Wound healing in horses: What went wrong?

Managing skin wounds is a very common task for equine practitioners, but it remains a challenging topic because there is no well-defined therapeutic protocol that guarantees successful healing for all wounds. Each wound is unique, and we cannot always predict how the treatment will progress, which can lead to frustration for the horse owner regarding the time and cost spent until the wound is fully healed. In the case series associated with this clinical commentary, the authors describe the use of negative pressure wound therapy (NPWT) in combination with punch grafting for treating distal limb wounds in three horses (Schnierer et al., 2026). The authors report success with the therapy, but this is not the only information we can glean from this report. Before discussing the therapy, I invite readers to take a closer look at other important points presented in the reports, such as the characteristics of the wounds and the treatments performed prior to the grafts. The purpose of analysing these points is to contextualize the moment of decision-making regarding the described treatment and to highlight the fact that we are often forced to change the initially adopted therapeutic plan because the healing process did not progress as expected. Whenever possible, primary wound closure is preferable because second-intention wound healing in horses can become prolonged and accompanied by complications, such as exuberant granulation tissue, and consequent delay in epithelialisation and contraction (Theoret et al., 2001). However, we are often unable to achieve primary wound closure for various reasons, such as undue time elapsed since injury, excessive contamination or significant tissue loss (Theoret & Wilmink, 2013), or we may even be able to perform the suture, but we are unsuccessful in this initial approach. In the case series presented, some wounds were primarily closed; others were not due to significant tissue loss, and one wound was closed but subsequently dehisced. When the second-intention healing is the only option, we must decide how the wound will be managed, what products will be used for antisepsis, whether the wound lavage will be with water or saline solution, whether any topical product will be used, whether the wound will remain open or bandaged, whether the removal of excessive granulation tissue will be chemical or surgical, whether we will use any cell therapy, or any gas, or any physiotherapy. In short, each veterinarian will make their decision according to their own experience and what they consider best practice. The fact is that several protocols have already been described for the treatment of equine skin wounds by second-intention healing, but recent reviews of the literature concluded that, to date, there is no solid evidence on best practices and many results are controversial (Anantama et al., 2022; Freeman et al., 2021; Ribeiro et al., 2024). The location of the wounds is a complicating factor that must be considered during patient assessment and decision-making, since distal limb wounds are often associated with excessive granulation tissue. The process that stimulates hypergranulation tissue formation is multifactorial and not fully understood, and may involve hyperproliferative fibroblasts, dysfunctional keratinocyte differentiation, suboptimal wound contraction, dysfunctional vascularisation and chronic inflammation (Anantama et al., 2022). Several factors can contribute to the development of this process, such as anatomy and function of the distal limb, areas of high movement, low oxygen tension and chronic contamination (Lepault et al., 2005). The wounds treated by Schnierer et al. (2026) are considered difficult-to-heal wounds because they were located on distal hindlimbs, in a region of great mobility, and involved the tarsocrural joints. The management of wounds involving synovial structures is more complex and has a less favourable prognosis; furthermore, treatment is usually more prolonged and much more expensive than the treatment of wounds without synovial involvement. The higher cost can be attributed to factors such as performing arthroscopies for joints flush, longer antibiotic therapy, longer hospitalisation time and daily hospitalisation costs (Albanese et al., 2025). All these aspects should be discussed in detail with the horse owner upon admission. Negative pressure wound therapy (NPWT) is a widely used wound treatment option in human medicine, and its application has been reported in horses. There are several NPWT units available on the market at relatively affordable prices, but their use in horses faces some limitations due to difficulties in attaching the pump and canister to the horse or the need to keep the animal tied up for long periods (Cantatore et al., 2023). The lightweight, disposable, canister-free NPWT system (PICO®) had already been tested by Kamus et al. (2019) with the aim of improving the use of this therapy in horses, but despite being well-tolerated by these animals, the authors reported some difficulties with the dressing design, mainly related to the adhesive component, which would not be suitable for use on open wounds. However, Schnierer et al. (2026) managed to