Abdominal pain (colic) is common in horses and can be caused by a variety of intestinal pathological conditions. Approximately 2-17% of the horses that show signs of colic need emergency surgery to survive. The abdomen is typically approached through the ‘linea alba’, which is the anatomical junction of the two rectus abdominis abdominal muscle sheaths at the level of the ventral midline. After surgery, the incision is typically closed using a simple continuous suture pattern but several variations exist.
Wound complications after surgery are very common (up to 20-22% of patients) and include severe oedema, wound infection, hernia development and acute dehiscence (Fig. 1). Several risk factors for wound complications have been identified: some are patient-related and cannot be influenced, but others are related to the surgical technique and could be optimised to minimise these complications. Recent research into the biomechanical behaviour of the abdominal wall revealed that the length and width of the linea alba changes when the horse changes position (Fig. 2). The linea alba is sutured when the horse is under general anaesthesia in dorsal recumbency. When the horse awakes and changes from dorsal recumbency to a standing position, the linea alba expands and therefore the tension on the incision and sutures increases. Excessive tension on the tissues entrapped by sutures could negatively influence wound healing, but different suture patterns might results in different tissue tension taking the length and width expansion into account. In vitro testing of suture patterns on abdominal wall tissue brings several difficulties, hence why alternative research models are sought after.
|Fig 1. Complete wound dehiscence after infection of a ventral midline incision with evisceration of the intestines.||
Fig. 2 Expansion of the abdominal wall and linea alba when the horse changes position
The aim of this project is to design a computational model to simulate the tension on the equine abdominal wall and use this model to determine the ideal suture pattern for closure of the linea alba. The ideal suture pattern must (1) withstand the tension on the abdominal wall after abdominal surgery and (2) comply with the biomechanical behaviour of the equine abdominal wall, to reduce tissue impairment post-operatively. The data achieved from this model can contribute to an improvement in incisional complications in horses post-operatively.