Skin grafts and skin flaps in the horse.

Although most equine wounds can be easily treated and heal without consequence, there are many that present special challenges. Skin grafts area valuable part of the veterinarian's armamentarium for treatment of complicated wounds, particularly limb wounds. Attention to preparation of the recipient site and proper aftercare are critical to successful grafting. With better understanding of equine wound and graft physiology and the promise foretold by advances in human skin grafting, the outcome of treatments of difficult equine wounds should continue to improve in the future.     

Bandages and topical agents

Bandages are included in the regimen of therapy of superficial wounds. Bandages have varying functions depending upon the type of wound to which they are applied. When bandaging recently inflicted open wounds, the primary bandage layer may be dry-to-dry, wet-to-dry, or wet-to-wet, depending upon the type of tissue and exudate present on the wound. These bandages aid in debriding and cleansing a wound. The secondary layer of such bandages serves primarily to absorb material from the wound, and the tertiary bandage layer serves to hold the other bandage layers in place. Once an open wound is well into the repair stage of healing, an occlusive bandage may be considered to help enhance epithelialization of the wound. Bandages for wounds associated with compound fractures must include some form of fixation for the fracture. Other types of bandages are designed to (1) cover closed wounds, (2) provide pressure over a wound, and (3) relieve pressure over wounds or impending wounds. Bandages for closed wounds provide protection and allow for absorption of exudate that may be present. Pressure bandages are used to control minor hemorrhage, edema, and excess granulation tissue. With impending decubital ulcers, actual decubital ulcers, or repaired decubital ulcers, it is necessary to have a bandage designed to relieve pressure over the lesion. Many substances have been described for topical application to wounds. This section presents information on some substances available to or commonly used by veterinarians. It includes information on the wound lavage solutions chlorhexidine diacetate, povidone-iodine, hydrogen peroxide, and sodium hypochlorite solutions. Topical antibacterial agents are used to help prevent wound infection. The triple antibiotics, silver sulfadiazine, nitrofurazones, and gentamicin sulfate are some commonly used antibacterial agents. Hydrophilic agents are used to diffuse fluids through the wound tissues to bathe the tissues from the inside. Dry starch copolymer flakes and dextran polymer beads are two substances that help bathe the wound with the body's own fluids. Other topical medications are used to selectively act upon various wound tissues and exudates to aid in cleansing the wound; these include organic acid preparations and enzymatic debriding agents. In addition, a live yeast-cell derivative has been described for enhancing tissue oxygen consumption, epithelialization, and collagen synthesis in wounds.     

Platelet-Rich Plasma as an Adjunctive Therapy for the Management of a Severe Chronic Distal Limb Wound in a Foal

Distal limb wounds are frequent in horses after traumatic events. The use of platelet-rich plasma (PRP) represents a simple method of treating wounds in equines. A case of a chronic severely contaminated distal limb wound in an 8-month-old foal is presented. The patient was managed with the combination of standard wound therapy (debridement and bandages), surgery, and PRP obtained by a manual tube protocol. No complications were observed with the PRP treatment, and the foal was fully recovered 2 months later. The results from this case report indicate that PRP and its by-products (platelet-poor plasma) could be used as an adjunctive treatment in severe distal limb wounds in horses. A clinical controlled study should be performed to test this hypothesis.     

Wound management in rodents.

Successful wound management requires appropriate evaluation of the wound at the time of initial physical examination, an all throughout the healing process. Factors affecting wound healing need to be identified though a complete patient history and addressed to ensure proper healing. The clinician must have current knowledge of topical medications and bandages available and their clinical applications according to the stage of healing. It is essential to remember that wounds are painful; therefore, analgesics should be administered to render the animal pain-free during wound cleaning, debridement, bandaging, and surgical procedures.     

