We propose here the use of a computer-aided design (CAD) system in the treatment of fractures in small animals. During surgical planning, the veterinarian sketches a simple plate referring to computed tomography images. A CAD operator then models the plate by polygonal approximation (triangulation) of the surface of the bone region. After importing the approximated shape into the CAD system as a triangulation mesh, a detailed design of the plate is then prepared in the CAD system by referring to the abovementioned sketch. The plate can be designed to match the bone surface since the plate surface follows the curvature of the surface of the exported triangulation mesh. Furthermore, the bone shape and plate are eventually converted into polygon shapes, and a structural model identical to the fractured part of the bone can be reproduced using a 3D printer, allowing for alignment to be performed at full scale. In this study, we examined the applicability of the proposed system by designing the most appropriately shaped plate for bone fracture therapy in small dogs brought to a veterinary clinic for treatment.