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 are supplied separate from their suture thread. Such suture must be threaded on site, as is done in embroidery sewing. The advantage of this is that any thread and needle combination is possible to suit the job at hand. Swaged, or atraumatic, needles with sutures consist of a pre-packed eyeless needle attached to a specific length of suture thread. The suture manufacturer swages the suture thread to the eyeless atraumatic needle at the factory. The chief advantage of this is that the doctor or the nurse does not have to spend time threading the suture on the needle, which may be difficult for very fine needles and sutures. Also, the suture end of a swaged needle is narrower than the needle body, eliminating drag from the thread attachment site. In eyed needles, the thread protrudes from the needle body on both sides, and at best causes drag. When passing through friable tissues, the eye needle and suture combination may thus traumatise tissues more than a swaged needle, hence the designation of the latter as "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.