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of diagnostics, including manual exploration and probing, ultrasound, contrast or plain radiographs, CT, or MRI of the wound [7]. If self‐mutilation was the cause of the dehiscence, it is usually diagnosed through observation or evidence of a rough anesthetic recovery, rubbing, biting, or pawing [6]. Cytological or histopathological examination may be indicated to identify an underlying cause such as neoplasia [5].

       Treatment

      Treatment will vary depending on the identified cause of incisional dehiscence and whether it is a partial or completed dehiscence. Location, size, tissue viability, reason for the dehiscence, owner expectations and financial concerns will all play a critical role in how the dehisced sutured line is treated. Examination of the dehisced incision and determination of cause is the first step in determining a course of treatment. Early and meticulous evaluation of the dehisced incision along with appropriate management using a combination of timely surgical and medical treatments are used to promote the best healing outcome [6].

      If there is no suspicion of infection then the dehisced sutures are removed, the wound cleansed, without the use of antiseptics, debrided, lavaged, and primary closure can be performed [5]. If excessive tension is suspected, additional steps are taken as needed, such as incorporating tension relieving suture patterns, walking sutures, or tension relieving techniques such as tissue undermining, relief incisions, or plasties can be performed [7]. If excessive motion is thought to be involved, increasing incisional support through bandaging, splinting, or casting is recommended. In addition, stricter confinement may be necessary, such as cross‐tying, smaller stall confinement, no hand‐walking, etc.

      Partial dehiscence or intentional partial dehiscence, in the case when dependent sutures are removed to allow for adequate drainage, can be managed with appropriate wound care including cleansing, debridement, lavaging, and appropriate wound dressings.

      Passive or active drains are incorporated to ensure adequate drainage and obliteration of dead space if discharge, fluid, or gas build‐up within the repair was suspected to have contributed to the dehiscence. Drains will function by channeling undesired discharge, fluid, gas, or debris and usually promotes faster healing and decreases the chance of dehiscence reoccurring [3]. Incorporation of a compression bandage when applicable will help with the elimination of dead space.

      Common isolates from infected equine wounds include Streptococcus spp, Staphylococcus spp, Enterobacteriaceae, Pseudomonas spp, and anaerobes [6]. With the suspicion of infection of the suture line, a course of broad‐spectrum antibiotics and or regional limb perfusions are recommended and initiated until culture and sensitivity results have been obtained. Delayed primary closure, secondary closure, or second intention healing are recommended in cases where there is a presence of infection, necrotic or compromised tissue, or if additional debridement is needed [5]. The degree of bacterial contamination, determined by qualitative and quantitative culture, will help identify the most appropriate wound management [7]. Appropriate wound care and wound dressings are essential and are dictated by the wound characteristics and phase of wound healing.

Sequesta formation may not be evident on radiographs until 3–4 weeks after injury [6, 7, 14]. Similarly, healing is delayed in most horses with foreign bodies present and are prone to dehiscence of the suture line and development of a persistent draining tract [6, 14]. Prolonged medical treatments are usually unsuccessful in resolving the infection and the drainage returns once treatment is discontinued. Complete removal of the fistulous tract, sequestrum and debridement of the underlying bone or removal of the foreign body usually results in a positive outcome [6]. The dehisced incision may be managed by primary closure or second intention healing [6]. In dehisced cases not managed by closure, skin grafting can improve the cosmetic appearance [6, 7].

      In the case of self‐mutilation, applying cayenne pepper or similar substances on the outside of the bandage may deter the behavior in some horses. Medicating with tranquilizers or other calming agents may also be indicated in horses not tolerant of stall confinement. Different bandaging techniques can be tried in certain cases, such as with head surgeries where the use of a stockinette or nothing in place of an Elastikon bandage may be more beneficial for the outcome of the incision healing.

      Systemic diseases that could be playing a factor in delayed wound healing and dehiscence should be addressed, diagnosed, and treated accordingly.

      Incisions over areas of motion should be immobilized appropriately, depending on the predicted amount of movement. This may be achieved with a bandage or a splint or cast in certain circumstances [7].

       Expected outcome

      The prognosis after treatment and/or repair of a dehisced wound is usually good as long as the initiating factors are recognized and eliminated. However, outcome will be impacted by blood supply and location of the dehisced wound. Dehisced incisions that are left to heal by second intention are at increased risk of decreased cosmetic appearance (hairless scar formation) and tissue strength, depending on size and location of the dehisced wound. Owners should be notified that financially the cost of extended periods of proper wound dressings, bandaging, and recheck examinations required for wound healing by second intention can easily exceed the cost of repairing the dehiscence via primary or secondary closure when indicated.

Infection Without Dehiscence

      Surgical site and suture line infections can lead to wound dehiscence as discussed earlier. However, suture‐related surgical site infections do not always lead to dehiscence, although risk factors, diagnosis, treatment, and prevention are similar to that of dehisced wounds due to infection. Details are discussed in Chapter 17: Complications Associated with Surgical Site Infections.

Suture Reactions

       Definition

      Suture‐related tissue reaction is a local inflammatory response induced by the suture material.

       Risk factors

       Suture material

       Inappropriately large suture

       Excessive suture material

       Inappropriate suture technique

       Excessive tension

       Pathogenesis

      Tissues react to all suture material regardless of the type of suture material used [9]. Excessive tissue reaction to suture results in edema, tissue friability, and subsequent suture failure [9]. Usually, the inflammatory reaction is most prominent at the knot site, since the knot represents the major foreign body mass and density, and causes the most mechanical trauma to the tissues [22].

       Suture material

      Both the physical (monofilament vs. multifilament) and the chemical composition influence the reaction that takes place within the tissues [23]. Monofilament suture material withstands contamination better than multifilament suture material, while also having less tissue reactivity properties [23, 24]. Multifilament material results in more tissue trauma and has more capillary action, which may increase the potential for bacterial contamination [5]. Although bacteria can adhere to any suture material, multifilament suture surfaces tend to adhere to higher numbers of bacteria when compared to monofilament suture [4, 23]. Antibacterial‐coated suture may be responsible for increased risk of development of incisional edema [16]. Chronic granulomatous or abscess formation is a reaction that can occur secondary to suture material placement, which may result in a discharging sinus [9]. Surgical gut is a capillary multifilament suture that elicits a marked foreign body reaction when implanted in tissues because it is composed of collagen [23, 24]. In contrast, synthetic monofilament absorbable sutures such as polydioxanone, polyglyconate, and polyglecaprone 25 as well as synthetic multifilament

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