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Sutures are filaments, fibers, or thread-like materials used to hold wounds or tissues together. In surgical language, sutures are used for alignment—that is, (tissue) positioned side by side to allow healing. The suture provides tensile support for the wound until the healing tissue has recovered enough strength to exist without the suture. As a ligation thread, suture thread is also used to tie blood vessels to stop bleeding. Today, these tools are taken for granted because they have become common, and without them, it is difficult to consider any type of surgery.

In fact, sutures have been used before there are recorded memories, and long before the earliest period of civilization. The eye needles used for stitching can be traced back to Europe nearly 30,000 BC. By 20,000 BC, spicules began to be used and remained the most advanced until the 14th century.

It is said that East Africans used tendons as ligatures to tie blood vessels, and acacia thorns with plant strips as sutures. By 2000 BC, sutures were made of plant fibers, such as hemp, cotton, flax, bark fibers, and even hair. By 1600 BC, gut (woven or twisted animal intestines) and later silk had become the main suture material.

In addition to the suture material itself, early doctors also knew how these ancient devices worked. For example, the Greek surgeon Galen (approximately 150 AD) suggested that the sutures should be made of materials that would not “rot”, which may have given birth to the concept of permanent implantable sutures. Later, in parallel with this idea, the 11th-century Persian physician Avicenna believed that sutures made of certain natural fibers tend to decompose quickly when used in infected wounds.

To overcome this problem, Avicenna used pig bristles and invented the first monofilament suture. Avicenna realized that the sutures might break down, which hinted at the possibility of deliberately designing soluble sutures.

Although they have long existed in medicine, by the turn of the 18th century, sutures were still not the universal first choice. Many well-known doctors still choose to adhere to methods such as cauterization to stop bleeding and wound closure. In addition, some tapes are known to dissolve when they come into contact with wound drainage fluid. Philip Syng Physick, an American-born and Scottish-trained physician, quickly realized that ligation performed in this way could be of great value and much less painful than cauterization. Physick's experimental and absorbable deerskin ligation was indeed a success.

Pushing this idea forward, Joseph Lister (1827-1912), the founder of aseptic technology, created aseptic sutures treated with his special carbolic acid solution. Lister's carbonized absorbable catgut ligation was quickly used almost everywhere.

Today’s sutures are diverse, made in many forms and a wide range of materials. Absorbable and non-absorbable sutures are widely used. Most people will have them in their lifetime. Absorbable sutures have reached a new level of specialization and precision, and can be customized to stay in the body for a predetermined length of time.

The non-absorbable sutures resist the body's efforts to dissolve them and have been reinforced to support tissue growth. Non-absorbable sutures can be removed or left in the body as a permanent implant. Absorbable and non-absorbable sutures have their specific applications and provide a wide range of surgical combinations.

As early doctors knew, suture materials play a considerable role in the application of sutures. Today, sutures are made of natural and man-made materials. Silk, catgut and flax are only a small part of the natural materials used, while man-made materials include poly(p-dioxanone), polyglycolic acid and nylon. Polyester, nylon, steel, and silk represent some popular non-absorbable suture types, while catgut and glycolide are some common absorbable suture types. The location of the suture, such as the outside or the inside of the body, and the ease and requirements of the suture removal will affect the decision whether to apply an absorbable or non-absorbable suture.

Also important in controlling how the suture is applied is the type of suture: monofilament or multifilament. Monofilament sutures consist of single threads or fibers. Multifilament sutures are composed of many strands or fibers that can be woven or twisted together to form larger filaments. Monofilament sutures have low surface resistance and are easier to pass through tissue than woven or twisted multifilament sutures; these sutures generally have a lower risk of infection. On the other hand, multifilament sutures are easier to knot and have greater knot strength.

In addition to the form of the suture, the mechanical properties of the suture greatly affect its performance and application. Tensile strength, elasticity and knot strength are all important attributes determined by the stitching material, form and size. For example, the knot strength can be as low as 50% of the tensile strength of a knotless straight suture. As another example, stiffness (sometimes called memory) can affect how easy it is to handle and stitch sutures. Sutures with high memory are hard and resistant to mechanical deformation; this may mean that they are easy to unravel or difficult to manipulate during the suturing process. In short, the mechanical properties of the suture help guide the surgeon to choose suture materials for a specific operation.

