Cannula

The invention relates to a cannula with a rigid cannula tube whose one wall side at the front end of the cannula tube having a directed towards the opposite axial wall side curved bend, in the course of which in the axial wall side, a lumen opening is formed, which runs approximately parallel to the cannula tube longitudinal axis, and which a front piercing member and a need in the course of the inner surface of said axial wall side rear inner cutting edge is associated.

Such a cannula is known from US-A-2,746,454. It is needles, their introduction should be facilitated in the vein without risk of injury to the opposite vessel wall characterized in that the front punctuating portion of the cannula is replaced by a hook shape, said the relatively short lumen opening opposed strongly curved back surface acts as a sliding surface. The front edge of the round Einstechteils is directed transversely to the longitudinal axis of the cannula tube to the side and is in alignment with the outer surface of the cannula tube. It is free of a flat polished section, while the rear edge of the lumen opening is ground flat to form an inner edge. Such a cannula is inserted to the advantage of their curved sliding surface on a curved path into a blood vessel, the course of which corresponds approximately to the radius of curvature of the sliding surface of the piercing part. This enforced by the hook-shaped bend angular adjustment of the needle during puncture causes the sharp rear edge of the lumen opening punches into this hineindrängendes material to be pierced surface, whereby the puncture hole is enlarged. This is disadvantageous in tissue biopsies because of the trauma. Undesirable, however, the punchout is also when the cannula for refilling of drug-application devices is used with an implanted capsule having a cavity for receiving the medicament to which a catheter is connected. The free end of the catheter is guided to an infusion site and directs this medication. The (toward the skin of the patient) outwardly directed wall of the implanted capsule comprises a pierceable elastomeric membrane which is pierced with the needle in order to refill medicament into the cavity of the capsule.

The repeated insertion of a needle into the membrane of the capsule caused previously leaks in the membrane in that is stamped with the edge of the bevel eye elastomer material so that holes are formed that no longer close itself. After a relatively small number of punctures, the capsule begins to leak, which the user to replace at least the capsule of the applier can force. Moreover, the transportation of the punched material particles leading to the drug system to contamination of the drug.

As Nachfüllkanülen you previously used so-called Huber needles. In the presently used embodiment, the entire cannula tube at the front end is obliquely bent to the side and extending with a substantially parallel to the longitudinal axis of the cannula tube, provided round sanded lumen opening at the front end of the bent cannula tube section.

The lumen opening is located far outside the contour of the straight cannula tube. This fact causes even with proper vertical placement of the Huber needle punched material particles because of the angled front cannula tube portion on one side like a wedge penetrate through the surface and the wedge remote from rear edge of Anschliffes the lumen opening is pressed laterally against the material to be penetrated and in the opening penetrated material shears. Improper oblique insertion of the needle tip in the to be punctured surface results in an increased penetration of the wall material in the lumen opening with the result that even more sections of material with the exposed edge of the rear bevel eye of the lumen opening are sheared.

In another embodiment of the Huber needle with sideways directed lumen opening (US Patent 2,409,979) which has a wall side of the cannula tube without curvature is obliquely bent toward the opposite axial wall side. The surrounding the lumen opening border is ground flat tangentially to the cannula tube outer surface and at the rear edge with a sloping from the outside inwards, ie outer, provided cutting edge. The piercing, the tip of which is in alignment with the outer circumference of the axial wall side, is provided on the boundary of the lumen opening with bevelled edge. It has been shown that even the bent inclined surface of the cannula tube causes a unilateral wedge effect when puncturing an artificial or natural surface that impairs the formation of a non-expanded, sharp cut and material urges during the advance of the cannula into the lumen opening, which at the is planed rear cutting and damaged by crushing. The problem of considerable Wandausstanzungen with the rear edge of a bevel eye also results in another known cannula (DE-OS 30 13 384) having a sharpened oblique lumen opening in its front region, from the front end of a tip is bent. The outer end of the angled tip is in this case approximately on the center axis of the cannula tube, while the rear edge of the bevel eye is located within the contour of the cannula tube at the rear end of the lumen opening. The conditional by the mutual alignment of the parts of the front cannula tube end guide the tip of an S-shaped curved path during the puncture in a puncture area leads to considerable punching effect which is equally undesirable in the puncture of artificial and natural walls (membrane or body tissue).

The invention has for its object to improve the aforementioned cannula so that in the puncture of a natural or artificial wall outs are avoided in order to prevent the application of the cannula, such as spinal tissue damage and when used as Nachfüllkanüle a leak-free status of to ensure implanted capsule of a drug delivery device after several hundred punctures.

