Catheter for use in pain therapy

Abstract

To provide a catheter which enables improved pain therapy.SOLUTION: 1. A catheter (1) for use in pain therapy. 2.1. Such a catheter comprising a catheter shaft (2) which is elongated between a proximal end and a distal end, a catheter tip which is arranged at the distal end, and a catheter hub which is arranged at the proximal end is known. 2.2. According to the invention, the catheter shaft has a pre-tensioning section which is elastically deformable between a pre-tensioning state and a compensation state, wherein the pre-tensioning section is axially elastically compressed in the pre-tensioning state and has a first length, and wherein the pre-tensioning section is not or less axially compressed in the compensation state and has a greater second length, whereby a proximal dislocation of the catheter tip is avoided in the event of a proximal dislocation of the catheter hub. 2.3. Use in pain therapy.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a catheter for use in treating pain, the catheter having a catheter shaft extending between a proximal end and a distal end, a catheter tip disposed at the distal end, and a catheter hub disposed at the proximal end. [Background technology]

[0002] Such catheters are generally known in the field of medical engineering and are used in pain therapy. In a pain therapy called peripheral nerve block (PNB), the catheter is advanced distally using an insertion aid until the catheter tip is positioned directly on the nerve to be anesthetized. As an insertion aid, a cannula and / or capillary is used, and in principle, different attachment techniques can be distinguished ("cannula over the needle," "cannula through the needle," "cannula through the capillary"). In pain therapy, catheters may also be used to administer local anesthetics. To anesthetize the nerve, the local anesthetic is administered through one or more catheter outlets located in the area of the catheter tip. In another pain therapy, catheters are used for electrical nerve stimulation. In electrical nerve stimulation (abbreviated as neurostimulation or neuromodulation), current pulses are applied in the immediate vicinity of the nerve to influence the nerve's conduction behavior in response to painful stimuli. Summary of the Invention [Problem to be solved by the invention]

[0003] The object of the present invention is to provide a catheter of the above kind which allows for improved pain treatment. [Means for solving the problem]

[0004] This problem is solved by having a catheter shaft with a pretensioning section that is elastically deformable between a pretensioned state and a compensation state. In the pretensioned state, the pretensioning section is elastically compressed in the axial direction and has a first length. In the compensation state, the pretensioning section is not axially compressed or is less axially compressed and has a second, larger length. Between the pretensioned state and the compensation state, the pretensioning section undergoes a compensatory movement, provided by the elastic pretensioning, which can prevent and / or compensate for proximal displacement of the catheter tip in the event of proximal displacement of the catheter hub. The present invention is based on the recognition that when a catheter is used to administer a local anesthetic, unintentional retraction of the catheter tip (proximal displacement) can result in insufficient flow of the local anesthetic around the nerve. When a catheter is used for nerve stimulation, proximal displacement can lead to suboptimal stimulation of the nerve. In both treatments, this can impair the effectiveness of pain treatment. The solution according to the present invention avoids such proximal displacement of the catheter tip. For this purpose, the catheter shaft has the above-mentioned pretensioning section. The pretensioned section can be compressed by applying an external axial compressive load. In this case, the axial length of the pretensioned section is shortened, and simultaneously, the axial length of the catheter shaft is shortened. This state is called the pretensioned state. In this state, the pretensioned section has the aforementioned (compressed) first length. In the pretensioned state, the pretensioned section applies pretension to the distal and proximal ends, so that the ends are pretensioned away from each other in the axial direction. The pretensioned section is compressed until its elastic pretension is equal to the external compressive load. The compressive load is understood to be an axial force acting on the pretensioned section from both axial sides toward each other. As soon as the compressive load is reduced or completely removed, the pretensioned section elastically elongates until the balance between the external compressive load and the pretension is restored. This state is called the compensated state. In the compensated state, the pretensioned section has a second axial length greater than the aforementioned first length.Due to the elastic compensating movement of the pretensioning section when transitioning from the pretensioning state to the compensating state, the pretensioning section compensates for the proximal displacement of the catheter hub, so that no proximal displacement of the catheter tip occurs or at least is reduced.

