Non-Absorbable Sutures, Explained

The fundamental purpose of suturing is to bring two soft tissues together, keeping them in place until they join; typically about ten days. Sutures fall into two main categories: absorbable and non-absorbable. As the name implies, absorbable sutures are absorbed by the tissues they are holding together, making removal unnecessary. Conversely, non-absorbable sutures are not absorbed. While they can be removed if used to close skin incisions, for stitches deep within the body they are often left indefinitely. Conventional materials for non-absorbable sutures are linen, cotton, silk, stainless steel wire, polyamide (nylon), polypropylene (Prolene) and polyethylene (courlene). 

Non-Absorbable Types, Advantages and Disadvantages

• Silk suturing has been practiced since the 1890s, and its advantages tend to set the standards for all other sutures. It is easy-to-handle, has excellent knot-tying properties and is very unlikely to cause an allergic reaction in the patient. While it's considered to be a non-absorbable, silk sutures do degrade in about two years. Its soft structure is comfortable for patients and makes it gentle on delicate tissues. On the downside, silk tends to become infiltrated with the cells it is suturing, making it difficult and painful to remove, however, it is available coated with silicone or specialty wax to limit capillarity.  Silk also has low tensile strength, making it likely to break under high tension. It's often used to suture mucosal tissues or to close intertriginous areas. Because of its easy handling, silk is also helpful as a temporary suture during surgery.
• Twisted linen sutures are also easy to work with. Linen has high tensile strength, unlike silk, and its strength increases in a moist environment. However, they lose 50 percent of their strength over a six to nine-month period. They are most useful for procedures where tissue support is unnecessary for an extended period, such as general surgery, gastrointestinal, gynecology and obstetrics, and ligatures in general. The main drawback is that the linen strands produce high tissue reaction and are of high capillarity, which can promote infection. Because of this, linen is not recommended if an infection is present.

• Stainless steel wire sutures are most commonly used for abdominal wound closure, hernia repair, sternal closure and orthopedic procedures. The most significant advantage is that it does not promote infection. Even infected tissues can be repaired using stainless steel. For example, a burst abdomen with the presence of sepsis could be repaired with this suture. Other advantages are that it is inexpensive, hypoallergenic for most patients, has optimum strength and flexibility, and offers excellent knot security. While it is soft and malleable, the wire's springy nature can make it difficult to work with.
• Polyamide or nylon is the most commonly used non-absorbable suture. It is most often used as a percutaneous suture because of its low tissue reactivity. It is excellent for general soft tissue approximation or ligation, including use in cardiovascular, ophthalmic and neurological procedures. It has high tensile strength but loses it over time when buried in tissue. When used as a multifilament, it retains no tensile strength after being in the tissue for six months. Monofilament forms maintain two-thirds of their original strength for about 11 years. Nylon is stiff, making handling and tying difficult. However, multifilament forms have better handling properties.
• Polypropylene (Prolene) is the suture of choice for long-term dermal support because gradual absorption does not occur. It accommodates tissue swelling, making crosshatching less likely than in other materials. However, as wounds heal, the suture will remain loose. It is stiff and has a high memory, making knot security poor. Clinicians often use thermocautery to fuse knots.
• Polyethylene (courlene) sutures are flexible, nonabrasive, and have a silk-like feel, making them gentle on tissues and gloves. Orthopedic clinicians and cardiovascular surgeons prefer it because of its knot properties, including tighter knot security during the tying process, a low knot profile to allow precise placement and a smooth tie down, and superior knot break strength.

Watch our video series about biomedical innovation.

Multifilaments Vs. Monofilaments

Synthetic non-absorbable sutures are typically made of polyamide, polypropylene, and polyethylene. The combination of these three is often referred to as a multifilament. Monofilaments have a smoother texture, making them easier to handle and causing less tissue damage. Multifilaments have the advantage of being more flexible and easier to work with. However, their braided design makes them more prone to capturing bacteria.