## 1 Introduction  
### Background  
Treatment of some bone fracture cases in horses is difficult. Due to a large variety of bones and their different sizes and shapes, there is no universal method that could be used in treatment of fractures. Each bone requires an individual approach. Complex fractures of long bones that consist of many bone fragments often lead to euthanasia. Open fractures pose a greater challenge as they often become contaminated and infected. Fractures need to be stabilised well in order to achieve bone union. However, using plates fixed directly on a bone in such case would constitute poor practice. External fixators could become an acceptable solution. The following types of fixators may be distinguished: Unilateral, bilateral, trilateral, quadrilateral, semi-circular, and circular. Each of them may be used to treat different fractures depending on its location and pattern. Unilateral fixators provide the least stabilisation, but they are the easiest to use and do not disturb normal everyday functioning of an animal. The others are a lot more complex. This is why unilateral fixators stabilise bone fragments to a greater extent. A very extensive structure fixated externally, however, interferes with the normal functioning of a horse. Mandibular fractures are the most common among all skull fractures [1; 2; 3; 4; 5]. Most of them result from an injury, such as hitting an obstacle or being kicked by another horse, or when horses play with metal objects in the stable. Other possible causes include iatrogenic damage during tooth extraction or secondary damage due to ongoing disease processes, such as osteosarcoma or osteomyelitisitis [6]. A mandibular fracture can create many different clinical signs, like dysphagia, pain, malalignment of incisors, displacement of teeth in the arcade, instability of the jaw, creipitation, excessive salivation, swelling, and enlargement of the affected region. Some horses with displaced fractures are not able to eat and drink. In order to establish a precise diagnosis, it is very important to perform clinical and radiological examinations. In very complicated cases, CT exam can also be helpful in considering the proper methods of treatment. On the basis of anatomical location, fractures are classified as fractures of the incisive area, interdental space, horizontal ramus, and the vertical part of the jaw, the most common being fractures of the incisive area. Only stable and non-displaced fractures can be considered for conservative treatment [5; 7]. Fractures of the mandibular body pose the greatest challenge to a practitioner among all mandibular fractures. The majority of them are opened, which makes their treatment much more difficult [3; 8; 9]. Depending on location and fracture configuration, the following surgical methods can be used: Wire loops in the oral cavity, wire loops enforced with synthetic materials, screws, U-shaped plate placed in the oral cavity, transmandibular Steinmann pins, steel plates (DCP, dynamic compression plates; LCP, locking compression plates) [10; 11; 12; 13; 14; 15]. The use of DCP or LCP plates fixated directly on the bone at the ventrolateral site of the jaw provide the best stabilisation [17] but for opened infected fractures, this is not recommended. For the fixation of some fractures, only screws were needed. Biodegradable magnesium alloys can also be considered in the future [18]. Fractures of incisive bone, although being opened, are successfully treated using wire loops, which stabilise the bone to a required extent [1; 2; 3; 10; 11; 12; 16]. External fixators are a separate method. They are especially indicated for the treatment of open fractures. Sometimes, for successful treatment, it is necessary to use a combination of a few methods [16; 19]. The use of external fixators in the treatment of selected fractures, mainly animal limb bones, has been described since the 1930s [20]. External skeletal fixation is quite popular for the treatment of fractures in cattle [21].