Basic plastic surgery techniques and principles: How to suture

In the second article of our series, Ben Taylor and Ardeshir Bayat explain suture techniques, how to prepare a wound, and how to get the best possible scar

Stitching (suturing) a wound is a surgical skill which also has widespread applications outside the field of surgery. We are all likely to be called on to suture a wound at some point in our training. Few students have enough confidence, however, to deal with wounds, and it can be hard to learn. In this article we look at the basics of wound healing suturing technique. We discuss a few more advanced techniques and share the secrets of getting best possible results.

SATURN STILLS/SPL

To understand the basis of suturing, it is important to know how wounded skin heals. This occurs in four phases (although there is some overlap).

Haemostasis--Immediately after wounding, a platelet plug forms and blood vessels vasoconstrict. Later, a thrombus develops to seal the wound.

Inflammation--This occurs in the first two to three days after the injury, causing swelling of the wound edges. White blood cells remove necrotic tissue, and control infection.1

Proliferation--Beginning on the second or third day after the injury, and lasting for two to four weeks, structure forming cells called fibroblasts proliferate into the wound, and produce structural proteins such as glycosaminoglycans, collagen, and elastin.2 New capillaries form at this time, and epithelial cells migrate across the top of the wound. Areas where this is occurring are known as "granulation tissue."

Remodelling--After the proliferative phase subsides, the new capillaries atrophy and collagen changes from type III to type I and is rearranged so that it gives the best tensile strength. Myofibroblasts cause scar contracture. Strength of the wound increases to almost 80% of the original strength over this period of up to a year.2 Because the forces acting on the wound shape its remodelling,2 the best result is obtained when the force is uniaxial (only acts in one direction).

Primary closure is where the wound edges are neatly brought together. Healing by secondary intention differs, in that the wound heals from the base up, which takes longer with a potentially worse cosmetic result. Delayed primary closure is used in situations where early primary closure is inappropriate, and allows a period of secondary healing to occur before the wound is closed. The aim of a suture is to splint the wound edges in the best position for direct primary closure to occur. If the suture has to pull the wound edges together under tension, the sutures will act like a noose to cause local ischaemia of the tissues, which may lead to breakdown.

When closing a wound, you need to assess it first (box 1 opposite).3 Many simple wounds will heal by themselves, without any intervention. A suture should be used as a splint to hold the wound in the best possible position, rather than to hold it together. If you judge that there is too much tension to close the wound directly, consider discussing the case with a plastic surgeon, or leaving the wound for delayed primary closure.

Many tools are available for wound closure--for example, wound glue, staples, and sutures--and the most appropriate means of closing a wound must be given some thought. This article focuses on sutures, but there are alternatives which find a place in some specialties. In paediatrics, for example, wound glue is often used in scalp injuries, to save the child the stress of having his or her head sutured.

Wounds can be frightening things, and they immediately attract attention. For larger wounds, always think about airway, breathing, and circulation first, and make sure that the wound is an isolated injury.

Before suturing, ensure the patient has adequate anaesthesia (either local or general). Irrigate the wound, and remove any foreign bodies and any non-viable or infected tissue (debridement). Debridement is particularly important as dead tissue will not heal and acts as a reservoir for infection.4 The integrity of the deep structures must be checked in any wound. Refer damage to tendons, nerves, viscerae, etc, to an appropriate specialist for assessment or primary repair. The wound edges must have a good blood supply and be free from infection to ensure healing. You must follow strict aseptic techniques. It may be worth delaying primary closure if there is oedema or doubt as to the viability of tissue. Systemic factors, such as malnutrition, diabetes mellitus, peripheral vascular disease, and corticosteroid therapy may delay wound healing.2

The simple suture is a technique taught to most medical students, and often used in wound closure. It has the advantage of being quick and relatively easy, and usually gives an adequate cosmetic finish. However it is often done poorly, and can cause long lasting damage to a patient if care is not taken. It is known as an "interrupted suture," because several individual stitches are needed to close a wound.

When suturing, the deep layers should be closed below if necessary. Any deep tissue gaps may become infected. Make sure the wound stops bleeding because if a haematoma forms it can act as a barrier between the wound edges and be a potential source of infection. Use a needle holder where possible, to minimise the risk of needlestick injury.5 The skin edges should be accurately apposed, and not under undue tension. If forceps are used to align the tissues they should be used gently: it is better to use the closed forceps to nudge the skin edges together, than to grab them.6 The inside of the skin is delicate, as it does not have a protective layer of keratinocytes and is also where the blood supply is richest. Therefore skin trauma will impair healing. A skin stitch should gently evert the wound edges, as the deeper layer is alive and capable of regenerating, whereas the superficial layers are mostly dead keratinocytes.