This object is achieved in that the piercing part having a lancet tip with bevelled edge, the imaginary in the region between two parallel lines which continue to extend the inner surface and the outer surface of the axial wall side across the rear edge of the elongate lumen opening out to the front.

The cannula according to the invention, a reduced punching effect results when puncturing artificial or natural walls, because the position of the lancet, sharp through facet cut tip of Einstechteils effected in the radial zone of the axial wall together with the curved bend the back of the cannula tube, that no harmful wedge effect is generated in the to be penetrated wall a sharp separate slot is expanded concentrically from the opposite of the lumen opening bent back down to the outside diameter of the straight cannula tube and always closes tightly after removal of the cannula. The combined features make it easier to budget for the prevention of material loss vertical insertion direction of the cannula, and the puncture remains small because the lateral displacement of the tip of the Einstechteils is offset to the longitudinal central axis by the curvature of the bend that the effect of puncturing a central conical tip results. The precise without side deviations taking place coaxially through the piercing part of the cannula through the separating slot in living tissue to prevent tissue trauma and speeds up the healing process. The knife-like cutting through the layer of material without removal of material allows for up to several thousand punctures the elastic membrane of the implanted capsule of a drug delivery device, without leaks occur. The capsule can therefore remain implanted as the particular therapy required.

The patient is subjected to by the omission of multiple subcutaneous implanting a capsule and by preventing the entrainment of particles punched into his body. The therapy is more reliable in this manner.

The ground inner rear edge of the lumen opening extends in alignment with the inner surface of the cannula tube, and the tip of Einstechteils lies either in alignment with the rear edge or at any point between the imaginary cutting extension and the flight of the outer circumference of the cannula tube.

In an advantageous embodiment of the invention provides that the bevelled edge is incorporated into the flat edge of the lumen opening. On both sides of the longitudinal center plane of the lumen opening of the cannula tube arranged cut surfaces of a pulp refiner facets are formed in two levels, so that a sharp and pointed tip of Einstechteils arises. The bevelled edge may end at the lumen opening. Alternatively, the facet cut end at a distance in front of the lumen opening. In this case, the bevelled edge is limited to a short distance of the tip of the piercing part and surrounding the lumen opening flat edge has the form of a closed unfaceted Anschliffes.

To form the lancet tip of the piercing part may have a bevelled edge in another embodiment of the invention, the piercing on the back side. In this case, the entire edge of the lumen opening at the level of a smooth flat Randa ground surrounded closed. This embodiment is making moderately low.

The ground rear edge of the lumen opening is preferably inwardly rounded. Rounding also contributes to avoiding Materialausstanzungen because it pushes the material during the passage of the cannula through the dotted area and no scrapes.

The bending angle of the curved bend of a side wall of the cannula tube is advantageously in a range of 13 ° ± 3 °, preferably 14 °. As a bending angle of the angle between the longitudinal central axis of the cannula tube and to which the lumen opening opposite curved back side of the front end of the cannula tube tangent is designated.

In the drawing, embodiments of the invention are shown schematically. It shows:<ul><li>Fig. 1 is a side view of a cannula,</li><li>Fig. 2 shows a 90 ° rotated plan view of the cannula of Figure 1, </li><li>Fig. 3 shows a longitudinal section through the piercing member of the cannula of Figure 2 along the line III-III on an enlarged scale,</li><li>Fig. 4 is a side view of a second embodiment of a cannula,</li><li>Fig. 5 shows a 90 ° rotated plan view of the cannula of Figure 4,</li><li>Fig. 6 is a side view of a third embodiment of a cannula and</li><li>FIG. 7 rotated by 90 ° top view of the cannula of Figure 6.</li></ul>

