Cannula.

p0001The invention relates to a cannula according to the preamble of claim 1.

p0002Such 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.

p0003The 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.

p0004As 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.

p0005In 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).

p0006The 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.

p0007This object is achieved by the features of claim 1.

p0008The cannula according to the invention, a reduced punching effect results when puncturing artificial or natural walls, because the position of the tip of Einstechteils effected in the radial zone of the axial wall together with the curved bend the back of the cannula tube that is to be penetrated without harmful wedge effect in the wall a sharp separate slot is generated, which 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 severing of the material layer 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.

p0009The 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.

p0010The 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.

p0011This cannula is making moderately low because once to grind the closed surrounding the lumen opening edge degree of accuracy is achieved. The syringe is arranged with respect to the axial wall of the cannula tube as well as in the other embodiment of the invention and a punching effect is avoided.

p0012The 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.

p0013The 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.

p0014In the drawing an embodiment of the invention is shown schematically.

p0015It shows:<dl id="dl0001"><dt>Fig. 1</dt><dd>a plan view of a cannula and a cross-section through the tip.</dd></dl>

p0016The cannula 50 comprises a rigid cylindrical cannula tube 51 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 51 is over most of its length precisely. Its outer diameter is 0.7 mm in the example shown. The passageway may have a diameter of 0.4 mm. The front end of the cannula tube 51 is on one side of the wall is curved to form a piercing part 43 obliquely bent to the side, while the opposite wall side 51a axially stops so that an oval lumen opening formed 45 which runs approximately parallel to the cannula tube longitudinal axis 44 and the edge 46 is round sanded. The bend is carried out during the lumen opening 45. The bevel of the rear half of the edge 46 forms a rear bevel eye with a circular cutting edge 48, which is in the course of the inner surface of said axial wall side 51a. The top 47 is substantially in alignment between two imaginary parallel lines 51a extending from the inner surface and the outer surface of the axial wall side of the cannula tube 51 forward. The piercing and cutting parts of the cannula tube 51 lie within the contour of the cannula tube 51 in the area of ​​the wall thickness of the axial wall side 51a, 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 50 is penetrated when using the cannula 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 of the piercing part 43 between the outer point of the top 47 and the cutting edge 48 of the lumen opening 45 is in the example shown 3.6 d ± 0.42 d. You may be longer within the claimed tolerance, provided that they in cut history remains. The bending angle alpha between the longitudinal central axis 44 of the cannula tube 51, and the voltage applied to the rounded curved back side of the piercing part 43 of the cannula tube 51 tangent is preferably 13 ° ± 1 °.

p0017The piercing part 43 is sideways, surrounded on all sides to the longitudinal axis 44 of the cannula tube 51 of the needle 50 approximately parallel lumen opening 45 of a planar sharpened edge 46, which leaves free the tip portion 47th The rear edge of the lumen opening 45 forms the sharpened inner edge 48. The cutting edge 48 may be rounded inwardly. Outside the sharpened edge 46 has the top 47 of Einstechteils 43 in cross-section the shape of the cross section of a lenticular lens with a sharp edge.