Risultati e complicanze incontrate nelle chirurgie ricostruttive con lembi cutanei nel cane e nel gatto

1 Dipartimento di Scienze Medico-Veterinarie Corso di Laurea Magistrale a Ciclo Unico in Medicina Veterinaria “OUTCOME AND CHALLENGES IN SKIN RECONSTRUCTION WITH DIFFERENT CUTANEOUS FLAPS IN DOGS AND CATS” “RISULTATI E COMPLICANZE INCONTRATE NELLE CHIRURGIE RICOSTRUTTIVE CON LEMBI CUTANEI NEL CANE E NEL GATTO” Relatore: Chiar.ma Prof.ssa MARINA MARTANO Correlatore: Dott. ANDREA FAVA Laureanda: SILVIA SUDIRO ANNO ACCADEMICO 2023-2024 2 Sommario 1. RIASSUNTO .............................................................................................................................. 3 2. ABSTRACT ................................................................................................................................ 4 3. PARTE GENERALE ................................................................................................................. 5 3.1 The Skin ............................................................................................................................... 5 3.1.1 Skin Function and Anatomy ........................................................................................... 5 3.1.2 Cutaneous circulation ..................................................................................................... 6 3.2 Basic principles of wound healing ...................................................................................... 7 3.2.1 Introduction and Phases of Wound Healing ................................................................... 7 3.2.2 Wound Contraction ...................................................................................................... 10 3.2.3 Species Variations in Wound Healing ......................................................................... 11 3.2.4 Stages of Wound Healing and their Clinical Relevance .............................................. 12 3.3 Basic Principles of Wound Management ........................................................................ 12 3.3.1 Basic Wound Classification ......................................................................................... 12 3.3.2 Age of the Wound: Clinical Significance .................................................................... 14 3.3.3 Options for Wound Closure ......................................................................................... 14 3.3.4 Basic Wound Management .......................................................................................... 16 3.3.5 Topical Wound Care Products and Their Use .............................................................. 18 3.3.6 Dressing, Bandages and Protective Devices ................................................................ 20 3.4 Flap Classification ............................................................................................................. 22 3.4.1 Tension-relieving Techniques and Local Flaps ........................................................... 22 3.4.2 Local Flaps ................................................................................................................... 25 3.4.3 Distant flaps .................................................................................................................. 28 3.4.4 Axial Flap Techniques ................................................................................................. 29 3.4.5 Free Skin Grafts ........................................................................................................... 34 4. PARTE SPECIALE .................................................................................................................. 38 4.1 Materials and Methods ..................................................................................................... 38 4.2 Results ................................................................................................................................ 39 5. DISCUSSION ........................................................................................................................... 45 6. CONCLUSIONS ....................................................................................................................... 54 7. REFERENCES ........................................................................................................................ 55 3 1. RIASSUNTO Difetti cutanei di notevole entità conseguenti a interventi di chirurgia oncologica in cui vengono rimosse masse tumorali di dimensioni importanti o ferite superficiali caratterizzate da un’abbondante perdita di tessuto possono necessitare di tecniche di chirurgia ricostruttiva più o meno avanzata. In questi casi, quando la guarigione per prima intenzione non è possibile, la scelta terapeutica può ricadere sulla guarigione per seconda intenzione, sull’utilizzo di tecniche di chirurgia ricostruttiva o su un approccio combinato tra le due opzioni. La ricostruzione di tali difetti può avvenire mediante lembi locali, lembi assiali o innesti liberi, a tutto spessore o a spessore parziale. I lembi locali includono una vascolarizzazione casuale, motivo per cui sono detti “lembi casuali”, e possono essere preparati su uno stesso piano (lembi di avanzamento o lembi ad H) o su un piano di fulcro (lembi di rotazione, di trasposizione e di interpolazione). Al contrario, i lembi assiali comprendono una vena ed un’arteria cutanea diretta, che ne garantiscono una vascolarizzazione migliore. I lembi liberi sono invece innesti cutanei privi della loro vascolarizzazione e provenienti da un sito donatore lontano dal difetto cutaneo che si intende richiudere, i quali possono essere a tutto spessore (quando includono epidermide ed intero derma) o a spessore parziale (quando includono epidermide ed una porzione di derma variabile). Indipendentemente dal tipo di procedura chirurgica attuata, uno dei fattori più importanti per la sopravvivenza del lembo è la sua vascolarizzazione. Lo sviluppo di complicanze può palesarsi all’incirca 1 settimana dopo la chirurgia includono deiscenza, edema, sieroma, ematoma e necrosi del lembo, che possono essere classificate in minori o maggiori a seconda della necessità di un secondo intervento chirurgico per ottenere la guarigione completa della ferita. Questo studio comprende 28 casi di ricostruzione cutanea in 23 cani e 5 gatti, comprendenti di 13 lembi locali, 14 lembi assiali ed 1 lembo libero. Diciannove pazienti (70%) in totale sono andati incontro a complicanze post-operatorie, di cui 8 maggiori (29,6% dei pazienti totali) e 12 minori (42,8%). Inaspettatamente i lembi locali hanno avuto la più bassa percentuale di complicanze; tra i lembi assiali, l’85,7% ha sviluppato complicanze, di cui 6 (4,8%) maggiori, che hanno necessitato di una revisione chirurgica. L’unico soggetto a cui è stato praticato un lembo libero è andato incontro a complicanze maggiori (deiscenza totale del lembo) che hanno richiesto la revisione chirurgica. Per concludere, sebbene le chirurgie ricostruttive possano essere cruciali per la guarigione di ampi difetti cutanei, essere a conoscenza delle difficoltà associate ai vari tipi di lembo aiuta il medico 4 veterinario a prevedere eventuali complicanze e a gestire correttamente il post-operatorio, aumentando le probabilità di successo della procedura. 2. ABSTRACT Repairing large cutaneous defects may be necessary following oncological surgery involving the removal of large tumors, or to support the healing process of superficial wounds characterized by significant tissue loss. In these cases, in which healing by primary intention is not feasible, the remaining therapeutic options are healing by secondary intention, the use of reconstructive surgery techniques or a combination of the two. Defect reconstruction can be achieved using local flaps, axial flaps and free grafts, which may be full or partial thickness. Local flaps, also known as "random flaps," have an undefined vascular supply coming from the subdermal plexus and can be designed in the same plane (such as advancement or H flaps) or on a pivot point (such as rotation, transposition, and interpolation flaps). Axial flaps, in contrast, contain a defined cutaneous artery and vein, providing superior vascularization. Skin grafts lack direct vascularization, are harvested from a donor site distant from the defect, and can be full thickness (including the epidermis and the dermis) or partial thickness (including the epidermis and a partial portion of dermis). Regardless of the type of surgical procedure performed, one of the most important factors responsible for the survival of the flap is its vascularization. Complications are expected to occur about 1 week after surgery, and include dehiscence, edema, seroma, hematoma and flap necrosis, and they can be sub-classified as minor or major, depending on whether surgical revision is required to achieve successful wound healing. Minor complications can be treated medically, whereas major complications may require surgical revision and can subsequently heal by second intention, or through a new reconstructive and first intention closure. This study involved 28 cases of skin reconstruction in 23 dogs and 5 cats, consisting of 13 local flaps, 14 axial flaps and 1 free graft. Nineteen patients (70%) developed post-operative complications of any kind, with 8 patients (29,6% of all patients) experiencing major complications and 12 (42,8%) experiencing minor complications. Unexpectedly, local flaps had the fewest major complications rate (7,6%); of the axial flaps, 85,7% presented any complications, with 6 of them (42,8%) experiencing major complications that required revision surgery. The dog that underwent a free flap procedure experienced major complications (total dehiscence of the flap) that required surgical revision. 5 In conclusion, even though surgical reconstructive techniques may be crucial to support the healing process of large cutaneous defects, being aware of the challenges associated with each type of flap will help the veterinarian to foresee complications, managing the post-operative period correctly and improving the overall long-term success rates. 