09.03 Suturing Techniques - Simple Interrupted Sutures
Inserting each suture correctly is the key to good wound closure. Here you will learn how to place a suture and how to avoid damage to the wound edges.
You should be familiar with how to use the needle holder and suture needle to insert a suture with minimal tissue damage.
This module covers simple interrupted, continuous, subcuticular, mattress and pulley sutures and has plenty of tips on how to overcome common problems.
In this module
09.03 Simple Interrupted Sutures
Simple interrupted sutures are suitable for most wound closures. A series of independent sutures brings the wound edges gently together. The needle takes an adequate bite on each side of the wound, passing through all layers of the skin.
Sutures should be placed at regular intervals and should not be tied too tightly.
09.03.01 Principles Video 1
An instrument-tied knot is generally recommended for simple interrupted sutures. For optimum security, use a surgeon's knot, rather than a standard reef knot. This variant to the reef knot involves taking the suture twice around the needle holder for the first throw only.
If the wound is short and the sides of equal length, start suturing at one end and go to the other.
If the wound is long or the sides are unequal, use 'progressive halving'. Find the midpoint of each side of the wound and insert your first suture. Then insert sutures at the midpoint of each of the two resulting halves. Repeat this process along the whole wound. The extra length of the longer side is distributed equally along the wound. Even fairly large discrepancies become unnoticeable.
09.03.02 Principles Video 2
Aim to make the distance between sutures about the same as the distance between the wound edge and the point at which the needle enters or leaves the skin. This is usually between 3 and 5 mm.
Allow for postoperative swelling of the wound edge and do not tie the sutures tightly. The skin edges should come together without bunching up and the sutures should be tied so that there is room for closed forceps to get under them.
The finished result should look neat and symmetrical. Suture ends should be cut about 0.5cm long to allow enough length for grasping when removing.
09.03.03 Principles Video 3
Although we recommend you generally tie your interrupted sutures with an instrument, there will be occasions when you will want to tie by hand. This is more wasteful of suture material, but it does allow you to hold both suture strands under tension and to control slippage. If you are tying by hand it also makes more sense to use a larger hand-held needle to avoid having to put down your needle holder at the end of every suture.
To demonstrate the hand held technique here, our surgeon is using a 90mm curved hand-held cutting needle and a 2/0 silk suture. This is the type of suture you would use when fastening a drain. Note however, that silk should generally be avoided when closing skin because the synthetic alternatives produce much better results.
09.03.04 Instrument Tie On Skin Pad Model
The needle takes an adequate bite on each side of the wound, passing through all layers of skin and emerging precisely opposite the entry point.
After looping the suture around the needle holder, the needle holder's jaws pick up the free suture end and the throw is pulled flat. The suture is then looped around the needle holder in the opposite direction and the direction of pull is also reversed to ensure that the whole knot lies flat when tightened.
For a secure suture, up to 3 more throws are fashioned, each time reversing the direction of loop and pull. The suture ends are then cut about 0.5cm long to allow enough length for grasping when removing.
09.03.05 Practise
When first learning to tie interrupted sutures, we recommend you pass the needle through each edge of the wound separately, repositioning the needle in the needle holder after the first bite before taking the second one. This will help you to ensure that the entrance and exit point of the needle are precisely opposite and that your finished suture is at right angles to the incision. To practise this method, go to the Beginner topic in this section.
A more experienced surgeon suturing a straightforward incision will usually take both sides in a single bite. To practise this method, go to the Advanced topic in this section.
09.03.05.01 Setting Up the Skin Pad Jig
- To ensure a secure fix, make sure the work surface is smooth. Rough surfaces will not work with the sucker feet
- Make sure that the jig will be properly oriented and comfortably positioned in front of you before you secure it in place
- Moisten both sucker feet with a little water, place the jig on the work surface and push down along the centre of it
- Make sure the feet have stuck securely by trying to move the jig
- Insert the skin pad. You are now ready to start practising
- To easily remove the jig, completely slide the white part off to one side, leaving the sucker feet in place. Peel the sucker feet off individually. Slide the sucker feet back into the groove under the jig
09.03.05.02 Beginner Practise
Using an atraumatic curved needle, grasp the needle on its flat section, about two thirds of the way from the point, with the tip of your needle holder's jaws. Angle the needle slightly forward in the instrument's jaws and take a bite on the first side of the wound ensuring that the needle follows the line of its curvature.
