A surgical suture, commonly known as a stitch, is a medical device used to hold body tissues together after an injury or a surgical procedure. Its function is to provide temporary mechanical support to the wound edges, keeping them approximated until the body’s natural healing processes create enough structural integrity for permanent closure. Modern sutures are crafted from a variety of materials, each engineered with specific properties to meet the demands of diverse tissues and surgical environments.
The Primary Distinction: Absorbable Versus Non-Absorbable Materials
Suture material is classified based on whether the body can break it down over time. Absorbable sutures lose their tensile strength and eventually dissolve within the tissue, eliminating the need for manual removal. This absorption occurs either through enzymatic degradation (for natural materials) or through hydrolysis (the more common breakdown mechanism for synthetic polymers). They are used for internal closures where temporary support, lasting from a few days to several months, is sufficient for the tissue to heal.
Non-absorbable sutures remain intact indefinitely within the body or are manually removed after the wound has healed. These materials resist both enzymatic breakdown and hydrolysis, maintaining their physical structure and tensile strength for a prolonged period. Surgeons select these sutures for skin closures requiring removal, or for internal structures needing permanent support, such as high-tension areas like fascia or securing a heart valve. In permanent internal applications, the body forms a layer of scar tissue around the inert material, effectively encapsulating it.
Categorization by Raw Material Source: Natural and Synthetic Sutures
Sutures are categorized by their chemical origin, which influences their performance and how the body reacts to them. Natural sutures are derived from biological sources and tend to elicit a greater inflammatory response as the body’s enzymes attempt degradation. Surgical gut, or catgut, is a natural absorbable material made from purified collagen of animal intestines, and its absorption time can be inconsistent due to the enzymatic process. Silk is a common natural, non-absorbable, braided fiber frequently used for securing surgical drains or in mucosal surfaces, despite causing higher tissue reaction.
Synthetic sutures result from chemical synthesis, offering more predictable performance and generally lower tissue reactivity. Within the synthetic absorbable category, materials like Polyglycolic Acid (PGA) and Polydioxanone (PDS) are widely used. PGA is a braided material absorbed by hydrolysis within a couple of months, while PDS is a monofilament that provides longer-term strength retention. Key synthetic non-absorbable materials include Nylon (Polyamide) and Polypropylene (Prolene). Both are known for their minimal tissue reaction and high tensile strength, making them popular choices for skin and cardiovascular surgery.
Structural Differences: Monofilament and Multifilament Sutures
The physical construction of the suture thread is independent of its chemical makeup or absorbability. Monofilament sutures consist of a single, smooth strand, allowing them to pass through tissue with minimal friction and reducing trauma. This structure also prevents the harboring of bacteria, making them the preferred choice in contaminated wounds where infection risk is elevated. However, monofilaments are associated with greater material memory (retaining the spool’s shape) and can have poor knot security, sometimes requiring more throws to prevent slippage.
Multifilament sutures, also known as braided sutures, are composed of multiple fine filaments twisted or woven together. This construction provides superior flexibility and handling characteristics, making them easier to tie secure knots that hold well under tension. While offering better handling, the braided structure creates tiny spaces between the fibers that can harbor microorganisms and wick fluid along the suture’s length. Therefore, many multifilament materials are coated to reduce this wicking effect and minimize the sawing damage caused by the rough surface passing through tissue.
Factors Guiding Material Selection for Specific Procedures
The choice of suture material is guided by the surgeon’s assessment of biological and mechanical factors specific to the procedure. The required duration of support is a primary consideration, which must match the tissue’s healing rate. For example, a slow-healing structure like fascia requires a long-lasting non-absorbable or slowly absorbed synthetic material, while tissues that heal quickly, such as the stomach or bladder lining, rely on rapidly absorbing sutures for temporary approximation.
The mechanical forces acting on the wound dictate the necessary tensile strength of the suture, ensuring the material can withstand the stresses of patient movement and internal pressure without breaking. The risk of infection also influences the decision, as monofilament materials are favored in contaminated wounds due to their lower propensity to harbor bacteria. Finally, the location of the closure (internal or external) and cosmetic concerns play a role, with finer, less reactive monofilaments often chosen for visible skin closures to minimize scarring and tissue reaction.