3. PARTE GENERALE 3.1 The Skin 3.1.1 Skin Function and Anatomy The skin, being the body's largest and primary protective organ, covers the entire external surface and serves as the foremost physical barrier against environmental factors. Its roles include regulating temperature, protecting against ultraviolet (UV) light, trauma, pathogens, microorganisms, and toxins. The skin also contributes to sensory perception, immunologic surveillance, general homeostasis and control of insensible fluid loss. Additionally, it is highly adaptive, exhibiting different thicknesses and specialized functions across various body sites (Kanitakis, 2002). The skin is composed of three layers: the epidermis, the dermis and subcutaneous tissue (Kanitakis, 2002)(Fig. 1). The epidermis is a stratified, squamous epithelial layer that is primarily composed of two types of cells, dendritic cells and keratinocytes; the keratinocytes differ from the dendritic cells by possessing intercellular bridges and ample amounts of cytoplasm (Murphy, 1997). In hair-bearing areas, the epidermis consists of three major layers: the stratum cylindricum (stratum basale), the stratum spinosum (stratum malpighii or prickle cell layer) and the stratum corneum; the set of stratum cylindricum and stratum spinosum layers form the stratum germinativum (Pavletic, 2018). The epidermis is a continuously renewing layer that produces structures like swear glands, nails and pilosebaceous apparatuses; the basal cells of the epidermis undergo proliferation cycles, ensuring the renewal of the outer epidermis (Chu, 2008). The dermis consists of collagenous, reticular and elastic fibers embedded in a mucopolysaccharide ground substance, primarily made up of hyaluronic acid and chondroitin sulfuric acid. In dogs and cats, the dermis is divided into the superficial stratum papillare and the deep stratum reticulare; the stratum papillare contains fine elastic and reticular fibers, whereas the stratum reticolare is composed of coarse, densely interwoven collagen bundles (Pavletic, 2018). 6 The most pliable skin (axilla, flank, dorsum of the neck) has a greater number of elastic fibers in the papillary layer, as well as small and more loosely woven dermal collagen bundles, whereas less pliable skin, (on the tail, ear, digital pads) have wider, more closely packed collagen bundles with fewer elastic fibers (Pavletic, 2018). The hypodermis or superficial fascia is associated with the overlying dermis; this subcutaneous tissue is composed primarily of fat nestled in loosely organized collagenous and elastic fibers (Fahie & Shettko, 2007). The cutaneous appendages (adnexa) of the skin include the hair follicles, sebaceous glands and sweat glands. Other cutaneous glandular structures include the mammary glands, supracaudal glands, anal sacs, superficial circumanal glands and perianal glands; all these structures have an ectodermal origin (Pavletic, 2018) 3.1.2 Cutaneous circulation In dogs and cats, direct cutaneous arteries are responsible for supplying large areas of skin; they run parallel to the skin in the hypodermis and arise from perforator arteries. Musculocutaneous arteries, which run perpendicular to the surface of the skin, branch off the perforator arteries and supply small portions of the skin. Terminal arteries and veins branch from the direct cutaneous vessels and form the subdermal (deep or subcutaneous) plexus, cutaneous (middle) plexus and subpapillary (superficial) plexus (Kirpensteijn, 2013). Fig. 1: Cross-section of skin and panniculus. From Andrews’ Diseases of the Skin: Clinical Dermatology (10th ed., p.1) by W.D. James, T.G. Berger, and D.M. Elston, 2006, Philadelphia: Elsevier Saunders. Copyright 2006 by Elsevier Saunders. 7 The subdermal plexus (Fig. 2) is the primary vascular network for the skin, with vessels generally running in the subcutaneous fatty and areolar tissue on the deep face of the dermis, particularly in the middle to distal portions of the limbs where no panniculus muscle is present; the plexus supplies the hair bulb and follicle, tubular glands, deeper portions of the ducts and the arrector pili muscle. Branches of the subdermal plexus rise into the dermis to form the middle or cutaneous plexus. Branches of the cutaneous plexus ascend and descend into the dermis to supply the sebaceous glands and support the capillary networks around the hair follicles, tubular gland ducts and arrector pili muscle. The superficial plexus lies in the outer layer of the dermis, with capillary loops projecting into the dermal papillary bodies to supply the epidermal papillae and adjacent epidermis. (Pavletic, 2018; Mayhew, 2017) 3.2 Basic principles of wound healing 3.2.1 Introduction and Phases of Wound Healing By definition, a wound is a break or loss of cellular and anatomic continuity, with impairment of the tissue’s protective or physiological functions; in particular, surgical wounds are created in the process of resecting diseased or damaged skin regions (Pavletic, 2018). A thorough understanding of the wound healing process is vital for a correct approach to wound care. Fig. 2: Vascular supply to canine and feline skin. From BSAVA Manual of Canine and Feline Wound Management and Reconstruction, author Philipp Mayhew (2017). 8 Wound healing is a complex and dynamic process, that can be simplified into three phases: 1) the inflammatory phase; 2) the proliferative phase; 3) the maturation/remodeling phase (Sussman & Bates-Jensen, 2012). These phases overlap in time, since they’re not mutually exclusive. Each phase of wound healing is regulated by cytokines, signaling molecules that can direct cellular activities, leading to the production of proteins, enzymes, proteoglycans and other essential components for extracellular tissue repair. 1) The inflammatory phase is the initial stage of wound healing, characterized by hemostasis and inflammation. Hemostasis begins with collagen exposure during wound formation, activating both the intrinsic and extrinsic clotting cascades; tissue injury also releases thromboxane A2 and prostaglandin 2-alpha into the wound bed, inducing a strong vasoconstrictor response. Additionally, the extravasation of blood constituents forms a blood clot, reinforcing the hemostatic plug. Thus the initial response limits hemorrhage and provides an extracellular matrix for cell migration (Sinno, Sataya, 2013). Platelets are among the first responder cells in wound healing, playing a crucial role in forming the hemostatic plug; they secrete various chemokines, including epidermal growth factor (EGF), platelet-derived growth factor (PDGF), fibronectin, fibrinogen, von Willebrand factor, serotonin and histamine. These factors aid in stabilizing through clot formation and attract and activate macrophages and fibroblasts. Additionally, platelets help control bleeding and limit the extent of injury (Sinno, Sataya, 2013). Following complement activation and platelet recruitment, neutrophils are the next cells to migrate to the wound; they are responsible for scavenging debris, opsonizing and lysing foreign organisms via complement mediation and destroying bacteria through oxidative burst mechanisms, such as the formation of superoxide and hydrogen peroxide (Sinno, Sataya, 2013). The key role in wound healing is mediated by macrophages that not only directly phagocytose bacteria and foreign materials, but also secrete numerous enzymes and cytokines, collagenases, interleukins and transforming growth factor (TGF). Additionally, macrophages release platelet-derived growth factor and vascular endothelial growth factor (VEGF), initiating granulation tissue formation and thus transitioning into the proliferative phase and tissue regeneration (Sinno, Sataya, 2013). 2) The proliferative phase is usually considered to span over 5-20 days after injury, although some textbooks indicate it begins as early as 3 days after injury (Pavletic, 2018). The 9 proliferative phase consists of epithelialization, angiogenesis, granulation tissue formation and collagen deposition (Sinno, Sataya, 2013). Epithelialization begins with keratinocytes at the wound edge and from dermal appendages, such as hair follicles, sweat glands and sebaceous glands; this process involves cell detachment and mitotic division, stimulated by epidermal growth factor, fibroblast growth factor and various cytokines. Fibroblast growth factor, platelet-derived growth factor and vascular endothelial growth factor also initiate and promote angiogenesis (Janis, Harrison, 2016). A key event in the healing process is new blood vessel formation, termed neoangiogenesis. Neoangiogenesis is a complex process that relies on four interrelated phenomena, including: cell phenotype alteration, chemoattractant-driven migration, mitogenic stimulation and the local development of supportive extracellular matrix (Pavletic, 2018). Unlike vasculogenesis, which refers to the ex-novo formation of new vessels, angiogenesis involves the development of thin-walled endothelium form existing vessels (Janis, Harrison, 2016). A healing wound is defined by increased metabolic demands and shows high sensitivity to changes in oxygen availability. Fibroblasts first appear in the wound after 24 hours, and they require adequate oxygen supply for collagen production: without oxygen, chemical bonds will not form appropriately to form mature collagen (Janis, Harrison, 2016). The term granulation tissue is derived from the granular appearance of newly forming tissue when incised and its edge is visually examined (Fig. 3). Granulation tissue is a matrix of fibrin, fibronectin, collagen, proteoglycans and glycoproteins; it fills in body defects while providing a vascular scaffold for epithelial cell migration, and it also forms a barrier to invasive bacteria. Early granulation tissue begins to form approximately 4 days after an uncomplicated injury (Pavletic, 2018). 