JPH0254103B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to aliphatic polyamide surgical instruments and, more particularly, to thermally formed aliphatic polyamide surgical instruments having improved properties including flexibility or toughness and functional integrity. It is well known that in many surgical procedures, synthetic instrumentation, ie, instruments made of non-biological materials, are very often implanted. An example of such a method is surgery using various stainless steel or other metal clips that are used to ligate various blood vessels during surgery to control bleeding. Additionally, in other surgical procedures, various other metal rods, staples, clips or sheets of material are implanted for various support or other 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
At some point thereafter, it may be removed, 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 significantly impede the possibility of later using many new diagnostic imaging methods on patients. In order to
In many cases, it is desirable not to leave it in the human body. Metal surgical instruments interfere with radiography, computer-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 readily accepted as replacements for metal materials. This can be used either to close blood vessels or to bind materials such as tissue,
This is particularly true for relatively small devices, such as ligation clips and other types of clips. These clips are small and have a very small critical area within the device requiring significant strength, flexibility and functional integrity. One of the successful materials for various surgical instruments
The class is polyamide. Additionally, it is also known that the toughness and various other physical properties of polyamides can be improved by tempering. Methods and discussion of tempering polyamides (nylons) are described in more detail in "Nylon Plastics" by Melvin Cohan, John Wiley & Sons, 1973. In particular, Chapter 17 of this book entitled "Processing of Processed Nylon" describes various methods for tempering nylon products. Although it is known that tempering improves some properties of polyamides, injection molded products are generally not tempered for a variety of reasons. The inventors have determined that standard tempering of polyamides, as taught by the prior art, does not provide the desired properties for injection molded surgical instruments, particularly flexibility, which is critical for in-vivo use of plastic surgical instruments. They found that it does not improve all properties such as functional 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 provides a method for making aliphatic polyamide injection molded instruments, particularly clips used to close various small blood vessels during surgical procedures.
Improve the flexibility and functional integrity of. 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 wound closure process and subsequent closure. According to the present invention, the crystallinity of the polyamide and the functional integration of the thermally formed surgical instrument are achieved by treating the thermally formed aliphatic polyamide surgical instrument with moist heat for a specific period of time. It has been found that sexual performance can be improved. According to the invention, the thermally shaped device is prepared at a temperature above 60°C but below 100°C, preferably between 80°C and 100°C.
Treatment at a temperature of 90° C. in conditions essentially saturated with moisture, preferably in hot water, for at least 10 minutes substantially increases properties important for use as a surgical instrument. It was discovered that it is possible. The novel product of the present invention comprises aliphatic polyamides having an α-crystallinity of at least 15%, preferably at least about 20%, with a total crystallinity of 25%, preferably more than 30%. The surgical instrument comprises a thermally molded surgical instrument, preferably an injection molded surgical instrument of nylon-6. Although the present invention is applicable to many types of surgical instruments made of thermally formed aliphatic polyamide, for the sake of clarity it is directed to what is known as a ligation clip made of aliphatic polyamide. Explain in detail. Referring to FIG. 1, this figure shows a ligation clip 10 of the present invention. 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 adapted to be fixed in a latch manner at both ends 14 and 15.
In FIG. 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, so it is important to feel the resistance of the hinge and latching mechanism. That is, surgeons expect tactile feedback in surgical instruments. The surgeon also benefits from an audible clicking sound when the hook portion of one leg member 11 unravels and grasps the other leg member 12. Another thermally shaped surgical instrument is shown in FIG. This device is a two-part fastener 20 for closing wounds and the like. This fastener consists of a stapler 21 and a receiver 22 for it. In FIG. 4, another thermally shaped device 25 is shown which can be used to close wounds, whether in the skin or fascia or within 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 with a hollow needle to hold the instrument, insert the needle through the tissue and use the instrument to create an elongated portion 26 spanning the wound area and the wound, as shown in FIG. The wound is closed by means of a cross bar 27 which grasps the area on both sides. Other medical devices included within the scope of the invention include solid articles such as pins, clamps, screws and plates for orthopedic surgery; clips, staples, hooks, buttons and snaps; e.g. for jaw prostheses. needles; intrauterine instruments; various conduits such as ureters, cystic ducts, etc.; surgical tools, vascular grafts, connectors or supports;
and vertebropelvis, and other similar instrumentation. Preferably, the surgical instruments of the present invention are manufactured by injection molding. Polyamides are injection molded as is known in the art. Nylon-6
Molding temperatures in the range of about 40-90°C can be used during injection molding. Other processing conditions used in injection molding of nylon-6 are known. By treating an injection molded aliphatic polyamide surgical clip in accordance with the present invention with the presence of excess moisture, the properties of the injection molded clip can be maximally improved; It can be optimized according to the intended use. Desirable in vivo conditions of the clips are achieved by treating the clips at a temperature of at least 60°C but below 100°C, preferably at a temperature of about 80-90°C, in the presence of excess moisture, for a period of at least 10 minutes. It was found that the properties were improved. Although it is preferred to treat the clips in hot water, they may also be treated in steam 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 obtained using a Phillips 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 diffractogram obtained for the sample is 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 point, whereas gamma crystallinity 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 clip in the hinged area, and is 60
Measured by conditioning the clip for 16 hours at % relative humidity and a temperature of 70°. Cut off the latching mechanism at the tip of the conditioned clip and place the cut ends of the 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 pulling speed of 5 mm/min. Hinging 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 bias. Each group corresponds to one hinge strength testing interval. Specialized Long-Evans mice weighing 150-300 g are prepared for surgery and, after anesthesia, two clips are implanted in each mouse. The clips are implanted into the subcutaneous tissue of 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 off the latch mechanism at both ends 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 5 mm/min. Elongation Rate The elongation rate of a clip is a measure of its functional integrity and, in part, its dimensional stability. Clip elongation is equivalent to the apparent clip elongation determined by intro measurements and is calculated by the following formula: Elongation % = Crosshead speed x Chart length / Chart speed x Gauge length x 100 The following specific examples illustrate the invention. Examples 1 to 4 By Allied Chemical Corporation having the α-crystallinity and total crystallinity shown in Table 1,
Nylon-6 resin, commercially available as type 8207, is injection molded into the shape of the clip shown in FIG. A multi-cavity mold in an Arberg injection molding machine is used. The mold temperature is as shown in Table 1. The nozzle temperature is approximately 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 clips in hexane, they are dried at room temperature under a pressure of 0.1 mm. 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 was placed in an atmosphere of steam for 30 minutes in accordance with the present invention.
Temper it by letting it stand for a minute. 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 formed clip is tempered in accordance with the invention by immersion in water at 80° C. for the time indicated in Table 1. The tempered clips are tested for hinge strength, elongation, and total crystallinity. In Example 4, injection molded clips are tested for hinge strength, elongation, and total crystallinity. Some molded clips are tempered in accordance with the present invention by placing them in water at 80°C for 30 minutes. The tempered clips are sterilized by irradiation with 60Co radiation at a dose of 2.5 megarads. Hing strength with sterile clips,
Test for 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.

