JPS5827549A - Polyamide surgical instrument and production thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to aliphatic polyamide surgical instruments, and more particularly to
The present invention relates to thermally formed aliphatic polyamide surgical devices having improved properties including flexibility or toughness and functional integrity.

It is well known that many surgical procedures very often involve the implantation of synthetic instrumentation, ie, instruments made of non-biological materials. Examples of such methods are surgical procedures that use various stainless steel or other metal clips to ligate various blood vessels to control bleeding during surgery. Additionally, in other surgical procedures, various other metal rods, staples, clips or sheets of material are implanted for various support or support purposes during the surgical procedure. Although in most cases these devices remain in the patient's body for a considerable period of time, in some cases it may be necessary to remove them or
Or the human body's physiological functions may even reject it naturally.

Although these metal surgical instruments do not cause any harm from a medical point of view, they seriously interfere with the possibility of later using many new diagnostic imaging methods on the patient. Therefore, it is often desirable not to leave it in the human body. Metal surgical instruments interfere with radiography, computer imaging, controlled axial cross-sectional imaging, and other new diagnostic imaging methods.

It is thus desirable to replace these surgical instruments with plastic materials that do not have an interfering effect on diagnostic imaging methods. However, in attempts to develop plastic materials to replace metal materials, it has been recognized that it is extremely difficult to provide these plastic materials with a combination of strength, flexibility, and dimensional stability comparable to those of metal materials. It is being For this reason, plastic materials are not easily accepted as substitutes for metal materials. This is particularly true in relatively small devices, such as cerclage clips and other types of clips, used either to close blood vessels or to tie together materials such as tissue.

These clips are small and have a very small critical area within the device requiring considerable strength, flexibility and functional integrity.

One class of materials that has been successful in various surgical instruments is polyamide. Additionally, it is also known that the toughness and various other physical properties of polyamides can be improved by tempering. Detailed methods and discussion of tempering polyamide (nylon) are described in more detail in ``Nylon Plastics'' by Melvin Cohan, published by Joan Wiley and Sands, 1973.In particular, ``Processing of Processed Nylon'' and Chapter 17 of this book entitled, VF of nylon products,! Various methods for recovery are described.

Although it is known that tempering improves some properties of polyamides, injection molded products are generally not tempered for various reasons. The inventor is
Standard extinguishing bases of polyamide, as taught by the prior art, have the properties necessary for injection molded surgical instruments, especially flexibility and functionality, which are critical for in vivo use of plastic surgical instruments. We have found that it does not improve all properties such as integrity.

In accordance with the present invention, a new method has been discovered to improve the strength of thermally formed aliphatic polyamide surgical instruments. Additionally, the new and improved method of the present invention improves the flexibility and functional integrity of aliphatic polyamide injection molded devices, particularly clips used to close various small blood vessels during surgical procedures. Often, the novel surgical instruments of the present invention, in at least some embodiments, have improved in vivo properties. That is, when implanted with these devices, their strength and functional integrity are maintained during the surgical procedure and during and after the subsequent wound healing process.

According to the present invention, the crystallinity of the polyamide and the functional integrity of the thermally formed surgical instrument can be improved by treating the thermally formed aliphatic polyamide surgical instrument with moist heat for a specific period of time. It was discovered that According to the invention, thermally shaped devices are prepared in essentially water-saturated conditions, preferably in hot water, at a temperature above 60°C but below 100°C, preferably between 80 and 90°C. It has been found that treatment for at least 10 minutes can substantially enhance properties important for use as a surgical instrument.

The novel product of the invention has a total crystallinity of at least 15 kudzu, with a total crystallinity of 25%, preferably more than 30%.
The surgical device is comprised of an aliphatic polyamide thermally molded surgical device, preferably a nylon-6 injection molded surgical device, preferably having an α-crystallinity of at least about 20%.

Although the present invention can be applied to many types of surgical instruments made of thermally formed aliphatic polyamide, for the sake of clarity, what is known as a clip made of aliphatic polyamide is used. will be explained in detail.

