WO2007012486A1

WO2007012486A1 - Medical instrument and method for its production by sintering of plastic

Info

Publication number: WO2007012486A1
Application number: PCT/EP2006/007408
Authority: WO
Inventors: Herbert Maslanka
Original assignee: Herbert Maslanka
Priority date: 2005-07-26
Filing date: 2006-07-26
Publication date: 2007-02-01
Also published as: DE202006020327U1; DE102005034909A1

Abstract

A medical instrument is proposed, in particular a catheter (1) or a prosthesis, in the form of a flexurally elastic tube section (3) which is made of plastic material and which, at its proximal end, merges integrally into an end section (5) made of the same plastic material. While the plastic material in the tube section (3) is present as a solid material, the end section (5) is porous and therefore more pliable than the tube section (3). By virtue of its porosity, the end section (5) can be better seen in an ultrasound image than has previously been the case. The catheter (1) is extruded from sinterable plastic material. While the tube section (3) is sintered at the sintering temperature of the plastic material, the end section (5), in order to generate the porous material structure, is tempered at a temperature below the sintering temperature and, if appropriate, stretched.

Description

Medical instrument

description

The invention relates to a medical instrument, in particular a catheter, a vascular prosthesis or a probe, in the form of a flexurally elastic strand section of plastic material, which merges in at least a portion of its length into a partial section, which is flexurally soft than the strand section.

Catheters or vascular prostheses used in medical technology often have a flexurally elastic tube section, at the proximal end of which, to reduce the risk of injury when inserting the catheter or the prosthesis, a bending-softer end section is attached as a tip. In the case of a vascular prosthesis, the flexurally soft section may also be located in a middle region in accordance with the intended use. In conventional medical instruments of this type, the end or partial section is made of a different material than the remaining strand of the instrument and subsequently attached. The subsequent attachment requires additional manufacturing steps and is relatively expensive, especially if the diameter of the catheter or the prosthesis is only a few millimeters. Another disadvantage of conventional catheters or prostheses is that their tip is difficult to detect in ultrasound viewing procedures. The catheter or the vascular prosthesis is usually designed as a hose; However, the instrument can also have a solid material cross-section, for example when used as a probe or guidewire.

It is an object of the invention to provide a medical instrument, in particular a catheter, a vascular prosthesis or a probe, whose bending-soft portion is comparatively easy to produce. It is a further object of the invention to provide a medical instrument, in particular To provide a catheter, a vascular prosthesis or a probe whose bend soft subarea in an X-ray or ultrasound examination is better than previously represented. Finally, it is an object of the invention to specify a method for producing such a medical instrument.

The invention is based on a medical instrument, in particular a catheter, a vascular prosthesis or a probe, in the form of a flexurally elastic strand section made of plastic material, which in at least part of its length merges into a partial section which is more flexible than the strand section and is characterized in that in that the strand section and the sub-section are integrally made of the same plastic material, either the plastic material in the strand section being solid material and the sub-section being porous material, or the strand section and the sub-section being sintered, stretched plastic material in which the degree of sintering of the subsection is smaller is as the strand section.

The strand section and possibly also the section have expediently tube shape and can, as they are made of the same

Made of plastic material, are made integrally and in one piece by making sure that the portion of a porous

Material structure, while the instrument is otherwise made of non-porous solid material. This simple measure not only reduces the bending stiffness in the section compared to the main part of the instrument, but it has also surprisingly been found that the porosity reduces the ultrasonic reflectivity or the

X-ray visibility of the section significantly increases compared to the bulk. The subsection can thus be made better visible than previously in ultrasound or X-ray observation methods.

The porosity of the flexurally soft subsection could be achieved by gassing additives to the plastic material of the subsection. in the However, the scope of the invention provides for the strand section and the subsection to consist of a sinterable plastic material, the degree of sintering of the subsection being smaller than that of the strand section. While the particle structure of the sinterable starting material is essentially lost in the strand section by complete sintering, the particle structure remains recognizable when the starting material is sintered below its sintering temperature and provides the desired porous material consistency.A porous structure has both a closed-porous structure In principle, any sinterable material, such as, for example, polyethylene (PE) or polyurethane (PU), is suitable as the plastic material. Polytetrafluoroethylene (PTFE) has proven to be particularly suitable since this material does not shrink back later Warming tends.