Finally, the body's response to the suture must be considered. As a foreign body in the body, the suture can cause an immune response. In addition, the damaged tissue caused by the suture implantation will produce accompanying inflammation. Both absorbable and non-absorbable sutures can cause immune response and inflammation. Usually marked by redness and swelling (and pain) at the suture site, inflammation can be severe, leading to fever, allergic reactions, loss of function of the affected area, lowered blood pressure, and further tissue damage.

In some cases, the body will reject the absorbable suture instead of absorbing it. The degree of immune and inflammatory response produced by sutures plays an important role in determining the extent to which the wound site is repaired to its early state.

Based on many considerations for implantable sutures, this is a natural transition to artificial sutures, the characteristics of which can be customized to improve results. Usually made of polymer plastics, polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polycarbonate (PC), polyvinyl chloride (PVC) And polyether ether ketone (PEEK) and other materials have paved many new applications of plastics in the field of medical devices. Biocompatible plastics in their pure form have overall characteristics that are mainly suitable for medical use. For example, because there is little chemical reactivity in the body, many of these durable plastics are very suitable as removable or permanent implants with few fatal side effects.

For example, polytetrafluoroethylene has a wide and successful history of use in medical applications. For more than two decades, this very inactive fluoropolymer has been used in implantable device components, such as vascular stent coverings and anastomoses. An improved PTFE called expanded polytetrafluoroethylene (ePTFE) has also been approved in the field of medical devices. By expanding and developing PTFE after extrusion under specified conditions, ePTFE is a material with unique micropores and mechanical properties. ePTFE has been used in a variety of applications from membranes to gasket materials to flange joint sealants. In biomedical applications, ePTFE was used as an arterial tube as early as 1979. Current medical applications of ePTFE include surgical mesh, ligament and tendon repair, and vascular stent grafts.

The ePTFE suture marks the continued development of this extremely successful biocompatible material. These non-absorbable sutures are extruded into monofilaments and have been used for about 30 years. ePTFE monofilament is becoming more and more popular in the field of medical devices because it has several advantages over other non-absorbable sutures. ePTFE has a very low coefficient of friction, allowing sutures made of this material to pass through tissue easily. The compressible nature of expanded polymer materials also results in knots that do not slip or loosen. Compared with absorbable sutures and braided sutures, ePTFE monofilaments do not absorb bacteria, saliva or blood, thereby supporting healing. Finally, and perhaps most importantly, ePTFE sutures generally do not cause irritation.

A special consideration related to ePTFE sutures is the needle size. Early sutures (such as polypropylene) usually only allowed to swage (press in or crimp) needles with a diameter slightly larger than the suture fibers or filaments onto them. The result is that the suture creates a larger hole in the tissue than the suture fiber, leading to increased bleeding. However, ePTFE monofilaments are highly compressible. Therefore, when swaged onto the needle, the diameter of the un swaged portion of the filament is almost equal to the diameter of the swage itself. The result is sutures with filaments or fibers to more fully fill the holes in the tissue caused by the needles, thereby reducing bleeding. Another advantage of ePTFE sutures is that when switching from needles to filaments, they pass through the tissue more easily and cause much less trauma to the tissue.

Over the years, many types of ePTFE sutures have been available. However, under sporadic exemptions, these sutures are only sold on the market as branded and complete products, and they are die-forged onto the suture fibers. Considering this market situation, Zeus Industrial Products Inc. (headquartered in Orangeburg, South Carolina) has developed a unique ePTFE suture monofilament thread: Zeus's Aeos® ePTFE monofilament non-absorbable suture thread, as shown in Figure 1. . It is recommended to use this suture for permanent implantation in the body. These sutures are unbranded, and users who want to make their own sutures can buy them in bulk (no needles). Providing this unbranded suture material addresses significant market preferences and allows secondary suppliers such as packaging and swaging companies to increase their brand awareness.

Figure 1. Zeus Aeos® ePTFE monofilament non-absorbable suture. The Aeos® ePTFE monofilament on the left is molded onto the needle. Enlarged right view of Aeos® ePTFE monofilament.

