Sutures & Tying Techniques

01 Principles Before Pattern

Every stitch below is a variation on the same handful of goals: approximate the wound edge, evert slightly, distribute tension, and leave the least amount of foreign material behind that the job requires.

Knot vocabulary: half-hitch, square, hybrid, granny

Every knot in this guide is built from the same unit. The words below describe what you've actually tied, and whether it will hold.

A square knot can be converted into a slip knot after the fact simply by pulling one strand instead of both evenly. Even tension on both ends, every throw, is what keeps a square knot square.

02 One-Hand and Two-Hand Ties

Before instruments, learn the hand ties. Faster once fluent, and the only option when your driver is occupied or across the room. In two-handed tying, one hand does almost all the work: for a right-handed person, that's the left hand, which forms and delivers the loop, while the right hand mainly holds and repositions the strand.

Two-hand tie

1. Start with the strands already crossed, tying strand over the other, rather than parallel. A crossed start avoids tangling your hands and keeps the field visible.
2. Drape the tying strand over the index finger of the tying hand, with its tail anchored against the palm by the ring finger. Hold the other strand in the opposite hand.
3. Loop the second strand under the tip of the tying hand's index finger, then bring thumb and index fingertip together to trap it.
4. Push the thumb up through the loop, catch the free end of the second strand between thumb and index tip, then push the index finger back down to deliver that end through the loop. This completes one throw.
5. Lay the throw down flat by crossing the hands, then repeat with the strands reversed (second strand now draped over the tying hand) so the second throw opposes the first.

Grip the strands at a distance from the knot that lets you form the loop without dropping tension, not so close that you can't fit a finger through, not so far that you lose feel for how snug the throw is. Losing tension mid-throw is how "air knots" happen: the loop closes on itself before it ever reaches the tissue.

One-hand tie

1. Hold the long strand draped across the palm of one hand, with the short strand hanging free in front.
2. Flex the middle finger over the long strand to catch it, forming a loop, while the thumb and index finger control the short strand's position.
3. Walk the loop off the middle finger, past the short strand, and cinch by pulling both ends apart along the wound axis.
4. Repeat with the loop-forming motion reversed for the next throw. Fastest tie available once automatic, and the standard for deep or narrow spaces where a two-hand tie won't fit.

Hand ties use more suture length per throw than instrument ties. In a field or resource-limited setting where material is scarce, default to the instrument tie instead.

03 The Instrument Tie

The square knot is the currency every pattern below spends. Learn it one-handed, two-handed, and with instruments until it's boring. Instrument ties are the go-to whenever suture material is short or wound closure is the job: they conserve suture (up to ten instrument-tied knots from an 18-inch length, versus one to three hand-tied) and they're fast.

1. Place the stitch and pull the suture through until the tail is 2 to 3 cm long. Drop the needle.
2. Hold the long end in the non-dominant hand and form a "V" with the wound at the point: the long end runs to one side, the short tail to the other.
3. Place the needle driver in the middle of the V. Wrap the long end twice over the top and around the tip of the driver, then grasp the short tail with the driver jaws and pull it back through.
4. Cross your hands (non-dominant hand crosses over the driver hand) to lay the first throw down flat.
5. For the second throw, the long end and tail switch sides of the V from throw one. Place the driver back in the center, wrap the long end around it once this time, grasp the tail, and lay it flat by moving the driver and long end apart in opposite directions.
6. Repeat for a third throw (single wrap, sides switched again) to lock it. Keep the driver parallel to the wound throughout, and always tighten by pulling away from the short end, never straight up off the tissue.

Keep the needle driver parallel to the wound. Roll the long strand over the driver toward the short end, then tighten by pulling away from the short end, not straight up. Leave the free tail about 2 to 3 cm, long enough to grasp without fumbling, short enough not to tangle.

Grasping too much or too little suture tail with the driver is the most frequent instrument-tie mistake: too long and it's cumbersome in a deep space, too short and you can't get a grip to pull it through. With monofilament, repeated grasping and bending at the same point with the driver's jaws can nick or weaken the strand; regrasp at a slightly different point each throw.

