*4.1.2 Suture materials*

Most sutures used today are composed of either natural materials such as gut or silk or an increasing variety of manmade synthetic polymers [23]. Their physical formats can be either monofilament, multifilament (braids) or barbed monofilaments [23]. They can be nonabsorbable (permanent) or absorbable (temporary) [7]. Desirable characteristics of sutures include pliability for ease of handling, adequate tensile strength, knot security, minimal tissue reactivity, infection resistance, and good elasticity and plasticity to accommodate wound swelling or tissue growth [7]. The choice of a suture material depends on factors such as the number of tissue layers involved in wound closure, the critical wound healing period for the tissue involved, tension across the wound, depth of suture placement, presence of edema, and expected time of suture removal among others [24].

## *4.1.3 Absorbable versus nonabsorbable sutures*

While sutures can be made of many different natural and synthetic materials, the most significant categorization is that of their status as nonabsorbable versus absorbable sutures [21]. Nonabsorbable sutures which cannot be removed (e.g., those used below the skin surface) persist in the body even after tissue has regained enough tensile strength to be self-supporting and may elicit a foreign body response as they become encapsulated by fibrous connective tissue [7]. They may also be palpable and perceived as painful by the patient. Ideally, a suture material will remain strong enough to support the wound through the critical healing period and then gradually be absorbed [20]. With the advent of synthetic absorbable polymers for suture in the late 1960s, it became possible to design suture material that maintained its wound holding strength for specific durations of time (also called breaking strength retention or BSR) and were then absorbed by the body via hydrolysis and required no return visit for suture removal if used for skin closure [24]. The breaking strength retention times can be specifically controlled through the molecular composition of the polymers [21]. Among the various types of synthetic absorbable sutures, there are polymers that retain their breaking strength for one, two, four or six weeks before the absorption process significantly reduces it (**Table 1**).

The surgeon will choose the type of absorbable suture with the breaking strength retention period appropriate for the tissue being approximated and the specific clinical scenario [21]. For example, in a rapidly healing tissue such a mucosa, a shortterm absorbable suture such as low molecular weight polyglactin with a BSR of one week may be the optimal choice but for a longer healing tissue subject to mechanical stresses such as abdominal fascia, a slowly absorbable polydioxanone monofilament may be the best choice [7]. In fact, the EHS Guidelines just discussed have made that specific recommendation for fascial closure in elective midline incisions [23].

An initial concern with the advent of synthetic absorbable suture materials was their ability to maintain effective wound closure in different tissue types as compared to nonabsorbable suture materials [25]. There have been multiple meta-analyses performed to compare the performance of absorbable and nonabsorbable sutures for wound closure in various tissue types including skin, dermis, fascia, and muscle and comparing rates of wound healing complications [18, 25–28]. The largest such comparison across multiple procedure types reviewed outcomes post absorbable and nonabsorbable suture use in 25 randomized controlled trials and 5781 patients and


#### **Table 1.**

*Breaking strength retention times of different absorbable polymers.*

found no significant differences in surgical site infection, dehiscence, or other postoperative complications [25]. A 2016 meta-analysis compared outcomes for absorbable versus nonabsorbable sutures in skin closure (1748 patients in 19 RCTs) and confirmed that an absorbable suture for skin closure was an acceptable alternative for traditional nonabsorbable sutures with no significant differences between the two suture types in the incidence of wound infections, cosmetic outcomes, wound dehiscence, or patients' or caregivers' satisfaction [26]. In three large meta-analyses (56 RCT/14618 patients, 55 RCT/19174 patients, 8 RCT/426 patients) comparing the use of absorbable versus nonabsorbable sutures in fascial closure of laparotomy incisions, none demonstrated any significant differences in the surgical healing complication outcomes of incisional hernia, surgical wound dehiscence, or surgical site infection [18, 27, 28]. It should be noted that these comparisons focused on absorbable versus nonabsorbable sutures in general and not on specifically on slowly absorbable sutures which have been recommended by the European Hernia Society as the optimal fascial closure choice for elective midline incisions based on reduced risks of incisional hernia and dehiscence as previously discussed [23].

