Surgical sutures are fundamental tools in medicine, used to close wounds and approximate tissues following injury or surgery. These threads come in a variety of materials, each with distinct properties for various medical applications. A common question is whether certain sutures are absorbed by the body over time. Silk sutures, with their long history of widespread use, often prompt this inquiry.
Defining Suture Absorbability
Sutures are broadly categorized based on their interaction with the body’s tissues. An “absorbable” suture is broken down and eliminated by the body’s natural processes. This breakdown typically occurs through hydrolysis, where water molecules attack the polymer chains, or through enzymatic degradation.
The purpose of absorbable sutures is to provide temporary wound support until the tissue regains sufficient strength. After this, the material disappears, removing the need for removal. Examples include natural products like catgut, or synthetics such as polyglactin 910 (Vicryl) and polydioxanone (PDS).
Conversely, “non-absorbable” sutures remain within the body indefinitely or until removed. These materials are chosen when long-term tissue support is required, or when placed externally for easy removal. Unlike absorbable sutures, non-absorbable materials do not significantly degrade or lose structural integrity. Common non-absorbable materials include synthetic polymers like nylon and polypropylene, natural fibers, or metallic wires like stainless steel. The choice between absorbable and non-absorbable sutures depends on the specific surgical need and the expected healing time.
Silk Sutures and Their Behavior
Despite originating from natural silkworm fibers, silk sutures are classified as non-absorbable. This classification means the body does not fully break down and eliminate silk material like it does with absorbable sutures such as Vicryl or PDS. While silk does not undergo hydrolysis or enzymatic degradation, it loses a significant portion of its tensile strength, typically within six months to two years after implantation. This reduction in strength means it no longer provides significant support to the healing tissue.
Following implantation, the body’s immune system recognizes the silk material, causing a mild inflammatory response. Over time, this response results in the encapsulation of the silk thread by fibrous connective tissue. This process walls off the foreign material, integrating it as an inert component. Although the silk thread remains, it becomes isolated and no longer provides wound closure strength. This encapsulation explains why silk is considered non-absorbable; it persists in the tissue rather than being fully metabolized and cleared.
Specific Uses of Silk Sutures
Even though silk sutures are non-absorbable and lose tensile strength, they remain useful due to several advantageous properties. Silk is valued for its excellent handling characteristics, offering a smooth feel and reliable knot security. Its pliability allows for easy manipulation and tying, beneficial in intricate surgical fields. Silk sutures exhibit high initial tensile strength, providing strong immediate wound approximation.
These properties make silk suitable for specific applications where its characteristics outweigh the need for eventual absorption. For instance, silk is frequently used for skin closure where sutures will be removed after healing. Its ease of handling and secure knotting are advantageous in the ligation of blood vessels, where a permanent tie-off is required. In specialized fields like ophthalmology or dentistry, silk may be chosen for procedures needing a semi-permanent or permanent suture, or where ease of handling is important for precise placement.