04.03 Needles & Sutures - Choice of Suture
In this module you will learn about the different types and properties of needles and sutures.
In this module
04.03 Choice of Suture
Each suture type comes in a range of sizes. This leads to a bewildering array of possibilities, so it is worth getting to know a small number of sutures well. Your choice of suture will depend on the area of the body, the patient's age and health and the type of closure.
All suture packets have a two part outer covering made of a paper backing bonded to a transparent cover. Information about a suture and its needle is summarised on the suture packet and these details can be seen through the covering before opening. The suture is guaranteed sterile only if this outer covering is unbroken.
04.03.01 Monofilament Sutures
Because of their simple structure, monofilament sutures typically encounter less resistance than multifilament sutures as they pass through tissue. The simple structure also means they are less likely to harbour bacteria that could result in infection. For these reasons, monofilament sutures are highly suitable for vascular surgery.
However, their simple structure means they must be handled very carefully to avoid damage and weakening of the strand.
A monofilament suture can also be springy and resistant to being straightened after being coiled up in its packet. This is because it has what is referred to as 'memory': an inherent capability to return to or maintain its original gross shape.
04.03.02 Multifilament Sutures
Multifilament sutures have greater tensile strength achieved by twisting or braiding several strands together. They are more pliable and flexible. They have less memory than monofilament sutures, so stretching them will permanently remove most coils and zigzags.
Coated multifilament sutures are available to assist passage through tissue and minimise the risk of bacterial growth amongst strands. These are often the suture of choice for intestinal procedures.
04.03.03 Absorbable Sutures
Absorbable sutures allow temporary wound support until the wound heals well enough to withstand normal stress, and thereafter are gradually absorbed. Because they do not need to be removed, they are mainly used internally for continuous subcuticular closures, for suturing deep to the skin and for tying blood vessels.
Absorbable sutures may support a wound for only a very short period, but they may be present as a foreign body for a long time.
Absorbable sutures can be made of natural or synthetic material.
04.03.03.01 Natural Absorbable Sutures Video 1
Natural absorbable sutures are absorbed through a process of enzymic reaction. In other words, they are digested by enzymes that attack and break down the suture strand. These enzymes are brought to the wound site by white blood cells.
Catgut is an example of a natural monofilament, made from beef or sheep intestine. Note however that it has been withdrawn in many countries and that in most of Europe only non-absorbable natural sutures are available.
04.03.03.02 Natural Absorbable Sutures Video 2
Plain catgut loses its tensile strength after 7-10 days. It can produce a marked tissue reaction and has largely been replaced by synthetic absorbable sutures.
Chromic catgut is treated with chromium salt to slow absorption and retains tensile strength for longer. It can also produce a marked tissue reaction and has largely been replaced by synthetic absorbable sutures.
04.03.03.03 Synthetic Absorbable Sutures Video 1
Synthetic absorbable sutures are absorbed through a process of hydrolysis, which means that water penetrates the suture filaments and causes the polymer chain to break down.
Synthetic multifilament sutures, such as Vicryl (polyglactin) and Dexon (polyglycolic acid), last longer than the natural alternative, catgut, and produce less tissue reaction. They are also stronger and more predictable in terms of strength retention and absorption than catgut.
04.03.03.04 Synthetic Absorbable Sutures Video 2
Vicryl 2 metric (3-0) is recommended for subcuticular closures and is also useful for deep haemostatic sutures.
Vicryl 1.5 metric (4-0) is recommended for more delicate subcuticular closure or deep sutures.
04.03.03.05 Synthetic Absorbable Sutures Video 3
Multifilament Dexon sutures are recommended for use as absorbable sutures in general soft tissue approximation and/or ligation, including use in ophthalmic procedures. They are not recommended for use in cardiovascular or neural tissue.
04.03.03.06 Synthetic Absorbable Sutures Video 4
Monocryl is used for general soft tissue suturing and/or ligation. It is not suitable for use in cardiovascular or neurological tissues, ophthalmic and microsurgery, or where extended support is required.
04.03.04 Non Absorbable Sutures
Non-absorbable sutures are materials which are not broken down by the body, Some will lose tensile strength over time, but the mass of the material is not absorbed by the body. They can be removed once the wound has healed, or left in a wound indefinitely.
Non-absorbable sutures can be made of natural or synthetic material.
