A simple interrupted suture, the most common and versatile closure technique, involves driving a curved needle through both sides of a wound at a 90-degree angle, then securing the thread with a square knot. The process has several distinct phases: preparing the wound, numbing the area, placing stitches at even intervals, tying each knot flat, and cutting the thread. Below is the full sequence from setup to aftercare.
When Sutures Are the Right Choice
Not every wound needs stitches. Sutures are the best option for wounds that need multi-layer closure, require debridement of damaged tissue, or sit in areas of high skin tension like joints or the back. Skin adhesive glue works well for smaller, low-tension cuts on the face, shins, or hands, particularly in children. Staples are efficient for thick skin on the scalp, trunk, or extremities but should not be used on the face, neck, hands, or feet. Adhesive strips can handle small, shallow cuts where the edges already line up neatly, though they lack the holding strength of sutures and are more likely to come apart.
Gather Your Instruments
A basic suture kit includes a needle driver (the clamping tool that grips and rotates the needle), toothed forceps for gripping skin edges, and fine scissors for cutting thread. Toothed forceps, sometimes called Adson forceps, have small teeth at the tip that grip dense tissue without slipping. Iris scissors, originally designed for eye surgery, are small enough to make precise cuts on fine suture material.
You will also need antiseptic solution, sterile gloves, sterile drapes, gauze, a syringe with local anesthetic, and the suture material itself.
Choosing Suture Size and Material
Suture thread is numbered by thickness: smaller numbers mean thicker thread, and higher numbers (with a “-0” suffix) mean finer thread. The location of the wound determines which size to use.
- Face, forehead, nose, eyelid: 6-0 (very fine thread that minimizes scarring)
- Eyebrow: 5-0 or 6-0
- Scalp: 4-0 or 5-0, or staples
- Chest, abdomen, back: 4-0 or 5-0
- Arms and legs: 4-0 or 5-0
- Hands: 5-0
- Feet and joints: 4-0
Non-absorbable suture (typically nylon) is standard for skin closure on most of the body. Absorbable suture is preferred for facial repairs in children, since it dissolves on its own and avoids a potentially difficult removal visit. Fast-absorbing gut in 5-0 or 6-0 is a common choice for ears, eyelids, eyebrows, nose, lips, and face when removal may be challenging.
Preparing the Wound and Sterile Field
Clean the wound thoroughly with irrigation, typically using saline under gentle pressure to flush out debris. Clean the surrounding skin with antiseptic solution, working outward from the wound edges. Put on sterile gloves and lay sterile drapes around the wound to create a clean working area. Set up your instruments on a sterile surface as close to the start of the procedure as possible, and do not leave the field unattended once it is open.
Numbing the Area
Local anesthetic, most commonly lidocaine in a 1% or 2% solution, is injected into the tissue around the wound edges. The maximum safe dose of plain lidocaine is 4.5 mg per kilogram of body weight. When lidocaine is mixed with epinephrine (which constricts blood vessels, slows bleeding, and extends the numbing effect), the maximum rises to about 7 mg per kilogram. Inject slowly through the wound edges rather than through intact skin to reduce the sting. Wait a few minutes for full effect before placing any stitches.
Placing a Simple Interrupted Suture
Load the curved needle into the needle driver by clamping it about one-third of the way back from the tip, with the needle point curving away from you. Hold the forceps in your non-dominant hand to gently stabilize the skin edge.
Step 1: Enter the Skin
Pierce the skin at a 90-degree angle, about 3 to 5 mm from the wound edge. The exact distance depends on skin thickness and wound tension. The key principle is that the needle enters perpendicular to the skin surface, not at a slant.
Step 2: Follow the Curve
Rotate your wrist smoothly so the needle follows its own curvature through the tissue. Do not push the needle straight through, as this tears tissue and creates an irregular path. The bite should go deep enough that the tissue depth is greater than the horizontal distance from the entry point to the wound edge. This flask-shaped bite is what produces proper wound eversion.
