Sutures

Suture materials

The purpose of a suture

  • to hold a wound together in good apposition until such time as the natural healing process is sufficiently well established to make the support from the suture material unnecessary and redundant.

Choice of a suture will depend on:

  • Properties of suture material <
  • Absorption rate, handling characteristics and knotting properties
  • Size of suture
  • Type of needle

Natural suture materials

  • Absorbable
    • Catgut - Plain or chromic
  • Non-Absorbable
    • Silk
    • Linen
    • Stainless Steel Wire

Synthetic suture materials

  • Absorbable
    • Polyglycolic Acid (Dexon)
    • Polyglactin (Vicryl)
    • Polydioxone (PDS)
    • Polyglyconate (Maxon)
  • Non-Absorbable
    • Polyamide (Nylon)
    • Polyester (Dacron)
    • Polypropylene (Prolene)

Absorbable suture are broken down by either:

  • Proteolysis (e.g. Catgut)
  • Hydrolysis(e.g.Vicryl, Dexon)

Catgut

  • Made from the submucosa of sheep gastrointestinal tract
  • Broken down within about a week
  • Chromic acid delays hydrolysis
  • Even so it is destroyed before many wounds have healed

Silk

  • Strong and handles well but induces strong tissue reaction
  • Capillarity encourages infection causing suture sinuses and abscesses

Vicryl

  • Tensile strength
    • 65% @ 14 days
    • 40% @ 21 days
    • 10% @ 35 days
  • Absorption complete by 70 days

Polydioxone

  • Tensile strength
    • 70% @ 14 days
    • 50% @ 28 days
    • 14% @ 56 days
  • Absorption complete by 180 days

Common errors of suture use

  • Too many throws. Increases foreign body size. Causes stitch abscesses
  • Intra-cuticular rather than subcuticular sutures causing hypertrophic scars
  • Holding monofilament sutures with instruments reduces tensile strength by over 50%
  • Holding butt of needle causes needle and suture breakage

http://www.surgical-tutor.org.uk/default-home.htm?core/preop2/sutures.htm~right

SILK: animal protein, relatively inert for human tissue, loses strength over long periods. Silk sutures are multifilament and provide a potential haven for bacteria.

CATGUT: from the submucosa of the bovine intestine, eventually resorb. It excites considerable inflammatory reaction and tends to potenciate infections. It loses strength rapidly and it’s of little use in modern surgery.

SYNTHETIC NONABSORBABLE SUTURES: generally inert and retain strength longer than wire. They must usually be knotted at least four times because of their poor handling characteristics, resulting in retained foreign bodies.

SYNTHETIC ABSORBABLE SUTURES: strong, with predictable rates of loss of tensile strength, incite a minimal inflammatory response and may have special usefulness in gastrointestinal urologic and gynecological surgeries.

TAPES: skin closure of choice for clean or contaminated wounds, with minimal probability of infections. They cannot be used in actively bleeding or complex surface wounds.

Chronic Wounds

The first principle in managing chronic wounds is to diagnose and treat any underlying circulatory disease. The second principle is never to allow open wounds to dry. A third principle, but not less important, is to control any infections with adequate care of the lesion and systemic antibiotics. Finally, its also necessary to recognize that chronically scarred tissue is usually poor perfused. Debridement of unhealthy tissue, often followed by skin grafting, may be required for healing.

Wound Healing and Repair

Just after a surgical incision, a number of epithelial cells and connective tissue cells die and the basement membrane is disrupted. This clean and uninfected injury is enough to target an inflammatory response that will be absolutely necessary for the wound healing. Immediately after the incision, the wounds covered with clotted blood containing fibrin and blood cells. This fibrin clots receives within 24 hours an amount of neutrophils, attracted by inflammatory factors locally released. At this time, we also have mitotic activity of the basal layer of the epidermis. By the day 3, macrophages are the most common cells in the tissue, instead of neutrophils. The main feature at this moment is the granulation tissue, that consists of fibroblasts and new capillary with amorphous substance all around. By the 5th day, granulation tissue and neovascularization are maximal. Collagen fibrils are present and begin to bridge the incision, following the epithelial migration. After 1 week there is still connective tissue proliferation, but inflammatory features have virtually disappeared. At the end of the first month, the scar is completed within an intact epithelial layer, covering a new cellular connective tissue net, devoid of inflammation.

