Surgical suture


A surgical suture, also known as a stitch or stitches, is a medical device used to hold body tissues together and approximate wound edges after an injury or surgery. Application generally involves using a needle with an attached length of thread. There are numerous types of suture which differ by needle shape and size as well as thread material and characteristics. Selection of surgical suture should be determined by the characteristics and location of the wound or the specific body tissues being approximated.
In selecting the needle, thread, and suturing technique to use for a specific patient, a medical care provider must consider the tensile strength of the specific suture thread needed to efficiently hold the tissues together depending on the mechanical and shear forces acting on the wound as well as the thickness of the tissue being approximated. One must also consider the elasticity of the thread and ability to adapt to different tissues, as well as the memory of the thread material which lends to ease of use for the operator. Different suture characteristics lend way to differing degrees of tissue reaction and the operator must select a suture that minimizes the tissue reaction while still keeping with appropriate tensile strength.

Needles

Historically, surgeons used reusable needles with holes, which must be threaded before use just as is done with a needle and thread prior to sewing fabric. The advantage of this is that any combination of thread and needle may be chosen to suit the job at hand. Swaged needles with sutures consist of a pre-packed eyeless needle already attached to a specific length of suture thread. This saves time, and eliminates the most difficult threading of very fine needles and sutures.
Two additional benefits are reduced drag and less potential damage to friable tissue during suturing. In a swaged suture the thread is of narrower diameter than the needle, whereas it protrudes on both sides in an eyed needle. Being narrower, the thread in a swaged suture has less drag when passing through tissue than the needle, and, not protruding, is less likely to traumatize friable tissue, earning the combination the designation "atraumatic".
There are several shapes of surgical needles. These include:
  • Straight
  • 1/4 circle
  • 3/8 circle
  • 1/2 circle. Subtypes of this needle shape include, from larger to smaller size, CT, CT-1, CT-2 and CT-3.
  • 5/8 circle
  • compound curve
  • half curved
  • half curved at both ends of a straight segment
The ski and canoe needle design allows curved needles to be straight enough to be used in laparoscopic surgery, where instruments are inserted into the abdominal cavity through narrow cannulas.
Needles may also be classified by their point geometry; examples include:
  • taper
  • cutting
  • reverse cutting
  • trocar point or tapercut
  • blunt points for sewing friable tissues
  • side cutting or spatula points for eye surgery
Finally, atraumatic needles may be permanently swaged to the suture or may be designed to come off the suture with a sharp straight tug. These "pop-offs" are commonly used for interrupted sutures, where each suture is only passed once and then tied.
Sutures can withstand different amounts of force based on their size; this is quantified by the U.S.P. Needles Pull Specifications.

Thread

Materials

Suture material is often broken down into absorbable thread versus non-absorbable thread, which is further delineated into synthetic fibers versus natural fibers. Another important distinction among suture material is whether it is monofilament or polyfilament

Monofilament versus polyfilament

Monofilament fibers have less tensile strength but create less tissue trauma and are more appropriate with delicate tissues where tissue trauma can be more significant such as small blood vessels. Polyfilament sutures are composed of multiple fibers and are generally greater in diameter with greater tensile strength, however, they tend to have greater tissue reaction and theoretically have more propensity to harbor bacteria.

Other properties to consider

  • Tensile strength: the ability of the suture to hold tissues in place without breaking.
  • Elasticity: the ability of the suture material to adapt to changing tissues such as in cases of edema.
  • Tissue reactivity: inflammatory response of the surrounding tissue that can cause materials to break down quicker and lose tensile strength. Non absorbable synthetic suture have the lowest of tissue reactivity, while the absorbable natural fibers have the highest rates of tissue reactivity.
  • Knot security: the ability of the suture to maintain a knot that holds the thread in place.

    Absorbable

Absorbable sutures are either degraded via proteolysis or hydrolysis and should not be utilized on body tissue that would require greater than two months of tensile strength. It is generally used internally during surgery or to avoid further procedures for individuals with low likelihood of returning for suture removal. To-date, the available data indicates that the objective short-term wound outcomes are equivalent for absorbable and non-absorbable sutures, and there is equipoise amongst surgeons.

Natural absorbable

Natural absorbable material includes plain catgut, chromic catgut and fast catgut which are all produced from the collagen extracted from bovine intestines. They are all polyfilaments which have different degradations times ranging from 3–28 days. This material is often used for body tissue with low mechanical or shearing force and rapid healing time.

