## 1 Introduction  
Bone tissue is a dynamic structure that protects internal organs and is a rigid segment that allows the transfer of forces, among others. during locomotion. It is a living tissue whose mineralized structure covers two thirds of the bone's dry weight. There are three regions in horse bones: the body, the epiphysis, and the metaphysis. The diaphysis consists of cortical bone, while the epiphysis and metaphysis contain trabecular cancellous bone. The body contains bone marrow, initially red, which, over time, becomes yellow marrow. The bones are covered with periosteum, which changes as the horse ages, becoming thinner and less adherent to the bones. At the microstructural level, the basic unit of bone is the osteon, consisting of a Haversian canal surrounded by laminae of mineralized bone. There are three types of cells in bones: osteocytes, osteoblasts and osteoclasts. Osteoblasts, the bone-forming cells, produce most of the components of the organic bone matrix, including collagen. Osteocytes, derived from osteoblasts, maintain intercellular communication. Osteoclasts, osteocl cells, are responsible for bone resorption. The organic matrix of bone contains mainly collagen, and the inorganic part is mainly dihydroxyapatite, which gives the bone hardness [1]. Horse bone is a natural composite of two main components: collagen fibres (matrix) and a mineral part (reinforcement). Its trabecular structure makes it light yet highly durable, with mechanical properties oriented according to external loads. Cancellous bone is more plastic and has greater elasticity than cortical bone. The mechanical properties of bones are anisotropic, which means that they depend on the direction of force. Figure 1 shows possible bone loading conditions that may occur in a horse's long bones. Research shows large differences in bone strength, depending on, among others, age, bone density, and tissue type. The [PERSON]'s modulus of horse bone is 15 to 24 GPa for cortical bone and 0.12 to 0.59 GPa for cancellous bone, and the Poisson's ratio is approximately 0.3 for both types of tissue [2]. Depending on the stress conditions occurring on the bones, different types of fractures will occur, which may vary in terms of the complexity of subsequent treatment (Figures 1 and 2). The stabilization of third metacarpal bone fractures in horses is an important area of interest in orthopaedic veterinary medicine, which is crucial for the animal's return to full fitness. These fractures are a common condition among horses and may result from intense training, accidents, or natural degenerative processes. The effectiveness of treatment and the prognosis of recovery of the horse's motor function after a fracture depend largely on the appropriate stabilization of the broken bone and the body's ability to heal the bones [4; 5]. Numerical analysis, using advanced computer modelling methods, has become an indispensable tool in the diagnosis and treatment of fractures of the third metacarpal  
Figure 1: Possible bone stress conditions that may occur in the horse’s long bones [3]. Figure 2: Possible types of fractures depending on the type of load [3]. bone in horses. By precisely simulating the movement dynamics and mechanical loads, researchers can better understand the behaviour of broken bones in various conditions and assess the effectiveness of various stabilization methods. In 2007, the Journal of the American Veterinary Medical Association presented a scientific report on retrospective research in which external stabilization in the form of transfixation casting was used for a group of 29 adult horses and 8 foals with fractures of the third metacarpal or metatarsal bone. This method involves inserting transosseous pins proximally to the fracture site and placing it in a plaster cast for 45 days. To allow movement during treatment, the cast was constructed using plaster of Paris with the addition of fibreglass, Steinmann pins, and a metal walking frame.