Correct Answer: D. Monofilament
Polydioxanone (PDO, brand name Ethicon PDS II) is a monofilament synthetic absorbable suture composed of a homopolymer of dioxanone. The key discriminating feature is its monofilament structure—it consists of a single continuous strand of polymer, which confers several clinical advantages: superior tensile strength, lower tissue reactivity, and reduced bacterial colonization compared to braided materials. PDO is absorbed through hydrolysis over 180–210 days, with 50% strength retention at 4 weeks and complete absorption by 6 months. In Indian surgical practice, PDO is widely used for subcuticular closure, fascial repair, and gynecological procedures where prolonged support is needed without permanent foreign body. The monofilament nature makes it less prone to harbor bacteria and causes less tissue drag during passage, reducing inflammation—a critical advantage in clean-contaminated cases common in Indian operating theatres with variable infection control resources.
Why the other options are wrong
A. Braided multifilament — This is wrong because PDO is explicitly a monofilament suture, not braided. Braided multifilament sutures (e.g., Vicryl, Dexon) have multiple strands twisted together, which increases surface area and bacterial adhesion. PDO's monofilament design is one of its key advantages—it reduces capillarity and tissue drag. NBE may trap students who confuse PDO with other absorbable sutures like Vicryl (polyglactin 910), which is braided. B. Non-absorbable — This is wrong because PDO is definitively absorbable, not non-absorbable. It undergoes hydrolytic degradation over 6 months, with complete absorption by 180–210 days. Non-absorbable sutures (nylon, polypropylene, silk) persist indefinitely in tissue. This is a fundamental property of PDO and a common NBE trap—students may confuse it with permanent sutures used in similar applications (e.g., polypropylene for fascial closure). C. Derived from collagen — This is wrong because PDO is a synthetic polymer (homopolymer of dioxanone), not derived from collagen. Collagen-derived sutures (e.g., catgut, Vicryl Rapide) are natural or semi-synthetic and have different absorption profiles and handling characteristics. NBE may set this trap to confuse students between synthetic absorbable sutures and natural/collagen-based materials, which have distinct immunogenicity and absorption kinetics.
High-Yield Facts
- PDO (polydioxanone) is a monofilament synthetic absorbable suture with 50% strength at 4 weeks and complete absorption at 6 months.
- Monofilament structure of PDO reduces bacterial colonization, tissue drag, and inflammatory response compared to braided sutures.
- PDO absorption occurs via hydrolysis (not enzymatic), making it predictable and independent of tissue enzymes—critical in immunocompromised Indian patients.
- Common Indian applications: subcuticular skin closure, fascial repair, gynecological procedures, and ophthalmic surgery where prolonged support without permanent foreign body is needed.
- Comparison: Vicryl (braided, 60–90 days) vs. PDO (monofilament, 180 days)—PDO preferred for deeper layers needing longer support.
Mnemonics
PDO = Persistent Dioxanone Overkill Monofilament → Minimal bacterial adhesion; Absorbable → Hydrolysis over 6 months; Synthetic → Predictable degradation. Use when comparing PDO to braided or collagen-based sutures. MONO-PDO Rule MONOfilament + Persistent (6 months) + Synthetic = PDO. Helps distinguish from Vicryl (braided) and catgut (collagen).
NBE Trap
NBE pairs PDO with braided sutures (Vicryl) to trap students who know PDO is absorbable but confuse its structural form. The monofilament property is the discriminating feature that separates PDO from other absorbable materials in Indian surgical practice.
Clinical Pearl
In Indian teaching hospitals, PDO is the preferred choice for fascial closure in abdominal surgery because its monofilament structure and 6-month absorption profile provide adequate support during wound healing while minimizing chronic inflammation—especially important in patients with delayed wound healing or malnutrition, common in our population.
_Reference: Bailey & Love Ch. 5 (Surgical Materials); Robbins Ch. 3 (Tissue Repair)_