Remove the needle and reposition in the needle holder before taking a corresponding bite on the other side of the wound.
Pull the suture through so that only a short free end remains. If your suture material is very springy, we recommend that for this initial throw only you loop it twice around the needle holder as shown here. This will help the throw lie flat and form a more secure surgeon's knot. Now grasp the free end of the suture with the needle holder's jaws and pull it towards you to tighten the first throw. Make sure that it lies flat while being tightened.
Make a second throw by looping the suture once around the needle holder in the opposite direction to the first throw. Now grasp the free end of the suture with the needle holder's jaws and tighten, this time pulling it away from you.
Then make three further throws, changing both the direction of throw and pull at each stage.
Cut the suture ends with scissors, leaving the ends about 0.5 cm long.
09.03.05.03 Advanced Practise
Using an atraumatic curved needle, grasp the needle on its flat section, about two thirds of the way from the point, with the tip of your needle holder's jaws. Angle the needle slightly forward in the instrument's jaws and penetrate the skin at a 90 degree angle, taking an adequate bite and passing through all layers of the skin. Steady the exit side with dissecting forceps and watch the needle beginning to tent up the skin. Follow the curvature of the needle and emerge on the other side of the wound, precisely opposite the point at which you entered and at the same distance from the wound edge.
Pull the suture through so that only a short free end remains, then loop the end with the needle attached to it around the needle holder. If your suture material is very springy, we recommend that for this initial throw only you loop it twice around the needle holder, as shown here. This will help the throw lie flat and form a more secure surgeon's knot.
Now grasp the free end of the suture with the needle holder's jaws and pull it towards you to tighten.
Make a second throw by looping the suture once around the needle holder in the opposite direction to the first throw. Now grasp the free end of the suture with the needle holder's jaws and tighten, this time pulling it away from you. By changing the direction in which you loop and tighten each throw you are ensuring that a reef knot is formed.
Then make up to three further throws, changing both the direction of throw and pull at each stage.
Cut the suture ends with scissors, leaving the ends about 0.5 cm long.
09.03.05.04 Hand Tied Interrupted Sutures
Take the first bite exactly as you would for an instrument tied suture. Pull the suture through with your left hand and grasp the shorter end with your right. Make the first throw with your right index finger, pulling the short end towards you and pushing the long end away. Snug the knot down with your right index finger.
Form the second throw with your right middle finger and tighten in the opposite direction, i.e. pulling the short end away from you. Again, snug the knot down with your right index finger.
Continue to form alternate index and middle finger throws, each time tightening in the opposite direction and snugging down with your index finger. Cut the suture ends at a length of approximately 0.5cm.
09.03.06 Things to Avoid
The following videos provide examples of common problems with simple interrupted suturing, together with advice on how to solve them.
09.03.06.01 Knot Fails to Bed Down Video 1
Monofilament sutures have inherent memory, which makes them springy and resistant to being straightened after being coiled up in their packet. This may mean you have trouble getting your first throw to bed down and lie flat. A way to remedy this is to use a surgeon's knot for your first throw, ie. loop the suture twice around the needle holder, rather than once. This adds friction which will give extra grip and prevent the knot from coming undone.
09.03.06.02 Knot Fails to Bed Down Video 2
An alternative to using the surgeon's knot is to 'tweak' the first throw. Pull firmly on the suture end in your non-dominant hand while giving a sharp tug towards it with the needle holder in your dominant hand. This secures the knot temporarily while you make the second throw.
09.03.06.03 Incorrect Suture Spacing
Irregular intervals between sutures look untidy and unplanned.
Avoid placing sutures too close together. Crowded sutures produce too much tension and interfere with healing.
Excessively wide spacing allows subcutaneous fat to bulge through. It also puts undue tension on the few sutures present.
A useful rule of thumb is to make the distance between the sutures the same as the distance between each edge and the position of the suture bite. This is usually between 3 and 5 mm. If the wound is long, or the sides are unequal, use "progressive halving". Find the midpoint of each side of the wound and insert your first suture. Then insert sutures at the midpoint of each of the two resulting halves. Repeat this process along the whole wound.
09.03.06.04 Uneven of Inadequate Suture Bites Video 1
Uneven bites on each side of the wound produce an asymmetrical closure. This is caused by misjudging the entry and exit points when suturing.
Ensure that entry and exit points are at the same distance from the wound. Steady the exit side with dissecting forceps and watch the needle beginning to tent up the skin. Adjust it if necessary before it emerges.