Most skin wounds are best closed with synthetic, non-absorbable sutures because they are likely to produce a better cosmetic outcome.
Non-absorbable sutures are also used in stressful internal environments where absorbable sutures are not sufficient. Examples would include the heart (with its constant pressure and movement), or the bladder.
04.03.04.01 Natural Non Absorbable Sutures Video 1
Black silk is a braided, naturally-occurring material. It is made of raw silk spun by silkworms. It handles well and is easy to tie, but tends to excite a tissue reaction which can result in an unsightly scar.
Silk should generally be avoided because the synthetic alternatives produce much better results.
04.03.04.02 Natural Non Absorbable Sutures Video 2
Surgical cotton is made of twisted, long, staple cotton fibres. Tensile strength is 50% within 6 months and 30-40% by 2 years.
04.03.04.03 Natural Non Absorbable Sutures Video 3
Another example of a natural non-absorbable suture is surgical steel which has low tissue reactivity and holds knots well. However, it can be difficult to handle because of kinking, fragmentation, and barbing. The cutting, tearing, or pulling of other patient tissues is also a risk.
04.03.04.04 Synthetic Non Absorbable Sutures Video 1
There is a wide range of synthetic non-absorbable sutures. Polyester and polypropylene lose neither mass nor strength, whereas nylon can lose strength and gradually fragment over time.
Monofilament sutures in this category are excellent for skin closure. They glide smoothly through the tissues and excite very little reaction.
However, they are more difficult to tie than silk and knots can tend to come undone. There are various knot tying techniques for overcoming this problem.
04.03.04.05 Synthetic Non Absorbable Sutures Video 2
Prolene is a monofilament, synthetic non-absorbable suture made from polypropylene. It retains its tensile strength for up to 2 years.
Prolene holds knots better than other monofilament synthetic materials.
1.5 metric (4/0) is recommended for interrupted sutures in most sites.
Prolene 2 metric (3/0) is recommended for non-absorbable subcuticular closures. It is also useful for interrupted sutures in thick skin such as the back.
Prolene 0.7 (6/0) is recommended for fine facial sutures and in children.
04.03.04.06 Synthetic Non Absorbable Sutures Video 3
Ethilon is a good alternative to Prolene. 1.5 metric (4/0) is recommended for interrupted sutures in most sites.
Ethilon 2 metric (3/0) is recommended for non-absorbable subcuticular closures. It is also useful for interrupted sutures in thick skin such as the back.
Ethilon 0.7 (6/0) is recommended for fine facial sutures and in children.
04.03.04.07 Synthetic Non Absorbable Sutures Video 4
Ethibond is a braided polyester suture with indefinite tensile strength retention. It is recommended for cardio vascular and general surgery where permanent retention is important.
Ethibond has a highly adherent coating which acts as a lubricant and improves handling qualities.
04.03.04.08 Synthetic Non Absorbable Sutures Video 5
Nurolon and Surgilon are braided sutures made from nylon-polyamide polymers. They lose tensile strength at a rate of 15-20% per year and degrade at the same rate.
These sutures are suitable for suturing and ligating most body tissues.
04.03.05 Suture Sizes
There are two systems for describing the thickness of a suture: metric and traditional.
In the metric system, the number given to a suture is equivalent to its diameter in tenths of a millimetre. The number 1.5 suture shown here, for example, is 0.15 mm in diameter.
The traditional system is less rational but widely used. Suture thickness is expressed by a number followed by a zero (pronounced "oh"), or by an equivalent number of zeroes. e.g. 3-0, 3/0 or 000, 4-0, 4/0 or 0000, etc. The larger the number, the finer the suture.
6-0 is about the thickness of a human hair
4-0 is commonly used for skin closure.
3-0 is suitable for tough skin (e.g. on the back)
0-0 is about the size of a large fishing line. A typical application would be closure of the abdominal wall.
You generally will 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 small sutures on the face, such as 5-0 or 6-0, as this is likely to result in decreased scarrings. The tendency is also to use smaller sutures on children because of their more delicate skin.
04.03.06 Practise Opening A Suture Packet
To open a suture, peel apart the outer covering and deposit the inner packet onto a sterile field.
Pick up the inner packet and lift the card tab to reveal the needle with its attached suture neatly coiled. Grasp the needle with the needle holder (avoiding the needle's point) and gently pull in a straight line. This allows the suture to uncoil without becoming tangled.