Chapter 8 The smallest diameter suture that will adequately secure wounded tissue should be used in order to minimize trauma as the suture is passed through the tissue and to reduce the amount of foreign material left in the wound. There is no advantage to using a suture that is stronger than the tissue to be sutured. The most commonly used standard for suture size is the United States Pharmacopeia (USP), which denotes dimensions from fine to coarse (with diameters in inches) according to a numeric scale, with 12-0 being the smallest and 7 the largest. The USP uses different standards for surgical gut and for other materials (Table 8-1). The smaller the suture size, the less tensile strength it has. Stainless steel wire is sized according to the metric or USP scale or by the Brown and Sharpe (B and S) wire gauge (see Table 8-1). Suture materials may be classified according to their behavior in tissue (absorbable or nonabsorbable), their structure (monofilament or multifilament), or their origin (synthetic, organic, or metallic) (Fig. 8-1 and Table 8-2). Two major mechanisms of absorption result in the degradation of absorbable sutures. Sutures of organic origin, such as surgical gut, are gradually digested by tissue enzymes and phagocytized, whereas sutures manufactured from synthetic polymers are principally broken down by hydrolysis. Nonabsorbable sutures are ultimately encapsulated or walled off by fibrous tissue. Characteristics of Suture Materials Commonly Used in Veterinary Medicine *Values given are approximate. Actual loss of tensile strength may vary depending on suture and tissue. †(−), Poor (<60%); (+), fair (60% to 70%); (+ +), good (70% to 85%); (+ + +), excellent (>85%). ‡(−), Minimal to none; (+), mild; (+ +), moderate; (+ + +), severe. Absorbable suture materials (e.g., surgical gut, polyglycolic acid [Dexon, Covidien, Mansfield, Mass.], polyglactin 910 [Vicryl, Ethicon, Somerville, N.J.], polydioxanone [PDS II, Ethicon, Somerville, N.J.], polyglyconate [Maxon, Covidien, Mansfield Mass.], poliglecaprone 25 [Monocryl, Ethicon, Somerville, N.J.], glycomer 631 [Biosyn, Covidien, Mansfield, Mass.]) lose most of their tensile strength within 60 days and eventually disappear from the tissue implantation site because they have been phagocytized or hydrolyzed (see Figure 8-1 and Table 8-2). The time to loss of strength and for complete absorption varies among suture materials. Synthetic absorbable materials (see Table 8-2) generally are broken down by hydrolysis and cause minimal tissue reaction. The time to loss of strength and to absorption is fairly constant even in different tissue. Infection or exposure to digestive enzymes does not significantly influence the rate of absorption of most synthetic absorbable sutures. Polyglactin 910 and polyglycolic acid are more rapidly hydrolyzed in alkaline environments, but they are relatively stable in contaminated wounds. Polyglycolic acid, polyglactin 910, and poliglecaprone 25 may be rapidly degraded in infected urine; polydioxanone, polyglyconate, and glycomer 631 are acceptable for use in sterile bladders and those infected with E. coli. However, any suture that is degraded via hydrolysis may be at risk for accelerated degradation when the bladder is infected with Proteus spp. (see also p. 755), as all common monofilament absorbable sutures have been shown to degrade within 7 days in P. mirabilis–inoculated urine. The three basic components of a needle are the attachment end (i.e., swaged or eyed end), the body, and the point (Fig. 8-2, A). Eyed needles must be threaded, and because a double strand of suture is pulled through the tissue, a larger hole is created than when swaged suture material is used. Eyed needles may be closed (i.e., round, oblong, or square) or French (i.e., with a slit from the inside of the eye to the end of the needle for ease of threading) (Fig. 8-2, B). Eyed needles are threaded from the inside curvature. The use of eyed needles in veterinary practice has decreased substantially in recent years. With swaged sutures, the needle and suture form a continuous unit, which minimizes tissue trauma and increases ease of use. The needle body comes in a variety of shapes (Fig. 8-2, C); the tissue type and depth and the size of the wound determine the appropriate needle shape. Straight (Keith) needles generally are used in accessible places where the needle can be manipulated directly with the fingers (e.g., placement of purse-string sutures in the anus). Curved needles are manipulated with needle holders. The depth and diameter of a wound are important when selecting the most appropriate curved needle. One-fourth ( The needle point (i.e., cutting, taper, reverse cutting, or side cutting) (Fig. 8-2, D) affects the sharpness of a needle and the type of tissue in which the needle can be used. Cutting needles generally have two or three opposing cutting edges and are designed for use in tissues that are difficult to penetrate, such as skin. With conventional cutting needles, the third cutting edge is on the inside (i.e., concave) curvature of the needle. The location of the inside cutting edge may promote more “cut out” of tissue because it cuts toward the edges of the wound or incision. Reverse cutting needles have a third cutting edge on the outer (i.e., convex) curvature of the needle; this makes them stronger than similarly sized conventional cutting needles and reduces the amount of tissue cut out. Side cutting needles (i.e., spatula needles) are flat on the top and bottom and are generally used for ophthalmic procedures. Taper needles (i.e., round needles) have a sharp tip that pierces and spreads tissues without cutting them. They generally are used in easily penetrated tissues, such as the intestine, subcutaneous tissue, or fascia. Taper-cut needles, which are a combination of a reverse cutting edge tip and a taperpoint body, generally are used for suturing dense, tough fibrous tissue, such as a tendon, and for some cardiovascular procedures, such as vascular grafts. Bluntpoint needles have a rounded, blunt point that can dissect through friable tissue without cutting. They occasionally are used for suturing soft, parenchymal organs, such as the liver or kidney.
Biomaterials, Suturing, and Hemostasis
Sutures and Suture Selection
Suture Characteristics
Suture size
Specific Suturing Materials
TABLE 8-2
Absorbable Suture Materials
Synthetic absorbable materials
Nonabsorbable Suture Materials
Surgical Needles
) circle needles are primarily used in ophthalmic procedures. Three-eighths (
) and one-half (
) circle needles are the most commonly used surgical needles in veterinary medicine. Three-eighths circle needles are more easily manipulated than one-half circle needles because they require less pronation and supination of the wrist. However, because of the larger arc of manipulation required, they are awkward to use in deep or inaccessible locations. A one-half circle or five-eighths (
) circle needle, despite requiring more pronation and supination of the wrist, is easier to use in confined locations.
Biomaterials, Suturing, and Hemostasis
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