Dissolvable, or absorbable, stitches are specialized threads designed to close wounds and internal incisions without requiring removal. They are made from materials the body naturally breaks down and metabolizes over time. These sutures are widely used for internal closures, deep tissue layers, and in areas where removing traditional stitches would be inconvenient, such as the mouth or in young children. Failure to dissolve as expected defeats their purpose and is a source of concern.
How Absorbable Sutures Should Dissolve
The body breaks down absorbable sutures through a controlled biological process, primarily relying on hydrolysis. This chemical reaction involves water molecules penetrating the polymer chains of the suture material, slowly breaking the chemical bonds. Synthetic materials like polyglactin 910 (Vicryl) and polyglycolic acid (PGA) are designed to degrade via this predictable hydrolysis mechanism.
Natural sutures, such as catgut, use enzymatic degradation, where the body’s enzymes attack the material, leading to a less predictable absorption rate. The timeline for complete dissolution varies significantly by material, ranging from a few weeks to several months. Fast-absorbing materials may disappear in 10 to 21 days, while polydioxanone (PDS) can take up to 210 days to fully absorb, allowing for prolonged tissue support.
Factors That Cause Dissolution Failure
When absorbable sutures fail to dissolve on schedule, the cause relates to the local biological environment or the material properties. A frequent factor is the physical properties of the suture material, such as a diameter that is too large or a material type that is too strong for the implantation site. Robust materials require a longer duration for water penetration and bond breakdown, slowing the hydrolysis process.
Poor blood supply or low tissue reactivity at the wound site can impede the delivery of fluid and cellular components required for degradation. Sutures placed in areas with lower vascularity, such as fascial layers, dissolve slower than those in highly vascularized tissues. Sutures placed too superficially may also fail to absorb fully because they lack sufficient exposure to deep tissue fluids necessary for hydrolysis. While infection often accelerates breakdown, excessive or chronic inflammation can create a dense, fibrous capsule around the material, preventing the necessary water penetration and enzymatic access for proper dissolution.
Recognizing Symptoms of Retained Sutures
The most direct symptom of dissolution failure is the visible presence of the suture material long after the expected healing period. The thread or knot may remain visible on the skin’s surface or begin to protrude through the healed incision line, a phenomenon called a “spitting suture.” The material may appear as dark or colored fragments, depending on the dye used.
The body’s immune response to the foreign material can manifest as localized inflammation, presenting as persistent redness, swelling, or tenderness around the suture line that does not improve. In some cases, the body attempts to contain the material by forming a small, firm, and often painful lump called a foreign-body granuloma. The body may also try to expel the retained material, which can lead to a chronic, localized draining wound or a sinus tract that persists after the initial incision has healed.
Necessary Steps for Medical Removal
If dissolution failure is suspected, a medical professional must first confirm the presence of retained material through visual inspection or imaging like an ultrasound for deeper sutures. Once identified, the treatment plan focuses on removal and managing any residual inflammation or infection.
For superficial sutures or those spitting through the skin, removal is often a simple, quick in-office procedure. The physician uses sterile forceps to gently pull the exposed material and snip the thread close to the skin line, removing the undissolved segment. Deeper sutures that have caused a granuloma or a persistent draining tract may require a minor surgical procedure called an excision. This procedure removes the encapsulated suture material and surrounding inflamed tissue, eliminating the source of chronic irritation. Following removal, any resulting infection or inflammation is treated with localized wound care or a short course of antibiotics to ensure the wound closes cleanly.