Introduction

The choices that veterinarians make every day with regard to suture materials, needle choices and how to optimize their use in closure of all kinds of tissues tend to be automated and are generally given little consideration. Most veterinarian’s busy clinical lives leave little time for consideration of these more mundane-seeming points but these decisions can have profound effects on surgical outcomes including surgical site infections (SSI) and wound dehiscence. These complications can not only lead to a longer treatment course for the patient and increased costs for owners can even precipitate life-threatening or fatal results when procedures involve luminal organs of the gastro-intestinal or urinary tract. Over the last few years, much research in this field has emerged and medical device companies have introduced many new products in the wound closure space.

Needle selection in small animal surgery can be mind-boggling as a huge variety of choices that are on offer to the human medical world are also available to veterinarians. Needle point type is one important choice to make. Most commonly either taper point or cutting needles are used. Taper points are preferred for luminal organs, vascular surgery and subcutaneous closure. Taper point needles won’t cut through delicate tissues and tend to reduce the size of the hole created in the tissue. A variety of cutting needles exist that allow passage of the needle through fibrous or dense tissue such as fascia and the dermis/epidermis. Reverse cutting needles are often the preferred cutting needle type in order to prevent widening of the suture holes as the needle is drawn through the tissues. Regardless of needle type, it is essential to remember that the way a needle is passed through tissue has a major effect on the tissue track that a needle creates. Surgeons should always use a rotating wrist action to allow the curvature of the needle to pass through the tissue rather than pushing the needle through which tends to result in larger needle holes.

Suture should ideally only persist in tissue for as long as it is required and no longer. Suture materials are generally categorized according to whether they are monofilament, multifilament, absorbable or non-absorbable.

Monofilament sutures are generally preferred, as they have less tissue drag and are less likely to harbor bacteria, although there are also coated multifilaments that minimize the risk of bacterial colonization and improve handling. Multifilaments have the one distinct advantage of having less memory and therefore better handling properties. Absorbability occurs due a variety of mechanisms including proteolytic enzyme breakdown (chromic gut) and hydrolysis (polydioxanone, poliglecaprone 25, polyglactin 910). The rate of absorption is important to understand as well as the fact that absorption can be markedly affected in the face of different tissues as well as different environments such as infection. In healthy tissue loss of 50% of normal tensile strength for commonly used suture materials including poliglecaprone 25 (e.g., Monocryl), polyglactin (e.g., Vicryl), and polydioxanone (PDS) occurs at 1–2 weeks, 2–3 weeks and 5–6 weeks, respectively, with complete absorption occurring at 119 days, 56–70 days and around 180 days, respectively. However, an example of the effect of tissue environment on suture absorption is urinary tract infection.

Data from experimental studies where commonly used suture materials were bathed in urine containing bacteria commonly implicated in urinary tract infections showed profound effects in some cases.¹ In this study soaking of tested sutures in urine accelerated degraded of all suture types tested and Proteus infected urine caused poliglecaprone 25 to retain only 11–14% of tensile strength by day 14.¹ As a result, the authors suggested that poliglecaprone 25 may not be an appropriate suture type for use in animals that might be harboring such an infection. Data such as this should help inform surgeons suture choices and is the reason the author prefers longer lasting sutures such as polydioxanone in the urinary tract and why, if possible, an effort should be made to minimize exposure of suture material to urine when these cases are being operated. The gastro-intestinal tract environment can also have potential effects on the degradation of certain suture materials. One study evaluated the effect of pH on polydioxanone degradation and found that in acidic environments such as the stomach tensile strength degraded rapidly after 2 weeks immersion in a solution with a pH of 1.0, at which time there was no measurable tensile strength remaining.²

Other important considerations when choosing sutures are suture sizes and knot security. The weakest point of any continuous closure is the knot and so in these situations knot security is paramount. It is well known that extra throws should be placed on the ends of continuous closures and it is generally recommended that one extra throw should be placed at the beginning and 2–3 extra throws should be placed at the end of a continuous line.³ We also know that suture size is an important variable in knot size and secondarily tissue reactivity to the knot. For every suture size increase, knot volume increases by a factor of 4–6 with a consequent increase in tissue reactivity of 2–3 fold.⁴ Use of the smallest sized suture that is strong enough for any given indication is, therefore, encouraged.