#### *4.1.4 Antibacterial sutures versus non-antibacterial sutures*

Sutures with antibacterial coatings were developed to address an underappreciated yet known risk factor for surgical site infection– bacterial colonization and biofilm formation on the suture [24]. Currently, the only globally available antibacterial sutures are those coated with triclosan (Plus Antibacterial Sutures, Ethicon, Inc., Somerville NJ). There have been multiple randomized controlled trials (RCT) of triclosan coated sutures compared to non-triclosan sutures with the primary outcome of SSI within 30 days [29]. These studies have been performed in various procedure types encompassing all surgical wound classifications (clean, clean-contaminated, contaminated, and dirty) [30]. Subsequently, there have been serial meta-analyses of these randomized trials published over time. **Table 2** presents the most recent metaanalyses of triclosan coated sutures versus non-triclosan-coated sutures [29–33]. While each of these meta-analyses incorporates largely the same RCT data, none of the listed analyses completely replicates the data in another, either due to timing or to included surgical procedure types. Each meta-analysis, whether including all types of surgical procedures or limited to specific types of surgical procedures, found a


#### **Table 2.**

*Recent meta analyses of triclosan coated antibacterial sutures versus non-antibacterial sutures.*

significant difference in the performance outcome of reduced risk of SSI with the use of triclosan coated sutures. The average reduction in risk of SSI ranged from 27 to 33% [29, 31]. A large meta-analysis focused primarily on economic outcomes included observational studies as well as RCT and found a risk reduction of 39% [32].

Two meta-analyses also employed trial sequential analysis (TSA) to quantify the statistical reliability of data in the cumulative meta-analysis adjusting significance levels for sparse data and repetitive testing on accumulating data [30, 32]. TSA is increasingly used as a tool to quantify the reliability of a meta-analytic outcome [30]. The TSA outcome of the meta-analysis of abdominal fascial closure was that triclosan coated sutures decrease the risk of SSI significantly and that further RCTs will not change that outcome [33]. The TSA outcome in the meta-analysis of triclosan coated sutures for any tissue closure was similar, concluding that the effect of the sutures was robust, and that additional data are unlikely to alter the summary effect [30]. No meta-analysis of triclosan-coated sutures reported any significant differences in any safety outcomes. These data collectively support the conclusion that triclosan-coated sutures are a valuable technology for wound closure in a wide variety of tissue types and procedures encompassing all surgical wound classifications with the intention of reducing the risk of SSI.

Furthermore, given that systematic reviews and meta-analysis cannot directly calculate the pooled SSI-attributable excess costs to healthcare, one investigator conducted an economic study to estimate the potential clinical and economic impact for NHS of using these sutures compared with conventional non-antimicrobial-coated absorbable sutures for wound closure [32]. Results showed that antimicrobial sutures may result in significant savings across various surgical wound types [32].

In 2021 the National Institute for Health and Care Excellence (NICE) commissioned an external assessment center to analyze the evidence base for Ethicon's Plus triclosan coated sutures as an innovative technology which consisted of 31 RCT involving over 14,000 patients [34]. Their analysis consisted of six de novo metaanalyses to establish the overall pooled effect size associated with Plus Sutures on the incidence of surgical site infections [34]. The primary outcome was the relative risk of developing a surgical site infection between Plus Sutures and control groups [34]. The six separate meta-analyses were done using: (1) all studies that provided enough


**Table 3.**

*NICE meta-analyses of triclosan coated suture evidence.*

data; (2) a subset of studies in adults; (3) a subset of studies in children; (4) a subset of studies in patients with clean wounds; (5) a subset of studies in patients with non-clean wounds; and (6) all studies of Plus Sutures including STRATAFIX Plus that provided enough data, as a sensitivity analysis. The details and results of these meta-analyses are shown in **Table 3** and led to NICE making the following recommendations to the United Kingdom's National Health Service:

Recommendation 1.1: Evidence supports the case for adopting Plus Sutures as part of a bundle of care for preventing surgical site infection in the NHS for people who need wound closure after a surgical procedure when absorbable sutures are an appropriate option [34].

Recommendation 1.2: Cost modeling shows that Plus Sutures is cost saving compared with non-triclosan absorbable sutures by an average of £13.62 per patient. These savings are from reduced surgical site infections. Cost savings will vary by surgery type and baseline risk of surgical site infection [34].

#### **4.2 Suture alternatives for skin closure**

#### *4.2.1 Staples*

Skin staplers are medical devices that can be used to place "metallic sutures" or staples for closure of skin incisions. Skin staples provide a fast method for wound closure which allows for good eversion of skin edges without strangulation of tissue and minimal scarring [35]. Most modern skin staples are made from stainless steel. Skin staplers may be designed with a fixed head, a multi-directional release head or a 360° rotating head to improve visibility and facilitate access to wound areas, and with ergonomic handles (pistol-grip). The staples may have a dry film coating to facilitate removal which is accomplished with a special instrument called a staple extractor. The jaws of the device are used to grab the crossbar of the staple and bend the points out of the skin for removal. Both nonabsorbable/metallic and absorbable polymerbased skin staples are available [35].

