## 3 Materials and Methods  
### Preparation of a Numerical Model  
The bone model came from an adult horse from the Wroclaw University of Environmental and Life Sciences teaching materials; therefore, no animals were harmed for the purposes of creating this article (Figure 6); the bone length was 280 mm while the pony's third metacarpal is proportionately smaller due to its size. The length of the modelled bone was 148 mm, so the model was scaled. The next step was to perform a 3D scan of the supplied material and scale it to the dimensions described earlier. This allowed us to obtain two models in.stl format, trabecular bone and cortical bone. The basis for the creation of the model is composite X-ray images of the specimen taken from different directions;.stl format saves three-dimensional objects in the form of a mesh. As a result of this, a computer model was obtained with dimensions corresponding to the actual dimensions of the pony (Figure 7a). The model was cleaned of artifacts, so it consisted of the main part of cortical bone and 4 trabecular bone elements. Then, a crack was created throughout the entire volume of the bone (Figure 7b). Then, the model was imported into the Ansys and ABAQUS/Explicit computing environments. Stabilization models were prepared--anterior, lateral, and anterolateral. Example models in the ABAQUS program are presented below (Figure 8). Figure 6: Third metacarpal bone model: (**a**) left third metacarpal bone of an adult horse; (**b**) distal end; (**c**) proximal end; and (**d**) the body with splint bones. Figure 7: 3D bone model: (**a**) no fracture; and (**b**) after fracture formation. The geometric model used in static calculations in the Ansys Workbench 2024 R1 environment was divided using 10-node elements of a higher order. Static tests were carried out in the Ansys program in order to initially determine the stresses and displacements of the structure. The load values were 353 N for a horse standing still, 483 N for a horse moving at a speed of 2.5 km/h, and 2400 N for a horse moving at a speed of 5.0 km/h. The adopted values come from studies included in sources [27; 28], in which the authors calculated the N/kg value depending on the animal's movement speed. The model mesh has been refined in the areas of implant-bone contact, bone-screw contact, and implant-screw contact areas. The model assumed that the contact connections between bone screws and bone and between screws and bone plates are of the bonded type. Contacts between the bone plate and the bone surface were defined as frictional with a friction coefficient of 0.38 [29]. The model also generated the volume of bone scar in the form of a solid sphere, which was placed symmetrically between the bone fragments. The contact connection between the scar and the fragments was modelled as a bonded type contact. The connection between the bone scar and the implant was omitted. Fixing the implant was achieved by removing all degrees of freedom on the articular surface belonging to the distal end of the bone (Figure 9). The load in the form of nodal forces with specific values and directions of action was applied to the articular surfaces of the proximal end. As a result of the calculations, the distributions of reduced stresses and main stresses 1 and 3 in the volume of the bone and implant were obtained. Nodal displacements on the surfaces in contact with bone fragments were recorded in the volume of the bone scar. These displacements were then mapped onto an isolated bone scar model, in which changes in the density distribution depending on the type of stabilization were predicted using a program based on [PERSON]'s algorithm [30]. Figure 8: Numerical model in ABAQUS 6.13 software: (**a**) anterior stabilization; (**b**) lateral stabilization; and (**c**) anterolateral stabilization. After determining the initial loads during static analyses, a simulation was performed in the ABAQUS/Explicit solver to observe the propagation of damage during movement at a speed of 5.0 km/h.