Referring to FIG. 1, this figure shows a tying clip 1 of the present invention.
It shows 0. This clip is used to ligate blood vessels during various surgical procedures.

The clip consists of two leg members 11 and 12 joined by a hinged portion 13 at the proximal end.

These leg members are fixed at both ends 14 and 151 with a hook. In Figure 2,
The clip of FIG. 1 is shown in its closed position blocking the lumen of blood vessel 16. The hinge area, which is thinner than the rest of the clip, must be flexible yet strong. The main body of the leg member must have a balance of strength and rigidity, and depending on the configuration of the ends, it must have some degree of flexibility. The clip as a whole must have good dimensional stability in that it maintains its closed position when it is closed.

When surgeons use this clip, they very often place it in areas that cannot be seen with the naked eye.
Therefore, it is important to feel the resistance of the hinge and latch mechanism. That is, surgeons expect tactile feedback in surgical instruments6 and
An advantage is also provided by the audible clicking sound when the hook portion of the leg member 11 is deflected to grab the other leg member 12.

Another thermally shaped surgical instrument is shown in FIG. This device is a two-part fastener for closing wounds, etc.
It is 0. This fastener consists of a stapler 21, etc., and a receiver for it consists of a tool 22. In FIG. 4, another thermally shaped device 25 is shown which can be used to close wounds, whether in the skin or fascia or the muscle itself. The device consists of a thin elongated section 26 and a crossbar 27 located at each end thereof. Using a suitable tool to hold the hollow needle 1, insert the needle through the tissue and use the device to extend the elongated section 26 across the wound area, as shown in FIG. and the wound is closed by means of crossbars 27 that grip both sides of the wound area.

Other medical devices included within the scope of the invention include, for example, plastic surgery pins, clamps, nails and solid articles such as plates; clips, staples, hooks, buttons and snaps; for example jaw prostheses. needles; intrauterine instruments; various conduits such as ureters, cystic ducts, etc.; surgical instruments, vascular grafts, connectors or supports; and vertebropelvises, and others. Similar equipment.

Preferably, the surgical instruments of the present invention are manufactured by injection molding. Polyamides are injection molded as is known in the art. Molding temperatures in the range of about 40 DEG to 90 DEG C. can be used for injection molding of nylon-6.

Other processing conditions used in injection molding of nylon-6 are known.

In accordance with the present invention, by treating an injection molded aliphatic polyamide surgical clip in the presence of excess moisture,
The properties of the injection molded clip can be improved to a maximum extent; that is, its properties can be optimized for the intended use. Clip at least 60℃
at a temperature lower than 100°C, preferably about 80-90°C
It has been found that treatment for at least 10 minutes at a temperature of 100 mL and in the presence of excess moisture improves the desirable in-vivo properties of the clip. Although it is preferred to process the clip in hot water, it may also be processed in water vapor or in an extremely humid atmosphere for a sufficient period of time to obtain the desired results.

The following tests are used to measure the properties of surgical clips.

Crystallinity The crystallinity of a clip is a measure of its strength and functional integrity. X-ray diffraction is a convenient method for determining the amount and type of crystallization in clips. X-ray crystallinity data are acquired using a Philips vertical goniometer equipped with a graphite crystal monochromator and a scintillation detector connected to a strip chart recorder.

CuKα radiation is used and the sample is mounted and measured using parafocus geometry. The diffractograms obtained for the samples are analyzed for alpha crystallinity, gamma crystallinity and amorphous content using a DuPont curve analyzer.

Alpha crystallinity is a three-dimensional crystalline form that is stable up to the melting point9
In contrast, conjugate is a metastable, low-order structure that can be converted to the alpha form by various treatments.

Hinging Strength The hinge strength of a clip is the force required to break the clap in the hinged area and maintain the clip in place for 16 hours at 60% relative humidity and a temperature of 70°F! !
Measure by adjusting.

Cut off the latching mechanism on the tip of the conditioned clip and place the ends of the cut leg members into opposing grips of the Instron tensile tester.

The grip has a steel surface. The force required to break the hinge is measured in kg by moving the grip using a pull rate of 5 mn+/min.

