The simple interrupted suture is the most commonly used technique to close small, uncomplicated skin lacerations. Each stitch is placed and tied independently, which gives you precise control over tension and spacing. If one suture fails, the rest hold. Here’s how the technique works from start to finish.
When to Use a Simple Interrupted Suture
This technique is the default choice for most straightforward skin lacerations. It works well when wound edges come together without significant tension and when you need the flexibility to adjust spacing as you go. Wounds under high tension, such as those with tissue loss or extensive debridement, often benefit more from vertical or horizontal mattress sutures, which distribute force across a wider area. For long, straight wounds with minimal tension, a running (continuous) suture can save time, but you lose the safety net of independent stitches.
Equipment You’ll Need
- Needle holder: Clamps the curved suture needle and serves as your primary instrument for both placing stitches and tying knots.
- Tissue forceps: Used to gently grip and stabilize wound edges. Toothed forceps provide better grip on skin without crushing tissue.
- Suture scissors: For cutting suture material after each knot is tied.
- Suture material on a curved needle: The size depends on the body location. Finer sutures (5-0 or 6-0) are used on the face, where scarring matters most. Thicker sutures (3-0 or 4-0) are appropriate for the trunk, extremities, and areas under more tension.
For facial repairs, especially in children, absorbable sutures are often preferred because they dissolve on their own and spare the patient a removal visit.
Placing the Stitch
Load the needle into the needle holder about one-third to one-half of the way from the needle’s swaged (thread) end. Hold the needle holder like a pair of scissors or with your palm wrapped around it, whichever gives you stability.
Enter the skin perpendicular to the surface on one side of the wound. The needle should go in at a 90-degree angle to the skin, not at a slant. This is critical for what comes next: the bite needs to be wider at its deepest point than at the surface. Think of the needle path as a flask or pear shape, curving outward beneath the skin before coming back up. This geometry is what causes the wound edges to evert, or roll slightly outward, when you pull the suture tight.
Eversion is the single most important goal of suture placement. When wound edges evert slightly, they flatten naturally as healing progresses and the tissue contracts. If the edges sit flat at the time of closure, contraction will pull them inward and leave a depressed scar. If they invert (tuck under), the cosmetic result is even worse.
After passing through one wound edge, cross the wound and enter the opposite side from deep to superficial, mirroring the same flask-shaped path. The needle should exit the skin at the same distance from the wound margin as it entered on the first side. Symmetry matters: if you enter 3 mm from the edge on one side, you should exit 3 mm from the edge on the other.
The Spacing Rule
A useful principle governs both bite width and spacing. The distance between your needle entry point and the wound edge should roughly equal the spacing between adjacent sutures. So if you’re placing stitches 5 mm from the wound edge on each side, space them about 5 mm apart along the wound.
Deeper wounds require bites farther from the wound edge. This ensures you’re capturing enough tissue at depth to close the wound without leaving dead space underneath. A 2019 study found that placing sutures about 5 mm apart (high-density spacing) can improve early scar appearance, but spacing them about 10 mm apart reduces tissue trauma, leaves fewer puncture marks, and saves time. The right spacing depends on the wound’s location, depth, and tension.
Tying the Instrument Knot
Once the suture is through both wound edges, pull the thread until only a 2 to 3 cm tail remains on the entry side. Then drop the needle. The knot-tying sequence uses your needle holder as a tool to grab and pull the short tail.
Hold the long strand in your non-dominant hand. The long and short ends of the suture should form a V shape with the wound at the point. Place the needle holder in the center of that V. Wrap the long end of the suture over and around the tip of the needle holder twice (this double wrap is your first throw). Grab the short tail with the needle holder’s jaws and pull it through the loops. Lay the knot down flat by crossing your hands: the needle holder moves toward the short-tail side while your other hand pulls the long strand in the opposite direction.
For the second throw, reverse the direction. Wrap the long end around the needle holder once (a single wrap this time), grab the short tail again, and lay the knot flat by pulling in the opposite direction from the first throw. This creates a square knot, which lies flat and holds securely. If both throws are pulled in the same direction, you get a granny knot, which slips.
Most closures use a minimum of three throws for security. Cut both ends of the suture, leaving tails of about 3 to 5 mm so the knot doesn’t unravel but also doesn’t leave excessive material in the wound.
Common Mistakes to Avoid
The most frequent error is wound inversion, where the skin edges tuck downward instead of everting. This happens when the bite is too shallow or when the path of the needle doesn’t curve outward at depth. If you notice the edges pulling inward as you tighten, your needle trajectory needs adjustment.
Tying sutures too tightly is another common problem. Tissue swells after any procedure, and a suture tied snugly at the time of closure can strangle the tissue once edema sets in. You want the wound edges to be gently approximated, not compressed. The knot should bring the skin edges together without blanching (whitening) the surrounding skin.
Crosshatching, sometimes called “railroad tracks,” refers to the permanent marks sutures leave on either side of the scar. This happens when sutures stay in too long. The risk drops significantly with timely removal.
Suture Removal Timeline
How long sutures stay in place depends entirely on location. Areas with good blood supply heal faster and can have sutures removed sooner. Areas under mechanical stress need more time.
- Face and forehead: 5 days
- Ears, eyelids, eyebrows, nose: 5 to 7 days
- Scalp: 7 days
- Back: 7 to 10 days
- Extremities and hands: 7 to 10 days
- Chest and abdomen: 12 to 14 days
- Feet and soles: 12 to 14 days
- Joints (extensor surface): 10 to 14 days
Leaving sutures in beyond these windows increases the risk of permanent suture marks. Removing them too early risks the wound reopening.
Caring for the Wound Afterward
Keep the sutured area clean and dry for the first 24 to 48 hours. After that initial window, gently wash around the site once or twice daily with cool water and soap. Clean close to the stitches, but don’t scrub or rub them directly. Pat the area dry with a clean towel rather than rubbing. Replace any bandage with a fresh one as directed.
Minimize activity that could pull on the wound or reopen it. The goal is to keep the edges still and protected while the tissue bridges the gap underneath. Signs of infection to watch for include increasing redness, warmth, swelling, or drainage from the wound site after the first day or two.