[0005] In the solution according to the invention, the elastic deformability of the pretensioning section allows the pretensioning section to deform automatically from the pretensioned state to the compensation state when the compressive load is removed or reduced, i.e., without the action of any external force other than the compressive load. This, in particular, eliminates the need for tensile forces acting on the pretensioning section, the proximal end, or the catheter hub, which would cause axial elongation of the pretensioning section. In an advantageous embodiment, the elastic deformability is purely elastic, without substantial plastic or elastic-plastic deformation rates. The catheter according to the invention is attached to the body so that the catheter tip is placed in the biological tissue close to the nerve to be anesthetized and the pretensioning section is in a pretensioned state. The pretensioning section pretensions the catheter tip distally, so that the catheter tip is pressed axially against the biological tissue. The biological tissue exerts an axial counterforce (compressive load) on the catheter tip, thereby maintaining the pretensioning section in the pretensioned state. In the event of proximal displacement of the catheter hub, the catheter tip also first moves proximally by a small path length, thereby reducing the axial counterforce. This causes the distal pretension that the pretensioning section exerts on the catheter tip in the distal direction to exceed the opposing axial compressive load. As a result, the pretensioning section elongates until a force balance is achieved between the pretensioning force and the compressive load. An increase in the length of the catheter shaft in the region of the pretensioning section corresponds to a decrease in proximal displacement of the catheter tip, or in the best case, no proximal displacement. The pretensioning section can be described as elastically deformable, elastically compressible, and / or elastically crushable. An increase in the length of the pretensioning section can also be referred to as elongation.

[0006] In one embodiment of the invention, the pretensioning section is made of an elastically compressible material. Preferably, the elastically compressible material is an elastomeric material. Therefore, in this embodiment of the invention, the catheter shaft is made of the above-mentioned elastically compressible material at least in the region of the pretensioning section, and the catheter shaft is made of a less compressible material away from the pretensioning section. If the pretensioning section occupies the entire length of the catheter shaft, then the entire catheter shaft is made of the above-mentioned elastically compressible material.

[0007] In a further embodiment of the invention, the pretensioning element comprises a spring, preferably a coil spring.

[0008] In a further embodiment of the invention, the pretensioning section has an elastically compressible configuration. In this embodiment of the invention, the elastic deformability of the pretensioning section is not necessarily achieved by a suitable choice of material, but by a suitable configuration. The increase or decrease in length occurs by a change in the shape of the pretensioning section, for example by an accordion movement. Thus, in this embodiment of the invention, the catheter shaft has the above-mentioned elastically compressible configuration at least in the region of the pretensioning section, and in the part of the catheter shaft remote from the pretensioning section, it has a different, less compressible configuration, preferably a smooth-walled cylinder configuration known from the prior art. Insofar as the pretensioning section occupies the entire length of the catheter shaft, the entire catheter shaft consequently has the above-mentioned elastically compressible configuration.

[0009] In a further embodiment of the invention, the elastically compressible configuration is an accordion-like configuration. In this embodiment, the pretensioning section is configured like an accordion, so that the pretensioning section can be easily compressed when an appropriate compressive load is applied. The accordion-like configuration can be formed in particular by a folded, wavy or spiral shape of the pretensioning section.

[0010] In a further embodiment of the invention, the pretensioning section extends over the entire length of the catheter shaft. Thus, in this embodiment of the invention, the entire catheter shaft is elastically compressible. This embodiment of the invention can simplify manufacturing, since the catheter shaft can be made from one and the same material and / or have one and the same structure. This is in contrast to embodiments in which the pretensioning section occupies only a portion of the entire length of the catheter shaft.

[0011] In yet another embodiment of the present invention, the pretensioned section extends over only a portion of the entire length of the catheter shaft, and the catheter shaft has a compressive compliance at a distance from the pretensioned section that is less than the compressive compliance of the pretensioned section. Compliance is the reciprocal of stiffness. For example, the catheter shaft can have a compressive compliance at a distance from the pretensioned section that is at most 20%, preferably at most 5%, and particularly preferably at most 1% of the compressive compliance of the pretensioned section. This allows the pretensioned section to elastically deform when a compressive load is applied to the catheter shaft, while the catheter shaft at a distance from the pretensioned section undergoes reduced or no elastic deformation.

[0012] In a further embodiment of the invention, the catheter shaft has a different configuration away from the pretensioning section, whereby the pretensioning section and the catheter shaft away from the pretensioning section have different configurations, which allows the pretensioning section to have a greater compressive compliance than the catheter shaft away from the pretensioning section.

[0013] In a further embodiment of the invention, the catheter includes a length limiting device configured to limit the second length of the pretensioned section. The length limiting device limits the second length of the pretensioned section to a predetermined value, which may be referred to as a limiting length. The length limiting device prevents the pretensioned section from extending beyond the limiting length. It is also contemplated that the length limiting device can be used to compress the pretensioned section.

[0014] In further embodiments of the present invention, the length limiting device has an elongated tensioning element that bridges the pretensioning section to form a force relief section. The tensioning element mechanically bridges the pretensioning section as soon as the pretensioning section reaches its maximum allowable length. Once the maximum allowable length is reached, the tensioning element absorbs the compressive force applied by the pretensioning section, thereby forming the aforementioned force relief section, which may also be referred to as a pressure relief section. The tensioning element may be formed in any manner suitable for this purpose. In some embodiments, the tensioning elements are attached axially on both sides of the pretensioning section, for example, at both axial ends of the pretensioning section and / or at the distal and / or proximal ends of the catheter shaft.

