THE CORRELATION BETWEEN FUSION DEFECTS AND DAMAGE IN TIBIAL POLYETHYLENE BEARINGS

Recent reports of fatigue failures of polyethylene tibial and patellar components have led to investigation of the role of design and materi al properties in these failures. Earlier investigations, concluding th at high contact stress designs suffered greater damage in service, cou ld not account for some of the fatigue failures. The current study hyp othesizes that this failure is related to variations in the material p roperties of the polyethylene due to incomplete consolidation of the p owder during manufacture, resulting in fusion defects. Retrieved polye thylene components and samples of polyethylene stock were examined to gain insight into the relationship between fusion defects, component f ailure, material forming processes, and powder grade. Statistically si gnificant correlations (p < 0.05) were observed between the extent of defects and cracking, delamination, total wear damage, and duration in vivo. These correlations indicate that components manufactured from m aterial with fusion defects may be less resistant to fatigue than comp onents formed of fully consolidated material.