FINITE-ELEMENT STRESS-ANALYSIS OF A HYBRID FRACTURE FIXATION PLATE

Metal plates are commonly used in the operative treatment of bone frac tures. Rigid metal plates stabilize the fracture site, maintain good c ontact between bone fragments and allow early weight bearing and patie nt mobility. However, treatment with rigid metal plates can-cause loca lized bone atrophy due to stress-shielding and interference with blood circulation, and the weakened bone can refracture after plate removal . A hybrid bone plate system that combines the torsional and bending r igidity of a metal plate with the axial compliance of a polymer insert has been designed. A three-dimensional, quarter-symmetric finite elem ent model was generated for a canine femur diaphysis plated with this metal/polymer hybrid design. A model with a standard metal fixation pl ate was also generated for comparison purposes. The stress state in th e underlying bone was examined for several loading conditions taken fr om published in vivo studies. The finite plate reduced stress-shieldin g effects at the fracture site when subjected to an axial load. The be nding strength of the plate was not compromised by the addition of the polymer inserts. Biodegradable inserts further enhanced the performan ce of the new plate design, transferring less of the axial load to the plate as the inserts broke down. Copyright (C) 1996 Elsevier Science Ltd for IPEMB.