34th Annual Scientific Meeting proceedings

Naturally occurring wounds and complications of surgical incisions constitute one of the most frequent causes of consultation and concern in equine practice, with a daily occurrence.

Definition

A challenging or complex wound could be defined by the occurrence of one or several of the following criteria:

• Compromised viability of tissue, necrosis or circulation impairment
• Lack of available tissue to cover the defect, resulting in a lack of coverage of vital tissues and organs, or potential for complicated scarring and tissue retraction
• Association with systemic or local pathologies interfering with wound biology or classic management strategies
• Significant infection impairing normal tissue healing
• Lack of healing in a timely manner

Addressing Lower Limb Wounds

Complex lower limb wounds are known to heal with more difficulties than in other locations, due to several negative factors that need to be addressed.

Possible synovial structures involvement, due to limited joint and tendon sheath coverage at the time of injury, will require aggressive local, locoregional and/or general antibiotherapy as well as lavage and debridement. Complete closure of the wound may be delayed, to help drainage of heavily contaminated joints or tendon sheaths.

In case of underlying pathology such as fracture, tendon or ligament rupture with potential limb instability, temporary immobilization (vs immediate intervention) may allow recovery of enough tissue integrity to minimize the risk of implant infection.

Constant movement and tension applied on the wound edges, especially over a joint, can be partially overcome by heavy bandaging or whenever possible casting, which will also limit exposure to trauma and contamination.

Skin defects reconstruction are largely described, with a wide range of release procedures or transposition flaps techniques. Wherever skin is scarce, difficult to mobilize, with limited potential for expansion, functionality of the scar might be compromised by contracture of wound margins. Efforts should be made to preserve the epidermis and limit second intention healing for a functional outcome. Grafts (especially the Meek technique), should be considered, but can lead to over 50% wound contraction (Wilmink et al, EVJ 2006).

Addressing Complicated Abdominal Wounds

Those add to the challenge of tissue healing the potentially catastrophic complications associated with disruption of the abdominal integrity. The high morbidity of those wounds in human surgery has triggered the development of new techniques to address the life-threatening consequences of an open abdomen with intestinal exposure and fistulae. The current strategies include:

• Transposition of autologous material to bridge fascial and muscular gaps. In the “component separation technique”, parts of the abdominal musculature or fascia are transposed to cover defects, a technique rarely used by veterinarians (Caron et al).
• Prosthetic repair: various synthetic reabsorbable or non reabsorbable meshes offer different tensile properties, pro-inflammatory potential and porosity (associated with infectious risks) and are performed as an onlay, or (preperitoneal) sublay technique (Table 1). More recently biological materials have been developed in the human field.
• Vacum-assisted wound closure (more difficult to apply in the equine species).

Finally, when it comes to complex wound reconstruction and management, different steps and delayed reconstruction may be the best answer, depending on the patient’s status and underlying issues. Reconstructing major wounds is a dynamic process where unanticipated issues can arise before, during, and after surgery, requiring a thorough knowledge of physiology, as well as flexibility, creativity and an open-minded approach.

• Tóth, F. and Schumacher, J. (2018) “Prosthetic mesh repair of abdominal wall hernias in horses,” Veterinary surgery: VS, 47(4), pp. 536–542.
• Vilar, J.M. et al. (2009) “Double-Layer Mesh Hernioplasty for Repair of Incisional Hernias in 15 Horses,” Journal of Equine Veterinary Science, 29(3), pp. 172–176.
• Whitfield-Cargile C.M. et al. (2011) “Comparison of primary closure of incisional hernias in horses with and without the use of prosthetic mesh support,” Equine Veterinary Journal, 43(SUPPL.39), pp. 69–75.
• Wilderjans, H. and Meulyzer, M. (2022) “Laparoscopic closure of the vaginal rings in the standing horse using a tacked intraperitoneal slitted mesh (TISM) technique,” Equine Veterinary Journal, 54(2), pp. 359–367.
• Vilar, J.M. et al. (2009) “Double-Layer Mesh Hernioplasty for Repair of Incisional Hernias in 15 Horses,” Journal of Equine Veterinary Science, 29(3), pp. 172–176.
• Whitfield-Cargile C.M. et al. (2011) “Comparison of primary closure of incisional hernias in horses with and without the use of prosthetic mesh support,” Equine Veterinary Journal, 43(SUPPL.39), pp. 69–75.
• Wilmink, J.M. et al. (2006) “The modified Meek technique as a novel method for skin grafting in horses: evaluation of acceptance, wound contraction and closure in chronic wounds,” Equine veterinary journal, 38(4), pp. 324–9.

Table 1 – Prosthetic meshes used for hernia repair in large animals (adapted from Toth and Schumacher) - Abbreviations used:

PP – polypropylene, PE – polyester, ePTFE – expanded polytetrafluoroethylene, PH – poly 4-hydroxybutirate, PG – Polyglactin 910, K – knitted, W – woven, M – monofilament, P – polyfilament, A – absorbable