedge faces  70  and  72  intersect to form a first cutting edge  80 , the second and third wedge faces  72  and  74  intersect to form a second cutting edge  82 , the third and fourth wedge faces  74  and  76  intersect to form a third cutting edge  84 , and the fourth and first wedge faces  76  and  70  intersect to form a fourth cutting edge  86 . The cutting edges  80 - 86  preferably converge toward the insertion point  78  from the solid body portion  40  and are preferably circumferentially spaced about the central axis  54  at an angle C of approximately  90  degrees. Since the cutting edges extend along the intersection of the wedge faces, they also extend or slope from the solid body portion  40  to the central axis  78  at an angle A that is preferably in the range of approximately 5-30 degrees, and more preferably at an angle A of approximately 15 degrees.  
         [0026]    While the two embodiments of the invention shown in FIGS. 4 and 5 illustrate inserter needles with  3  and  4  edge faces, it should be understood that the invention is not so limited and that  5  or more faces can be used.  
         [0027]    While the invention has been taught with specific reference to the above-described embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and the scope of the invention. By way of example, it will be understood that the invention is not limited to the particular number of wedge faces and cutting edges illustrated, but may have more or less faces and cutting edges. In addition, the angles between the cutting edges and/or their slopes can be asymmetrical. Moreover, although the introducer needle has been taught for use with an inserter assembly, it will be understood that the introducer needle is not so limited, but may be used in other devices and/or methods for positioning a cannula or catheter in a membrane or tissue and/or for creating a passage or opening in a membrane or tissue. Thus, the described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.