As an ePTFE material, Zeus Aeos® sutures have all the advantages of PTFE: these sutures have the highest biocompatibility, excellent durability and are chemically inert in the body. The extremely low coefficient of friction of PTFE allows these sutures to pass through the tissue with edge resistance. These sutures can also be molded onto the needle, and the ratio of sutures (N:S) is as high as 1:1, as shown in Figure 2.

The latter two elements specifically reduce tissue trauma at the surgical site, thereby reducing bleeding and negligible related inflammation. As a microporous material, Aeos® suture is very suitable for new tissue growth into the suture, long-term implantation results in a very high level of tissue encapsulation. Aeos® ePTFE sutures can also be sterilized by autoclaving and ethylene oxide (ETO), and PTFE as a medical polymer plastic meets USP Class VI standards.

Figure 2. Comparison of the size ratio of stitches (N:S). The top Aeos® ePTFE suture thread monofilament is swaged onto the needle with a N:S ratio of 1:1. The bottom braided polyester stitched multifilament is molded onto the needle with N:S> 1:1. Aeos® ePTFE suture monofilament can be molded onto the needle with an N:S ratio as high as 1:1, allowing the monofilament to more completely fill the hole in the tissue formed by the needle, thereby reducing bleeding.

In the surgical environment, Zeus Aeos® ePTFE sutures can be easily integrated into any scene where ePTFE sutures are suitable. These sutures are easy to handle and have excellent drape and softness in the surgeon's hands. The memory or stiffness of Aeos® sutures provides them with reliable knot strength, and its high surface smoothness allows the surgeon to accurately locate the knot (Figure 3).

The white color of Aeos® suture provides excellent visibility at the application site. Once inside the body, the Aeos® ePTFE suture can maintain high tensile strength, making it suitable for stressful anatomical environments. Aeos® sutures are also radiologically transparent, so they will not interfere with procedures such as angiography, MRI or X-rays.

Figure 3. Aeos® ePTFE knotted suture monofilament.

Zeus Aeos® ePTFE suture monofilament is particularly suitable for applications as a permanently implantable medical device component. For example, for anastomoses, Aeos® ePTFE sutures can be used to merge blood vessels to prevent injury, clots, and other circulatory disorders. Aeos® suture can be used for hernia repair to directly close the abdominal wall or suture the mesh in place. For stent deployment, the high lubricity of Aeos® sutures allows the surgeon to effortlessly pull these sutures through the delivery system, releasing the stent for final placement.

For stent grafts or stent grafts, Aeos® sutures can be used to suture the graft material to the wire stent frame. Finally, and perhaps most importantly, ePTFE sutures have gained wide acceptance as replacements for cardiac chordae or mitral valve repairs. These sutures can effectively treat mitral regurgitation, and this type of suture has shown safe and repeatable long-term benefits. In fact, the biocompatibility and versatility of Aeos® ePTFE monofilaments make sutures made of this material more demanding.

Sutures were invented thousands of years ago to treat wounds. Trial and trial made the earliest humans realize that suture materials acted differently. Some materials would dissolve while others would not. With the development of civilization and the advancement and dissemination of human knowledge, early doctors thought that they might be able to guide certain suture types according to the material and type of wound.

Although the progress of substantial improvements to sutures was slow at the beginning, sterile soluble and insoluble sutures appeared in the 19th century. The invention of plastic and its application in sutures is an important step in the evolution of sutures. Currently, there are many types of sutures, including natural, synthetic, absorbable and non-absorbable materials.

One of the most pioneering uses of man-made materials in suture applications may be PTFE and its variants, namely expanded polytetrafluoroethylene (ePTFE). Due to its novel microporous characteristics, ePTFE has significant advantages over many other polymers used in medical devices, and has special advantages in its use as a suture thread. Zeus Aeos® ePTFE suture is the latest innovation in biocompatible sutures. With the proven durability and safety of Zeus' ePTFE solutions in recent years, Aeos® sutures can provide a wide range of applications.

Anastomosis, stent replacement, hernia repair, and cardiac chordal repair are just a few of the many applications that can be achieved with Aeos® ePTFE sutures. This specialized suture monofilament provides all the trademarks of safe surgical intervention and is easily available for non-exclusive or even unbranded use.

This information is derived from materials provided by Zeus Industrial Products, Inc. and has been reviewed and adapted.

For more information on this source, please visit Zeus Industrial Products, Inc.

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