Suture Materials and Needles
By Marie Høxbro Knudsen, MD and Flemming Bjerrum, MD, PhD
Sutures are used to approximate tissue, close dead space, or ligate blood vessels. Depending on what tissue and patient you are about to suture, you need to choose the right suture material and needle with the desirable properties.
When choosing a needle, you need to consider the size and shape of the body and the shape of the point, depending on which tissue to suture.
Most needles are circle-shaped, but straight needles do exist. Needles shaped like a 5/8 circle are often used in narrow places where you do not have much space to suture in. 3/8 circle needles are often used in superficial suturing.
The point can either be a round body taper point, spatulated, taper cutting, blunt, conventional cutting, or reverse cutting.
The blunt point is used in tissue that is easily traumatized, such as the liver.
The round body taper point is gentle to the tissue and is used in tissues that are easy to penetrate.
Cutting needles have both a cutting point and body. They are used in tissue that is difficult to penetrate, such as tendons. The cutting needles are divided into taper cutting, conventional cutting, reverse cutting, spatulated point, and reverse cutting prime needles.
Taper cutting needles are used in vascular surgery.
All needles except those with blunt points are sharp and able to cut. If you penetrate the tissue with the needle at a 90-degree angle to the tissue and follow through with the shape of the needle, you will easily penetrate the tissue with almost no resistance.
The gauge is a reference to the diameter of the needle and is popularly referred to as the size of the needle. The higher the gauge, the smaller the needle diameter, which means 3-0 has a larger diameter than 6-0. The very thick sutures are named from 1 upwards, with 1 being the thinnest and 3 the thickest. The thick sutures are often used when suturing connective tissue.
When choosing the right thread, you need to consider the type of material, thickness, and length.
Surgical sutures consist of different materials, which can be classified into their qualities (absorbable vs. non-absorbable) and their structure (monofilament vs. polyfilament). Some sutures may also be impregnated with antibacterial material to decrease the risk of infection.
Non-absorbable vs absorbable
Non-absorbable sutures are relatively unaffected by biological activities and have longer mechanical support. In most cases, they must be removed manually. Since non-absorbable sutures are made of materials that are not broken down by the body they can be used in inner tissues where absorbable sutures are not adequate. This is the case, for example in hernia or tendon repair surgery where the surgery requires the suture to stay longer than an absorbable suture would be able to. The same applies to sutures in the heart and blood vessels where the rhythmic movement requires a longer hold than an absorbable suture can provide.
Absorbable materials will break down in the body over time. They do not have to be removed, but may cause a more inflammatory response and may be more likely to be infected. The sutures offer temporary support and have a progressive loss of mass. The suture will absorb by hydrolysis and loses its 50 percent breaking strength retention after an average of 10−14 days, but this differs among sutures.
Polyglactin rapid loses its strength after 10 days (50 percent breaking strength after 5 days) and is completely absorbed after 42 days. The fast absorption makes it ideal for suturing oral mucosa, lips, ears, and the rest of the face.
Polyglactin loses its strength after 30 days (50 percent breaking strength after 21 days) and is completely absorbed after 56−70 days. The property of absorption and a moderate strength makes it suitable for inverted sutures in the tissue.
The amount of time the absorption takes depends on the location of the insertion and the individual patient characteristic. The time of absorption can increase if it is located in tissue with poor blood supply, in patients with ongoing infection or protein deficiency. A polyglactin suture can, therefore, be used to approximate subcutaneous fat in a deep wound or to ligate a small vessel. In contrast, a polydioxanone (PDS) suture should be used for closing abdominal wall fascia after laparotomy because this tissue heals more slowly and the suture is more slowly absorbed. For intestinal bowel anastomosis, a poliglecaprone or polydioxanone suture could be used.
When suturing joint capsules, you need to consider if the closure is made with or without tension and if the capsule is important in stabilizing the joint. If the joint capsule is without tension and not important for stabilizing, you can use an absorbable suture (2-0 – 4-0). On the other hand, if a closure is with tension and the capsule important for stabilizing, it is important to choose a non-absorbable suture (3-0 - 1) to ensure the tension over time.
Tendons are difficult to suture because sutures tend to cut through them, here the suture pattern becomes important. Monofilament material tends to work best in these types of tissues. A good choice would be an absorbable suture, for example, a PDS which still has 80% of tensile strength after two weeks’ bear in mind that some tendons require non-absorbable sutures.
Monofilament vs polyfilament
Monofilament sutures consist of a single strand and they are more resistant to microorganisms than polyfilament sutures. Because of the single strand, it encounters less damage when passing through tissue. Their delicate nature also makes them easy to break. Monofilament threads have “memory”; they have a tendency to return to original form if not handled, so it is a good idea to stretch them before use to avoid twisting. They also have a smooth surface, which means loosely tightened knots can loosen spontaneously. The smooth surface can also be damaged and weakened when handled with metal instruments.
Polyfilament sutures consist of several strands that are twisted or braided together. They have a stronger hold than monofilaments and tie well.
Some sutures are available with a coating. Some coatings can make passage through tissue easier, reduce tissue reaction, or make knotting easier. An antibacterial or antimicrobial coating reduces the risk of infection, and the more functional coating as stem cell coating can improve healing potential. Coatings are given to both mono- and polyfilament sutures. These sutures are called antimicrobial sutures.
Choosing the suture
A suture must be strong enough to keep the wound edges together while they heal and create as little risk of infection, tissue reaction, and scar formation as possible. For locations on the body where the cosmetic result is essential, such as the face, it is important to choose the smallest suture possible for wound closure. Non-absorbable sutures cause less scarring but give the patient an extra consult as they must be removed. Percutaneous deep closure should be avoided in cosmetic important areas as they have a tendency to form a mass of granulation tissue called granulomas; on the other hand, they may be necessary to avoid too much tension when suturing the skin.
When suturing thick skin on the lower extremities, the back, or the scalp, it is wise to choose a strong suture like 3-0, whereas in the face a thinner and more atraumatic suture like 5-0 or 6-0 is more preferable.
There should be minimal tension in the skin to obtain as narrow a scar as possible. Too much tension in the sutures in the skin will cause unnecessary patient discomfort, ischemia, tissue necrosis during healing, and can cause the tissues to withdraw from each other and increase the risk of infection and of a wide scar. An absorbable suture should be used to make percutaneous deep closure to reduce dead space and decrease tension in the skin in a deep or round wound with a lot of tension.
- Always choose the thinnest suture possible.
- When suturing skin and when the cosmetic result is important, choose sutures that are non-absorbable and close subcuticular whenever possible with as few percutaneous deep sutures as possible.
- Avoid tension in the skin with deep closure, but as few as possible in cosmetically important areas.
- Patients with a tendency for keloid scars should always be sewn with non-absorbable sutures.
- Absorbable sutures absorb faster in well-vascularized tissue.
- Remove sutures as soon as the wound is strong enough to hold to avoid a “railroad track” and minimize the risk of infection.