[0015] In a further embodiment of the invention, the elongate pulling element comprises a conductive wire configured to transmit and / or deliver current pulses for neural stimulation. The wire thus has an advantageous multi-function. On the one hand, the wire functions as a force reliever. On the other hand, the wire additionally functions as an electrical conductor for the above-mentioned neural stimulation. In this embodiment of the invention, the catheter shaft and / or the catheter tip comprise at least one stimulation electrode that is electrically conducted using or formed by the conductive wire.

[0016] In further embodiments of the present invention, the catheter includes a retaining device configured to protect the pretensioned section from deformation in the pretensioned state and to allow deformation toward the compensation state upon activation. Activation can determine the time or point at which possible extension of the pretensioned section is permitted. For example, the retaining device can fix the pretensioned section in the pretensioned state when the catheter is attached. This prevents the pretensioned section from transitioning to the compensation state before the catheter tip is finally positioned near the nerve to be anesthetized. In particular, the catheter is attached so that the catheter is advanced toward the nerve at the catheter tip while the retaining device maintains the pretensioned section in the pretensioned state and prevents its deformation. After the catheter tip reaches its final position, the retaining device can be activated, thereby releasing and finally allowing deformation of the pretensioned section. In some embodiments, the retaining device can be deactivated again after activation, thereby maintaining the pretensioned section in the state it was in when the retaining device was deactivated and preventing further extension and / or compression of the pretensioned section. In some embodiments, the length limiting device and the retaining device are formed by one and the same member that performs both functions. Actuation can also be called manipulation.

[0017] In some embodiments, when the catheter is installed, the pretensioned section is in a compensated state. When the catheter tip is advanced toward the nerve to be anesthetized, the anatomy to be penetrated exerts an axial compressive force on the catheter tip such that the pretensioned section is compressed. As soon as the catheter tip is positioned near the nerve, the pretensioned section can be in a pretensioned state.

[0018] In further embodiments of the invention, the catheter has a support structure that protects the pretensioned section from buckling transverse to the longitudinal extension. The support structure preferably radially stabilizes the pretensioned section, thereby ensuring that the pretensioned section retains its elastic deformability. In advantageous embodiments, the support structure completely surrounds the pretensioned section in the circumferential direction. In some embodiments, the support structure extends over a portion of the pretensioned section, while another portion of the pretensioned section is not surrounded by the support structure. In other embodiments, the support structure extends over the entire length of the pretensioned section or axially beyond the pretensioned section and over a portion of the catheter shaft away from the pretensioned section.

[0019] In further embodiments of the present invention, the catheter shaft has a catheter lumen for administering a local anesthetic, which can be administered directly through the catheter to the surrounding tissue. Preferably, at least one catheter outlet is present in the region of the catheter tip, through which the local anesthetic can be administered to the tissue. In some embodiments, the catheter lumen extends through the pretensioned section, while in other embodiments, the catheter lumen extends past the pretensioned section.

[0020] The present invention further relates to a catheter assembly comprising a catheter according to the above description and an insertion aid extending between the distal end and the proximal end and having an insertion lumen for inserting the catheter shaft. The insertion aid may also be called a capillary. In this embodiment, the catheter itself does not need to have a catheter lumen to be able to administer a local anesthetic.

[0021] In a further embodiment of the invention, the insertion aid serves as a support structure for the pretensioned portion of the catheter inserted into the insertion lumen, thereby fulfilling multiple functions: on the one hand, it assists in the installation of the catheter, and on the other hand, it protects the pretensioned portion from buckling movements transverse to its longitudinal extension.

[0022] Further advantages and features of the present invention will become apparent from the following description of preferred embodiments of the invention, which proceeds with reference to the claims and the drawings. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic side view of an embodiment of a catheter according to the present invention, comprising a catheter shaft with a pretensioned portion in a pretensioned state. FIG. [Figure 2] 2 is a further schematic side view of the catheter according to FIG. 1, with the pretensioning section in a compensated state; FIG. [Figure 3] 10A and 10B are schematic side views of an embodiment of a pretensioning portion having an elastically compressible configuration in a compressed state; [Figure 4] 10 is a schematic side view of an embodiment of a pretensioning portion having an elastically compressible configuration in an uncompressed state. FIG. [Figure 5] 10 is a schematic side view of a further embodiment of a catheter according to the present invention, with the pretensioned section extending over the entire length of the catheter shaft. FIG. [Figure 6] FIG. 1 is a schematic side view of a catheter assembly having a catheter with a pretensioned portion having a spring and an insertion aid, the insertion aid being shown in longitudinal section. [Figure 7] 10 is a schematic side view of a further embodiment of a catheter according to the present invention, comprising a length limiting device and a retaining device; FIG. DETAILED DESCRIPTION OF THE INVENTION

[0024] 1, there is provided a catheter 1 for use in treating pain, also known as peripheral nerve blocks. The catheter 1 may also be referred to as a pain catheter.