[Table] 2 Tested without preliminary conditioning.
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 elongation rate of the clip, it significantly increases the degree of crystallinity, thereby providing an excellent balance of strength, flexibility and functional integrity of the clip. As previously mentioned, tempering of thermally formed polyamides is not a common practice. Moreover, current tempering operations on polyamides do not improve the properties required for thermally formed surgical devices, particularly the flexibility and functional integrity required for in-vivo use of the device. Are known. To temper any polyamide, it is often heated in an oil bath at a temperature appropriate for the type of polyamide used (i.e., nylon-6
Heat to 130-149℃). On top of that,
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 formed surgical instruments at high temperatures (i.e., 50-150°C) under nitrogen for varying periods of time has little effect on the desirable properties of these instruments. There is. 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 clip as described above is injection molded using a molding temperature of 86°C. The molded clips were implanted into mice and removed after 14 days to find them dislodged from the implantation site and/or open. Other clips under nitrogen at 50-150℃ for 1.5-24
Temper for an hour. The properties of these clips are either not improved or are adversely affected as shown in Table 2.

Table: It can be seen that tempering under nitrogen at elevated temperatures causes discoloration and embrittlement as indicated by a decrease in elongation at break of the clip. 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 at a low level of crystallinity, consisting mostly of gamma, ie, metastable species. Only after 3 hours under nitrogen at a temperature of 150° C. is there an appreciable transition from gamma 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 in accordance with the present invention have improved flexibility and functional integrity, making them particularly suitable as surgical instruments. Additionally, nylon-6 can be easily sterilized with cobalt-60 to provide sterile surgical instruments. It should be pointed out that nylon-6 becomes less flexible when completely dry. Therefore, in the present invention, nylon-6 surgical instruments are packaged and maintained in a moisture-balanced environment during storage, thereby preserving the flexibility of the instruments and thereby allowing use in various surgical procedures. It is desirable that it be suitable for 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 present 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 position where the blood vessel is occluded. 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 a closed wound position; 10: Ligation clip, 11, 12: Leg member, 1
3: Hinge part, 16: Blood vessel, 20: Fastener,
21: Staple, 22: Receiver.

Claims (1)

[Scope of Claims] 1. A thermally formed aliphatic polyamide surgical instrument is heated in an environment essentially saturated with moisture for approximately 60 minutes.
heating to a temperature of ~100° C. for a period sufficient to increase the alpha crystallinity of the device to at least 15%, thereby improving the functional integrity of the device; A method for improving 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 connected at the proximal end by an elastic hinge and having fixing means located at the distal ends of the leg members. the method of. 5. The method according to claim 1, 3 or 4, wherein the polyamide is nylon-6. 6 The temperature is 80 to 90°C, Claim 1
Or the method described in Section 5. 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 device 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. The injection molded surgical device of claim 9 comprising a ligation clip having two leg members connected at the proximal end by an elastic hinge portion and having a locking mechanism at their distal ends. utensils. 11. The surgical instrument of claim 9 or 10, wherein the polyamide is nylon-6. 12. Having α-crystallinity of at least 20%,
A surgical instrument according to claim 9, 10 or 11. 13. The injection molded surgical device 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 elongated section and a cross bar located at each end of the section.