Microbiology of equine wounds and evidence of bacterial biofilms

Horse wounds have a high risk of becoming infected due to their environment. Infected wounds harbour diverse populations of microorganisms, however in some cases these microorganisms can be difficult to identify and fail to respond to antibiotic treatment, resulting in chronic non-healing wounds. In human wounds this has been attributed to the ability of bacteria to survive in a biofilm phenotypic state. Biofilms are known to delay wound healing, principally due to their recalcitrance towards antimicrobial therapies and components of the innate immune response. This study describes the presence of bacterial biofilms within equine wounds. Thirteen 8-mm diameter tissue samples were collected from (n=18) chronic wounds. Following histological staining, samples were observed for evidence of biofilms. Fifty one wounds and control skin sites were sampled using sterile swabs. Control skin sites were on the uninjured side of the horse at the same anatomical location as the wound. The isolated bacteria were cultured aerobically and anaerobically. The biofilm forming potential of all the isolated bacteria was determined using a standard crystal violet microtitre plate assay. Stained tissue samples provided evidence of biofilms within 61.5% (8 out of 13) equine wounds. In total 340 bacterial isolates were identified from all the equine wound and skin samples. Pseudomonas aeruginosa and Enterococcus faecium were the most predominantly isolated bacterial species from equine wound and skin samples respectively. Staphylococcus was the most commonly isolated genus in both environments. Bacteria cultured from chronic and acute wounds showed significantly (P<0.05) higher biofilm forming potential than bacteria isolated from skin. This paper highlights preliminary evidence supporting the presence of biofilms and a high microbial diversity in equine chronic wounds. The presence of biofilms in equine wounds partly explains the reluctance of many lower limb wounds to heal. Non-healing limb wounds in horses are a well documented welfare and economic concern. This knowledge can be used to shape future treatments in order to increase the healing rate and decrease the costs and suffering associate with equine wounds.     

The antimicrobial activity of honey against common equine wound bacterial isolates

Delayed healing associated with distal limb wounds is a particular problem in equine clinical practice. Recent studies in human beings and other species have demonstrated the beneficial wound healing properties of honey, and medical grade honey dressings are available commercially in equine practice. Equine clinicians are reported to source other non-medical grade honeys for the same purpose. This study aimed to assess the antimicrobial activity of a number of honey types against common equine wound bacterial pathogens. Twenty-nine honey products were sourced, including gamma-irradiated and non-irradiated commercial medical grade honeys, supermarket honeys, and honeys from local beekeepers. To exclude contaminated honeys from the project, all honeys were cultured aerobically for evidence of bacterial contamination. Aerobic bacteria or fungi were recovered from 18 products. The antimicrobial activity of the remaining 11 products was assessed against 10 wound bacteria, recovered from the wounds of horses, including methicillin resistant Staphylococcus aureus and Pseudomonas aeruginosa. Eight products were effective against all 10 bacterial isolates at concentrations varying from <2% to 16% (v/v). Overall, the Scottish Heather Honey was the best performing product, and inhibited the growth of all 10 bacterial isolates at concentrations ranging from <2% to 6% (v/v).Although Manuka has been the most studied honey to date, other sources may have valuable antimicrobial properties. Since some honeys were found to be contaminated with aerobic bacteria or fungi, non-sterile honeys may not be suitable for wound treatment. Further assessment of gamma-irradiated honeys from the best performing honeys would be useful.     

A review of research into second intention equine wound healing using manuka honey: Current recommendations and future applications

In addition to the generic properties of honey, manuka honey has a nonperoxide antimicrobial activity largely attributed to methylglyoxal. Commercially, manuka honey is graded against a standard antiseptic, phenol, to provide a measure of antimicrobial activity referred to as the unique manuka factor (UMF). The higher the UMF, the greater the antimicrobial activity. However, more recently, there is evidence that manuka honey can also modulate the initial inflammatory response through activation of toll‐like receptor 4 on monocytes to enhance production of cytokines important in tissue repair and regeneration. Recent studies investigating the effects of manuka honey on second intention healing of lower limb wounds in horses have shown that wounds treated with UMF 20 manuka honey retracted less and healed faster than untreated wounds. Using this wound healing model, the primary effects of manuka honey appeared to be associated with the modulation of the initial inflammatory reaction rather than its antimicrobial effects. Based on the current knowledge, treatment with manuka honey should be instituted as soon as possible after injury. Where bacterial contamination is substantial, manuka honey with a UMF ≥15 should be used. While bandages will improve the contact between the honey and the wound and may be indicated in the early stages of wound healing, prolonged bandaging may lead to the production of excessive granulation tissue. If topical treatment without a bandage is to be used, more honey is not necessarily better. Using a thin film combined with regular application, contact times may be optimised. Application 2–3 times daily to open wounds may improve efficacy. Manuka honey should be applied for at least 21 days after wounding but there may be beneficial effects if it is applied until wound healing is almost complete.     