[0025] The catheter 1 comprises a catheter shaft 2 , a catheter tip 3 and a catheter hub 4 .

[0026] The catheter shaft 2 extends between a proximal end 21 and a distal end 22 .

[0027] The catheter tip 3 is located at the distal end 22 of the catheter shaft 2. In the illustrated embodiment, the catheter tip 3 is formed separately from the catheter shaft 2 and is rigidly connected to the distal end 22 of the catheter shaft 2. Alternatively, the catheter tip 3 can be an integral part of the catheter shaft 2 and form the distal end 22 of the catheter shaft 2.

[0028] The catheter hub 4 is disposed at the proximal end 21 of the catheter shaft 2. The catheter hub 4 is rigidly connected to the proximal end 21. The catheter hub 4 may also be referred to as a catheter fitting.

[0029] Pain treatment includes the administration of a local anesthetic. In this case, it is clear that the catheter 1 can have at least one catheter lumen extending through the catheter shaft 2 and the catheter hub 4 and at least one catheter outlet connected to the catheter lumen for conducting a fluid for administering the local anesthetic. The at least one catheter outlet and the catheter lumen are not shown in detail here. The catheter outlet is preferably located in the region of the catheter tip 3. In this case, the at least one catheter outlet can extend axially through the catheter tip 3 and / or radially through the catheter shaft 2. The number and arrangement of the catheter outlets are not important for the present invention and will not be discussed in further detail. In another embodiment, the catheter 1 is used for electrical nerve stimulation. For this purpose, the catheter 1 can have one or more electrodes, as will be described in more detail below.

[0030] To administer a local anesthetic or to perform nerve stimulation, catheter 1 is attached in a manner known to those skilled in the art and advanced distally until catheter tip 3 is positioned immediately adjacent to the nerve to be anesthetized. Attachment of catheter 1 is preferably accomplished using an insertion aid, which is described in more detail below.

[0031] If unintentional proximal movement of the catheter tip 3, known as (proximal) displacement, occurs during pain treatment, in the case of local anesthetic administration, the nerve to be anesthetized may not flow sufficiently around the nerve, or in the case of electrical nerve stimulation, the nerve may be stimulated suboptimally. This may impair the effectiveness of the pain treatment. To counter this, the catheter shaft 2 has a pretensioned section 23.

[0032] The pretensioned section 23 is elastically deformable between a pretensioned state V and a compensated state A. In the pretensioned state V, the pretensioned section 23 is elastically compressed in the axial direction and has a first length L1. In the compensated state A, the pretensioned section 23 is not axially compressed or is only slightly axially compressed and has a second length L2. The second length L2 is greater than the first length L1. This can prevent or at least reduce proximal displacement of the catheter tip 3 in the event of proximal displacement of the catheter hub 4.

[0033] When the catheter 1 is mounted and the catheter tip 3 is positioned immediately adjacent to the nerve to be anesthetized, the pretensioning section 23 applies a pretensioning force F to the distal end 22 and a pretensioning force F to the proximal end 21. This causes the distal end 22, together with the catheter tip 3, to press distally against the tissue surrounding the nerve to be anesthetized with a pretensioning force F. Correspondingly, the tissue surrounding the catheter tip 3 exerts a compressive force, i.e., an axial counterforce (not shown in detail), on the catheter tip 3 and, via the distal end 22, on the pretensioning section 23. This maintains the pretensioning state V and its first length L1. When proximal displacement of the catheter hub 4 occurs in this state, the catheter tip 3 moves proximally by the small path length. This reduces or even eliminates the axial compressive force that the tissue exerts on the catheter tip 3, opposing the pretensioning force F. As a result, the pretensioned section 23 extends until the catheter tip 3 again abuts against the distal tissue and a balance of forces is again achieved between the pretensioned force F and the compressive force exerted by the tissue on the catheter tip 3. In this way, the pretensioned section 23 prevents proximal displacement of the catheter tip 3 even if proximal displacement of the catheter hub 4 occurs.