3) During the transition from granulation tissue to scar maturation, collagen remodeling occurs, with a balance between collagen deposition and collagen catabolism, and type III collagen gradually decreases, as type I collagen increases. Collagen deposition is directly related to the tensile strength of a wound: three weeks after injury, the scar has 20% of its final strength, and over the next several weeks the scar will achieve only 70-80% of the tensile strength of normal skin (Villedieu, 2023). The maturation phase usually takes 20365 days. 16 of financial constraints, that would preclude surgery in favor of open wound management) (Pavletic, 2018). Second intention healing is often a practical and economical method for wound closure, as long as adequate wound care is provided. However, in some cases, healing can be prolonged, with the costs of hospital visits, bandage material and topical medications equaling or exceeding those of surgical closure (Dernell, 2006). 3.3.4 Basic Wound Management Initial management of open wounds can be summarized in six simple steps: prevent further wound contamination, debride dead/dying tissue, remove foreign debris and contaminants, provide adequate wound drainage, establish a viable vascular bed and select the appropriate method of closure (Pavletic, 2018). Upon admission, the patient’s wounds should be temporarily protected from further trauma and hospital-borne bacteria with a topical antimicrobial, sterile dressing and protective wrap; sterile gauze moistened with saline containing an antibiotic or a non-irritating antimicrobial agent is useful for maintaining tissue hydration and controlling the infection until definitive wound repair can be performed. For definitive wound cleansing and surgical management, cover the exposed wound with sterile gauze pads soaked in sterile saline or antimicrobial solution before clipping the skin and preparing the defect for surgery. Fur should be removed from around the wound area, as it tends to retain discharge, leading to tissue maceration and bacterial growth; removing fur also makes periodic wound cleansing and bandages reapplications easier. Fig. 6: Large open wound healing by second intention, through contraction and epithelialization (right). Healing by second intention requires owner compliance, since frequent bandage changes are needed. On the left, the entity of the cutaneous defect the day of the surgery. 17 Debridement is necessary whenever necrotic tissue or debris remains in a wound after initial cleaning. While a small amount of debridement might be done without sedation or anesthesia, analgesia and chemical restraint are typically required, especially for aggressive surgical debridement (Dernell, 2006). Debris adherent to the subcutis should be manually removed to maintain cutaneous circulation; manual removal of gross debris followed by pressure lavage with isotonic liquids will eliminate any microscopic pollutants that remain after the first debridement. Small-to-moderate sized wounds are often lavaged with 500-1000 ml of regular saline or lactated Ringer’s solutions (Pavletic, 2018). Generally, leaving a wound exposed allows for the best drainage for contaminated or infected wounds. Drains may be employed during closure to limit dead space and provide an outlet for the evacuation of tissue fluids that may collect in that region; in the absence of devitalized tissue and foreign debris, drains can offer an outlet for purulent discharges that may otherwise collect or disseminate into surrounding tissues (Pavletic, 2018). 3.3.4.1 Wound Debridement Wound debridement falls into two broad categories: selective and non-selective. Selective debridement specifically targets necrotic tissue, whereas non-selective debridement is less precise and can unintentionally harm viable tissue to varying extents. Selective debridement methods include: autolytic debridement (using gels and dressings that create an optimal environment for the body’s natural processes to break down necrotic tissue), enzymatic debridement (applying exogenous proteolytic enzymes to separate nonviable tissues) and biotherapies, such as utilizing maggots to selectively consume necrotic tissue. Selective debridement, although slower and less aggressive, more accurately targets necrotic tissue and minimizes harm to healthy tissue. Non-selecting debridement includes surgical (scalpel, tissue excision)(Fig.7) and mechanical (wet-to-dry dressings) debridement (Pavletic, 2018). Initial surgical debridement is crucial for large wounds, or for those with deep tissue injury; the goal is to remove all obvious necrotic tissue and debris, often using a layered approach, starting with superficial devitalized tissues and moving to the deeper ones. Assessing tissue viability can be subjective, with the most reliable indicators being color and attachment: tissues that are extremely light or dark and not attached to deeper planes should be 18 removed, while questionable tissues should be left for reevaluation. Active bleeding from the cut surface indicates viability, but factors such as systemic or local hypotension, tissue temperature, vasoconstriction and coagulation defects can affect bleeding, therefore relying solely on bleeding to determine tissue viability may result in removing viable tissue. (Dernell, 2006). En-bloc debridement, involving the complete excision of all affected tissue with a border of normal tissue, is another surgical debridement method; this technique is similar to removing a malignancy, and is reserved for wounds that are clearly infected or where layered debridement is unlikely to result in a healthy wound (Dernell, 2006). Multiple debridement procedures could be necessary, since a single debridement attempt is often not sufficient to achieve a healthy wound bed that could undergo primary or delayed primary closure; this is especially true for wounds with progressive tissue changes in relations to vascular compromise or deep tissue injury. 3.3.5 Topical Wound Care Products and Their Use The proper use of topical and systemic medications can significantly accelerate the healing process, when second intention healing is foreseen, leading to a faster recovery with fewer complications and side effects. Medication that enhance wound healing work in various ways, such as in maintaining a moist environment (e.g., hydrogels, hydrocolloids), providing a local Fig.7: Necrotic flap on a dog’s forelimb, before and after surgical debridement. 19 energy source (e.g., maltodextrin, honey, sugar), reducing wound edema by hydrophilic action, increasing the concentration of growth factors, providing a source of healing substance (e.g., collagen, biologic membrane bioscaffolds), controlling infection (e.g., topical and systemic antimicrobials), aiding debridement (e.g., topical enzymes), increasing the oxygen content and increasing blood flow (e.g., laser, UV radiation, electrical stimulation) (Krahwinkel, 2006). Autolytic debridement refers to the body’s natural process of debridement happening at a cellular level within a wound; moisture-retaining gels and dressings can be used to promote selective debridement by softening or macerating devitalized tissues, facilitating phagocytic cells activity, and enabling proteolytic enzyme liquefaction of nonviable tissue. Many of these topical gel-like compounds are laminated to synthetic membranes, creating a dressing platform for easier application to flat wound surfaces. Similarly, other moisture-retaining barrier dressings (occlusive and semi-occlusive) can be used to promote proteolysis within the wound (Pavletic, 2018) Hydrocolloids are typically composed of pectin, gelatin and carboxymethyl-cellulose, with a film or adhesive backing, thus acting as a bandage; they absorb wound fluid and exudate, swelling into a gel-like mass that maintains a moist environment conducive to healing. Hydrocolloids are recommended for partial and full-thickness wounds, and are safe for use on both granulating and necrotic wounds. Wounds covered with hydrocolloids have lower infection rates in human medicine than those covered with gauze, film, hydrogels or foams, as they also protect the wound from contamination and aid in autolytic debridement; dressings containing hydrocolloids require less frequent changes compared to conventional bandages, as they are formulated to remain on the wound for up to 7 days; however they should be replaced if strike-through is observed (Krahwinkel, 2006). Hydrogels are wound dressings composed by 80-90% of water or glycerin, available in sheet form to serve as bandages; they absorb a minimal amount of fluid but are capable of donating large amounts of moisture to the wound, making them suitable for minimally to moderately draining wounds, such as abrasions, blisters, burns, ulcers and partial-thickness donor sites. Hydrogels are beneficial in the late stages of wound healing, on wounds that have healthy granulation tissue, decreased drainage and evidence of epithelialization (Krahwinkel, 2006). (Fahie & Shettko, 2007) Maltodextrin is a D-glucose polysaccharide with 1% ascorbic acid that, when applied to a wound, forms a hydrophilic film dressing that creates a moist environment to nurture wound healing. 20 Maltodextrin seems to reduce pain and stimulate granulation and epithelialization. The product comes as a hydrophilic powder and as a gel: the powder is preferred for exudating wounds, and the gel is preferred for drier wounds (Krahwinkel, 2006). Sugar and honey are common and readily available substances that can aid in wound healing. Sugar is an excellent topical dressing for treating open and contaminated wounds. Its benefits include rapid antibacterial action, and osmotic properties for exudative wounds, enhancing granulation tissue formation and epithelialization and accelerating wound healing (Mathews & Binnington, Wound Management Using Sugar, 2002). Honey contains many nutrients and minerals, has a bactericidal effect due to hydrogel peroxide liberation and a phytochemical constituent; when used as a topical dressing, honey decreases inflammatory edema, accelerates sloughing of devitalized tissue and nourishes the wound. These factors contribute to enhance granulation and epithelialization (Mathews & Binnington, Wound Management Using Honey, 2001). 