Healing of equine heel bulb lacerations: Evidence behind casting compared to bandaging alone

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Appraisal, application and reflection

There are very few studies evaluating the efficacy of using distal limb casts when treating heel bulb lacerations compared with bandages alone in horses. Based on the publication from Janicek et al. (2005), casting as opposed to bandaging may reduce the treatment duration of heel bulb lacerations. However, the length of treatment and the success of wound healing are both directly related to the way these wounds are approached, namely if they are treated by primary or secondary closure (Janicek et al., 2005). Since the number of horses in each group (bandaging versus casting) treated with primary closure versus delayed primary or second intention healing was not specified, the conclusion that distal limb casting results in faster healing of heel bulb laceration remains questionable. Janicek et al. (2005) recommended all heel bulb wounds which are minimally contaminated with debris and of short duration following injury (< 8 hours) be managed by primary closure and physical support of the site with either a bandage or a cast. In cases of wounds severely contaminated or traumatised, the authors recommended a foot bandage for 7–10 days prior to cast immobilisation. While these recommendations are very logical and allow more frequent monitoring of the wound healing and care, the study results are inconclusive when it comes to favour bandaging or casting to speed up wound healing. On the other hand, Burba et al. (2013), an expert opinion article aimed at veterinary surgeons, stated that heel bulb lacerations were best treated by primary closure when possible and with the use of a foot cast. As this is an opinion piece rather than an original study, no compelling evidence in favour of using foot casts over bandaging was found for these cases.

The potential involvement and treatment of synovial sepsis appears to be an important factor influencing outcome in cases of heel bulb laceration. Janicek et al. (2005) reported that lacerations involving a synovial structure had a significantly poorer outcome than those without. Synovial involvement also influences the approach to the wound. In the study by Janicek et al. (2005), all wounds communicating with synovial structures were left to heal by second intention following surgical management of sepsis. The authors recommended that all lacerations involving synovial structures are considered contaminated and recommended delayed primary closure after repeated synovial lavages and natural sealing of the communication between the synovial structure and the wound itself. In the small case series from Booth and Knottenbelt (1999), 50 % of the lacerations were sutured, although the reason for this is not stated in the paper. In a similar publication from Ketzner et al. (2009), 63.6% of wounds were sutured and the authors found no significant difference in outcome between cases involving or not involving a synovial structure. In a more recent publication on wounds of the lower limb Eggleston (2018), recommends that a wound communicating with a synovial structure be managed with replaceable bandages until it can be confirmed that synovial communication is sealed and the infection resolved. Celeste and Szöke (2005) also recommended bandaging until infectious complications are resolved, after which casting the distal limb in successive periods of 2–3 weeks should be performed. Whilst these recommendations are logical, they constitute expert opinion and we have failed to find corroborating evidence in the literature gathered for this knowledge summary. Prospective studies comparing horses with heel bulb lacerations sutured (or not) in the same fashion, with and without synovial involvement, and divided into two separate groups (bandage versus ‘slipper cast’) are lacking. If such studies were performed, a standardised treatment plan prior to casting or bandaging would need to be implemented to allow direct comparison of the efficacy of the supportive dressing.

The incidence of cast sores with all types of cast is reported to be anywhere between 45% to 81% (Eggleston, 2018). However, if the cast is applied properly and is monitored regularly, the potential for serious complications is significantly reduced and are uncommon (Booth & Knottenbelt, 1999; and Eggleston, 2018). Janicek et al. (2005) reported that 2/15 horses managed with a cast alone developed pressure necrosis of the skin, which was of limited clinical significance. To further reduce this risk, a ‘slipper cast’ can be used for casting the foot. It reduces the risk of deep skin erosions if the cast material does not end in the mid-pastern region (Celeste and Szöke, 2005).

Closure of heel bulb lacerations can be challenging due to skin tension and the production of excessive granulation tissue (EGT) is a concern if these wounds are left to heal by second intention (Eggleston, 2018). Booth and Knottenbelt (1999) stated that when properly applied, distal limb casts improve the functional and cosmetic outcome of distal limb injuries. Indeed, since a cast is by definition sturdier than a bandage, is it thought to provide better immobilisation of the distal limb. This led to the clinical impression that casting prevents movement of the foot and wound dehiscence (Janicek et al., 2005; Milner, 2008; and Booth & Knottenbelt, 1999) as well as decreasing the production of EGT (Smith, 1993). We have failed to find evidence to support this assertion in the available literature and believe this should be considered as expert opinion as well. In the case series from Ketzner et al. (2009), 68.4% of wounds treated with casting healed with minimal scarring compared to 21.1% which healed without scarring. While this study includes wounds located to the pastern and hoof area, the number involving heel bulbs is not specified and all horses were treated with a casting, none with bandaging. An in vitro study comparing the immobilisation provided by both types of external coaptation would provide more information.

Casting is also potentially beneficial in cases of heel bulb laceration involving the coronet. When the coronary band is involved in the laceration, reconstructive surgery is paramount to decrease the risk of permanent deformation of the hoof wall and other complications such as hoof cracks and horn spurs (Celeste and Szöke, 2005). Of the 61 horses available at follow-up in the Janicek et al. (2005) study, 18% developed a hoof wall defect, but the number of horses treated with a foot cast compared to bandaging alone or a combination of the two is not stated. In the study from Ketzner et al. (2009), 10.5% of all wounds healed with excessive scarring at the coronary band and hoof. As previously mentioned, all horses in that cases series were treated with casting and the number of wounds involving the coronary band/hoof remains unclear. It is therefore not possible to determine if this excessive scarring of the coronet and hoof is the result of a cast complication or of to original injury. The duration of the casting period is also controversial and the ideal timeframe for this immobilisation method is currently unknown. While some authors (Janicek et al., 2005; and O'Neill & O'Meara, 2010) recommend that casts remain in place for 2–4 weeks in order to allow healthy granulation tissue to cover the wound, the publications identified in this submission each used casting for different periods of time, making it difficult to compare the benefit of shorter versus longer periods in casts.

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