[0034] FIG. 2 shows the pretensioned section 23 in a compensated state A. In the equilibrium state A, the pretensioned section 23 has a second length L2. The second length L2 is greater than the first length L1. The difference between the lengths L2 and L1 corresponds approximately or exactly to the proximal displacement of the catheter hub 4. In the compensated state A, the pretensioned section 23 compensates for the proximal displacement of the catheter hub 4 by changing its length. In the illustrated embodiment, the compensated state A corresponds to the rest state of the pretensioned section 23, in which no external axial force acts on the pretensioned section 23. Correspondingly, the pretensioned section 23 itself does not exert any pretensioning force F on the distal end 22. In the embodiment shown in FIG. 2, the pretensioned section 23 cannot be further elongated without the action of an external force, i.e., by itself. In other embodiments, the pretensioned section 23 exerts a pretensioning force F on the surrounding biological tissue even in the compensated state A, but the pretensioning force F is smaller than the pretensioning force F in the pretensioned state V. If the compressive force acting axially on the catheter tip 3 by the biological tissue further decreases, the pretensioned section 23 may further elongate. Correspondingly, the second length L2 of the pretensioned section 23 in the compensated state A is smaller than the maximum length of the pretensioned section 23. In the embodiment shown in Figures 1 and 2, the pretensioned section 23 extends over only a portion of the entire length of the catheter shaft 2. In this regard, the arrangement of the pretensioned section 23 and its proportion to the entire length should be understood as exemplary.

[0035] Here, the pretensioning section 23 is arranged in the region of the distal end 22 of the catheter shaft 2. The catheter shaft 2 further has a proximal shaft section 24 and a distal shaft section 25. The proximal shaft section 24 is arranged axially between the proximal end 21 and the pretensioning section 23. Here, the proximal shaft section 24 comprises the proximal end 21 of the catheter shaft 2 and is rigidly connected at one end to the catheter hub 4. At the other end, the proximal shaft section 24 is rigidly connected to the pretensioning section 23. The distal shaft section 25 is arranged axially between the catheter tip 3 and the pretensioning section 23. Here, the distal shaft section 25 comprises the distal end 22 and is rigidly connected at one end to the catheter tip 3. At the other end, the distal shaft section 25 is rigidly connected to the pretensioning section 23.

[0036] In an embodiment not shown, the distal shaft portion 25 is not present, and instead the pretensioning portion 23 is connected directly to the catheter tip 3 .

[0037] The proximal shaft portion 24 and the distal shaft portion 25 are slightly less axially deformable than the pretensioning portion 23. In other words, the pretensioning portion 23 has a greater compression compliance (lower spring stiffness) than the proximal shaft portion 24 and the distal shaft portion 25. Conversely, the proximal shaft portion 24 and the distal shaft portion 25 have a lesser compression compliance (higher spring stiffness) than the pretensioning portion 23. Different configurations with respect to elastic deformability can be obtained by correspondingly selecting different materials and / or shaping and / or by providing springs and / or compressible gas or liquid reservoirs, etc.

[0038] 1 and 2, the pretensioning section 23 has a compression compliance Z1. In the region away from the pretensioning section 23, i.e., the region of the proximal shaft section 24 and the distal shaft section 25, the catheter shaft 2 has a smaller compression compliance Z2. The two compression compliances Z1, Z2 can also be referred to as the first compression compliance Z1 and the second compression compliance Z2. In other words, due to the different materials, the pretensioning section 23 is elastically compressible, while in the region away from the pretensioning section 23 the catheter shaft 2 is stiff, or at least relatively hard or relatively stiff.

[0039] Here, the second compressive compliance Z2 of the catheter shaft 2 away from the pretensioning section 23 is only 2% of the first compressive compliance Z1. In a not shown embodiment, the second compressive compliance is at most 20%, preferably at most 5%, of the first compressive compliance Z1.

[0040] 1 and 2, the pretensioned section 23 is made of a material M1. In the areas away from the pretensioned section 23, i.e., the proximal and distal shaft sections 24 and 25, the catheter shaft 2 is made of a different material M2. The two materials M1 and M2 may also be referred to as a first material M1 and a second material M2.

[0041] Here, both materials M1, M2 are plastic materials suitable for medical applications. Materials M1, M2 differ at least with respect to their compression compliance and / or spring stiffness.

[0042] In the embodiment according to Figures 1 and 2, the elastic deformability of the pretensioned part 23 is therefore obtained by selecting a suitable material. Alternatively or additionally, the pretensioned part 23 can have an elastically compressible structure. Such an elastically compressible structure is exemplarily shown in Figures 3 and 4.

[0043] 3 and 4 show an embodiment of the catheter 1a in which the pretensioned section 23a has an elastically compressible structure G. In particular, the pretensioned section 23a is configured like an accordion and, in that respect, has an accordion-like structure H. Accordingly, the catheter shaft 2 is provided with radial protrusions W and radial depressions E in the region of the pretensioned section 23. The protrusions W and depressions E are arranged alternately in the axial direction and form the above-mentioned accordion-like structure H.

