Complications in Canine Cranial Cruciate Ligament Surgery. Ron Ben-Amotz

play a controversial role in SSI development. Surgical staples in comparison to intradermal skin closures have been reported to increase, decrease or not have any effect on surgical site inflammation and/or SSI development [6, 30, 32]. Skin closure using absorbable skin staples has shown no benefit over stainless steel surgical staples in reducing SSI development [20]. With inconclusive evidence to suggest superiority of one closure method over another, considerations such as time for closure, associated tissue trauma, and potential irritation to the patient must play a role in decision making. While staples may reduce the closure time and thus overall surgery time, this is likely to be negligible for an experienced surgeon. Tissue trauma may also be reduced with skin staples due to minimal manipulation required for placement, but increased inflammation has been noted when surgical staples are used compared to intradermal sutures [6]. Finally, the noncompliant nature of skin staples may lead to increased local irritation and thus potential for self‐trauma from licking or chewing at the surgical site, if not adequately protected from access.

      Suture has the proven propensity for biofilm formation and as such may act as a nidus for SSI development [76]. Antimicrobial‐coated suture, specifically triclosan‐coated suture, has been assessed in vitro and in vivo for its ability to resist or reduce SSI development. In vitro, triclosan‐coated monofilament suture had the least bacterial adherence compared to other monofilament and braided suture materials and had greater inhibition for S. pseudintermedius, including MRSP, than Escherichia coli [77, 78]. In vivo, the use of triclosan‐coated monofilament suture was not shown to significantly reduce the risk of SSI in one hospital, while its use contributed to a reduction in SSI rates in another hospital [32, 64]. Further investigation of the use of antimicrobial‐coated suture is warranted. While a true benefit to antimicrobial‐coated suture remains unclear, the only limitation to its use is its increased cost, and as such, use of antimicrobial‐coated sutures should be considered.

      Postoperative fibrin formation to create a complete seal of a surgical wound takes 3–5 hours and therefore protection of the fresh surgical wound from its environment is recommended [79]. Considering evidence for environmental contamination from the anesthesia transportation gurney and radiology table used for postoperative radiographs, immediate protection with a sterile dressing is recommended [46]. Despite these recommendations, direct comparison of a topical adhesive applied to the incision, an adhesive antimicrobial barrier dressing, and no dressing following TPLO surgery found no significant difference in SSI rates amongst the dressing options [28]. In another study involving significant protocol changes for animals undergoing TPLO surgery, the addition of a soft padded bandage with mupirocin ointment directly on the surgical wound, use of single‐use gloves for all postoperative patient interactions, and placement of an Elizabethan collar for additional barrier protection resulted in an 88% reduction in the odds ratio for developing an SSI [64]. While many factors likely contributed to this SSI reduction, simple incisional protective measures are easy to implement into routine postoperative care. Additionally, while the use of gloves does not replace appropriate hand hygiene, sterile gloves are recommended to be worn during examination of clean surgical wounds to prevent transmission of bacteria to the surgical site [80].

2.5 Antimicrobial Use

The overall goal of antimicrobial therapy in orthopedic surgery is to reduce the bacterial load present at the time of surgery. The bacteria of concern are skin commensals, most commonly Staphylococcus spp., and are most susceptible to cefazolin. The administration of antimicrobials for this purpose is required only during the period of risk (i.e., the surgical procedure) and is not required preoperatively and rarely required postoperatively.

      2.5.1 Preoperative

      The use of preoperative antimicrobials is most often associated with a distant active infection, most commonly associated with wound and skin infections [70]. The use of preoperative antimicrobials has been associated with an increased risk for SSI and as such, postponement of elective orthopedic cases requiring preoperative antimicrobials is recommended [2]. Misuse and overuse of antimicrobials are known to contribute to antimicrobial resistance, therefore avoiding the potential for SSI development by postponing surgery in the face of active antimicrobial use should limit the animal's risk of developing a multidrug‐resistant SSI.

      2.5.2 Perioperative

      The use of perioperative antimicrobials for reduction of SSI is widely practiced in veterinary medicine. Few studies exist in veterinary medicine that provide insight into the appropriate timing for administration of perioperative antimicrobials. Therefore, guidelines followed for perioperative antimicrobial prophylaxis are largely adapted from human medicine. Current guidelines in human medicine state that an appropriate antimicrobial should be administered at least 60 minutes before the first surgical incision to allow time to achieve high serum levels, readministration of said antimicrobial should be performed every two half‐lives, and antimicrobial administration should be discontinued within 24 hours of surgery [81]. A few older veterinary studies provide evidence for perioperative antimicrobial prophylaxis as a protective factor against SSI development. These studies suggest that administration of antimicrobials should be limited to procedures longer than 90 minutes, the first dose of antimicrobial should be administered within 30 minutes of the first surgical incision, and if used appropriately, perioperative antimicrobial prophylaxis can reduce the SSI rate by 6–7 times [2, 7, 82].

      Recently, appropriate perioperative antimicrobial administration has been documented to be received by 42.5–85% of animals [13, 83, 84]. Generally, more animals receive an appropriately timed first dose than those requiring additional dosing over the course of surgery. However, in one study, the previously recommended initial dosing of perioperative antimicrobial administration 30 minutes before incision was challenged, as antimicrobial administration 60 minutes or more before incision was protective against development of SSI in a cohort of animals undergoing TPLO procedures [84]. In another study, inappropriate timing of perioperative administration was not significantly associated with the development of an SSI [13]. As this is a single finding, further supportive evidence is required before considering this association to be true and thus alter perioperative antimicrobial prophylaxis recommendations.

      At this time, evidence suggests that there is major room for improvement regarding compliance of perioperative antimicrobial prophylaxis, and implementation of a preoperative surgical safety checklist may improve compliance rates [67]. This lack of compliance may be leading to increased SSI rates being reported. Current recommendations for orthopedic antimicrobial prophylaxis include the use of cefazolin (22 mg/kg), administered 30 minutes before the first surgical incision, readministration every 90 minutes intraoperatively until skin closure, and discontinuation of antimicrobial therapy within 24 hours of surgery.

      2.5.3 Postoperative

While perioperative antimicrobial prophylaxis is recommended to be discontinued within 24 hours of surgery, a definition of when perioperative prophylaxis ends and postoperative antimicrobial therapy begins remains unknown. In human medicine, it is rare for antimicrobials to be continued beyond 24–48 hours postoperatively, even in the case of transplanted organs. Despite this knowledge, the increased incidence of SSI in clean elective orthopedic procedures has led to an increased use of postoperative antimicrobials. This is a controversial topic amongst veterinary surgeons, with evidence to both support and refute its use. Several studies including mainly TPLO surgeries, fewer TTA surgeries and some broad clean orthopedic procedures have identified a protective effect against SSI when postoperative antimicrobials are used [4, 9, 13, 21, 22, 30, 70, 83]. Fewer studies have identified a lack of effect on alteration of the SSI rate when postoperative antimicrobials are administered [8, 14, 16, 27, 29]. Additional studies identify postoperative antimicrobial use in clean orthopedic procedures including TPLO and the Arthrex Canine Cruciate Ligament Repair Anchor System™, without evaluating their effect on SSI rates [12, 19, 28, 52].

      At this time, there are a greater number of studies to support the use of postoperative antimicrobial use following TPLO surgery; however, the duration of treatment has been variable and specific recommendations cannot be made, although short