The use of magnetic resonance imaging for the assessment of distal limb wounds in horses: A pilot study

The utility of magnetic resonance (MR) imaging in the evaluation of equine solar foot penetrations is well established. The objective of this pilot study was to evaluate the utility of MR imaging in assessment of equine distal limb wounds excluding solar penetrations. Low-field MR images of 23 horses that had previously sustained distal limb wounds were reviewed in consensus by two ECVDI diplomats. Structures (bone; synovial structure; subcutaneous tissue and skin; and ligament/tendon) were identified as normal or abnormal on MR images, radiographs and ultrasound images and reports. All abnormalities were described. The presence of artefacts and their effect on image interpretation were also noted for each modality. Comparisons were made between imaging modalities, and it was noted if MR imaging influenced case management. Abnormalities of the bone were identified in 26% of horses on MR images and 17% of horses on radiographs; there were no osseous abnormalities identified on radiographs that were not identified on MR images, and additional features and better characterisation of lesions were noted on MR images. Tendon/ligament abnormalities were identified in 57% horses on MR and 47% of horses on ultrasound images. Magnetic susceptibility artefacts compromised MR image interpretation in 17% of horses. MR imaging of equine distal limb wounds allowed identification of both osseous and tendon/ligament abnormalities in more cases than either radiography or ultrasonography, and altered case management in 20/23 horses. Although MR imaging should not replace conventional imaging, this study highlights that MR imaging of equine distal limb wounds can yield information not detected on conventional imaging which may direct treatment and affect prognostication.     

The effect of equine recombinant growth hormone on second intention wound healing in horses

OBJECTIVE: To evaluate the effect of intramuscular administration of recombinant equine growth hormone on healing of full thickness skin wounds on equine limbs. STUDY DESIGN: Experimental. ANIMALS: Nine Standardbred horses. METHODS: In study 1, standardized full thickness skin wounds (2.5 x 2.5 cm) were made over the dorsomedial aspect of the mid-cannon bone of 1 forelimb and 1 hindlimb in 9 horses. Wounds were bandaged without treatment (control subjects) and videorecorded twice weekly until healed. Then, in study 2, similar wounds were created on the opposite limbs; 6 horses were administered intramuscular recombinant equine growth hormone (10 microg/kg daily for 7 days, then 20 microg/kg daily for 49 days), and 3 horses (control subjects) were administered equivalent volumes of sterile water. Wounds were videorecorded twice weekly until healed. Wound healing variables were measured from the videorecordings using a computer software package and analyzed as a randomized complete block design factorial analysis of variance; significance was set at P <.05. RESULTS: No differences in the measured variables were detected between wounds in study 1 and the control wounds in study 2. In recombinant equine growth hormone-treated horses, wounds retracted more during treatment and contracted faster after treatment stopped when compared with wounds from untreated horses. No other treatment effects were detected. CONCLUSIONS: Recombinant equine growth hormone seemingly increases wound retraction. After treatment ceases, wound contraction increases. CLINICAL RELEVANCE: Intramuscular administration of recombinant equine growth hormone (10 microg/kg daily for 7 days, then 20 microg/kg daily for 49 days) does not appear to have any beneficial clinical effect on healing of equine limb wounds.     

External coaptation

External coaptation includes the use of casts, splints, bandages, or slings to help stabilize fractures or luxations, reduce postoperative swelling, or help to protect wounds. Although each of these can be highly effective, it is very important to understand the various types of devices available and the indications for each. Inappropriate use of an external coaptation device can lead to unsatisfactory results.     

Spatial and temporal expression of types I and II receptors for transforming growth factor beta in normal equine skin and dermal wounds