In some instances, the wound (not surgical ones) has a large loss of cells and tissues, which makes the normal healing event impossible. In this case, we have the healing by second intention. This is characterized by a more complicated process with much more inflammation and granulation tissue. The original architecture is never attained and the main feature of the phenomemon is called “wound contraction”. The wound contraction is caused, at least in part, by the presence of myofibroblasts ¾ altered fibroblasts that have ultrastructural characteristics of smooth muscle cells.

As noted, the disposition of connective tissue matrix, specially collagen, its remodeling into a scar and the acquisition of wound strength are the ultimate effects of the repair.

The wound healing process is influenced by many systemic and local host factors. Nutrition state of the patient is very important. Protein deficiency and particularly ascorbic acid deficiency inhibits collagen synthesis and impairs healing. Glucocorticoids therapy, by its anti-inflammatory aspects, retards healing. Patient’s age is also an systemic factor that plays a role. Local infections are important causes of complicating and delaying healing process. Hemorrhagic factors, such as ischemia, play a role and foreign bodies, such as sutures and/or other fragments constitute impediments to healing.

The healing process may occur abnormally. There are many aberrations of growth, but the most common is called keloid. Keloid is a tumoral scar resulted from accumulation os excessive amounts of collagen. The reasons for keloid formation still remain unknown, but is known that it’s more common in afro-caribbeans.

http://www.medstudents.com.br/cirur/cirur3.htm

Suture size is based on strength and diameter as decided by the United States Pharmacopeia (U.S.P.)  This system uses "0" as the baseline, average size suture.  As suture diameter decreases, "0's" are added or numbers followed by a "0" (for example, 000 and 3-0 are the same size).  As suture diameter increases above "0", numbers are assigned to the suture material.

http://cal.vet.upenn.edu/surgery/5051.htm

http://www.favormed.com/e18.htm

Examples of Suture Sizes for Use in Animals

10-0 - 8-0

7-0 - 5-0

4-0 - 3-0

2-0 - 0

1 - 2

Microvascular
Corneal/ophthalmic

Vein/arterty repair

Skin & Subcutis
Bowel
Bladder

Abdominal Fascia
Stomach
Hernia

Rib Retention
Cutaneous Stents

Increase or decrease abdominal fascia and retention sutures appropriately based on weight & suture pattern

http://www.vetmed.auburn.edu/~hendera/guide/sutsize1.htm

General

Un-coated braided sutures may provide increased resistance to passage through the tissues and may harbour bacteria within the braid.
Braided sutures are however easier to use and knots tend to be more secure
Coating a braided suture gives the suture qualities more like a mono-filament suture
Mono-filament sutures are generally easy to use with easy passage through tissue but may not hold a knot well. They also usually result in low tissue reactivity and the smooth surface does not harbour bacteria.
Natural materials generally result in greater tissue reactivity

http://www.orthoteers.co.uk/Nrujp~ij33lm/Orthsutures.htm

Suturing Tips
  • In larger wounds muscle, membranes, fat and skin should be sutured separately.
  • Subcutaneous sutures should be absorbable.
  • Suturing goal should eliminate all pockets and dead space below skin; else allow drainage for fluid buildup.
  • Suturing of fat reduces dead space.
  • Use minimal tension on skin closures to prevent crushing injuries which delay healing.
  • Cleansing of wound should only be done by lavage of sterile fluids. Never use caustic cleansing agents such as alcohol, hydrogen peroxide or other anti-bacterial agents; these will distrupt the natural inflammatory response and fibrin clot necessary for healing and potentially damage surrounding healthy tissue.

    http://www.ussdgsutures.com/knot-tying/index.html

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