3.3.6 Dressing, Bandages and Protective Devices Bandaging open wounds is essential for effective wound management: unbandaged wounds are prone to desiccation which can lead to healing delay and higher incidence of infection and scarring; moreover, veterinary patients are likely to lick unprotected wounds, further compromising the healing process. An optimal bandage serves to shield the wound from contamination and external mechanical forces, manage exudate, provide structural support and comfort, and create a microenvironment conducive to active wound healing (Campell, 2006). The primary layer of the bandage, also known as the contact layer or dressing, is the material that comes directly in contact with the wound, and thus should be sterile. This layer serves several roles, including protection, debridement, absorption of exudate, delivery of topical medications and promotion of healing. The qualities of primary dressings vary, with occlusiveness and absorption being two of the most important. Wet-to-dry and dry-to-dry bandages have always been used for debriding wounds. The wet-to-dry technique involves moistening a gauze with sterile saline (0.9% NaCl) or lactated Ringer solution before applying it to wounds with viscous exudate or necrotic tissues. The exudate is then diluted and absorbed into the outer bandage layer, the fluid evaporates and the bandage dries and adheres to the wound. The dry-to-dry approach involves applying dry gauze to wounds with low-viscosity 21 exudate, where the exudate is absorbed, evaporates from the outer bandage layers and the dressing dries and adheres to the wound (Campell, 2006). Although efficient in eliminating necrotic tissue, wet-to-dry and dry-to-dry bandages have several disadvantages: both healthy and unhealthy tissue could adhere to the gauze and be removed with the dressing; a dry environment does not support the cells or proteases involved in cleanup and repair of the wound; bacteria can penetrate moistened gauze more easily than occlusive dressings, thus increasing the risk for infection; and fibers form the adhered gauze may remain in the wound bed and act as a nidus for inflammation. For all these reasons, wet-to-dry and dry-to-dry bandages are no longer considered the standard of care in human medicine, and their use should be limited in veterinary medicine (Campell, 2006). The second layer of a bandage serves as the bulk or absorptive component, commonly comprising rolled cotton, cast padding, absorptive combination pads, gauze pads and roll gauze. In cases of wounds with copious discharge, this layer facilitates the wicking and retention of fluids from the wound surface. The ability of this intermediate layer to retain moisture hinges on the volume of fluid released from the wound, the dressing’s absorptive properties and the rate at which moisture evaporates through the outer wrap (Pavletic, 2018). To construct the secondary layer, cotton padding is overlapped by 50% to provide an orderly, more uniformly thick supportive layer, from a distal to proximal direction. Tape stirrups and padding around pressure points are commonly applied prior to application of the second layer. Following one or two rounds of cotton padding, self-adherent gauze is used to stabilize the cotton layer before adding more layers of cotton or gauze. The final outer cover of gauze prepares the bandage for the tertiary layer, providing uniform compression, enhancing stability and minimizing the risk of the bandage being too tight. A thicker secondary layer can reduce the risk of circulatory compromise that may occur if the outer elastic cover is applied with moderate tension (Pavletic, 2018). The outer or tertiary layer functions as the securing component for the bandaged inner layer. Most tertiary wraps are self-adherent due to their texture and slightly tacky surface. However, applying excessive elastic tension, especially on bandages covering the extremities with a thin secondary layer, can jeopardize circulation (Pavletic, 2018). Bandages can shift or slip as a result of a number of factors, including the contour of the body region bandages, the lack of a frictional body surface to resist slippage, the normal effects of gravity and body motion, and subsequent stretching and loosening of the bandage layers. 22 The tie-over dressing technique is employed to secure bandages in areas where conventional wraps are less effective, such as the trunk, head or neck. This method involves placing 2-0 monofilament suture loops in the skin surrounding the wound, approximately 2-3 cm from the wound’s edge. After positioning the dressing on the wound surface, the suture is laced between opposing loops in a crisscross pattern, effectively immobilizing the wound without restricting nearby movement (Pavletic, 2018). 3.4 Flap Classification 3.4.1 Tension-relieving Techniques and Local Flaps Skin defects seen in small animals typically result from traumatic injuries or surgical removal of diseased tissue. In cats and dogs the natural elasticity of the skin, along with the presence of loose skin in many areas of the body, often allows for primary wound closure; however, in some cases it is necessary to seek for tension-relieving techniques or to use skin flaps to achieve a tension-free closure and minimize the risk of complications during healing. Excessive tension can lead to dehiscence by tearing sutures or disrupting the blood supply to the skin; this issue is particularly pronounced in highly mobile areas, such as the joints, where movement amplifies the effects of tension. High-tension closures can also lead to increased scar tissue formation and greater postoperative pain (Mayhew, 2017). To manage skin tension, several techniques can be chosen, including skin undermining, manipulating wound geometry, walking sutures, creating relaxing incisions, skin expanders, incisional ‘plasty’ techniques (such as the Z-plasty or the V-Y plasty) (Mayhew, 2017). Surgeons should also carefully consider the direction of incisions, ideally aligning them parallel to the lines of skin tension to minimize stress. Additionally, the closure technique should be planned to avoid or reduce the formation of “dog ears”, or puckers, at the ends of the suture line (Hedlund, 2006). Undermining the skin around a wound is the simplest method to relieve tension, allowing the full elasticity of the skin to be used. The skin should be undermined deep to the panniculus muscle layer to preserve the subdermal plexus and direct cutaneous vessels, or in the loose areolar fascia deep to the dermis if the panniculus muscle is absent. Elevated skin should include a portion of the superficial fascia with the dermis to preserve the direct cutaneous arteries; it is crucial to use atraumatic techniques, such as cutting with a sharp scalpel blade instead of scissors, and avoiding 23 instruments that crush tissue, such as Allis tissue forceps, to avoid injury to the subdermal plexus (Hedlund, 2006). The shape of the wound can also influence tension at the wound margins. Closing circular, square or rectangular defects through simple apposition can lead to the formation of “dog ears”, a term that refers to an excess folding or gathering of skin and fatty tissue at the end of an incision line, commonly seen in procedures that involve a significant amount of skin, fat or tissue. Converting these shapes into an ellipse, when possible, can improve the cosmetic outcome, though it requires the removal of more skin. Circular and square wounds can also be closed by creation of a triangulating or star-shaped closure made up of small flaps that form as skin is advanced inward form the sides of the circle; this technique may reduce tension at the margins, although the central point may still be prone to dehiscence due to limited blood supply or residual tension (Mayhew, 2017). The walking suture is a method of distributing tension sutures over a wide surface area when skin undermining and suture closure techniques alone are insufficient for wound apposition. Individual “walking” sutures pull the skin toward the defect in small increments; multiple sutures have a cumulative effect in maintaining the undermined skin in position as it is advanced to the center of the defect (Pavletic, 2018). This tension-relieving technique has several disadvantages: excessive placement of sutures must be avoided to prevent occlusion of the subdermal plexus blood supply or inadvertent ligation of direct cutaneous vessels. Moreover, walking sutures should not be utilized alongside axial pattern flaps. Additionally, walking sutures may exacerbate wound infections, as the bacterial load required to initiate infection decreases as the quantity fo suture material in a wound increases; in the event of infection, walking sutures can also create compartments that obstruct effective drainage (Mayhew, 2017). Multiple punctate relaxing incisions (Fig. 8), or mesh expansion, involve placing staggered parallel rows of stab incisions through skin surrounding the wound to facilitate advancement of skin margins over the wound. In essence, this technique converts a single large wound into multiple small wounds that heal much more rapidly by second intention. Incisions are made parallel to and approximately 1 to 2 cm from the skin margins on both sides of the wound, and they are approximately 1 cm in length and are spaced 1 to 2 cm apart. The second row of relaxing incisions, if needed, is placed approximately 1 to 2 cm from the first row, with incisions again parallel to the skin margins but staggered in position relative to those in the first row. Staggering of relaxing 24 incisions helps to ensure vascularity of skin margins. After reconstruction, contact dressings and protective bandages are applied until the expanded punctuate incisions have healed by contraction and epithelialization (Fowler, 2006). Tissue expanders are inflatable devices that are surgically placed near a wound, to stretch the skin over time; once the skin has been sufficiently stretched, the expanders are removed, and the newly created loose skin is used to cover the defect. This method is especially useful in distal limbs where other reconstruction options are limited, but it requires multiple surgical procedures (Mayhew, 2017). Incisional plasty techniques, such as the V-Y and Z-plasty are useful for providing moderate tension relief in cases where primary closure is not possible due to excessive tension, but raising a local flap should could be avoided or not possible. (Mayhew, 2017). A V-Y plasty can be considered when a small amount of relaxation is needed. A V-shaped incision is made adjacent to the wound with the point of the “V” facing away from the wound; after undermining the skin between the V and the wound, the primary defect is closed. The “V” incision is then sutured by placing sutures alternately back and forth between the two arms of the V; when Fig. 8: Multiple punctate relaxing incisions, to allow wound closure. 