Step 3: Cross the Wound and Exit
The needle should emerge from the deep tissue on the opposite side of the wound, passing through and exiting the skin at the same 90-degree angle. The exit point should be the same distance from the wound edge as the entry point. Match the depth on both sides so the wound edges sit evenly when tied.
Step 4: Pull the Thread Through
Release the needle from the driver, then re-grasp the needle tip to pull it and the thread through. Leave a short tail of about 2 to 3 centimeters on the entry side.
Tying the Instrument Square Knot
The knot is what holds each stitch in place. An instrument tie uses the needle driver to form the knot, which saves suture material and gives precise control.
Hold the long end of the thread (attached to the needle) in your non-dominant hand. Lay both strands out so they form a V shape with the wound at the point. Place the needle driver in the center of that V.
For the first throw, wrap the long strand over and around the tip of the needle driver twice. This double loop is what makes the first throw a “surgeon’s throw,” which holds tension while you complete the knot. With the needle driver still wrapped, open its jaws, grasp the short tail, and pull it through the loops. Lay the knot flat by crossing your hands: the hand holding the long strand moves to the side where the short tail was, and vice versa.
For the second throw, reset your V shape (the strands will have swapped sides). Place the needle driver in the center again, but this time wrap the long strand around it only once, and in the opposite direction from the first throw. Grab the short tail through this single loop and lay it flat by pulling in the opposite direction from the first throw. This opposing direction is what creates a true square knot. If both throws go the same direction, the knot slips.
The finished knot should sit snugly against the skin without blanching or compressing the tissue. Pull just tight enough to bring the wound edges together.
Spacing and Repeating Stitches
Cut the thread, leaving tails of about 5 mm for easy removal later. The spacing between each suture should roughly equal the distance from the needle entry point to the wound edge. If your stitches enter 4 mm from the edge, place the next stitch about 4 mm further along the wound. This even spacing distributes tension and produces a cleaner closure.
Work from one end of the wound to the other, or start at the midpoint and bisect each remaining gap. The bisection method helps distribute tension evenly along the full length of the wound, which is especially useful for longer lacerations where the edges may not line up perfectly.
The Vertical Mattress Suture
Some wounds need more help everting their edges, particularly on concave surfaces, the back of the neck, or the groin where skin tends to roll inward. The vertical mattress suture handles this by making two passes through the tissue in a “far-far, near-near” pattern.
First, take a wide, deep bite 4 to 8 mm from the wound edge, passing well below the deepest skin layer and exiting the same distance from the opposite edge. Before tying, reverse the needle in the driver so it faces back toward the starting side. Now take a second, shallow bite only 1 to 2 mm from the wound edge, passing through just the upper layer of skin at about 1 mm depth. Both ends of the thread end up on the same side, where you tie the knot just as you would for a simple interrupted suture. The deep pass provides strength, while the shallow pass lifts and everts the edges.
Aftercare and Removal Timeline
Keep the sutured wound clean and dry for the first 24 to 48 hours. After that, gentle washing with soap and water is typically fine. Apply a thin layer of petroleum-based ointment and a clean bandage to keep the area moist, which promotes healing and reduces scabbing over the sutures.
Removal timing depends on location. Leaving stitches in too long increases scarring; removing them too early risks the wound opening.
- Face: 4 to 5 days
- Scalp: 7 to 10 days
- Arms and backs of hands: 7 days
- Chest, abdomen, or back: 7 to 10 days
- Legs and tops of feet: 10 days
- Palms, soles, fingers, or toes: 12 to 14 days
Signs of Infection After Suturing
Some redness and mild swelling immediately around the stitches is normal. Warning signs that suggest infection include increasing redness that spreads beyond the wound edges, worsening pain rather than improving pain, cloudy or foul-smelling drainage from the wound, warmth around the site, and fever. If the wound edges pull apart (dehiscence), the closure has failed and needs to be re-evaluated.