09.03.06.05 Uneven or Inadequate Suture Bites Video 2
Too superficial a bite will bring the skin edges together but will leave dead space beneath. Dead space permits the accumulation of blood or serum which can act as a focus for infection and result in delayed healing.
Tiny bites increase wound edge tension without improving closure, while a very superficial bite may allow the suture to tear out. Ensure that you take an adequate bite of tissue on each side of the wound, passing through all layers of the skin and bringing the edges together without tension.
09.03.06.06 Slanting Sutures
Sutures which are not at right angles to the long axis of the wound exert a shearing force on the wound edges. Irregular slanting sutures also look untidy.
Slanting sutures are caused by failing to ensure that the entrance and exit point of the needle are precisely opposite.
Ensure that sutures are placed at right angles to the long axis of the wound. A useful rule of thumb is to make the distance between sutures the same as the distance between each edge and the position of the suture bite.
09.03.06.07 Wound Edge Inversion
As the wound heals, its edges sink down slightly. If the edges are inverted (i.e. the epidermis turns in and touches the epidermis of the other side), a depressed and ugly scar will form.
Ensure that the wound edges are everted by taking a larger bite of the deeper part of the tissue.
09.03.06.08 Sutures Too Tight/Loose
All wounds swell after suturing. Tight sutures will become even tighter after 24 hours, causing pressure on the crucial wound edges. This leads to ischaemia, poor healing and bad results.
Allow for swelling by deliberately tying sutures so that closed forceps can get under them. The skin edges should come together without bunching up. This allows for postoperative swelling. If a suture is too tight, cut it out and reinsert it.
If the suture is too loose it will not appose the wound edges at all. This often happens if the knot comes loose after your initial throw.
Gently tighten the knot if possible. If this does not work, cut out the suture and reinsert it. Aim to appose the wound edges neatly with the minimum of tension.
09.03.06.09 'Dog Ear'
Sometimes one side of the wound is longer than the other. Inserting sutures progressively from one end will create an excess of tissue at the other. This is a ‘dog ear’.
Progressive halving minimizes the effect of a discrepancy in length. Find the midpoint of each side of the wound and insert your first suture. Then insert sutures at the midpoint of each of the two resulting halves. Continue this process along the whole wound.
The extra length of the longer side is distributed equally along the wound. Even fairly large discrepancies become unnoticeable.
09.03.06.10 Wrong Suture Thickness
Too fine an interrupted suture will cause a cheese-wire effect on the skin edge by cutting in.
Too coarse an interrupted suture will be difficult to tie neatly and will cause unnecessary tension on the wound.
You will generally use sizes in the middle range: 3-0 to 5-0. On areas where cosmetic concerns are not of the utmost importance, 3-0 or 4-0 sutures are best, because the larger size makes the technique easier and the thicker sutures are stronger.
It is best to use 5-0 or 6-0 sutures on the face in order to minimise scarring. The tendency is also to use smaller sutures on children because of their more delicate skin.
09.03.06.11 Too Long a Loop of Suture
Leaving too long a free end wastes suture material. This can also lead to the formation of a troublesome loop when tying.
Pull the suture through until only a short length protrudes, then tie the knot.
Cut suture ends about 0.5cm long to allow enough length for grasping when removing.
09.03.06.12 Wound Edge Tension
You must avoid suturing under excessive tension as this will lead to ischaemia and poor healing. The skin edges should come together without bunching up, as shown here.
Progressive halving can help to distribute tension evenly over the length of the wound. Find the midpoint of each side of the wound and insert your first suture. Then insert sutures at the midpoint of each of the two resulting halves. Repeat this process along the whole wound. The extra length of the longer side is distributed equally along the wound. Even fairly large discrepancies become unnoticeable. A temporary suture at the midpoint of the wound can be useful. At the end of the procedure, remove this initial suture and replace it.
Judicious undermining of the wound edge with a scalpel blade held flat may sometimes be needed to relieve tension. This technique is covered in detail in the chapter on Undermining which you'll find later in this Suturing Techniques module.
In extreme cases, a pulley stitch may be useful. A pulley suture starts like a mattress suture with a deep bite on each side and a more superficial one nearer the wound edge. Then the needle is passed back through a loop of suture and tied on the other side. This acts like a pulley, distributing wound tension evenly and bringing the wound edges together while further sutures are inserted. This technique is covered in detail in the chapter on Mattress and Pulley sutures which you'll find later in this Suturing Techniques module.