25 tension begins to develop in closure, the remaining area is closed to form the stem of the “Y” (Fowler, 2006) In a Z-plasty procedure, two adjacent equilateral traingular flaps are formed and transposed to extend the length of their long axis, thereby decreasing tension at the primary wound site. This method is designed to achieve a moderate reduction in tension; however, multiple Z-plasties can be arranged in series to increase the extent of tension relief. This technique is effective only when the skin around the Z can be readily undermined and is sufficiently lax; in areas with significant scar tissue formation where the skin is immobile, tension may not be adequately relieved (Mayhew, 2017). 3.4.2 Local Flaps Local subdermal plexus flaps are typically harvested from skin adjacent to the primary defect; they cannot be converted into an “island” flap (meaning the base cannot be completely severed) and generally support smaller areas of skin compared to axial pattern flaps. Nevertheless, they are among the most commonly used flaps in general practice, because of their simplicity and versatility (Mayhew, 2017). Local flaps can be classified as advancement, rotational, transposition and interpolation flaps. This classification is based according on their method of transfer; for example, advancement flaps are moved in a forward direction and rotational flaps are rotated or pivoted into position. Local flaps depend on the subdermal plexus circulation, unless a direct cutaneous artery and vein are included in the base of the flap (Pavletic, 2018). Selecting the appropriate flap type depends on various factors, but the simplest flap with the highest likelihood of success should always be chosen (Mayhew, 2017). Ideal donor sites have sufficient skin to elevate a flap without creating a secondary defect that is difficult to close, and donor sites prone to excessive motion and stress should be avoided whenever possible, as they are susceptible to wound dehiscence or may impair local mobility (Pavletic, 2018). As a general guideline, surgeons should design flaps with a base slightly wider than its body to avoid unintentional narrowing of the pedicle. Flaps should be sized appropriately to cover the recipient bed without excessive tension; in some cases, using two or more small flaps may be preferable to a single large pedicle graft, where circulation at the distal end of the flap might be compromised (Pavletic, 2018). 32 The dorsal branch of the deep circumflex iliac vessel is employed in flaps for covering defects in the caudal thorax, lateral abdominal wall, ipsilateral flank, lateral lumbar area, medial or lateral thigh, great trochanter and pelvic area. The ventral branch of the deep circumflex iliac artery supplies the flank fold, utilized to cover defects in the caudolateral abdominal wall, inguinal, pelvic or sacral defects. Both the dorsal and ventral branches originate cranioventral to the wing of the ilium (Hedlund, 2006). The flank fold flap, a more limited variation of the ventral deep circumflex iliac axial pattern flap, is effectively employed for closing challenging wounds in the inguinal region. Precise flap measurement is essential in this area, as excessive tension during donor site closure can result in restricted limb mobility and increased risk of dehiscence (Pavletic, 2018)- The genicular axial pattern flap is supplied by the genicular branches of the saphenous artery and medial saphenous vein. The genicular artery extends cranially over the medial aspect of the stifle and terminates on its cranio-lateral surface; this flap is employed to cover defects in the proximal two-thirds of the tibia and has been described for repairing defects extending from the stifle to the tibiotarsal joint on both the lateral and medial sides of the hindlimb (Ober, et al., 2019). Fig. 13: Caudal superficial epigastric flap, used to close a large cutaneous defect on the thigh of a mixed-breed dog following mast cell tumor removal. 33 The caudal auricular artery axial pattern flap, classified as a transposition flap, utilizes the sternocleidomastoid branches of the caudal auricular artery and vein (Pope, 2006). The inclusion of these direct cutaneous vessels enables the construction of flaps longer than conventional transposition flaps reliant on the subdermal plexus. This flap originates at the caudal aspect of the ear and may extend to the cranial or midscapular region; however, the risk of flap failure increases with greater extension toward the scapula (Pope, 2006). The caudal auricular axial pattern flap can be used to reconstruct the ear, dorsum of the head, or extend further rostrally to close defects overlying the orbital area (Pavletic, 2018). The lateral caudal arteries of the tail are utilized for reconstructing defects involving the perineum and caudodorsal trunk. Additionally, the tail skin may serve as a flap for covering defects on the hind limb. These lateral caudal vessels originate from the caudal gluteal arteries and have multiple anastomotic connections with the medial caudal artery. The use of this flap necessitates amputation of the tail (Hedlund, 2006). The cutaneous branch of the superficial temporal artery can be developed into an axial pattern flap using the skin overlying the temporal muscle. This flap is particularly suitable for repairing facial defects within its arc of rotation and is most effective for midfacial defects, as lateral facial defects may be closed with a simpler local flap (advancement or transposition), depending on the size and location of the wound (Pavletic, 2018). The reverse saphenous conduit flap, while not a true axial pattern flap, is dissected and functions similarly to axial pattern flaps. Its vascular supply originates from the medial saphenous vessels. Unlike axial pattern flaps, these vessels do not establish a direct cutaneous vascular supply but instead give rise to numerous small cutaneous branches along their pathway, serving as a vascular conduit that supports multiple small cutaneous angiosomes. This flap is highly effective for reconstructing wounds involving the tarsus and metatarsus. The primary prerequisites for the success of this flap are the absence of trauma to the deep vascular structures of the metatarsus and paw. Typically, arterial blood flow through the medial saphenous vessels is directed from proximal to distal, with venous return flowing in the opposite direction. In the creation of the reverse saphenous flap, however, the medial saphenous artery and vein are ligated at their point of origin from the femoral artery and vein; as a result, blood flow through these vessels becomes retrograde, 34 facilitated by collateral connections between the saphenous vessels and other arteries and veins in the distal extremity, hence the term reverse saphenous conduit flap (Fowler, 2006). 3.4.5 Free Skin Grafts Skin grafting is a surgical procedure used to speed up healing in wounds with severe skin abnormalities and produce both functional and esthetic results. This treatment entails transferring skin from a donor location to a recipient site or utilizing skin from other sources to promote wound epithelialization and contraction while shortening healing time. Grafts can be classified as autografts, allografts, or xenografts. Autografts are derived from the same animal, allografts from other members of the same species, and xenografts from different species. Autografts, which entail transferring skin from one part of the patient's body (the donor site) to the injured region, are the most widely used due to their ease of application and minimal risk of skin graft rejection (Ibrahim, Soliman, Kotb, & Ali, 2020) Based on vascular supply, grafts are classified in pedicle grafts, which maintain an attached vascular supply to the wound, and free grafts, which lack vascular attachments. Free grafts further divide into sheet or island grafts, including techniques such as pinch, punch and tunnel grafting. Island grafts provide focal coverage, promoting epithelial growth from the surrounding edges and filling intervening spaces; in contrast, sheet skin grafts (Fig. 14) offer comprehensive dermal coverage and may involve meshing or surgically created fenestrations (Schumacher & Hanselka, 1989). 35 The recipient wound bed site may require several weeks of medical management to create an environment conducive to graft acceptance. To enhance graft uptake, granulation tissue should be even with the surrounding skin to promote epithelialization and contraction. Any suspected infections should be cultured to identify specific bacterial populations, along with antimicrobial sensitivity and specificity testing, as reducing the bacterial load with antibiotherapy and correct debridement of the wound is critical for graft success (Pezzanite & Hendrickson, 2021). Grafts can be harvested using manual or motorized techniques to ensure uniform thickness of the graft; however, manual methods are more commonly used in veterinary medicine settings due to practical and financial considerations (Williams, Pezzanite, & Hendrickson, 2024). Pinch grafting (Fig. 15), the simplest technique, requires minimal equipment: a scalpel blade, thumb forceps and Mayo scissors. The forceps are used to tent to the skin, and grafts measuring Fig. 14: Mesh skin graft on the hindleg of a dog. 36 8-10 mm in diameter are excised. Excess subcutaneous tissue is trimmed, and the grafts are stored in saline-soaked gauze. Small pockets, approximately 1 cm in diameter, are created in the recipient bed’s granulation tissue using a scalpel blade, into which the grafts are placed. The graft site is covered with non-adherent or petroleum-impregnated dressings, followed by a pressure bandage (Williams, Pezzanite, & Hendrickson, 2024). Overall, pinch grafting has a 75% success rate, with minimal donor site defects (Schumacher & Hanselka, 1989). Punch grafting, similar to pinch grafting, utilizes additional