The final thesis discusses the treatment of a bone fracture with different methods of plate attachment with screws. In the first part, we briefly describe structure and mechanical properties of the bone, we examine the materials and present different plate fixations. Later on, we made numerical simulations, to study stresses in the bone due to bending by two different methods of implant attachment – a classical connection and a locking connection. In the Ansys program environment, four different models of fixture were designed and loaded in an elastic range. Results showed that in all cases the highest stress was found in holes nearest to the fracture site. In cases where plate and bone are connected, high local stress is found on the edge of the fracture and contact. It was found that in the case of a locking plate, the stress is transmitted only through the screw to bone contact; while in the case of conventional plate, the stress is also transmitted through the contact between plate and bone. Mechanical and biological advantages and disadvantages were discussed, according to the literature.