Plain gut (polyfilament)

  • Description: Maintains original strength for 7–10 days and full degradation occurs in 10 weeks.
  • Advantages/disadvantages: Excellent elasticity allowing for adaptation to tissue swelling. Passes through the skin with very little tissue trauma occurrence. Poor handling and high tissue reactivity causing quick loss of tensile strength.
  • Common use: best used in rapidly healing tissues with good blood supply i.e. mucosal tissues.

    Chromic gut (polyfilament)

  • Description: Maintains original strength for 21–28 days and full degradation occurs in 16–18 weeks.
  • Advantages/disadvantages: Excellent elasticity allowing for adaptation to tissue swelling. Passes through the skin with very little tissue trauma occurrence. Improved handling and decreased tissue reactivity due to chromic salt coating.
  • Common use: skin closure, mucosa, genitalia.

    Fast gut (polyfilament)

  • Description: Treated with heat to further break down protein and allow for more rapid absorption in bodily tissues. Tensile strength less than a week.
  • Advantages/disadvantages: Excellent elasticity allowing for adaptation to tissue swelling. Passes through the skin with very little tissue trauma occurrence.
  • Common use: Advised for skin closure only generally on the mucosa or face.

    Synthetic absorbable

Synthetic absorbable material includes polyglactic acid, polyglycolic acid, poliglecaprone, polydioxanone, and polytrimethylene carbonate. Among these are monofilaments, polyfilaments and braided sutures. In general synthetic materials will keep tensile strength for longer due to less local tissue inflammation.

Poliglecaprone (monofilament, Monocryl, Monocryl Plus, Suruglyde)

  • Description: copolymer of synthetic materials. Loses tensile strength quickly; sixty percent lost in the first week. All strength lost within 3 weeks.
  • Advantages/disadvantages: high tensile strength, excellent elasticity, excellent cosmetic outcomes, decreased hypertrophic scarring, minimal tissue reaction, good knot security originally; however, the material makes the security unreliable over time, thus it is important to keep ears of material long.
  • Common use: Advised for subcutaneous and superficial tissue closure.

    Polyglycolic acid (polyfilament, Dexon)

  • Description: synthetic polymer that loses all tensile strength in by 25 days. Either dyed green for visibility or undyed.
  • Advantages/disadvantages: minimal tissue reaction, good tensile strength, good handling, but poor knot security.
  • Common use: subcutaneous tissue.

    Polyglactin 910 (polyfilament, Vicryl)

  • Description: loss of all tensile strength in 28 days.
  • Advantages/disadvantages: minimal tissue reaction, good tensile strength, good knot security,
  • Common use: subcutaneous tissue, skin closure.

    Polyglactin 910 Irradiated (polyfilament, Vicryl Rapid)

  • Description: sourced as vicryl is with irradiation to break down material for quicker absorption. Loss of all tensile strength in 5–7 days.
  • Advantages/disadvantages: minimal tissue reaction, good tensile strength, fair good handling and good knot security.
  • Common use: scalp and facial laceration closure.

    Polyglyconate (monofilament, Maxon)

  • Description: co polymer product of synthetic materials. Loses 75% of the tensile strength after 40 days.
  • Advantages/disadvantages: minimal tissue reaction, excellent tensile strength, good handling.
  • Common use: subcutaneous use often an alternative to PDS due to better handling and slightly superior tensile strength.

    Polydioxanone closures (PDS, monofilament)

  • Description: loss of tensile strength in 36–53 days.
  • Advantages/disadvantages: minimal tissue reaction, good tensile strength, but poor handling.
  • Common use: subcutaneous with need of high tensile strength.

    Non-absorbable

These sutures hold greater tensile strength for longer periods of time and are not subject to degradation. They are appropriate for tissues with a high degree of mechanical or shear force. They also supply the operator with greater ease of use due to less thread memory.
Natural
  • Description: surgical silk is a protein derived from silkworms that is coated to minimize friction and water absorption.
  • Advantages/disadvantages: This material has good tensile strength, is easy to handle and has excellent knot security. However, it is rarely used internally due to its significant tissue reaction which causes loss of tensile strength over months.
  • Common use: Due to advancements in sutures, there is no longer indication for use of surgical silk. However, it is still commonly used in dentistry for mucosal surfaces or to secure surgical tubes on the bodies surface.