tools, including 6 and 8 mm skin punches. The 8 mm punch harvests grafts, including epidermis and dermis, from the donor site. After removing subcutaneous tissue, the grafts are placed in saline-soaked gauze. A 6 mm punch creates holes in the granulation tissue at the wound site, which are then cleaned and filled with skin plugs. The graft site is dressed as in pinch grafting (Williams, Pezzanite, & Hendrickson, 2024). This method has demonstrated up to a 95% success rate, with epithelialization occurring within 47 days when grafts are placed at 5-15 mm apart (Schumacher & Hanselka, 1989). Tunnel grafting includes extracting lengthy strips of skin from the donor location; these grafts can be full or partial thickness, 2-5 mm broad, and somewhat longer than the recipient wound bed. A sheet skin transplant is frequently taken from the donor site and split into strips to remove the underlying fascia and subcutaneous adipose tissue, which improves graft viability, and the donor location is then largely closed using sutures. Tunnels are formed in the recipient granulation tissue, at least one centimeter apart, and long forceps are used to guide the transplant through these tunnels and secure it to the surrounding skin; the wound is then treated as directed for pinch and punch grafting, and granulation tissue covering the grafts is surgically removed in 6-10 days. This Fig. 15: Pinch grafting, to aid second intention healing in a large open wound on the trunk of a mixed-breed dog. The donor site (left) was the skin on the side of the neck, just cranial to the defect. The graft was then protected with a tie-over bandage. 37 approach takes more donor tissue than pinch or punch grafting and has an 80% success rate, making it appropriate for difficult-to-bandage locations, such as highly mobile regions (Kalamanova, Anderson, Cust, & Fulton, 2020). Skin graft healing occurs in four main stages: adhesion, plasmatic imbibition, revascularization, and organization (Hendrickson, 2021). In the adhesion stage, fibrin forms between the graft and the wound bed within hours of placement, so it is important to minimize any gap to avoid complications. Another factor leading to graft failure is movement, so bandaging and immobilizing the area is advised to minimize the risk for complications. Plasmatic imbibition occurs during day 1-4 following grafting when nutrition and oxygen to support the graft comes from the fibrin clot surrounding the graft. Revascularisation occurs during days 3-7 via inosculation and capillary buds from the recipient bed penetrating into preexisting vessels of the graft. Then the organization phase occurs, when the original fibrin clot is replaced by fibrous tissue as the graft is anchored in place permanently. A proper attachment between the recipient bed and the graft occurs within 9 days (Hendrickson, 2021). The key to ensure a successful healing and graft retention is postoperative management in each of these critical stages; in particular, it is advised to leave the first bandage change, to minimize the risk of graft dislodgement. In regions where bandaging is difficult, tieover bandages may be considered (Williams, Pezzanite, & Hendrickson, 2024). 38 4. PARTE SPECIALE 4.1 Materials and Methods Medical records of 28 patients (23 dogs and 5 cats) that underwent reconstruction of extensive skin defects at the Veterinary Teaching Hospital (OVUD) of the Department of Veterinary Medical Sciences of Parma between 2021 and 2024 were retrieved and analyzed. Twenty-five cases involved surgical excision of malignant tumors with wide margins, 2 involved the excisions of benign masses that did not necessitate wide margins and 1 involved the reconstruction of a large skin defect originated from the dehiscence of a surgical wound performed at another veterinary clinic. Data collected included signalment (age, sex, species, breed), etiology of the surgical defect, tumor type and location (in case of tumor excision), status of clinical margins (clean or infiltrated by the tumor), duration of post-operative NSAIDs (Non-Steroidal Anti-Inflammatory Drugs) administration, insertion of surgical closed drains, days of hospitalization and occurrence of postoperative complications. All treatment options were thoroughly discussed with the owners prior to surgery, who were informed that patients undergoing wide neoplastic excision and possible subsequent second intention healing would require prolonged post-operative care, such as frequent bandage changes. The pre-operative treatment plan suggested to the owners involved a complete blood count (CBC), a biochemical panel to assess hepatic and renal function, fine-needle aspiration (FNA) of the lesion, staging with 3 views thoracic radiographs and abdominal ultrasound to detect distant metastasis, and CT scan when needed for surgical planning; cardiopathic patients were also advised to undergo an echocardiography to ensure that they could withstand anesthesia. When major bleeding during surgery was anticipated, a coagulation panel was also performed and the animal blood-typed. All feline patients were required FIV/FeLV screening. The staging of patients with mast cell tumors also included guided FNA of the spleen and liver, to evaluate metastatic spread, and a CT scan with contrast medium inoculation and CT lymphangiography for sentinel lymph node research. The incidence of complications and clinical outcomes were evaluated by clinical examination and documented by pictures of the surgical site during follow-up appointments scheduled according to the type of wound, surgical technique utilized and healing process. Post-operative complications recorded were: edema, seroma, hematoma, dehiscence (partial or total) and necrosis (partial or total). Complications were sub-classified as minor when they were 39 managed conservatively, and major when surgical intervention was necessary according to le Blanc et al (2000). The surgical wound was managed either with bandages or tie-over dressings and the application of topical wound care products, to promote healing and provide protection. Bandage change frequency was determined by wound appearance and by the condition of the bandage, typically occurring every 1-3 days until granulation tissue formation. During each bandage change, the wound was irrigated with sterile saline (0.9% NaCl) solution and cleansed with gauze swabs. Initial follow-up appointments were scheduled 5 days after discharge, in case of primary closure, every day when an open wound was present, and subsequently planned according to the wound’s state and eventual complications. When a close drain tube was applied during surgery, the animal was hospitalized until its removal. Eight procedures (29.6%) were associated with an excellent outcome, meaning they healed successfully without any complications; a good outcome was achieved in 40% of cases, which healed well and only presented minor complications. 4.2 Results Signalment Twenty-three dogs and 5 cats were included in this study. Dog breeds included 9 mixed-breed dogs, 3 Labrador Retrievers, 2 Golden Retrievers, and 1 each of the following breeds: American Staffordshire Terrier, Bernese Mountain Dog, Boxer, Cocker Spaniel, French Bulldog, German Shepherd, Italian Greyhound, Pug, whereas all 5 cats were Domestic Shorthair cats. Body weight ranged from 8.5 kg to 43kg (mean 25.17 kg) for dogs and from 2.5kg to 7 kg (mean 4.86 kg) for cats. Age at presentation ranged from 2 to 14 years old (mean 8.3 years old). The study included 9 intact males, 2 castrated males, 2 intact females and 15 spayed females. Presenting complaint The skin defect was the result of tumor removal in 22 dogs and 5 cats, and of a chronic open wound in 1 dog. Tumors included 16 mast cell tumors (57.1%), 6 soft-tissue sarcomas (21.4%), 2 squamous cell carcinomas (7.1%), 1 fibrosarcoma (3.5%) and 1 malignant epithelioma (3.5%); the benign masses were 2 infundibular cysts (7.1%). The completeness of excision was evaluated histologically in all cases; tumor excision was classified as complete in all patients except one, in the case of a mixed-breed dog that presented a large (7x7 cm) cutaneous mass on the right side of 40 the trunk, diagnosed as a malignant epithelioma, that was excised and then managed as an open wound. One dog presented for a large skin defect derived from the dehiscence of a surgical wound after foreign body removal. Five patients suffering from mast cell tumor underwent 2 to 3 rounds of adjuvant cytoreductive chemotherapy before the surgical procedure, with Vinblastine at a dose of 2 mg/m² and were operated between 12 to 15 days (mean 14 days) after the last treatment. Preoperative diagnostic tests Cytology examination by FNA was performed in every patient undergoing neoplastic excision, and 3 of these patients also underwent incisional biopsies to confirm through histopathology the initial diagnosis. Computed tomography (CT) was performed for surgical planning in 17 patients; 11 patients did not undergo a CT scan because it was deemed not necessary for surgical planning, but received either abdominal ultrasounds, 3 view thoracic radiographs or both to complete the oncological the staging and ensure metastasis were not already present. Before surgery, a CBC was performed, as well as a biochemical panel including kidney and liver profiles; in patients in which renal function was not optimal, a urinalysis was also performed, in order to accurately assess renal function. Complete blood count revealed abnormalities in 12 patients (44%): mild anemia in was observed in 5 cases (18.5%), mild leukopenia in 2 (7.4%), moderate neutrophilic leukocytosis in 3 (11%), mild neutrophilic leukocytosis in 2 (7.4%), severe thrombocytopenia in 1 (3.7%) and mild thrombocytopenia in 1 (3.7%). The coagulation profile revealed abnormalities in 4 patients (14.8%), with 2 of them presenting mildly higher prothrombin and activated coagulation times, and 2 patients presenting mildly lower times. (Willard & Tvedten, 2011). The biochemical panel revealed abnormalities in 11 patients (40.7%): severely elevated alkaline phosphatase was noted in 2 patients (7.4%), mildly elevated alkaline phosphatase in 4 (14.8%), severely elevated C-Reactive Protein (CRP) in 2 (7.4%), severely elevated transaminases in 1 (3.7%) and mildly elevated transaminases in 1 (3.7%) (Oikonomidis & Milne, 2023); 2 patients were diagnosed with Chronic Kidney Disease (CKD). One cat presented hyperglycemia, but diabetes mellitus was excluded, and a stress origin was suspected. One patient was diagnosed with Cushing’s disease before the revision surgery. The day of the procedure blood gasses analysis and microhematocrit were conducted for all patients. 