The cannula 10 of Figures 1 and 2 consists of a cylindrical rigid cannula tube 11 of metal, for example with the rear end of an injection syringe or a tube and the like for connecting a liquid transfer line system is connectable. The cannula tube 11 is over most of its length precisely. Its outer diameter<u>d</u> is in the example shown 0.7 mm. The passage 12 may have a diameter of 0.4 mm. The front end of the cannula tube 11 is on one side of the wall is curved to form a piercing part 13 obliquely to the side bent, while the opposite wall side 11a axially stops so that an oval lumen opening formed 20 which runs approximately parallel to the cannula tube longitudinal axis 14 and the edge 16 is round sanded. The bend is carried out during the lumen opening 20. The edge 16 is designed on the front half of the facet cut with two symmetrically arranged in two planes cut surfaces 8,9 that an axially directed sharp tip 17 is formed at the front bevel eye. The bevel of the rear half of the edge 16 constitutes a rear bevel eye with a circular cutting edge 18, which is in the course of the inner surface of said axial wall side 11a. The sharp edge of the rear edge 18 is at 21 by glass bead blasting rounded (Fig. 3). The two cut eyes are separated by two sloping ridges 19 and the Anschliffpartie of the rear bevel eye between the ridges 19 and the cutter 18 is concave (Fig. 1). In this way, the cutting 18 of the rear bevel eye remains without bending so stand as the bevelled edge of a non-angled straight hypodermic needle, ie it is not beyond the contour of the cannula tube 11 outwardly, but is by the amount of the wall thickness of the cannula tube 11 within its contour , The tip 17, which has an oblique axial sharp Einstechkante 17a, of the run, the cut surfaces 8, 9 of the facet ground section to the ridges 19 symmetrically on both sides, is situated substantially in the alignment between two imaginary parallel lines to that of the inner surface and out outer surface of the axial wall side 11a of the cannula tube 11 forward. The piercing and cutting parts of the cannula tube 11 lie within the contour of the cannula tube 11 in the area of ​​the wall thickness of the axial wall side 11a, which together with an excellent release property punching out of particles from the at penetrating natural or artificial material layer is prevented. Under natural tissue material layer is understood to mean, which is penetrated in use of the cannula 10 as a spinal needle. An artificial material layer would be as an elastomeric membrane with an implanted capsule of a drug delivery system. The length of the bending of the back side 15 of the piercing part 13 between the outer point of the tip 17 and the cutting edge 18 of the lumen opening 20 is in the example shown 3.6 d ± 0.42 d. It can be longer within the claimed tolerance, provided that it remains in the grinding process. The bending angle alpha between the longitudinal central axis 14 of the cannula tube 11, and the voltage applied to the rounded bent back side 15 of the piercing part 13 of the cannula tube 11 tangent is preferably 13 ° ± 1 °.

Of the sharpened edge 16 surrounded directed to the side lumen opening 20 of the cannula tube 11 has the form of a elongated Doppellanzette whose two longitudinal halves are symmetrical about the plane passing through the longitudinal axis 14 of the cannula tube 11 level and whose front transverse half of the facet cut 8.9.

In the example of Figures 4 and 5 a circular cylindrical rigid cannula tube 31 of a cannula 30 is provided with a modified piercing 33rd In this case, the cannula tube longitudinal axis 34 approximately parallel oval lumen opening 40 is surrounded by a rim 36 which is round grinded planar. The rear edge of the lumen opening 40 forms a sharp inner edge 38, which is in the course of the inside of the axial wall 31a and - may be rounded inwardly - as shown in Fig. 3 On the planar ground section of the rim 36 joins the top 37 a bevelled edge, who is composed of two ground surfaces 28, 29, which are symmetrically arranged in two levels and collide at an axial sharp Einstechkante 37a of the tip 37 of Einstechteils 33rd The tip 37 with the Einstechkante 37a is also in this example in the region between two imaginary parallel lines which extend the inner surface and the outer surface of said axial wall side 31a on the rear cutting edge 38 of the lumen opening 40 facing outside. This training ensures that virtually no particles are punched out of the material to be penetrated layer. 5 shows a cross-section of the piercing part 33 is shown in the area of ​​the facet ground section.

The curved back side 35, during which the opposing lumen opening 40 is located, has a length of 3.6 d ± 0,42d. The bending angle alpha may be 13 ° ± 1 °, also in this example.

According to Figures 6 and 7, a cannula tube 61 is a cannula 60 at the front end thereof to form a rounded bent back side 55 with a puncturing member 53 having a laterally directed lumen opening 70 which runs approximately parallel to the longitudinal axis 54 of the cannula tube 61st The edge 56 of the lumen opening 70 is ground planar and surrounds the lumen opening 70 round. Your rear edge forms an inner edge 52. A tip 57 of the piercing part 53 is laterally offset from the longitudinal axis 54 of the cannula tube 61 and thereby sharpened, that it on the back side 55, ie opposite the sharpened edge 56, a called relief facet cut with two ground faces 58, 59 has. Preferably, the running in two levels ground surfaces 58,59 of the facets are polished section at an angle of 30 ° to each other. In this example, the edge 56 of the lumen opening 70 by the cutter 52 to the tip 57 straight and is planar. The arrangement of the tip 57 with respect to the axial wall 61a side of the cannula tube 61 corresponds to that of the preceding examples.