Hinge strength (in vivo) The in-vivo strength of the clip is measured as follows.

Divide the clips into groups of 10 clips each without any obvious shuffling. Each group corresponds to one hinge strength test interval. 150-30
Specialized Long-Evans mice weighing 0 g are prepared for surgery and, after anesthesia, two clips are implanted in each mouse. The clips are implanted into the subcutaneous tissue on the left and right posterior dorsal surfaces of the mouse. After each implantation period, 5 mice are euthanized and the clips are carefully removed.

Cut out the latch mechanism at the tip of the clip,
Place the cut ends of both leg members into opposing grips of the Instron tensile testing machine. The grip has a steel surface. The force required to break the hinge is measured in kg by pulling the grips apart using a pull rate of 5ffIII/min.

Elongation Rate The elongation rate of a clip is a measure of its functional integrity and, in part, its dimensional stability. The percentage elongation of the clip is equivalent to the apparent elongation of the clip as determined by intro measurements and is calculated by the following formula: The following specific examples illustrate the invention.

Examples 1-4 Nylon-6 resin, commercially available as type 8207 by Allied Chemical Corporation, having the a-crystallinity and total crystallinity shown in Table 1, was shaped into the clip shown in FIG. Injection mold. A multi-cavity mold in an Arberg injection molding machine is used. The mold temperature is as shown in Table 4, and the nozzle temperature is about 240'C. Other conditions of the injection molding process are similar to those commonly used in injection molding of nylon-6. After washing the molded clip in hexane, 0.
Dry at room temperature under 1 inch pressure.

In Example 1, injection molded clips are tested for hinge strength, elongation, total crystallinity, and in vivo hinge strength. Several clips are implanted into animals to examine the possibility of spontaneous opening during implantation indicating a lack of functional integrity.

In Example 2, a portion of the clip from Example 1 is tempered in accordance with the present invention by placing it in a steam atmosphere for 30 minutes. The tempered clips are tested for hinge strength, elongation, total crystallinity, and in vivo hinge strength.

In Example 3, injection molded clips are tested for hinge strength, elongation, and total crystallinity. A portion of the molded clip is tempered in accordance with the present invention by immersing it in water at 80° C. for the time indicated in Table 1. Tempered clips are tested for hinge strength, elongation rate,
and total crystallinity.

In Example 4, injection molded clips are tested for hinge strength, elongation, and total crystallinity. Some molded clips are immersed in water at 80°C for 30 minutes in accordance with the present invention.
Temper it by letting it sit for a minute. The tempered clips are sterilized by irradiation with 60CO radiation at a dose of 2.5 megarads. Sterilized clips are tested for hinge strength, elongation, total crystallinity, and in vivo hinge strength. These clips are flexible when implanted in an animal, have excellent functional integrity, and do not open during use.

Table 1 shows the treatment conditions and test results used in the examples.

As is clear from Table 1, the tempered clips are not brittle and have excellent hinge strength that is maintained in vivo. Although tempering does not have a negative effect on the clip's elongation rate, it does significantly increase the crystallinity, thereby providing an excellent balance of clip strength, flexibility, and functional integrity.

As previously mentioned, tempering of thermally formed polyamides is not a common practice. Furthermore, current baking processes for polyamides do not improve the properties necessary for thermally formed surgical devices, particularly the flexibility and functional integrity necessary for in-vivo use of the device. It is also known that

To temper any polyamide, often in an oil bath at a temperature appropriate for the type of polyamide used (i.e. 130-140 for nylon-6).
Heat to 9°C. Furthermore, it is known that this method can be used to improve the lubricity of parts by absorbing the tempering medium for this treatment.

Additionally, it has been recognized that this method has the negative effect of discoloration of the tempered parts and requires an expensive oil removal step.

A second method for tempering polyamides is by heating to high temperatures (ie up to 50° C. below the melting point) in the presence of an inert gas to prevent oxidation.

The inventors have recognized that heating thermally shaped surgical instruments at high temperatures (i.e., 50-150°C) under nitrogen for varying amounts of time has little effect on the desirable properties of these instruments. ing. Furthermore, it has been recognized that this tempering process can sometimes have significant negative effects on these appliances.