41 Surgical procedure All patients were administered prophylactic cephazolin (22 mg/kg, IV) 30 minutes prior to surgery, and the administration was repeated every 90 of surgery; cephazolin was also administered until 24 hours post-operatively in all animals. Patients were anesthetized, and the affected area of the body was widely clipped, both at the surgical site and donor site, in case a reconstructive technique was planned, and prepared for aseptic surgery. Depending on the location of the lesion, then moved to the operating room and while the patient was appropriately positioned on the operating table. Malignant tumors were excised with a lateral margin of 1 to 3 cm (median 2 cm), and a depth of 1 fascial plane, while benignant masses were excised with a lateral margin of 0.5 to 1 cm, assuring to remove the macroscopically abnormal tissue. The excision was performed using a combination of sharp and blunt dissection and electrocautery, with hemostasis also achieved via electrocautery. Reconstruction of the surgical wounds was achieved using various flap techniques: 13 local flaps (5 advancement flaps, 4 rotation flaps and 4 transposition flaps, with no interpolation flaps utilized), 14 axial pattern flaps (1 thoracodorsal flap, 2 superficial brachial flaps, 2 caudal superficial epigastric flaps, 3 flank fold flaps, 1 genicular flap, 2 caudal auricular flaps, 1 angularis oris and 2 superficial temporal flaps) and 1 skin graft. One large tumor was excised and left to heal by second intention, using tension-relieving techniques to bring the wound margins towards the center of the defect. Intraoperative complications recorded were 1 case of anaphylaxis due to methylene blue inoculation (for sentinel lymph node identification) and 1 case of hypotension due to profuse bleeding, as a consequence of the excision of a very large mass (7x7 cm), diagnosed as a malignant epithelioma, on the left side of the trunk. The majority (89%) of the patients were hospitalized for 1 to 3 days (mean 1.7 days) following the surgery, in order to receive appropriate pain management and monitoring. 48 meaning that neoplastic development may still occur on the mammary glands or pseudopregnancy may develop, and for this reason ovariohysterectomy should be considered if not already performed. The only skin graft procedure performed (case n. 28), intended to close a wound on a dog forelimb, resulted in dehiscence and required a second surgical procedure, despite proper harvesting and correct post-operative management. Potential causes to justify this graft failure may include excessive tension, inadequate graft adherence to the recipient bed and insufficient immobilization. The key points for flap survival are minimizing tension and ensuring adequate blood supply; any disturbance of these two factors can lead to complications. When planning a surgery involving large skin defects closure, tension of the surgical breach can be reduced by aligning the suture lines parallel to the skin tension lines; tension-relieving techniques, such as undermining, relaxing incisions, and tension-relieving sutures can also be employed to reduce tension of closure. However, care must be taken in applying these methods, and tension-relieving sutures such as interrupted horizontal mattress sutures in particular, as they tend to obstruct capillary blood flow that can lead to necrosis. The tension at the closure site can be affected by the anatomical location of the wound: this is particularly true for wounds in close proximity of joint, since articular movement can increase strain on the suture lines. Additionally, the choice of suture pattern can affect wound tension, therefore clinical judgment is required to select a monofilament material of a sufficient size to suture the wound without traumatizing the skin. For example, in sensible areas, good tension distribution is obtained by involving plastic tubing bolters in knots. A potential complication following the closure of large cutaneous wounds is the development of dead space leading to seromas or hematomas when complete hemostasis is not achieved or the animal recovers from anesthesia too quickly and too anxiously. To prevent this, active drains such as Jackson Pratt drains, can be used, since they pull serous fluid from the dead space, promoting adhesion of the flap. Seroma and hematoma are generally minor complications that usually do not require surgical revision of the wound, however the fluid built-up can increase tension of the suture lines and cause discomfort to the patient, heightening the chance of dehiscence and self-trauma. In this study 8 Jackson Pratt drains were placed, nonetheless 2 of these patients developed seroma which was treated conservatively; this complication may have been due to incorrect drain placement or its malfunction, or because the drain was removed too early, while excessive 49 inflammatory fluid was still being produced. Ensuring proper hemostasis and drainage of the wound are always indicated to avoid post-operative complications, since fluid built-up not only puts tension on the suture lines, but also creates and environment conducive to infection. Excessive tension is the most common cause of flap dehiscence. Since dehiscence is the main complication leading to flap failure, the surgeon must take every precaution to reduce closure site tension; this includes assessing the presence of adequate loose skin before surgery, using tensionrelieving techniques when needed during surgery, applying bandages and splints to reduce motion in the post-operative period and even leaving a part of the wound open to heal by second intention if necessary. Also, when attempting to close a chronic wound or revise a failed flap, non-viable tissue must be identified and removed before closure. Fig. 17: Seroma formation of a dog’s elbow following a thoracodorsal axial pattern flap procedure; distal flap necrosis can also be seen. 50 To prevent necrosis, the vasculature of the flap, including the direct cutaneous vessels and the subdermal plexus, must be carefully preserved; this requires that tissues be handled delicately during surgery and adequately protected in the post-operative period, avoiding tight bandages that could limit the circulation to the flap. In local flap procedures, to prevent this complication from happening the base of the flap should be wider than its tip, and the extremities of the flap should be rounded, avoiding sharp angles. Notably, none of the 5 cats included in the study developed major complications; this is uncommon in veterinary reconstructive surgery, given the fact that many direct cutaneous arteries have been mapped in dogs, but only a few flaps – such as the thoracodorsal, caudal superficial epigastric, Fig. 18: Necrosis and dehiscence of a caudal auricular axial pattern flap, performed to reconstruct a large cutaneous defect after mast cell tumor excision. 51 reverse saphenous conduit, superficial temporal and caudal auricular - have been described in cats (Moores, 2009). This highlights the need for caution when using canine data for raising flaps in cats, due to differences in the amount of skin that can be raised and in flap coverage. The success observed in this study suggests that results like this can be achieved by extensive knowledge of surgical technique and differences in wound healing between species, moreover, the high elasticity of the feline skin compared to dogs may help in achieving wound closure without tension. Infection is a common complication (16-60% according Pavletic, 1981) reported in the veterinary literature about reconstructive surgery; however, in this study it was only observed in two patients (7%) (cases n. 2 and case n. 15), in both of which microbial cultures revealed the presence of multiresistant bacteria that were treated according to the culture and sensitivity tests results. Both of these patients were managed as an open wound, healing by second intention, without developing further infection. Surgical site infections usually present as serosanguinous or purulent discharge from the wound. Discharge was noted in one case (case n. 12) and this finding was followed by a single course of antimicrobials for treatment without previous culture and sensitivity test, therefore, although the wound healed uneventfully, the actual presence of an infection could not be proved. Furthermore, discharge may be noted without an underlying infection and can be attributable to the inflammatory and debridement phases of wound healing, since in both of them the presence serosangiunous inflammatory exudate can be expected. Therefore it is essential to correctly interpret the cause of discharge to avoid improper use of antimicrobials. The lower infection rate reported in this study, compared with the literature (Pavletic, 2018; Moores, 2009; Nelson, 2011) may be attributed to optimal surgical standards of sterility, the administration of prophylactic Cefazolin in the peri-operative period, and the topical use of antimicrobial creams containing Chloramphenicol and collagenase in the management of open wounds. However, these findings may be biased due to the fact that the majority (96.5%) of the reconstructive surgeries involved in this study are surgical cutaneous reconstructions following tumor excision, meaning that the wound undergoing reconstruction was surgically created, therefore clean and sterile. Infection rates could be way higher if contaminated or chronic wounds were part of the study, which happened only in case n. 15: these contaminated or infected wounds should be managed by delayed closure, meaning that they should be treated as an open wound until a healthy granulation bed can be observed, and contamination is resolved. 