04 Simple Interrupted

The default stitch. Learn this one first because every pattern below is a modification of it.

1. Enter the needle perpendicular to the skin, 2 to 3 mm from the wound edge (wider for thicker or higher tension skin).
2. Pass through the dermis, curving under the wound base, and exit the opposite wound edge at the same depth and same distance from the edge.
3. Tie an instrument square knot (Fig. 1), snugging just enough to appose the edges with slight eversion, not enough to strangulate tissue.
4. Cut, leaving 3 to 4 mm tails. Repeat, spacing subsequent stitches roughly the width of one bite apart.

Angle the needle slightly outward and down as it enters, away from the wound edge, rather than straight down toward it. Followed through its own curvature, this produces the wide-based flask shape in Fig. 2, not a shallow arc, and the flask shape is what everts the edge.

05 Vertical Mattress

A far-far, near-near stitch. Reach for it when a simple interrupted keeps inverting, or when you need extra eversion on thin, lax skin.

1. Far-far pass: enter 6 to 8 mm from the wound edge, pass deep through the dermis, exit the opposite side at the same distance and depth. Don't tie yet.
2. Near-near pass: reverse direction. Re-enter the skin 1 to 2 mm from the wound edge on the side you just exited, take a superficial bite, and exit the original side at the same narrow distance.
3. Tie the knot to one side of the wound, away from the incision line, with adequate eversion but no strangulation.

Far-far, near-near, opposite direction each pass. If you cross the wound the same way twice, the geometry collapses.

06 Horizontal Mattress

Two parallel bites side by side rather than stacked. Best reserved for high tension wounds or fragile, friable edges where you need to buy time, not necessarily precision.

1. Enter 5 mm to 1 cm from the wound edge, pass deep through the dermis, exit the opposite edge equidistant.
2. Re-enter the skin on that same opposite side, 5 mm to 1 cm lateral to the exit point, and pass back across the wound at the same depth, exiting near the original entry point's side.
3. Tie, leaving two parallel horizontal loops flanking the wound. Watch tension: this pattern crosshatches easily, so remove early if cosmesis matters.

07 Running (Continuous) Suture

Fast closure for long, low-tension, well-approximated wounds. One knot at the start, one at the end, nothing but speed in between.

1. Place a single simple interrupted stitch at one end of the wound and tie, but do not cut the long end.
2. Advance the needle in a continuous spiral: enter one side, cross under the wound, exit the other side, and re-enter directly across without cutting between passes.
3. Keep bite spacing and depth consistent; this pattern distributes tension evenly only if every pass matches the last.
4. At the far end, tie off using the last loop as your tail (a "loop-to-strand" tie), and cut.

A running suture is one continuous strand: cut it anywhere and the whole line loosens. Use it only where the wound has minimal tension and reliable edges.

08 Subcuticular (Running Intradermal)

The cosmetic closure. No visible cross marks, no suture removal if absorbable material is used. Slower to place, best result on a face or any high-visibility line.

1. Anchor the first bite at one apex of the wound, buried, with the knot tucked below the dermis.
2. Advance horizontally within the dermal layer just below the epidermis: enter one side, take a short horizontal bite, exit, then cross to the same depth on the opposite side without ever surfacing.
3. Alternate sides in a zigzag, keeping every bite at the same dermal depth so the skin lies flat once tightened.
4. Exit at the far apex, tension gently to approximate, and either tie buried (absorbable) or leave a small external loop to snip out later (nonabsorbable, monofilament).

09 Less Common Sutures

Patterns you won't reach for daily, but that solve a specific problem better than anything above when that problem shows up.

Half-buried (tip) horizontal mattress

Used for closing the tip of a V-shaped or angled skin flap (stellate lacerations, flap avulsions). The needle passes full thickness through the two wound bases but only partial thickness, buried, through the flap's tip, so the delicate point of the flap never takes a surface bite that could strangulate its blood supply.

Purse-string suture

A continuous circular stitch placed around a round defect, then cinched down like closing a drawstring bag. Used to close small circular wounds (punch biopsy sites, drain exit sites) or to secure a catheter or tube at a skin entry point.

