Wound Closure Materials and Instruments

Sutures

Since prehistoric times, humans have been using various materials to sew skin wounds. The first known reference appears in the Edwin Smith Papyrus (c. 1600 BC) . Although the precise suture material was not described, examination of artifacts from that time period suggests it was most likely linen. Hippocrates has been credited with being the first, in 400 BC, to use the term “suture” in reference to sewing human tissue.

Over the centuries, suture materials that have been employed include cotton, leather, flax, insect mandibles, horse hair, and even human hair . Ancient Roman physicians would braid the hair of gladiators tightly in order to close their scalp wounds, thus demonstrating that sutures can produce immediate hemostasis in addition to wound edge approximation.

The ideal suture, were it to exist, would handle easily, hold a secure knot, and have high tensile strength. It would neither cause inflammation nor promote infection, and it would gradually dissolve, thereby obviating the need for suture removal. Unfortunately, the perfect suture material does not exist. However, the ever-widening array of choices available to the dermatologic surgeon and a knowledge of each suture's individual characteristics increases the likelihood of choosing the best possible materials for each surgical situation.

Suture materials are divided into two categories: (1) absorbable; and (2) non-absorbable. Studies of wound-healing have shown that during the first 1–2 weeks after surgery, the intrinsic tensile strength of the wound is approximately 7–10% of native bursting pressure . At 5 weeks, the intrinsic tensile strength is ~60%; therefore, in general, after 1 month dehiscence is unlikely with normal activity. During this time period, absorbable, buried, dermal sutures are utilized to alleviate tension and maintain wound edge approximation. Transepidermal, non-absorbable sutures are non-tension-bearing, but allow for fine adjustments of the epidermal edges.

The characteristic attributes ascribed to a suture are defined and standardized by the United States Pharmacopeia (USP) as follows:

• Two physical configurations exist: monofilament and multifilament. Multifilament suture can be spun, twisted or braided. Braiding serves to increase pliability, strength, knot security and handling , but may abrade or shear tissue. Braiding also potentially increases the risk of infection by allowing bacteria to become entrapped within the suture . Monofilament sutures have a low coefficient of friction and slide easily through tissue (see below) . Their drawback is that they are traditionally more stiff than braided suture and may have decreased knot security, requiring additional throws to ensure that the knot is secure. Until recently, monofilament sutures were used primarily for exterior suturing, and most buried sutures were braided. With the introduction of poliglecaprone 25 (Monocryl®), monofilament absorbable suture is now regularly employed for deep sutures.

• Capillarity is defined as the ability of a suture to absorb and transfer fluid. Multifilament sutures have greater capillarity than monofilament sutures.

• The USP size of a suture is determined by the diameter needed to achieve a given tensile strength and this is expressed in multiples of zeros; the smaller the cross-sectional diameter of the suture, the more zeros. For example, 7–0 polyglactin 910 (Vicryl®, Polysorb®) is a much finer suture than 3–0 polyglactin. The actual diameter of a given USP size varies depending upon the composition of the suture, e.g. a 4–0 surgical gut is a larger-diameter suture than 4–0 polypropylene because polypropylene is innately stronger. In general, the smallest suture that will provide adequate tensile strength for the indicated repair should be utilized.

• Elasticity refers to the ability of a suture to regain its original length after being stretched. An elastic suture, such as polybutester, allows for tissue swelling and then maintains tension on the wound edges after the edema has resolved.

• The coefficient of friction determines the ease with which a suture will pull through tissue. A suture with a low friction coefficient, such as polypropylene, slides easily through tissue. For this reason, polypropylene is commonly used for the running subcuticular suture (see Ch. 146 ). Knot strength is directly proportional to the friction coefficient of the suture material. The more slippery the suture material, the more likely it is that the resulting knot will unravel. Hence, when suturing with polypropylene, it is prudent to place several additional throws for each knot.

• Memory is defined as a suture's tendency to retain its natural configuration and is determined by the elasticity and plasticity of the suture material. Memory is a useful property for maintaining closure during the postoperative period, and high-memory sutures such as nylon are widely used for surface approximation. Drawbacks of high-memory sutures are that they do not handle very easily and have a relatively low knot strength. As with sutures that have a low coefficient of friction, a few extra throws may help to ensure a secure knot. Suture material with low memory, such as silk, is easy to handle and rarely becomes untied.

• Plasticity is the ability of the suture to be molded or retain its new length and form as well as tensile strength after it has been stretched. This is an important characteristic for a suture material that is to be used in situations with tissue edema. Sutures with plasticity, such as polypropylene, will stretch to accommodate edema and not cut into tissue .

• Pliability refers to how easily the suture can be bent. Braided suture materials, such as silk, are the most pliable, and they are capable of readily being tied into a knot.

• The tensile strength of a suture is determined by measuring the force (in pounds) required to snap it and then dividing that force by the cross-sectional diameter of the suture. In general, synthetic materials are stronger than natural materials. A suture that has been knotted has approximately one-third the tensile strength of the same material unknotted .

• Tissue reactivity is the degree of foreign body inflammatory response evoked by a suture when placed into a wound. In general, natural materials (e.g. surgical gut) are degraded by proteolytic enzymes and cause a much greater inflammatory response than do synthetic materials (e.g. polypropylene) which are absorbed via hydrolysis .

Types of Suture Material

Sutures are characterized as absorbable or non-absorbable, based upon their ability to be enzymatically digested or hydrolyzed. Most absorbable sutures lose the majority of their tensile strength long before they are fully absorbed. In general, absorbable sutures are used to close the dermis and deeper subcutaneous layers and are not removed.

Non-absorbable sutures are resistant to hydrolysis and enzymatic degradation. Non-absorbable sutures such as nylon and polypropylene are usually used as surface (or cutaneous) sutures, and they are routinely removed 5–14 days after surgery (earlier on the face and later on the trunk and extremities).

Absorbable Sutures

The most commonly used absorbable sutures are described below and summarized in Table 144.1 .