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 (called "eyes"), 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 (or "atraumatic") needles with sutures consist of a pre-packed eyeless needle already attached (by swaging) 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 (also known as ski) half curved at both ends of a straight segment (also known as canoe) 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 (needle body is round and tapers smoothly to a point) cutting (needle body is triangular and has a sharpened cutting edge on the inside curve) reverse cutting (cutting edge on the outside) trocar point or tapercut (needle body is round and tapered, but ends in a small triangular cutting point) blunt points for sewing friable tissues side cutting or spatula points (flat on top and bottom with a cutting edge along the front to one side) 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 (braided)
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 (braided) 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.
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