Suture Materials, Needles, and Basic Wound Closure Concepts

Suture Materials, Needles, and Basic Wound Closure Concepts

As a veterinary technician or assistant, you will handle suture materials and instruments daily. While independent suturing is outside the scope of practice for assistants and is delegated by the supervising veterinarian for technicians, understanding suture classification, needle types, and closure patterns is essential for efficient surgical assist, correct instrument passing, and patient safety.

Classifying Suture Materials

Every suture is described by three properties: absorbability, origin, and structure.

Absorbability

Absorbable sutures are broken down by the body — either by hydrolysis (synthetic materials) or by enzymatic digestion (natural materials). They are used in tissue layers that heal relatively quickly and where a permanent foreign body would be harmful: subcutaneous tissue, muscle, mucosa, and internal organ repairs. Common examples include:

• Polyglactin 910 (Vicryl®) — synthetic, braided; loses most tensile strength within about 3–4 weeks; fully absorbed by 56–70 days.
• Poliglecaprone 25 (Monocryl®) — synthetic, monofilament; loses tensile strength faster than polyglactin 910; absorbed in approximately 90–120 days; excellent for subcuticular closures.
• Chromic gut — natural (collagen from sheep or cattle submucosa), treated with chromium salts to slow absorption; digested enzymatically; more tissue reaction than synthetic options.

Non-absorbable sutures remain in tissue indefinitely or are removed after healing. They are used for skin closures (removed at 10–14 days), orthopedic repairs, cardiovascular work, and situations requiring permanent support.

• Nylon (Ethilon®, Dermalon®) — synthetic, monofilament or multifilament; low tissue reactivity; standard for skin closure.
• Polypropylene (Prolene®) — synthetic, monofilament; very low tissue reactivity; used in cardiovascular and ophthalmic surgery.

Origin

Sutures are either natural (derived from biological tissue — gut, silk, cotton) or synthetic (polymer-based — nylon, polyglactin, polypropylene). Synthetic sutures generally produce less tissue inflammation and have more predictable tensile strength loss.

Structure

Monofilament sutures are a single strand. They pass through tissue smoothly and harbor fewer bacteria, making them preferable in contaminated or potentially infected wounds. They require more throws per knot to prevent slippage.

Multifilament (braided or twisted) sutures handle and tie easily, hold knots well, but their interstices can harbor bacteria — a critical safety concern. Braided non-absorbable sutures should not be used in contaminated or infected wounds because the wicking action promotes bacterial colonization.

Needle Types

Surgical needles are almost always swaged (permanently attached to the suture) to minimize tissue trauma. The needle has three parts: the swage point, body, and tip. The cross-section of the body tells you the needle type:

• Cutting needle — triangular cross-section with the cutting edge on the inside curve; cuts through tough tissue like skin; higher risk of tissue tear-through.
• Reverse-cutting needle — triangular cross-section with the cutting edge on the outside curve; stronger than cutting needle; preferred for skin, ligaments, and oral mucosa because the suture is less likely to pull through.
• Taper (round) needle — round cross-section; separates tissue fibers rather than cutting; used in fascia, muscle, subcutaneous tissue, and viscera (intestine, bladder) where a clean hole and minimal cutting is desired.
• Taper-cut needle — taper body with a cutting tip; a compromise for dense tissues like tendon or uterus.

Always confirm the needle type before passing instruments to the surgeon — handing a cutting needle when a taper is requested can damage delicate visceral tissue.

Suture Size

Size is expressed in the USP system (0, 1, 2 for larger; 2-0 [2/0], 3-0, 4-0 … for smaller). Smaller numbers (e.g., 4-0 or 5-0) mean a finer suture. Select size based on the strength needed and the tissue involved: fine sutures (4-0 or smaller) for delicate structures, heavier sutures (0 or 1) for fascia or orthopedic repair. Following the surgeon's preference card or veterinarian instructions is essential.

Common Closure Patterns

Appositional patterns bring wound edges together without inverting or everting them — used for skin and many soft tissue layers.

• Simple interrupted — individual throws; if one fails the rest hold; easy to adjust tension; most commonly used pattern.
• Simple continuous (simple running) — one unbroken strand; faster than interrupted; if the strand breaks or a knot fails, the entire line is compromised.

Inverting patterns turn tissue edges inward — used for hollow viscera (stomach, intestine, bladder) to create a watertight seal and reduce leakage risk.

• Cushing and Lembert — common inverting patterns for GI and bladder closures.
• Cruciate (cross) mattress — provides broad tissue apposition; can be used in skin under tension.

Subcuticular (intradermal) — a running pattern placed within the dermis; suture ends buried; cosmetically excellent; eliminates need for skin staple or suture removal in some patients. Poliglecaprone 25 is frequently chosen for this pattern.

Safety Principles

• Never use braided non-absorbable suture in a contaminated or infected wound. Bacterial wicking increases infection risk.
• Sharps safety — needles are sharps. Count all needles at the start and end of a procedure. Never recap by hand. Dispose in an approved sharps container.
• Scope of practice — placing sutures in tissue is the veterinarian's or, where delegated by state practice act, the credentialed veterinary technician's task. Veterinary assistants do not independently suture. Know your state's veterinary practice act.
• Labeling — if suture packets are opened and staged, label them clearly so the correct material reaches the surgeon.
• Sterility — inspect every packet for integrity before opening onto the sterile field. A compromised package is discarded regardless of expiration date.