Surgical stitches (sutures) are specialized medical devices used to hold body tissue together after injury or incision. Their primary purpose is to maintain the approximation of wound edges until the body’s natural healing process creates sufficient strength in the tissue. This mechanical support allows tissues like skin, muscle, and organs to properly rejoin and heal, preventing the wound from reopening and leading to complications.
The Fundamental Difference: Absorbable vs. Non-Absorbable
Sutures are broadly classified into two categories based on how they interact with the body over time. Absorbable sutures are designed to lose their tensile strength and eventually dissolve within the body, eliminating the need for manual removal. The body’s natural processes, primarily hydrolysis or enzymatic action, break down these materials into smaller, excretable compounds.
Non-absorbable sutures are made from materials that resist biological degradation and remain intact indefinitely, or for a period much longer than required for healing. These sutures must either be manually removed after the wound has closed, such as with skin stitches, or remain permanently encapsulated within the body’s tissues when used internally. Surgeons choose between the two types based on the healing time of the tissue being closed; fast-healing internal layers often receive absorbable materials, while slow-healing or high-tension areas require non-absorbable support.
Dissolving Stitches: Common Absorbable Materials
The breakdown of synthetic absorbable sutures occurs mainly through hydrolysis, a chemical reaction where water molecules penetrate the polymer structure and break the chemical bonds. This process leads to a gradual, predictable loss of strength and mass until the material is completely metabolized and eliminated by the body. Natural absorbable materials, conversely, are typically degraded by the body’s enzymes and absorbed through macrophage activity and phagocytosis.
Chromic or Plain Catgut is a natural absorbable suture derived from purified collagen. It is a monofilament material absorbed by enzymatic action, which can lead to an unpredictable absorption rate and greater tissue reaction compared to modern synthetics. Chromic Catgut is sometimes chosen for tissues that heal quickly, such as in the gastrointestinal tract, and is treated with chromic salts to slow its degradation.
Polyglycolic Acid (PGA), one of the earliest synthetic absorbable polymers, is a homopolymer of glycolic acid, often formed into a braided, multifilament structure. It loses most of its strength within two to three weeks, with complete absorption occurring over two to four months via hydrolysis. Polyglactin 910, a copolymer of glycolic acid and lactic acid, is another popular braided synthetic that offers excellent handling and reliable absorption profiles.
Polydioxanone (PDS) is a synthetic monofilament polymer that provides much longer tensile strength retention, with significant strength remaining after six weeks. This slow-absorbing property makes PDS a preferred choice for closing tissues that heal slowly or require extended support, such as fascia in abdominal closures. Polyglecaprone (Monocryl) is a synthetic monofilament absorbed more rapidly than PDS, making it useful for soft tissue approximation, particularly for subcuticular skin closures.
Permanent Stitches: Common Non-Absorbable Materials
Non-absorbable sutures are used when prolonged or permanent tissue support is required, or for external skin closures that will be manually removed. These materials are often classified by their physical structure: monofilament sutures are a single strand, while multifilament (braided or twisted) sutures consist of multiple strands woven together. Monofilaments, such as Polypropylene, pass through tissue with less drag and have a lower risk of harboring bacteria, but they are stiffer and harder to knot securely.
Polypropylene, commonly known as Prolene, is a synthetic monofilament with high tensile strength and minimal tissue reactivity. It is chemically inert and retains its strength indefinitely, making it a standard for cardiovascular surgery and vascular anastomoses. Nylon, a polyamide polymer, is another synthetic monofilament often used for skin closure and microsurgery due to its smooth passage through tissue, though it can gradually lose some tensile strength over time if buried.
Polyester sutures are synthetic multifilament materials that exhibit high tensile strength, used in procedures requiring very long-term support, such as orthopedic repairs and cardiac valve placement. Silk, a natural multifilament material, offers exceptional handling and knot security, which makes it easy for surgeons to work with. Although categorized as non-absorbable, silk loses significant tensile strength over time and is eventually absorbed by the body, typically over several years, and is primarily used in mucosal or dental surgeries.
Metallic sutures, most notably 316L stainless steel, are the strongest and least reactive of all non-absorbable materials. Stainless steel is available in both monofilament and multifilament forms and is reserved for high-stress applications, such as closing the sternum after open-heart surgery or certain orthopedic procedures. These materials provide permanent support where high tension and strength are required.