Figure-of-eight

A crossing, figure-8 shaped stitch placed over a discrete bleeding point (a scalp vessel, a bleeding tonsillar bed). It compresses the vessel from two directions at once. Faster than isolating and ligating the vessel individually when the bleeding source is small and superficial.

Pulley stitch (near-far, far-near modification)

A modified vertical mattress that adds mechanical advantage: after the first far-far pass, the suture is looped back through the original entry loop before the near-near pass, creating a pulley effect that lets you close wounds under tension that would otherwise tear through a standard mattress stitch. Reach for it on high-tension extremity wounds where you're buying time before definitive closure.

Retention sutures

Heavy-gauge (0 or #1), widely spaced sutures placed through the full abdominal wall thickness, well lateral to a laparotomy incision, often bolstered with a bridge or bolster to prevent the suture from cutting through skin. Used to reinforce a closure at high risk of dehiscence: malnutrition, obesity, prior wound infection, emergent re-exploration. Not a routine closure. It's a backup system for a wall that might fail.

10 Less Common Knots

Variations on the square knot for situations the standard three-throw tie doesn't handle well.

Surgeon's knot

Identical to the standard instrument tie, except the first throw is wrapped twice around the driver instead of once. The extra friction holds the first throw in place under tension while you form the second throw, which matters when you're tying under load (deep tissue, high-tension skin) and a standard first throw would loosen before you can lock it down. Subsequent throws revert to single wraps, alternating direction as usual.

Terminology overlaps here depending on where you trained: some curricula teach the doubled first throw as the routine instrument tie by default, since the extra friction rarely hurts and often helps (see Section 03). Others reserve two wraps specifically for the term "surgeon's knot" and default to a single-wrap first throw otherwise. If both half-hitches of a surgeon's-style first throw are doubled and opposed, that's sometimes called a double-double knot; it adds friction on both sides but also adds bulk, so reach for it only when tension genuinely demands it.

Aberdeen knot

The finishing knot for a running suture, used instead of tying the final loop to the strand directly. Form a series of slip-knot loops, each pulled through the last (like a crochet chain), then pass the tail fully through the last loop and cinch. Testing to failure has found three throws with two turns to be the strongest reliable configuration; fewer than three tends to slip, and more adds bulk without adding strength. It locks flat, uses less material than repeated square knots, and is the standard way to finish a running subcuticular closure.

Slip knot

A single throw tied so it slides along the strand under tension rather than locking, used to snug down the first throw of a knot in a deep or narrow space before locking it with a proper square throw on top. Common in laparoscopic and deep cavity closures where you can't get a finger down to the tissue to hold tension by hand. Never leave a slip knot as the final throw; it must always be capped with at least one square throw or it will back out.

11 Needle Selection: Curved vs. Keith (Straight)

The needle shape changes how you hold it, how much space you need, and what it's actually for. Reaching for a curved needle out of habit when a straight one is the right tool costs time and control.

Practical differences that matter

1. Instrumentation: a curved needle is designed for a needle driver; grabbing it with fingers is awkward and imprecise. A Keith needle is designed to be gripped and pushed by hand, though a driver can still be used to finish a pass in tight tissue.
2. Path predictability: the curved needle's arc gives a fixed, repeatable path once you match your wrist rotation to its radius. The Keith needle only goes where you point it in a straight line, so bite depth and angle are entirely on the operator with no geometry to fall back on.
3. Space requirements: curved needles work in confined or deep spaces because the arc lets them turn a corner inside the tissue. A straight needle needs a clear straight shot, which is why it's a poor choice for anything deep or angled.
4. Needlestick risk: passing a Keith needle by hand puts fingers directly in the needle's path in a way an instrument-driven curved needle does not. Use forceps to control the far side of a Keith needle pass whenever possible.
5. Typical role: curved needles do the bulk of the closure work in this guide, from simple interrupted through subcuticular. Keith needles show up specifically for retention suture bolsters, purse-string anchoring around tubes and drains, and any pass where you need to push straight through skin without maneuvering around a curve.

12 Quick Reference