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    suture basics

    Many animals, (insects, spiders, shrimp, crabs) have an exoskeleton as a protective covering. Humans have their skeleton on the inside, so we depend on the largest organ of the body, our skin, instead.

    Skin represents the armor that protects the body from invasion by debris and microbes. A breach in that armor increases the chance of infection that may spread throughout (called “sepsis”) and become life-threatening.

    As such, there are circumstances where a break in the skin should be closed with materials known as sutures. The decision to close skin should not be automatic and depends on many factors (discussed in previous articles on this site). Once that decision is made, however, the correct choice of suture material impacts the strength and effectiveness of the healing process.

    THE IDEAL SUTURE

    All wound closure methods have their advantages and disadvantages. Your choice should depend on the careful evaluation of the wound, as well as an understanding of the properties of a given suture material.

    The optimal suture should be:

    ·           Sterile

    ·           Easy to use

    ·           Strong enough to hold wound edges together

    ·           Able to retain strength for the time needed to heal

    ·           Unlikely to cause infection, tissue reaction, or significant scarring

    ·           Reliable in its everyday use with every type of wound

    It’s difficult to find a single suture type that meets all of the above criteria, but there are many that will do if chosen properly.

    TISSUE HEALING

    The time needed for healing should impact the choice of suture materials. The interval it takes for a tissue to no longer require support from sutures will vary depending on tissue type:

    Days: Muscle, subcutaneous tissue like fat, and skin

    Subcutaneous fat between skin and muscle on face

    Subcutaneous tissue is sometimes called the “hypoderm”. It’s connected to the deep layer of skin (the “dermis”). The skin and muscle in many areas of the body are separated by a layer of subcutaneous fat. Fat will appear as yellowish globules below the whitish dermis.

    Weeks to Months:  Fascia or tendons

    Fascial tissue

    Fascia is connective tissue beneath the skin that attaches, covers, stabilizes, and compartmentalizes muscles and other internal organs. A tendon is connective tissue attaching a muscle to a bone.

    CATEGORIZING SUTURE DIAMETERS

    Around a century ago, the average suture consisted of a needle through which a separate string was threaded. This method was used for thousands of years until the process of swaging was invented. A swaged suture has the thread built into the blunt end of the needle, making surgical sutures a single unit for the first time.

    In the United States and many other countries, a standard classification of sutures has been in place since the 1930s.  This classification identifies stitches by type of material and size of the “thread”.

    The first manufactured sutures were given sizes from #1 (thinnest) to #6 (thickest). #4 suture would approximate the string on a tennis racquet.

    As technology advanced, even thinner sutures were produced that were titled beginning at 0 (pronounced “oh”). Just like double-ought buckshot is bigger than triple-ought, 2-0 (pronounced “two-oh”) suture is thicker than 3-0 (pronounced “three-oh”). If you are doing microsurgery, you’re going down all the way to 8-0, 9-0, or 10-0. Size 7-0 is about the diameter of a human hair.

    The suture thread used should be the smallest size which will give adequate tensile strength to keep skin together. Finer sutures have less tissue reaction but are more difficult to handle for the inexperienced. The off-grid medic should consider using somewhat thicker sutures that can be more easily handled.

    ABSORBABLE SUTURES

    Absorbable chromic gut suture

    In addition to diameters, 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 mostly healed).

    Absorbable sutures have the advantage of not requiring removal.  They can be used in a number of deep layers, such as muscle, fat, organs, etc.  A classic example of this is “catgut”, actually made from the intestines of cows or sheep. Since these sutures are made from multiple fibers, they remain extremely strong in the first few days of healing.  

    plain “catgut”

    Catgut is usually found in “plain” and “chromic” varieties. Plain gut absorbs very quickly but has a tendency to cause tissue inflammation. When dipped in a chromic salt solution, catgut retains tensile strength in the body longer and causes less of a reaction, while still remaining absorbable. 

    Gut sutures are used today to close tissue that heals rapidly, such as vaginal lacerations from childbirth or in the oral cavity.

    Newer absorbables are synthetic. These include:

    • PDS (polydiaxonone)
    • Monocryl (poliglecaprone 25)
    • Vicryl (polyglactin)
    • Maxon (polyglyconate)
    • Dexon (polyglycolic acid)

    These sutures retain their tensile strength for varying lengths of time. They cause less tissue inflammation due to an absorption process different than that of gut.

    Vicryl sutures are used for approximating muscle or fat layers, as well as lower layers of skin. Maxon and Monocryl can also be used for soft tissue as well as for cosmetic procedures where visible sutures aren’t desired. PDS is used to stitch muscle and fascia tissue.

    Besides the classic synthetic sutures, new subtypes such as Vicryl Rapide, Vicryl Plus and PDS II exist. These may take less or more time to dissolve than the originals.

    (Aside: Every physician has their own preference for sutures that relate to their experience, schooling, and other factors. For example, it is considered old-fashioned by many to use stitches for closing surgical incisions on skin, as most close skin wounds with staples. A randomized, clinical trial, however, found that women who had C-sections with dissolvable stitches were 57% less likely to have wound complications than those whose wounds were closed with staples. I used this method (known as a “subcuticular” closure) with good results for 20 years.)

    NONABSORBABLE SUTURES

    Nonabsorbable sutures are those that stay in the body indefinitely or, at least, for a very long time. Normally. They are best used in skin closures or situations that require prolonged tensile strength.

    Nonabsorbable sutures can be used in deep layers in certain situations. They cause less tissue reaction, although a small remnant may be felt where the body’s immune system walled it off (known as a “granuloma” or “encapsulation”).

    Nonabsorbable sutures can be separated into synthetic single-stranded monofilaments and braided natural or synthetic multifilaments.  

    Single-stranded monofilaments include Ethilon (nylon) and Prolene (polypropylene). Braided natural multifilaments include braided surgical silk or cotton. Ethibond is the most commonly-used synthetic multifilament.

    Nylon monofilament suture

    Monofilaments like Nylon are slightly less likely to harbor bacteria, whereas braided multifilaments have tiny nooks and crannies which may serve as hideouts for microbes. The difference in infection rate is very small, however.

    Monofilaments also glide more easily through tissue, but may require more knots to stay in place than a braided multifilament like silk. While multifilamentous thread tends to come out straight, monofilaments retain the same S-shape in which they were packaged. This is more an annoyance for the inexperienced than anything else.

    Braided surgical silk suture

    Braided surgical silk is easier to handle than nylon, especially for novices, and is often used for teaching purposes. 2-0 and 3-0 are sizes considered too thick by many surgeons, but are useful for teaching aspiring off-grid medics to learn surgical knot-tying. Although scarring may be more noticeable, this is a secondary issue in survival scenarios.

    The off-grid medic must know skills ordinarily not taught to the average citizen. Wound closure is one of these skills, but must be combined with a working knowledge of when closure is appropriate and when it isn’t. We’ll discuss these issues in future articles.

    Joe Alton MD

    Dr. Alton

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