OBJECTIVE : To describe immunolocalization of TGF-beta receptors (RI and RII) in normal equine skin and in thoracic or limb wounds, healing normally or with exuberant granulation tissue (EGT). STUDY DESIGN : Group A: six wounds on one metacarpus and one midthoracic area. Group B: six wounds on both metacarpi, one of which was bandaged to stimulate EGT. Immunohistochemistry was used to detect RI and RII expression in wound margins. ANIMALS : Eight horses, randomly assigned to one of two study groups. METHODS : Neutralizing polyclonal anti-rabbit RI and RII antibodies were used to detect spatial expression of RI and RII in biopsies obtained before wounding, at 12 and 24 hours, and 5, 10 and 14 days after wounding. RESULTS : RI and RII were co-localized in both unwounded and wounded skin. There were no differences in cell types staining positively between tissues obtained from the limb and the thorax, or from normally healing limb wounds and limb wounds with EGT, at any time. Because of increased cellularity within EGT, staining intensity of limb wounds with 'proud flesh' was greater than limb wounds healing normally, and thoracic wounds, during the proliferative phase of repair. CONCLUSIONS : Strong expression of RI and RII, particularly in limb wounds with EGT, suggested that signalling for stimulation of matrix proteins is in place to contribute to scarring. CLINICAL RELEVANCE : This information may help determine the appropriate time for using receptor antagonists to prevent scarring of limb wounds of horses.     

The pathophysiology of wound repair.

The equine practitioner who is presented with a wounded horse should fully understand the physiologic mechanisms involved in repair so as to design an appropriate treatment plan. In the following articles of this issue,experienced authors share their thoughts on the management of specific injuries, and the reader should benefit from acquisition of knowledge about the different phases of healing as well as the cytokines that regulate them,because these data dictate the approach to follow, particularly in com-plicated wounds, such as those afflicted by chronic inflammation and/or an excessive proliferative response.     

Second-intention repair in the horse and pony and management of exuberant granulation tissue.

Second-intention repair is faster in ponies than in horses and faster in body wounds than in limb wounds. To a large extent, the differences between horses and ponies can be explained by differences in the local inflammatory response, which are a result of the functional capacity of leukocytes. In ponies, leukocytes produce more inflammatory mediators,resulting in better local defense, faster cellular debridement, and a faster transition to the repair phases, with more wound contraction. In horses,leukocytes produce fewer mediators, initiating a weak inflammatory response, which becomes chronic. This inhibits wound contraction and gives rise to the formation of exuberant granulation tissue. The anatomic environment that influences the inflammatory response and wound contraction most probably determines the differences between body and limb wounds. In body wounds, better perfusion results in faster initiation of the inflammatory phase. The weaker local resistance results in a greater degree of contraction. In limb wounds, particularly of horses, the initial inflammatory response is weak and wound contraction is restricted. Both factors give rise to chronic inflammation, which further inhibits wound contraction and promotes exuberant granulation tissue. The high incidence of exuberant granulation tissue in limb wounds of horses can thus be explained by the chronicity of the inflammatory response as well as by the common use of bandages during treatment. Chronic inflammation is often not recognized as a cause of exuberant granulation tissue. It must be prevented and treated to promote the healing process. Bandages and casts stimulate the formation of exuberant granulation tissue; however, they are advantageous in many respects and play an important role in support of the overall healing process.     

Viability of split-thickness skin grafts attached with fibrin glue.

Full-thickness, circular, cutaneous wounds (4 cm diameter) were created on metacarpi and metatarsi of 5 horses. On day 6, all 4 wounds on each horse received a stored autogenous split-thickness sheet graft. Grafts were obtained from the horse's ventrolateral thorax with a pneumatic dermatome at the time the cutaneous wounds were created. Grafts were coapted to the granulation bed of 2 wounds of each horse with fibrin glue. Grafts were coapted to the cutaneous margin of all 4 wounds of each horse with cyanoacrylate glue. Bandages were changed daily until the study ended at 14 d. When the bandages were changed, ointment containing neomycin, polymyxin B, and bacitracin was applied to all wounds. The viable area of graft was measured on post-grafting d 14 and calculated with a micro-processor. Split-thickness sheet-grafts attached to granulation beds on the metacarpi and metatarsi with fibrin glue had no greater survival than did grafts attached without fibrin glue (P > 0.05).     

Chemotactic and chemokinetic activity of Streptococcus faecalis culture supernatant for equine neutrophils

Although equine neutrophils did not respond towards formylated methionyl peptides, Streptococcus faecalis culture supernatant caused an in vitro stimulation of equine neutrophil motility when measured by an under-agarose assay. The migration of neutrophils towards the culture supernatant increased sigmoidally with the logarithmic concentration of the culture supernatant in the chemoattractant wells. The streptococcal culture supernatant was chemokinetic because it stimulated the random motility of the phagocytes. Because granulocytes migrated further towards the supernatant than could be explained by the chemokinetic activity of the bacterial products, the streptococcal culture fluid also exerted a chemotactic effect on the leukocytes. The chemotactic activity of the supernatant was further confirmed by the changes in the orientation of the migrating cells during incubation. These results indicate that bacteria produce cytotaxins other than formylmethionyl peptides which are recognized by equine neutrophils.     