The examples below illustrate this point.

Example 5 A lip as described above is injection molded using a molding temperature of 86°C. The molded clip was transplanted into a mouse, and 14
When removed after a day, they were found to be displaced from the transplant site and/or open. The other clip is tempered under nitrogen at 50-150°C for 1.5-24 hours.

The properties of these clips are either not improved or are adversely affected as shown in Table 2.

11111 -≦ It can be seen that baking under nitrogen at elevated temperatures causes discoloration and embrittlement, as indicated by a decrease in clip elongation at break. The test rod used in this experiment was of the same thickness as the clip.

X-ray studies show that these as-molded polyamide clips and rods are mostly in a low level of crystallinity, consisting of semistable species. Only after 3 hours under nitrogen at a temperature of 150° C. is there an appreciable transition from umma to alpha.

Rods and clips treated under these conditions are extremely brittle and the clips are completely non-functional and break at the latch when closing.

Polyamide injection molded polymers treated according to the present invention are
They have improved flexibility and functional integrity, making them particularly suitable as surgical instruments. Moreover, nylon-6 (Kobal)-60 is used to provide sterile surgical instruments.
can be easily sterilized by

It should be pointed out that nylon-6 becomes less flexible when completely dry. Therefore, in the present invention,
It is desirable to package and maintain nylon-6 surgical instruments in a moisture-balanced environment during storage to maintain the flexibility of the instruments, thereby making them suitable for use in a variety of surgical procedures.

Having thus described the present invention and several specific embodiments, it will be apparent to those skilled in the art that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention. It should be obvious that it can be done.

We would like to point out that the invention is limited only by the scope of the claims appended hereto.

[Brief explanation of the drawing]

FIG. 1 is an enlarged perspective view of the ligation clip of the present invention. FIG. 2 is an enlarged perspective view showing the clip of FIG. 1 in a blood vessel occluded position. FIG. 3 is an enlarged perspective view of another surgical instrument according to the present invention. FIG. 4 is an enlarged perspective view of yet another surgical instrument according to the present invention. FIG. 5 is a cross-sectional view of the device of FIG. 4 in the closed position. 10: Closure clip, i Ll 2: Leg member 13: Hinge part, 16: Blood vessel 20: Fastener, 21: Stapler 22: Uke is a soldier

Claims (1)

Claims: 1. A thermally formed aliphatic polyamide surgical instrument is heated at approximately 60-100°C in an environment essentially saturated with moisture.
The alpha crystallinity of the device is at least 15
12. A method for improving the in-vivo properties of a device, characterized in that heating for a period sufficient to increase the in-vivo properties of the device by heating the device for a sufficient period of time to increase the in-vivo properties of the device. 2. The method of claim 1, wherein the device is heated for at least 10 minutes. 3. The method of claim 1, wherein the device is an injection molded device. 4. The surgical instrument is a ligating clip consisting of two leg members joined by an elastic hinge at the proximal end and having fixing means located at the distal ends of the leg members. Method. 5. The method according to claim 1.3 or 4, wherein the polyamide is nylon-6. 6. The method according to claim 1 or 5, wherein the temperature is 80 to 90°C. 7. The method according to claim 1.5 or 6, wherein the shaped device is heated in water. 8. A thermally formed aliphatic polyamide surgical instrument having an α-crystallinity of at least 15% and a total crystallinity of greater than 25%. 9. The device of claim 8, which is an injection molded device. 10. An injection molded surgical instrument according to claim 9, comprising a ligation clip having two leg members connected at their proximal ends by a resilient hinge portion and having a locking mechanism at their distal ends. . 11. The surgical instrument according to claim 9 or 10, wherein the polyamide is nylon-6. 12. A surgical instrument according to claim 9.10 or claim 11, having an α-crystallinity of at least 20%. 13. The injection molded surgical instrument of claim 9.10.11 or 12, having a total crystallinity of at least 30%. 14. The surgical instrument of claim 9, comprising a wound closure device having a thin, flexible elongate section and a cross bar located at each end of the section.