Staples are often used for skin closure due to the rapidity of deployment compared to sutures [35]. A 2020 systematic review and meta-analysis of 42 RCT involving 11,067 patients comparing staples to sutures for skin closure in adults undergoing any type of surgery in a hospital setting examined primary outcomes of any SSI and severe SSI (defined as deep incisional or organ/space) and secondary outcomes of post-operative hospital stay, rates of readmission for wound complication, adverse events within 30 days and patient satisfaction with cosmetic results [36]. It was

#### *Surgical Wound Closure and Healing DOI: http://dx.doi.org/10.5772/intechopen.105978*

noted that overall, the body of evidence was low to very low quality and that many of the studies did not report on all desired outcomes [36]. The authors concluded that sutures may reduce pain and provide better satisfaction with the cosmetic results than staples; however, it was uncertain whether using sutures decreased the risk of overall and severe SSI, readmission rates, adverse events and postoperative pain compared to wound closure with staples [36]. A more recent meta-analysis compared staples to sutures for skin closure elective knee and hip arthroplasties with primary outcomes of SSI [37]. Eight RCT involving 1120 patients were included. The studies were classified using the Cochrane risk of bias tool: two were low risk, four had some concerns and two were high risk. Five of the studies involved knees only, two involved hips only, and one involved both knees and hips. When all eight studies were combined for meta-analysis, no significant differences in the risk of SSI were found between sutures and staples; but when limited to only the studies with low risk of bias, there was a significantly higher risk of SSI with staples versus sutures [37]. After additional subgroup analysis, the authors concluded that "stapling might carry a higher risk of surgical site infection than suturing in elective knee and hip arthroplasties, especially in hip arthroplasty" [37].

### *4.2.2 Topical skin adhesives*

Tissue adhesives are a newer and potential alternative method of skin closure in surgical wounds (deeper tissue layers must still be closed with suture) [7]. Topical skin adhesives are commonly used in the emergency room setting for closure of acute traumatic lacerations and offer the advantage of reduced application time and reduced pain with no need for anesthesia as compared with standard wound-closure methods, which can be especially useful in pediatric patients [7]. Additionally, patients also avoid the need to return for removal of stitches or staples.

Topical skin adhesives come in a liquid monomer formulation and undergo a polymerization reaction when encountering moisture or a chemical initiator, leading to a slightly exothermic reaction and bonding to skin [38]. A chemical initiator can ensure consistent, dependable, and predictable polymerization times and is often located in the tip of the liquid adhesive applicator [38]. Monomers used in topical skin adhesives are cyanoacrylate-based (including n-butyl or 2-octyl side chains) and may contain other formulation additives to enhance strength, flexibility, or modulate viscosity and adherence to the skin [38]. Some topical skin adhesives incorporate a mesh patch. The purpose of combining a mesh patch with a topical adhesive as a system is to allow for temporary approximation of wound edges, (as opposed to digital approximation) prior to deployment of the liquid adhesive component which provides the definitive wound closure strength [39]. This temporary approximation can be especially useful in longer incisions where digital approximation along the length of the incision can be time-consuming [39]. In addition, the mesh component can provide added strength to the closure.

Topical skin adhesives can be used alone or in conjunction with other skin closure methods (sutures, staples). They provide sufficient strength to maintain skin edges approximation and distribute tension along the entire incision, preventing skin gaps from forming when the skin is stressed [38]. They can also create a strong, flexible barrier to prevent exogenous bacteria from entering the incision until the epidermis has fully resurfaced to re-establish the skin barrier [38]. Although initially widely used in the emergency room, surgeons are increasingly using topical skin adhesives for closure of surgical incisions in the operating room.

The most recent Cochrane systematic review of topical skin adhesives for closure of surgical incisions identified 33 RCT with 2793 patients [40]. Adhesives were compared to other methods of skin wound closure for outcomes of surgical wound dehiscence and infection and cosmesis. Meta-analysis found that sutures performed significantly better than adhesives for reducing the risk of wound dehiscence, but there were no significant differences between sutures and adhesives for wound infection or cosmesis [40].