The needle should be held in needle holders two thirds of the way from the needle tip to the swage (point where the needle becomes attached to the thread). Take a square bite of skin, entering perpendicular to the wound surface, and taking a smooth semicircular course to exit at 90 degrees to the wound edge. The needle should then be removed from the wound, readjusted on the needle holder, and the second half of the arc done in the same way. This method ensures a square bite, and good eversion of the wound. Bites of skin should be equal on both sides of the wound, and sutures should be spaced evenly.

Use a surgical knot to close the wound, which must be tied tight enough to adequately splint the wound. However, if it is too tight, there will be local ischaemia underneath the suture tracks leading to an ugly crosshatched scar. An instrument knot is shown in the figure. The concept is simple in that the long end of the thread is wrapped around the needle holder, which is used to transfer the coil around the short end. This cycle is repeated to create a surgeon's knot. Once tied, the knot should be left to one side, so that it does not become involved in the clot.

This is similar to a simple suture, except that there are no individual sutures, just a long coil of material. They are used in abdominal wall closure,7 and in places where haemostasis is important, such as on the scalp, because the suture compresses the wound edges.8

The buried suture is circular in profile, and is used to close the deep layers of tissue. The knot should be placed deep to prevent it coming out. Absorbable sutures should be used, as the suture cannot be removed from the skin.

This technique produces more eversion than a simple suture. It is similar to a simple suture, but a second, superficial bite is taken in the same vertical plane (see figure). Although it may evert skin in areas with a natural tendency to invert, it does produce more crosshatching due to increased dermal ischaemia.8

This is a similar concept to the vertical suture, except that it extends along a horizontal plane, almost like two simple sutures next to each other (see figure) It is useful in areas with thick glabrous skin, such as the soles of the feet. But it also causes more dermal ischaemia than simple or even vertical mattress sutures, and if tied too tightly, can over-evert the wound edges.5

Subcuticular or intradermal sutures give the best cosmetic result, and are simple and quick to place.9­11 They run in the dermis in the same plane as the subdermal plexus, the main blood supply to the skin,12 and therefore do not "strangle" wounds in the same way as simple sutures. They do not cause crosshatching, and mechanically provide the best internal splinting of a wound.

Monofilament sutures are used, as they do not exhibit as much tissue drag as braided sutures. There are many different ways to start and finish such a suture,10 13­15 but generally, non-absorbable sutures should enter the skin at the apex of the wound, and absorbable sutures are often tied in the dermis. Bites should be parallel to the wound edges, and through the dermis. Take care to ensure that all bites are placed in the same vertical plane, otherwise the wound edges will be misaligned with poor healing. Long wounds should have bridges (loops of suture) brought out over the wound.16

This is used where either a single wound edge is friable, or the knots can be hidden on one side (such as the areola of the breast). It is a combination of a mattress suture and a subcuticular suture (see figure).

A variation where the subcuticular component is used to close the corners of several different lacerations is known as a three-corner suture (see figure).

Infection was a significant problem when sutures were carried in the buttonholes of surgeons. Today it can be a problem if there are breaks in aseptic technique or from hospital acquired infection. Wounds must be adequately debrided to remove any contaminated tissue, and may need to be irrigated or cleaning with abrasion under anaesthetic may be required.4

This is a rare complication of using dyed sutures, and it is best to avoid dyed sutures on the skin. Other sources of tattooing are grit and dirt. Abrasions are particularly liable to tattoo, and should be thoroughly scrubbed with a wire brush, under anaesthetic of course.

Scarring is a natural process, and occurs as the result of any wound. However, large, stretched or hypertrophic scars can look ugly and are occasionally a source of psychological trauma, even if the scar looks acceptable to the medical professional.17 Scars contract, which is troublesome around joints. It is very important to minimise scarring, and take every effort to do so (box 2).

The simple suture does an adequate job of internally splinting the wound but in doing so can create lines of traction and counter traction, which can result in a poor scar. Ideally, subcuticular sutures should be used for skin closure, as they have a better cosmetic result.

Dehiscence is the term used for the breakdown of a wound postoperatively. Common causes include lack of surgical experience,6 (implying that poor technique is to blame). Other important factors are wound tension and infection. Dehiscence is associated with a mortality of 25% in the case of general surgical wounds. Other complications include chronic wounds and infection of deep structures.

Suturing is an important skill for any medical student or junior doctor to learn. There are a few key messages to remember to suture effectively and avoid damaging your patient.

Ben Taylor, third year medical student

Ardeshir Bayat, specialist registrar in plastic surgery, University of Manchester
Email: ardeshir.bayat@man.ac.uk


studentBMJ 2003;11:175-218 June ISSN 0966-6494

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