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A suture is synonymously used to refer to the thread, the finished stitch, or the delicate procedure of closing a surgical wound or traumatic injury. A subcuticular suture refers to the more difficult technique of repairing a deep wound that extends below the top layer of skin, or epidermis. It is also called a subdermal, or subcutaneous suture. For surgeons, suturing is considered an indispensable skill.
The purpose of a suture is securing an edge-to-edge seamless seal to give a previously open wound the means and the time to heal itself. For a cut or wound through thick skin tissue, however, it is insufficient to merely cosmetically stitch the outer skin together — the underlying tissue would not heal. Early methods of addressing thicker body tissues meant simply ensuring that a larger surgical needle penetrated deeply enough for a larger stitch, tied more tightly to compress everything together.
A more modern approach recognizes that skin is made of layers of different tissue with properties which may be better served with different threads and stitches. The subcutis, also called the hypoderm, is the innermost layer of skin. Composed of several types of loose connective tissue, this layer of skin when healthy is strong and durable. A subcuticular suture repairs this skin layer first. Suturing of the outer epidermis follows, often using techniques to minimize scarring.
The use of dissolving thread is preferred for a subcuticular suture buried under the skin. Made of various bio-degradable synthetic material, these sutures are absorbed by the body and disappear over time. Traditional sutures such as silk can also be used, but their tagged ends are exposed outside the skin for ease of removal after sufficient time.
A surgical needle is quite different from needles typically used for sewing cloth. They are curved, semi-circular in shape and of varying length and diameter. Some have eyelets, but most are manufactured with a pre-determined length of suture thread attached to its sharpened tip. These are called swaged needles and are meant to be disposed after use.
The basic motion is to corkscrew the needle’s curved shape along the seam of a wound. When done continuously with a long thread, this is called a running suture. Most surgeons have a preference instead for so-called interrupted sutures, which are individually tied stitches using very short thread. The subcuticular suture employs an additional stitch called a running horizontal mattress suture, in which individually tied stitches remain continuously connected to adjacent stitches. The suture is finished with a double overhand or surgeon’s knot.