Absorbable sutures, commonly called dissolvable stitches, are specialized medical devices designed to close wounds temporarily before being metabolized by the body. These materials are crafted from natural substances, such as purified animal collagen, or synthetic polymers like polyglycolic acid. Their primary function is to provide tensile strength to hold tissue edges together during the initial phase of wound healing. Once the wound’s integrity is restored, the suture material is broken down through hydrolysis or enzymatic degradation. Failure of this absorption process leads to the retention of foreign material, which can result in various localized problems.
Normal Dissolution Timelines
The expected time frame for a dissolvable stitch to disappear is a broad range determined by the material composition. The timeline for the loss of tensile strength is much shorter than the time required for complete absorption. For example, fast-absorbing gut sutures may lose strength in 7 to 10 days, but full absorption can take up to four weeks.
Sutures placed close to the skin or mucous membranes generally dissolve faster due to increased moisture and cellular activity. Conversely, synthetic polymers like polydioxanone, often used for deep internal closure, are engineered for prolonged strength retention, sometimes lasting up to 180 days before being fully absorbed. The material choice is made to match the expected healing time of the tissue layer being closed, with most fully dissolving between 60 and 90 days. Complete disappearance can therefore range from a few weeks to several months.
Factors That Impede Absorption
When a dissolvable suture does not break down as expected, the cause often relates to the local biological environment or the material’s physical properties. One primary factor is a lack of sufficient blood flow, or ischemia, where the suture is placed. Since the body’s metabolic processes, including the hydrolysis that degrades synthetic sutures, rely on fluid transport, poor vascularity can significantly slow the rate of absorption.
Another element is the physical mass of the suture, particularly the knot. An excessively large or tight knot, especially when placed superficially, may resist degradation and remain as a palpable foreign body. The body’s immune system may react by encapsulating the foreign material in scar tissue, walling off the stitch from the enzymes and water necessary for its breakdown. Chronic infection and inflammation at the surgical site can also alter the chemical environment, interfering with the intended breakdown sequence. Individual patient metabolic variations also influence the pace at which the foreign material is processed.
Symptoms and Potential Complications of Retention
The most common sign of delayed absorption is “suture spitting,” where the retained stitch material is extruded through the skin surface. This presents as a visible thread or a palpable knot under the skin that causes localized irritation, mild redness, or discharge. While often benign, this extrusion indicates the body is actively trying to expel the foreign object.
More serious consequences develop when the body mounts a sustained inflammatory reaction, leading to a complication called a suture granuloma. A granuloma is a localized mass of immune cells and fibrous tissue that forms around the stitch to isolate it, presenting as a firm, tender lump at the incision site. This chronic inflammation can also lead to the formation of a sinus tract, which is a small tunnel extending from the retained suture to the skin surface. The tract may chronically discharge a clear or pus-like fluid, increasing the risk of persistent infection or abscess formation. Signs such as spreading redness, fever, or worsening pain require immediate medical evaluation, as they suggest a more severe infection.
Management and Removal of Undissolved Sutures
If a dissolvable stitch remains visible, palpable, or causes irritation beyond the expected healing window, professional medical assessment is necessary. Patients should avoid attempting to pull or cut the stitch themselves, as this risks reopening the wound or introducing bacteria. A healthcare provider can determine if the retained material is simply an external end that needs trimming or a more complex issue.
For exposed suture ends causing irritation, the procedure is often a simple snip or trim performed in an outpatient setting. However, if the retained suture has caused a granuloma or is deeply embedded, a minor surgical procedure may be required. This usually involves a small incision under local anesthesia to identify and excise the offending foreign material and any associated inflammatory tissue. Timely removal of the retained material typically resolves chronic inflammation and eliminates the risk of further complications.