A porous structure occurs in particular when the strand material is stretched after sintering. By stretching, pore-like voids are formed in the material. In a variant of the invention, the entire strand is sintered and stretched and accordingly receives a porous structure. Except for the above-mentioned sections, the strand section is subsequently sintered ready, with the result of a reduction in the pore size and stiffening in this area, optionally up to the solid material.

Depending on the later use of the instrument, the porous section may be provided at the end, for example, at the proximal end of the strand section, as desired for catheter applications, for example. The same applies to vascular prostheses in which, however, the bending-softer subregion can optionally also be located at a distance from both ends of the strand section. It is understood that, if appropriate, several such subsections can be provided. For the two aforementioned applications, the strand section is um a hose section. For other applications, for example as a probe or as a guide wire, the strand section can also have solid material cross-section.

Catheter-designed instruments can be used for gastrology or cardiology or the like. The outer diameter of the tubular strand section can in this case be in a range between 1, 8 mm and 6 mm. For vascular prostheses, for example, for the gastrointestinal area, the diameter may be larger, z. B. up to 50 mm.

The inventive method for producing the medical instrument is characterized in that in a first step of a sinterable plastic starting material, a strand is extruded. In a second step, in a first variant, only the subsection of the strand determined for the subsection is annealed to a porous structure at a temperature below its sintering temperature and, in a third step, a section of the strand adjoining this subregion is further sintered at the sintering temperature, in particular completely sintered.

In a second variant, the strand extruded in the first step is tempered or "sintered" to form a porous structure and then stretched overall, thus creating voids or pores in the strand, in the third step excluding the strand which is later softer The second variant facilitates production since the strand can be continuously sintered and stretched For ready sintering, the strand can be produced in a continuous production process by means of suitable heating devices easily locally heated and finished sintered. The sinterable plastic starting material may be in a manner known per se a powder of the plastic material prepared by a volatile binder or lubricant to form an extrudable paste, which in the second step of the production process is "sintered" and thus into a flexible part of the plastic material Instrument forming, porous material structure is connected.

The extrusion process can be carried out at a slightly elevated temperature between 23 ° to 80 ⁰ C, for example, 40 ⁰ C or the like, wherein the extrusion process expediently followed by a drying step for vaporizing any residues of the binder or lubricant. The binder or lubricant is, for example, mineral spirits or another volatile substance.

The bending softness of the section can be influenced by the height or / and contact time of the tempering temperature. To set the porosity and thus the flexural softness, at least the partial section, if appropriate also the strand as a whole, is stretched during the tempering or afterward. It will be understood that the strand portion of the instrument may also be stretched to some extent during or after sintering to adjust the flexural elasticity. In particular, the bending-softer section can also be stretched more than the strand section. During the stretching process, the partial section or the strand section on the inside is e.g. supported by a mandrel or other guide tool or by compressed gas. It is understood that the outer diameter of the section can be guided mechanically during stretching.

The temperature of the annealing and / or the stretching treatment in the second fabrication step is advantageously carried out at 350 ⁰ C to 440 ⁰ C, preferably at about 390 ⁰ C to a maximum of 440 ⁰ C, z. B. at about 415 ° C as far as the plastic material is polytetrafluoroethylene (PTFE). The sintering temperature of this material for the third Depending on the treatment time, the preparation step should be between 440 ^° C. and 600 ^° C., for example about 450 ^° C.

As an alternative to different tempering or sintering temperatures for the "sintering" of the bend-softer subsection and the complete sintering of the strand section of the instrument, the heat-action time can also be varied, In particular, the sub-section of the instrument can also be produced in an annealing process at or above the sintering temperature. if the annealing time is chosen so short that only a porous structure can form.

In the following the invention will be explained in more detail with reference to a drawing.

The drawing shows a medical instrument in the form of a catheter according to the invention.

The catheter 1 shown in the drawing is formed as a plastic tube of polytetrafluoroethylene (PTFE) and comprises a flexurally elastic tube portion 3 of non-porous solid material, which integrally and integrally merges at its proximal end in an end portion 5 of a porous form of the same plastic material. Due to its porosity is also tubular only a few millimeters, for example 5 to 10 mm long end portion 5 flexurally soft than the main part of the catheter 1 forming tube section 3. The flexible end portion 5 reduces the risk of injury during insertion of the catheter and can due to the porosity on ultrasound - Viewing methods are better presented.

