NA = Not Applicable.
Chu et al. (1997) and Capperauld (1989).
http://www.medtronic.com/covidien/en‐us/products/wound‐closure.html.
http://woundclosure.ethicon.com/traditional‐suture‐search.
2.1.1 Predictable Absorption Profile
Suture materials are manufactured from natural and synthetic sources. Natural absorbable sutures mentioned in this chapter include catgut and chromic catgut. Absorption of catgut is unpredictable because it is degraded by proteolytic enzymes and phagocytosis and causes a marked tissue inflammatory response that may be detrimental to healing. Pre‐existing tissue inflammation and enzymatic digestion from gastric enzymes can lead to rapid catgut suture degradation. These aforementioned suture characteristics have nearly made natural sutures made of catgut obsolete in small animal surgery.
Synthetic absorbable monofilament suture materials are preferred for gastrointestinal surgery. Synthetic sutures are degraded by controlled hydrolysis making their absorption from tissue highly predictable. The degradation of most synthetic sutures is accelerated in alkaline environments, except for polydioxanone. This suture degrades rapidly in highly acidic environments, so, theoretically, other synthetic absorbable sutures may be better choices when exposed to gastric contents (Freudenberg et al. 2004). The stomach generally heals quickly, so more rapid absorption of polydioxanone from the wall may not be clinically important.
2.1.2 Tensile Strength and Knot Security
Most suture materials out of the package have adequate strength to hold gastrointestinal wound edges together until adequate wound strength is regained (Table 2.1). Knot security is influenced by suture diameter, coefficient of friction, and, most of all, quality of the tied knot. In general, braided suture materials have greater tensile strength than monofilament sutures. Coating of braided sutures negatively affects knot security. Some sutures, particularly glycomer (Biosyn) and polyglytone 6211 (Caprosyn), may been found to have decreased knot security when incubated in canine serum for 24 hours (Marturello et al. 2014). For most sutures within the size range of 3‐0 and 4‐0, at least four square throws are necessary to secure knots effectively. Care should be taken when tying monofilament sutures, particularly nylon, that the knots are pulled tight enough to cause “plastic deformation.”
Tightening monofilament suture materials to ensure security by “plastic deformation” is important, but overtightening of the stitch can occur due to their slippery, smooth surface. With multifilament suture materials, on the second square throw, the knot is set when snugged firmly. Therefore, the tightness of the first throw is locked in place when the second throw is snugged down. Subsequent square throws are placed to ensure permanent knot security. For monofilament sutures, however, tightening the second throw to create plastic deformation will continue to tighten down the stitch because the smooth suture strands slip somewhat. Therefore, use this characteristic when tensioning throws on monofilament suture. The first throw is left somewhat loose, the second throw is tightened until the stitch apposes the tissue edges (but the knot is still not fully plastically deformed), and subsequent throws are firmly tensioned to deform and lock the throws securely together (Zimmer et al. 1991).
2.1.3 Low Capillarity and Bacterial Adhesion
The degree of fluid and bacteria transport along suture fibers is determined by the fluid absorption and capillarity of the suture material. Multifilament sutures that penetrate contaminated areas have the potential to wick bacteria and toxic fluid into adjacent sterile areas, and this can increase tissue inflammation and delay wound healing. In addition, the interstices within capillary multifilament sutures can help shield or slow bacteria clearance from the material (Osterberg 1983). Bacteria adhere more readily to the increased surface area around and within multifilament sutures. For these reasons, multifilament sutures are falling out of favor in gastrointestinal surgery (Thornton and Barbul 2014).
2.1.4 Handling Characteristics
Much of the desirable handling properties of suture are associated with the degree of “stiffness” or inherent memory of the suture material. As a rule, multifilament sutures handle better than the monofilaments because they are softer and more flexible. Smaller, more pliable sutures tend to hold their position when inserted and knotted in soft tissues, just as the surgeon intended. Sutures with “memory” that are stiff can force or shift stitches away from their intended path in tissue as they are secured, and this can cause unwanted malapposition and gap formation. The cut ends of stiff sutures can also result in significant mechanical irritation of adjacent tissues, and this can increase adhesion formation, and even cause erosion of adjacent friable tissue. A suture's handling quality is also related to its elasticity, or its tendency to elongate under tensile force. Smaller, more elastic suture materials are desirable because they can elongate with increased tensile loads, and this may help reduce suture cut‐out in tissue.
Multifilament sutures have rough surfaces compared to monofilaments, and they may cause considerable friction and trauma when pulled through tissues, particularly when used in continuous suture lines. Coating is often applied to help smooth out the surface of multifilament sutures so they pass through tissue without “drag.” However, suture coating causes other less desirable handling qualities as it tends to increase the stiffness of the material, and it often reduces its knot security.