52 Five patients (cases n. 5, 9, 10, 21, 28) suffering from mast cell tumor underwent 2 to 3 sessions of adjuvant chemotherapy prior to the surgical procedure, receiving a dose of 2 mg/m² of Vinblastine to reduce the tumor size in order to facilitate skin reconstruction. Of these patients, four (80%) developed post-operative complications, with the most common being dehiscence (2 cases of partial dehiscence and 2 of total dehiscence); two of these patients (40%) (case n. 21 and n. 28) required surgical revision, and their healing times (72 and 124 days) were some of the longest recorded in this study. This may suggest that chemotherapy can cause delays in wound healing and likely affects wound strength (Cornell & Walters, 1995). Anyways, this is not only due to the effect of chemotherapeutic drugs on rapidly dividing cells, but also to the immunodeficiency that can occur in oncologic patients undergoing chemotherapy, that can lead to being more exposed to post-operative infections. However, cytoreductive chemotherapy may be extremely beneficial to those patients with large neoplasm, whose excision would otherwise lead to more extensive reconstructive surgery. The timing of administration, mechanism of action and dose of the drug are factors that affect wound healing, so extensive knowledge of chemotherapeutic drugs is important in order to correctly administer them without increasing the risk for complications. In these cases, the delay in wound healing may also be related to the fact that mast cell tumors may affect the healing process due to the release of histamine and heparin from their cytoplasmic granules. This suggests that the administration of histamine blockers before surgery may be helpful in lowering the risk for healing complications, although there is not published data. Supporting this theory, one of the five dogs (case n. 21) mentioned previously experienced perioperative anaphylactic shock due to the mast cell tumor degranulation, and later developed total dehiscence of the flap, leading to the need for surgical revision. However, this correlation is based on a small sample size, and a larger number of cases would be needed to properly support this theory. Chemotherapy may also induce immunodeficiency, and that could cause complications in wound healing; similarly, immunocompromised cats with FIV (Feline Immunodeficiency Virus) or FeLV (Feline Leukemia Virus) may also not represent ideal candidates for reconstructive procedures. Of the 3 non-oncologic patients, only 1 (case n. 15) developed complications, a case of partial dehiscence and partial necrosis that did not require additional surgery and was treated medically. While these results may lead us to believe that non-oncologic patients have better overall surgical outcomes, it must be remembered that neoplastic excision was the main reason for skin reconstruction in this study, so results may be biased due to the lack of sufficient cases to support this theory. 53 In this study, a patient (case n. 22) undergoing reconstructive surgery following a soft-tissue sarcoma removal experienced both minor and major complications, leading to the need for three surgical revisions of the flap. Each time, dehiscence occurred in the post-operative period, and other complications associated were edema, seroma formation and necrosis; the flap ultimately healed by second intention after almost three months of care. It was lately discovered that this patient suffers from hyperadrenocorticisms, therefore the delayed wound healing may be attributed to excessive corticosteroids produced by the adrenal glands; this could not have been observed before surgery, since no biochemical alterations associated with Cushing’s syndrome (such as increased alkaline phosphatase and transaminases) were present. This observation highlights how underlying metabolic diseases such as Cushing’s syndrome affect wound healing, but also how corticosteroids can be detrimental to the healing process. Patients with CKD, diabete mellitus and hypothyroidism could also take longer to heal. Therefore, a complete thorough preoperative examination of the patient should always be performed. This finding supports the principle that a complete blood count (CBC) and biochemical panel should be mandatory for every patient before surgery, in order to foresee possible complications, warn the owner about the additional risks for flap failure and begin medical treatment. Conditions commonly diagnosed through CBC and biochemical panels that could lead to complications in wound healing include anemia, thrombocytopenia, leukopenia, coagulative disorders and chronic inflammation. Malnutrition can also lead to difficulties in wound healing, especially when lacking proteins or an adequate caloric intake. Finally, another important factor in wound healing that is often overlooked is owner compliance. Owners must be fully informed about the risks associated with these procedures and the need for frequent follow-up appointments; they should also always be educated on how to properly manage their pet in the post-operative period, and the importance of keeping their pet on strict rest and in a safe and clean environment. The importance of keeping an Elizabethan collar on their pet at all times should always be emphasized, as a major cause of wound disruption in veterinary medicine is self trauma: it is well known that sutures can be painful or itch, thus leading animals to bite, scratch or lick the wound that could cause very severe damage to the area. This occurrence unfortunately happened in one patient (case n. 21), leading to a case of total dehiscence that required a second surgical intervention followed by second intention healing of the wound, leading to the longest recorded healing time in this study, of 124 days. This study has several limitations that should be taken into consideration. 54 Due to its retrospective nature, the completeness of the data obtained and the sample size could not be controlled: ideally, an equal number of dogs and cats should be included, as well as an adequate number of cases for every type of procedure. The procedures were all conducted in the same Veterinary Teaching Hospital by a very restricted group of surgeons; hence, a multi-institutional prospective study may be recommended. Future studies should include defined surgical protocols for all types of reconstructive procedure; it may also be useful to include the measurements of the skin defects and flaps, as well as recording the measurements of the dehiscence area to accurately estimate it in percentages. Another noteworthy limitation is to the fact that most of the reconstructions (27 out of 28) were for defects created following tumor excision, excluding procedures involving the reconstruction of acute or chronic wounds, which can influence the results. Open wounds are generally more difficult to clean and prepare for aseptic surgery than intact skin, and chronic wounds may also have altered skin flora that could impact on wound healing– this may be the reason why postoperative infection rates in veterinary literature are lower than those recorded in other studies. 6. CONCLUSIONS The original purpose of this study was to evaluate challenges and outcomes associated with various skin reconstruction techniques following large wounds creation in veterinary medicine. It can be concluded that the simplest techniques, such as local flaps should always be preferred over the more complex ones, such as axial flaps, whenever possible; this is due to lower complication rates and reduced healing time, particularly for the reconstruction of smaller defects. Axial flaps included in this study resulted in higher complication rates, and this contradicts the data in veterinary literature (Moores, 2009): axial flaps usually result in less complications, due to their known vascularization. The difference in results may derive from the excessive length of the flaps, leading to distal flap necrosis, and to the fact that these reconstructive procedures usually are performed to cover more extensive defects. The most commonly encountered complication was dehiscence. In order to minimize the risk for complications, proper preoperative planning and skin mobility evaluation are crucial, as well as a correct surgical technique and appropriate haemostasis. The chances of flap survival will increase if the wound site and size are suitable for reconstruction, if the wound is neither contaminated or infected and if it is not older than 4–6 hours. It is also critical that the recipient bed for the flap is adequately prepared. The flap should be examined at regular intervals following surgery, to assess wound healing and manage complications. 55 Minor complications can be treated medically, whereas major complications may require surgical revision or can heal by second intention, or through a new reconstructive and first intention closure. Complications are expected to occur within 1 week after surgery; nevertheless, a good to excellent outcome appears possible if the wound is properly managed in the post-operative period. Owner compliance is a key factor in the success of the procedure, and they should be informed about the probable need for additional visits and costs involved with treatment of major complications. The additional cost of a revision surgery and of the subsequent medications should be considered, particularly in cases in which protracted open wound treatment may be necessary. To conclude, while cutaneous flaps may be crucial to aid the healing process of large skin defects, recognizing the limitations and challenges associated with each type of flap will enable surgeons to foresee complications, managing the post-operative period correctly and improving the overall long-term success rates. 7. REFERENCES Amsellem, P. (2011, Sep). "Complications of Reconstructive Surgery in Companion Animals". Veterinary Clinics of Noth America: Small Animal Practice, p. 995-1006. Bohling et al. (2004, Nov-Dec). Cutaneous Wound Healing In The Cat: a Macroscopic Description and Comparison With Cutaneous Wound Healing in The Dog. Veterinary Surgery, Volume 33, Issue 6, p. 579-587. Campell. (2006). Dressings, Bandages and Splints for Wound Management in Dogs and Cats. 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