The catheter 1 is brought into its tube raw form by extruding a sinterable plastic starting material. The purpose powdery plastic material is prepared by means of a volatile binder or lubricant, for example, light gasoline or the like to form an extrudable paste and is after the extrusion through Evaporation of the binder dried. The end portion 5 is "sintered" after drying at a temperature of less than 32O ⁰ C _1, for example in the order of 300 ⁰ C and thus solidified into a porous material structure During this annealing process or shortly thereafter, the end portion 5 is stretched per se By the degree of stretching and the temperature and the exposure time of the annealing process, the bending softness of the end portion 5 can be adjusted plastic material, which is PTFE, conveniently at about 400 ⁰ C to 450 ⁰ C, sintered to form a non-porous solid material structure. Depending upon the contact time may be the sintering temperature in a range between 320 ° C and 600 ⁰ C. the "sintering" of the end portion 5 and the "Durchsintern" of the hose section 3 can in a conventional annealing furnace, in particular a continuous furnace with variable temperature or in a hot air stream or by means of another heat or energy source, for example, a microwave heating source, wherein the flow rate determines the exposure time.

Alternatively, the catheter 1 can be produced in such a way that the tube raw form extruded from the sinterable plastic starting material is "sintered" as a whole and thus solidified, and the pores or pores present in this material structure are stretched during or after this tempering treatment. The degree of stretching and the temperature and the exposure time of the tempering process influences the subsequent bending softness of the end section 5. The tube section 3 forming the main part of the catheter 1 is finished outside the end sections 5 The pores, which are enlarged by the stretching, can be reduced to a solid material structure if necessary.The flexible end sections can be easily connected by local heating Limiting hose sections, so that if necessary, also several flexible sections can be produced in a continuous process in a simple manner. The preparation of vascular prostheses or probes or the like is carried out in a corresponding manner.

Claims

claims

1. Medical instrument, in particular catheter, vascular prosthesis or probe, in the form of a flexurally elastic strand section (3)

Plastic material which in at least part of its length merges into a section (5) which is softer than the strand section (3), characterized in that the strand section (3) and the section (5) are integrally formed of the same plastic material, either the plastic material is present in the strand section (3) as a solid material and in the subsection (5) as a porous material, or the strand section (3) and the subsection (5) consist of sintered, stretched plastic material in which the degree of sintering of the subsection (5) is less than that of the strand section (3).

2. Medical instrument according to claim 1, characterized in that the strand section (3) and / or the partial section (5) is designed as a tube section.

3. Medical instrument according to claim 1 or 2, characterized in that the partial section is an end portion (5) of the strand section (3).

4. Medical instrument according to claim 1 to 3, characterized in that the solid material existing strand section (3) and the subsection (5) consist of a sinterable plastic material and the degree of sintering of the subsection (5) is less than that of the strand section (3). ,

5. Medical instrument according to claim 1 to 4, characterized in that the strand section (3) and the partial section (5) made of polytetrafluoroethylene (PTFE).

6. A method for producing a medical instrument, in particular a catheter, a vascular prosthesis or a probe, in the form of a flexurally elastic strand section (3) made of plastic material, which merges in at least a portion of its length in a section (5), the flexurally soft than the

Strand section (3), characterized in that in a first step of a sinterable plastic starting material, in particular a tubular strand is extruded, in a second step, either of the partial section (5) certain portion of the

Strand is annealed at a temperature below its sintering temperature to a porous structure or the strand is sintered below its sintering temperature total and then partially stretched and in a third step to the subsection for the (5) certain subsection subsequent section of the strand in the

Sintering temperature is further sintered.

7. The method according to claim 6, characterized in that only the tempered to the porous structure portion of the strand is stretched in the second step after or during annealing.

8. The method according to claim 6 or 7, characterized in that the strand is dried in the first step after the [extrusion.

9. The method according to any one of claims 6 to 8, characterized in that in the first step, a strand of polytetrafluoroethylene (PTFE) is extruded.

10. The method according to claim 9, characterized in that the first section in the second step at a temperature between 350 ⁰ C and less than 440 ⁰ C, is annealed in particular at a temperature between 390 ⁰ C and 440 ⁰ C.

11. The method according to claim 9 or 10, characterized in that the second portion of the strand is sintered in the third step at a temperature between 440 ⁰ C and 600 ⁰ C, in particular at about 450 ⁰ C.

12. The method according to any one of claims 7 to 11, characterized in that the strand but at least the subsection

(5) is supported during stretching at least on the inside, preferably on the outside, by a guide tool and / or by compressed gas.