Investigation of interfacial strength and its structure on the development of a new design of UHMWPE acetabular component.

Abstract

Previous studies associated with the development of a new ultra-high-molecular-weight polyethylene (UHMWPE) acetabular component have shown high interfacial tensile strengths through chemical and mechanical bonds between virgin UHMWPE or polymethylmethacrylate (PMMA) and PMMA/methylmethacrylate (MMA) monomer treated UHMWPE. Along with the interfacial strength, the mechanism of interfacial strength development has been investigated, correlating the interfacial strength to its structure, with the different molding temperatures or amount of PMMA in the treated UHMWPE. Of three different fracture patterns-adhesive, mixed, and cohesive-most fractures occurred in the mixed or cohesive mode, indicating either a strong interface or a weak bulk phase. Load-displacement plots from the interfacial tensile tests represented two distinct fracture patterns, suggesting the nature of interfacial structure. Comparison of theoretical and real interfacial strength showed a close match between the two strengths for the interface between PMMA and treated UHMWPE, but a large difference for the interface between UHMWPE and treated UHMWPE. This result hints that although the PMMA/treated UHMWPE interface develops its interfacial strength in a relatively simple mechanism of direct chemical bonds, the UHMWPE/treated-UHMWPE interface builds its strength in a complex way.