overcome these limitations by using a support bandage over the dressing and concluded that the model is easier to apply than conventional systems. According to Cantatore et al. (2023), randomised controlled trials should be conducted to quantify the benefits and establish precise protocols in horses, because there is conflicting evidence regarding recommended settings in relation to the therapeutic range of negative pressure and the use of continuous or intermittent mode. Furthermore, publications on the use of NPWT in horses present controversial results: While case reports and case series have shown positive results (Florczyk & Rosser, 2017; Launois et al., 2021), experimental studies have found no differences between NPWT-treated and control groups (Gaus et al., 2017; Haspeslagh et al., 2022). In the cases reported by Schnierer et al. (2026), the isolated use of NPWT (PICO® system) was not sufficient to stimulate the healing process, as the authors did not observe a reduction in wound size, indicating impaired healing, which motivated the application of skin grafts. Skin grafting is often a good option to improve the aesthetic results of wounds with large skin defects or to help treat wounds that do not heal satisfactorily with routine wound management interventions. The decision to perform a skin graft is influenced by multiple factors, including the size and location of the wound, the presence of underlying structures such as joints and bones, client financial constraints and the overall systemic health of the patient (Williams et al., 2024). Skin grafts are classified as autografts, allografts and xenografts. Autografts, that is, skin grafts from a region of the animal's own body, are most frequently performed in horses because they are more practical and present a lower risk of immune rejection compared to allografts, which use skin from another horse. Xenografts are tissues taken from another species. The use of fish skin has been reported in donkey wounds, promoting a significant reduction in microbial count and better healing compared to untreated wounds (Ibrahim et al., 2020), but in this case, the tissue does not integrate into the wound bed of the recipient animal and should be considered a biological dressing and not a graft. Regarding thickness, grafts can be classified as split-thickness, composed of the epidermis and only a superficial part of the dermis, or full-thickness when they include the epidermis and the entire dermis, with its associated structures such as glands and hair follicles. Full-thickness grafts are considered more difficult to apply and take longer to vascularise, but are associated with better cosmetic results (Van Wicklin, 2022). Several grafting techniques have been described, ranging from the simplest, performed manually with the horse standing, to the most complex, requiring general anaesthesia and specialised equipment for harvesting or processing the grafts before application. Known techniques in equine practice include Pinch grafting, Punch grafting, Tunnel grafting, Sheet grafting, MEEK micrografting and Pedicle grafting. Manual techniques are more commonly used in horses due to practical and financial considerations (Williams et al., 2024). The success of skin grafting depends on proper wound bed preparation prior to application and careful wound management in the early postoperative period. Skin grafts should be placed over healthy granulation tissue levelled with the surrounding skin edge, wounds should be free of infection, and movement in the graft area should be reduced with effective immobilisation, because the main causes related to graft failure include movement, infection and accumulation of exudative material under the graft (Tóth et al., 2010). The main benefits reported with the use of NPWT include the removal of exudate and debris from the wound, reduction in dead space, decreased oedema and a reduction in the number of bacteria (Cantatore et al., 2023). All of these effects seem to contribute to the success of wound skin grafting. The combination of these two therapies had previously been reported in two horses by Rijkenhuizen et al. (2005), using the micrograft method with an acceptance of 75%, and subsequently in one horse by Jordana et al. (2011), using the full-thickness punch graft technique and an acceptance of nearly 100%. The series of three cases reported by Schnierer et al. (2026) confirms the benefits of using NPWT (PICO®) in the postoperative period of skin grafting in horses' wounds. Furthermore, it reports the use of NPWT also to prepare the wound bed for grafting. Second-intention healing of skin wounds in horses is complex and can become a slow and costly process, depending on the type of injury. It is important to recognise the risk factors for complications and understand the right time to make decisions. Sometimes, it is necessary to change the initially adopted therapeutic protocol, as not all wounds heal as expected, and clear communication with the owner is an important step in these situations. Open access publication funding provided by FCT (b-on). There are no funders to report for this clinical commentary. No conflicts of interest have been declared. Not applicable to this clinical commentary.