Surgical sutures, commonly known as stitches, are medical devices designed to hold body tissues together after injury or surgery, allowing the natural healing process to occur. These specialized threads provide mechanical support until the wound site gains enough strength to withstand tension independently. Material selection depends on the type of tissue, the tension on the wound, and the required duration of support. The fundamental choice is whether the suture will remain in the body permanently or dissolve harmlessly over time.
Absorbable Sutures: Materials Designed to Dissolve
Absorbable sutures are constructed from materials the body’s biological processes can break down and absorb, eliminating the need for manual removal. The most widely used types are synthetic polymers, which offer predictable strength loss and absorption rates. These include Polyglycolic Acid (PGA) and Polyglactin 910 (often known as Vicryl), which are copolymers providing temporary wound support for several weeks.
Synthetic absorbable sutures dissolve through hydrolysis, where water molecules break down the polymer chains into smaller, metabolizable compounds. Polyglactin 910, for instance, loses significant tensile strength within two to three weeks and is fully absorbed within 56 to 70 days. Polydioxanone (PDS) is a synthetic monofilament used when longer support is required, retaining strength for up to six weeks and taking up to 180 days for complete absorption.
Natural absorbable materials, such as Catgut (derived from animal intestines), are broken down by enzymatic degradation, which is less predictable than hydrolysis. Due to their consistent performance and minimal tissue reaction, synthetic materials have largely replaced natural options in modern surgery. Absorbable materials are preferred for internal closures, such as deep skin layers, internal organs, and blood vessel ligatures, where manual removal is impossible.
Non-Absorbable Sutures: Permanent Materials
Non-absorbable sutures resist breakdown by the body’s enzymes and fluids, providing long-term or permanent mechanical support. These threads maintain tensile strength and remain encapsulated by tissue if placed internally, or they must be manually removed if used for external skin closure. This durability makes them the material of choice for tissues that heal slowly or are subjected to constant, high mechanical stress.
Synthetic non-absorbable polymers are widely used for their strength and minimal tissue reactivity. Polypropylene (Prolene) is a common monofilament known for its chemical inertness, making it highly suitable for cardiovascular surgeries to secure vascular grafts and heart valves. Nylon, a strong and flexible polyamide, is frequently employed for skin closure, though it slowly loses tensile strength over time.
Natural materials in this category include Silk. Although classified as non-absorbable, silk is a braided protein fiber that slowly degrades over years, but its excellent knot security makes it useful for ligating blood vessels and in oral surgery. Polyester sutures, typically braided, offer superior strength and are commonly used in orthopedic procedures or for repairing tendons and ligaments requiring prolonged support.
Physical Forms: Monofilament and Braided
Sutures are defined by their physical construction, falling into two main categories: monofilament and braided. A monofilament suture consists of a single, uniform strand of material, resembling a fishing line. This smooth surface allows the suture to pass through tissue with minimal friction, a property known as low tissue drag, which reduces trauma and irritation to the wound.
The single-strand structure also prevents wicking or capillarity, where fluids and potential bacteria can travel along the thread into the wound site. This makes monofilaments, such as Nylon and Polydioxanone, the preferred choice for contaminated surgical fields where minimizing bacterial adherence is paramount. However, monofilaments are often stiffer, tend to return to their original coiled shape, and require more throws to secure a knot.
Braided, or multifilament, sutures are constructed by weaving or twisting multiple fine strands together, as seen in materials like Silk and Polyglactin 910. The textured surface provides superior handling and flexibility, making them easier for the surgeon to work with, and offers excellent knot security with fewer throws. The trade-off is that the braided structure increases friction as the thread passes through tissue, resulting in higher tissue drag. Furthermore, the microscopic spaces between the woven filaments can harbor bacteria, increasing the risk of infection in certain surgical contexts.