As we go around the country teaching the art of suturing pig’s feet to aspiring porcine podiatrists, we are often asked about how to choose the appropriate suture needles and material for different types of injuries. There are a wide variety of choices and, today, we’ll discuss what is available and what is most effective for different types of wounds.
First, let’s identify some of the qualities of the optimal suture. The suture should:
· Be sterile
· Be easily worked with
· Be strong enough to hold wound edges together while they heal
· Be unlikely to cause infection, tissue reaction or significant scar formation
· Be reliable in its everyday use with every type of wound
It is rare, if not impossible, to find a single suture type that meets all of the above criteria, but there are many that will serve if chosen properly.
In the United States and many other countries, a standard classification of suture has been in place since the 1930s. This classification identified stitches by type of material and the size of the “thread”. Suture diameters most commonly used in humans (and pigs, I would think) is measured in zeroes, much like buckshot. 2-0 (00) suture, for example, is thicker than 5-0 (00000) suture. The more zeroes, the finer the “thread”. Finer sutures have less tissue reaction and heal faster, but are more difficult to handle for those without experience.
In addition to size, sutures are classified as absorbable and non-absorbable. An absorbable suture is one that will break down spontaneously over time but not before the tissue has had sufficient time to heal. Absorbable sutures have the advantage of not requiring removal after healing has taken place. This type of suture is commonly used in deep layers, such as muscle, fat, organs, etc. A classic example of this is “catgut”, actually made from the intestines of sheep or cows.
(Aside: Catgut was once also used in the manufacture of stringed musical instruments and tennis racquets.)
Catgut is usually found in “plain” and “chromic” varieties. When dipped in a chromic acid salt solution, catgut lasts longer in the body while remaining absorbable.
Although still popular, catgut has been replaced by synthetic absorbables for many applications. examples of synthetic absorbable suture include “Vicryl” (polyglycolic acid), “PDS” (polydiaxanone), and others. These tend to last longer than catgut sutures, but will eventually be absorbed by the body.
Nylon suture package depicting size, needle shape, and length of “thread”
Nonabsorbable sutures are those that retain their character for a very long time, and will stay in the body until removed. As such, normal immune response will cause the development of scar tissue, sometimes called “encapsulation”, around these sutures if used in internal body structures.
Nonabsorbable sutures are best used in skin closures and situations that require prolonged tensile strength. They include monofilaments (such as “Nylon” and “Prolene”) and braided multifilaments (such as ”Surgical Silk”). Monofilaments like Nylon are useful because of less likelihood of harboring bacteria, whereas braided multifilaments have nooks and crannies for these organisms to hide. Monofilament also glide more easily through tissue. In trade, braided Silk is somewhat easier to handle than Nylon for many and often used for teaching purposes.
I recommend Nylon in most survival situations, with 2-0 or 3-0 Nylon ideal for those new to the suturing skill. This size “thread” is easy to handle and useful for aspiring medics to learn surgical knot-tying.
The size of the “thread” you’ll use depends on the area of the body being repaired. Slowly healing tissues such as skin and tendons require nonabsorbable sutures; wounds in rapidly healing areas such as the inside of the cheek and vagina (childbirth) are best repaired with absorbables.
In survival settings, cosmetic results are less important, but surgeons generally use smaller sutures in delicate areas such as areas on the head and face. 5-0 or 6-0 Nylon would normally be the choice here, but require more skill in handling. Skin sutures should be placed, in my opinion, about 1/2 inch or so apart in most instances. This will allow drainage while keeping the wound together. Areas over joints or other moving parts should be closer together. In wounds not near joints, say, the forearm, the sutures may be further apart and could be interspersed with Steri-Strips or butterfly closures.
typical suture needles (chromic catgut)
The type of needle is also an important factor in choosing suture material. Needle that are less traumatic to sensitive tissues, like the lining of the bowel and other deep structures, are round on cross-section. These are known as “atraumatic” or “tapered”. Needles that are best on tough areas like skin are triangular in shape on cross-section and are referred to as “cutting” needles. Most suture needles that are useful for skin form a 3/8 circle; needles for deep work are often ½ circle in shape.
Having said all of the above, the choice of suture needles and material will vary depending on the user. Each surgeon will have his or her preferences based on their experience.
How long skin sutures remain in place before removal is dependent on the body part repaired. Face wound sutures are usually removed relatively soon (5 days) compared to, say, a forearm wound (7-10 days). Thicker skins, such as the sole of the foot should stay in somewhat longer. Sutures placed over the knee or other joints should remain in place longer, 2-3 weeks, in my opinion.
Remember that the act of suturing is more traumatic than using butterfly closures, Steri-Strips, surgical glue, and others due to the fact that you are making more punctures in an area of skin already injured. Each extra “hole” you create could allow the entry of bacteria into the wound.
One last relevant point: When you practice suturing on your pig’s foot, you are learning a skill, not a trade. The practice of medicine without a license is illegal and punishable by law; as long as modern medical care exists, seek it out.
We’ll talk about staples, medical glues, and Steri-Strips/butterfly closures in future articles.
To see me suture in real time, here’s my YouTube video:
Joe Alton, MD
Find out more about wound closure and 150 other topics in our 700 page Third Edition of the Survival Medicine Handbook: The Essential Guide for when Medical Help is Not on the Way“. Find suture kits and individual sutures at Nurse Amy’s store.