[0044] FIG. 3 shows the pretensioned section 23a in a pretensioned state V. FIG. 4 shows the pretensioned section 23a in a compensated state A. In the pretensioned state V, the pretensioned section 23a exerts a distal pretensioning force F toward the tissue distal to the catheter tip and an equal and opposite proximal pretensioning force F' toward the catheter hub, directed away from the distal pretensioning force F. When proximal displacement occurs, the distal pretensioning force F is no longer resisted by an equal proximal compressive force, and the accordion-like structure H expands axially until the proximal compressive force exerted by the tissue on the catheter tip 3 again equals the distal pretensioning force F. The pretensioning force F is smaller in the compensated state A according to FIG. 4 than in the pretensioned state V according to FIG. 3, as indicated by the shorter force arrow. Similarly, the proximal pretensioning force F' also decreases between the pretensioned state V and the compensated state A. In the compensated state A, the accordion-like structure H compensates for the proximal displacement with a length corresponding to the difference between the second length L2 of the accordion-like structure H in the compensated state A and the first length L1 of the accordion-like structure H in the pretensioned state V.

[0045] It will be appreciated that the number, shape and dimensions of the protrusions W and depressions E shown in Figures 3 and 4 are to be understood as purely exemplary.

[0046] Figures 5 to 7 show further embodiments of catheters 1b, 1c, and 1d according to the present invention. To avoid repetition, the following will first describe the main differences between catheters 1b, 1c, and 1d and catheters 1 and 1a according to Figures 1 to 4. Functionally identical members and / or parts of catheters 1b, 1c, and 1d are designated by the same reference numerals with the addition of lowercase letters. Unless otherwise stated, what is disclosed with respect to catheters 1 and 1a according to Figures 1 to 4 also applies mutatis mutandis to catheters 1b, 1c, and 1d according to Figures 5 to 7.

[0047] In the catheter 1b according to Figure 5, the pretensioning section 23b extends over the entire length of the catheter shaft 2b, which makes it easier to manufacture than the catheter 1 according to Figures 1 and 2. Furthermore, the pretensioning section 23 can be elastically compressed over a greater length, which can compensate for a greater proximal displacement of the catheter hub 4.

[0048] The catheter 1b includes a length limiting device 5b configured to limit the length or increase in length of the pretensioned section 23b. The length limiting device 5b may have different configurations in different embodiments.

[0049] In the embodiment shown in FIG. 5, the length limiting device 5b has a tensioning element 51b bridging the pretensioning section 23b to form a force relief. As soon as the pretensioning section 23b reaches the maximum allowable second length L2 in the compensation state A, the length limiting device 5b acts as a force relief D, providing force compensation for the pretensioning force F inside the catheter shaft, preventing further extension of the pretensioning section 23b. In this state, proximal displacement of the catheter hub 4b can directly lead to proximal displacement of the catheter tip 3b. For example, when the pretensioning section 23b is force relieved by the tensioning element 51b, withdrawal of the catheter 1b from the living tissue is facilitated.

[0050] 5, the pretensioning section 23b extends over the entire length of the catheter shaft 2b, and therefore the tensioning element 51b also extends over the entire length of the catheter shaft 2b. In other embodiments (not shown) in which the pretensioning section extends over only a portion of the entire length of the catheter shaft, the tensioning element may also extend only over the length of the pretensioning section, or alternatively, over the entire length of the catheter shaft.

[0051] The embodiment shown in FIG. 5 further includes a retaining device 6b, which is configured to protect the pretensioned portion 23b from deformation in the pretensioned state V. The retaining device 6b is actuatable. Upon activation, the retaining device 6b allows deformation of the pretensioned portion 23b. That is, deformation of the pretensioned portion 23b is only possible after activation of the retaining device 6b. In some embodiments, the retaining device 6b may be configured to allow compression of the pretensioned portion 23b before activation, while preventing extension of the pretensioned portion 23b. In other embodiments, the retaining device 6b may be configured to allow neither compression nor extension of the pretensioned portion 23b before activation.

[0052] The retaining device 6b can facilitate placement of the catheter 1b in close proximity to the nerve to be anesthetized and distal advancement of the catheter tip 3b by not actuating the retaining device 6b during advancement, so that the catheter 1b can be advanced distally at a fixed or unalterable length. After positioning the catheter tip 3b in close proximity to the nerve to be anesthetized, actuation of the retaining device 6b occurs, so that the pretensioning section 23b can compensate for proximal displacement.

[0053] In the illustrated embodiment, the tension element 51b also functions as a retaining device 6b, thus performing both a length limiting function and a release function.

[0054] 6, the pretensioning portion 23c extends over only a portion of the entire length of the catheter shaft 2c. The pretensioning portion 23c includes a spring S. In particular, the spring S is configured as a compression coil spring.