As it is well recognized that there is an inverse relationship between the volume of suture material in a wound and the number of bacteria needed for an SSI to develop, considerable interest in the role of antibacterial sutures has developed. Most antibacterial sutures use a coating of triclosan as their active agent, which has been shown to have in vitro activity against Staphylococcus aureus and epidermidis, methicillin-resistant staphylococcus aureus, Enterococcus sp., Pseudomonas sp., and Escherichia coli.⁵ While several large studies have struggled to demonstrate wholesale improvements in SSI or other wound complication rates both in veterinary^6,7 and human studies⁸, other studies have shown interesting findings in certain procedure types, notably in gastrointestinal applications, where inflammatory and wound healing parameters were improved with the use of triclosan-coated antibacterial suture materials.⁹ Further larger studies in veterinary species will be required to fully elucidate the quantitative benefit if any in our small animal species.

One new and exciting development in the suture space recently has been the availability of barbed sutures designed to facilitate knotless continuous suturing. While primarily developed to facilitate intracorporeal suturing where knot tying is a significant challenge, they are also being used extensively in open surgical techniques. Barbs cut into the body of the suture create friction as they pass through tissues thereby maintaining tension and negating the need for knots to be tied at the end of the continuous line. At the start of a suture line barbed sutures either incorporate a loop (VLOC, Medtronic Inc., Stratafix, Ethicon Inc.) through which the suture is passed after the first bite has been thrown or a fixation tab (Stratafix, Ethicon Inc.), which will anchor the suture end as it will not easily pass through the tissue after the first bite has been taken. These sutures have been used extensively in minimally invasive procedures such as intracorporeal gastropexy¹⁰ but also have been described for open gastro-intestinal suturing as even tendon repair.

References

1.  Greenberg CB, Davidson EB, Bellmer DD et al. Evaluation of the tensile strengths of four monofilament absorbable suture materials after immersion in canine urine with or without bacteria. Am J Vet Res. 2004;65:847–853.

2.  Tomihata K, Suzuki M, Kada Y. The pH dependence of monofilament sutures on hydrolytic degradation. J Biomed Mater Res. 2001:58;511.

3.  Rosin E, Robinson GM. Knot security of suture materials. Vet Surg. 1989;18:269–273.

4.  Van Rijssel EJ, Brand R, Admiraal C et al.  Tissue reaction and surgical knots: The effect of suture size, knot configuration and knot volume. Obstet Gynecol. 1989;74:64–68.

5.  Jones RD, Jampani HB, Newman JL. et al. Triclosan: a review of effectiveness and safety in health care settings. Am J Infect Control. 2000;28:184–186.

6.  Bischofberger AS, Brauer T, Gugelchuk G et al. Difference in incisional complications following exploratory celiotomies using antibacterial-coated suture material for subcutaneous closure: Prospective randomized study in 100 horses. Equine Vet J. 2010;42:304–309.

7.  Etter SW, Ragetly GR, Bennett RA et al. Effect of triclosan-impregnated suture for incisional closure on surgical site infection and inflammation following tibial plateau leveling osteotomy in dogs. J Am Vet Med Assoc. 2013;242:355–8.

8.  Chang WK, Srinivasa S, Morton R et al. Triclosan-impregnated sutures to decrease surgical site infections. Systematic review and met-analysis of randomized trials. Ann Surg. 2012;255:854–859.

9.  Gomez-Alonso A, Garcia-Criado FJ, Parreno-Manchado FC et al. Study of the efficacy of coated Vicryl Plus antibacterial suture (coated polyglactin 910 suture with triclosan) in two animal models of general surgery. J Infect. 2007;54:82–88.

10.  Takacs JD, Singh A, Case JB et al. Total laparoscopic gastropexy using 1 simple continuous barbed suture line in 63 dogs. Vet Surg. 2017;46:233–241.