A cross-sectional survey on wounds in horses in New Zealand

AIM: To determine the frequency and type of skin wounds encountered by New Zealand veterinarians in their equine patients, the duration and estimated costs of treatment as well as the expected outcomes for these wounds.

METHODS: An online survey was sent to all veterinarians registered with the New Zealand Equine Veterinary Association. The survey comprised questions on the location and experience of respondents, the number of wound-related cases in relation to the total equine caseload, the type and anatomical location of wounds treated, the frequency, duration and costs of treatments, the outcome of wound treatment and an estimate of the most common causes of death or euthanasia in their equine patients.

RESULTS: The survey response rate was 110/262 (41.9%). The median number of equine cases seen by respondents was 20 (interquartile range (IQR) 6–60) per month; of these, five (IQR 2–10) were wound related. Wounds ranked third after lameness and respiratory disease for the relative frequency with which respondents encountered them. Of 102 respondents 59 (58%) reported that their clients frequently treated wounds incurred by their horse without consulting a veterinarian. Wounds on the distal limb, whether involving only the skin or also deeper structures, were reported by 86/101 (85%) respondents as the most frequently encountered. Wounds in this location also incurred the longest treatment period and were the most prone to develop complications. Finally, wounds ranked second, after colic, as the most common cause of death/euthanasia in the veterinary respondents’ equine patients.

CONCLUSIONS: The data obtained via the survey indicate that skin wounds, particularly on the distal limb, are a common occurrence in horses in New Zealand and, when they involve structures underlying the skin, are costly and time-consuming to manage and may lead to decreased performance, retirement or euthanasia. Consequently, we recommend that more effort be devoted to the education of equine veterinarians and owners, and that appropriate research funds be allocated to help improve patient outcomes.     

BONE SEQUESTRATION AS A CONSEQUENCE OF LIMB WOUNDS IN THE HORSE

Thirty-five horses that had bone sequestration as a consequence of limb wounds were examined clinically and radiographically. It is possible to diagnose bone sequestra as early as 10 to 15 days after injury. Periosteal defects and infection appear to be the basis for bone sequestrum formation. The early radiographic signs of bone sequestration and progress to mature sequestrum formation are described. Treatment is the surgical removal of the sequestrum. In the presence of equine limb wounds in which the periosteum may have been damaged, it is advisable to radiograph the limb at the initial examination and again in 10 to 15 days.     

英国兽药理事会批准的可用于马匹的兽药产品分析

为了探究英国兽药理事会(VMD)批准上市的马匹兽药产品情况,从VMD 2016年3月提供的产品信息数据库统计分析。结果显示,上市的可用于马匹的兽药产品占兽药总数的12%,而马匹专属产品占6%;1990年-2015年年均批准马匹用兽药产品约12个;持有上市总兽药以及马匹兽药数量最多的前3个企业依次为Norbrook laboratories Ltd,Zoetis UK Ltd和Intervet UK Ltd;批准产品中抗炎药、中枢神经系统药和抗寄生虫药比例最高;优势兽药活性成分中非甾体抗炎药美洛昔康、抗寄生虫药伊维菌素及其同吡喹酮复方和镇静剂甲苯噻嗪获批产品数名列前3位;从给药途径来看,注射给药产品占62%,而口服产品占27%,外用和吸入给药产品比例较低。以上统计结果说明国际兽药企业注重马匹用药在英国的审批和上市,从马匹用兽药优势品种和主要活性成分可以提示马匹用药热点,该统计结果为管理和制定同国际接轨的我国马匹用药标准提供参考。     

Delayed Wound Closure A Review and Report of Use of the Technique on Three Equine Limb Wounds

Limb wounds of three horses were managed by delayed wound closure. In each, the wound was such that it was unlikely that healing would occur following primary closure and that second intention healing would have been unsatisfactory. Wounds were cleaned and debrided at the time of admission and maintained under sterile pressure bandages until free of infection and devitalized tissue. Suture closure of the wound at that time resulted in satisfactory healing in each case.