[0055] The catheter 1d shown in FIG. 7 is configured as a stimulation catheter for electrical nerve stimulation. For this purpose, the catheter 1d has multiple stimulation electrodes 8 at the catheter tip 3d, and five stimulation electrodes 8 are shown. The catheter 1d can deliver current pulses to the biological tissue surrounding the catheter tip 3d via the stimulation electrodes 8. The stimulation electrodes 8 are connected to the catheter hub 4d through a conductive wire T. Thus, the wire T extends from the catheter tip 3d along the entire length of the catheter shaft 2d to the catheter hub 4d. In particular, the wire T extends along the entire length of the pretensioning section 23d, adjoining the distal shaft section 25d and the proximal shaft section 24d. The wire T is configured to deliver current pulses for neural stimulation of the surrounding biological tissue. Furthermore, the wire T can function as a tension element 51d and form a force relief section to bridge the pretensioning section 23d. Furthermore, the conductive wire T functions as a length limiting device 5d to limit the second length L2 of the pretensioning section 23d. To perform the functions of the length limiting device 5d and the retaining device 6d, the conductive wire T may be connected to the pretensioning section 23d at the points of contact with the proximal and distal shaft sections 24d and 25d, respectively.

[0056] In embodiments not shown, the catheter may be configured for administering a local anesthetic and for providing electrical nerve stimulation and may accordingly have a catheter lumen, at least one catheter outlet, and at least one stimulation electrode.

[0057] FIG. 6 shows a catheter assembly 100 including the catheter 1c and an insertion aid 10 described above. Here, the insertion aid 10 is configured as a capillary K. The insertion aid 10 has an insertion lumen 9 configured to receive a catheter shaft 2c. In the configuration shown in FIG. 6, the catheter shaft 2c is pushed into the insertion lumen 9 through the proximal end of the insertion aid 10 (not shown in detail), and a portion of the distal end 22c of the catheter shaft 2c, together with the catheter tip 3c, protrudes distally from the insertion lumen 9 of the insertion aid 10. The pretensioning portion 23c is positioned entirely, i.e., over its entire length, within the insertion lumen 9. The catheter hub 4c and the proximal end of the insertion aid 10 are preferably configured to form a releasable connection. The releasable connection may be a threaded, luer, or other connection suitable for this purpose.

[0058] In the embodiment shown in FIG. 6, the insertion aid 10 performs multiple functions. On the one hand, it assists in the installation of the catheter 1c. On the other hand, it serves as a support structure 7 that protects the pretensioned portion 23c from buckling movements transverse to the longitudinal extension of the catheter shaft 2c. Because the insertion aid 10 surrounds the spring S over its entire length and circumference, the pressurized spring S cannot escape or buckle to the side. This ensures reliable functioning of the spring S. Furthermore, the insertion aid 10 serves to protect the pretensioned portion 23c from external influences, which, for example, facilitates transportation of the catheter assembly 100.

[0059] Additionally, it is conceivable to administer a local anesthetic through the insertion lumen and apply a current pulse to the surrounding biological tissue through a stimulation catheter disposed in the insertion lumen, in which case the local anesthetic can be guided to the distal end of the insertion aid, for example, through a gap between the insertion aid and the stimulation catheter.

[0060] In an alternative, not shown, embodiment, a separate support structure is provided to protect the pretensioning section from buckling, and may be fixed, for example, to the distal shaft and / or the proximal shaft and / or the pretensioning section.

[0061] It will be appreciated that individual features of the catheters 1, 1a, 1b, 1c, 1d can be combined with one another to form further embodiments of the invention. [Explanation of symbols]

[0062] 1, 1a, 1b, 1c, 1d catheters 2, 2b, 2c, 2d Catheter shaft 3, 3b, 3c, 3d Catheter tip 4, 4b, 4c, 4d Catheter hub 5b, 5d Length limiting device 6b, 6d holding device 7 Support structure 8 stimulation electrodes 9 Insertion Lumens 10 Insertion aid 21, 21b, 21c, 21d proximal end 22, 22b, 22c, 22d distal end 23, 23a, 23b, 23c, 23d Pretension section 24, 24d Proximal shaft 25, 25d Distal shaft 51b, 51d tension elements 100 catheter assembly A Compensation status D Force removal part E recess F, F' pretension force G Elastically compressible structure H Accordion-like structure K Capillary L1 First length L2 Second length M1 First Material M2 Second material S spring T-wire V Pretensioned state W protrusion Z1, Z2 compression compliance

