Biomechanical Researches On The Feasible Application Of Degradable Biological PLLA To The Plate Internal Fixation System

Experience in clinics shows that metal plates used in clinics could cause great effect of stress shielding on bone tissue. Though they could provide stability for fracture zones, which is beneficial for initial healing of the fracture, the stress shielding effect could induce later osteoporosis and the decrease of bone strength, even the refracture after the plate is moved.Poly lactic acid is a kind of polymer with excellent biocompatibility, degradability, mechanical strength, elastic module and thermoplasticity. Since it degrades gradually and has few negative effects to human body, poly lactic acid has become the researching focus in clinical fields.In this paper, a kind of degradable cushion made of PLLA was placed under the metal plate, and then a new internal fixation was created. By introducing the PLLA cushion, the stiffness of the plate fixation may decrease and then the stress shielding effects of the plate to the bone tissue may be relieved. There were mainly two parts of work in this paper. First, animal tibia fracture models of internal plate fixation with and without degradable PLLA cushion were established, and then histological tests and stress shielding tests in vitro were carried on these models. Secondly, several relatively accurate three dimensional finite models of internal plate fixation for animal tibia fracture were established. A pressure of 50 N was applied to both models at initial healing and 50% healing periods, and also the effects of stress...