Claims

1. A catheter (1, 1a, 1b, 1c, 1d) for use in treating pain, a catheter shaft (2, 2b, 2c, 2d) extending between a proximal end (21, 21b, 21c, 21d) and a distal end (22, 22b, 22c, 22d); a catheter tip (3, 3b, 3c, 3d) disposed at the distal end (22, 22b, 22c, 22d); A catheter (1, 1a, 1b, 1c, 1d) having a catheter hub (4, 4b, 4c, 4d) disposed at the proximal end (21, 21b, 21c, 21d), the catheter shaft (2, 2b, 2c, 2d) has pretensioned sections (23, 23a, 23b, 23c, 23d) that are elastically deformable between a pretensioned state (V) and a compensated state (A); The pretensioned portion (23, 23a, 23b, 23c, 23d) is elastically compressed in the axial direction in the pretensioned state (V) and has a first length (L1); The catheter (1, 1a, 1b, 1c, 1d) is characterized in that, in the compensation state (A), the pretensioning portion (23, 23a, 23b, 23c, 23d) is not axially compressed or is less axially compressed and has a larger second length (L2), thereby preventing proximal displacement of the catheter tip (3, 3b, 3c, 3d) when proximal displacement of the catheter hub (4, 4b, 4c, 4d) occurs.

2. 2. The catheter (1, 1a, 1b, 1c, 1d) according to claim 1, characterized in that the pretensioning portion (23, 23a, 23b, 23c, 23d) has an elastically compressible configuration (G) and / or is made of an elastically compressible material (M1) and / or comprises a spring (S).

3. 3. The catheter (1, 1a, 1b, 1c, 1d) according to claim 2, characterized in that said elastically compressible configuration (G) is an accordion-like configuration (H).

4. A catheter (1, 1a, 1b, 1c, 1d) according to any one of claims 1 to 3, characterized in that the pretensioning section (23, 23a, 23b, 23c, 23d) extends over the entire length of the catheter shaft (2, 2b, 2c, 2d).

5. 4. A catheter (1, 1a, 1b, 1c, 1d) according to any one of claims 1 to 3, characterized in that the pretensioned section (23, 23a, 23b, 23c, 23d) extends over only a portion of the total length of the catheter shaft (2, 2b, 2c, 2d), and the catheter shaft (2, 2b, 2c, 2d) has, in parts remote from the pretensioned section (23, 23a, 23b, 23c, 23d), a compression compliance (Z2) that is smaller than the compression compliance (Z1) of the pretensioned section (23, 23a, 23b, 23c, 23d).

6. 6. The catheter (1, 1a, 1b, 1c, 1d) according to claim 5, characterized in that the catheter shaft (2, 2b, 2c, 2d) has a different configuration and / or is made of a different material (M2) in the part away from the pretensioning section (23, 23a, 23b, 23c, 23d).

7. A catheter (1, 1a, 1b, 1c, 1d) according to any one of claims 1 to 6, characterized in that it is provided with a length limiting device (5) configured to limit the second length (L2) of the pretensioning portion (23, 23a, 23b, 23c, 23d).

8. 8. The catheter (1, 1a, 1b, 1c, 1d) according to claim 7, characterized in that the length limiting device (5b, 5d) has an elongated tension element (51b, 51d) bridging the pretensioning section (23, 23a, 23b, 23c, 23d) to form a force relief section (D).

9. 9. The catheter (1, 1a, 1b, 1c, 1d) according to claim 8, characterized in that the elongated pulling element (51b, 51d) comprises a conductive wire (T) configured to conduct and / or deliver current pulses for neural stimulation.

10. A catheter (1, 1a, 1b, 1c, 1d) according to any one of claims 1 to 9, characterized in that it is provided with a retaining device (6b, 6d) configured to protect the pretensioned portion (23, 23a, 23b, 23c, 23d) from deformation in the pretensioned state (V) and to allow deformation of the pretensioned portion (23, 23a, 23b, 23c, 23d) upon activation.

11. A catheter (1, 1a, 1b, 1c, 1d) according to any one of claims 1 to 10, characterized in that it is provided with a support structure (7) that protects the pretensioned portion (23, 23a, 23b, 23c, 23d) from buckling movements transverse to the longitudinal extension.

12. A catheter (1, 1a, 1b, 1c, 1d) according to any one of claims 1 to 11, characterized in that the catheter shaft (2, 2b, 2c, 2d) has a catheter lumen for administering a local anesthetic.

13. A catheter assembly (100) comprising: a catheter (1, 1a, 1b, 1c, 1d) according to any one of claims 1 to 12; and an insertion aid (10) extending between a distal end and a proximal end and having an insertion lumen (9) for inserting the catheter shaft (2, 2b, 2c, 2d).

14. 14. The catheter assembly (100) according to claim 13, wherein the insertion aid (10) functions as a support structure (7) for the pretensioning portion (23, 23a, 23b, 23c, 23d) of the catheter (1, 1a, 1b, 1c, 1d) inserted into the insertion lumen (9).

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