Modified PMMA cements for a hydrolysis resistant metal-polymer interface in orthopaedic applications

Amongst the many factors influencing the long-term stability of cemented hip prostheses, the interface between the implant and bone cement is considered to be one of the most susceptible to failure. Osteolysis and loosening of the implant can occur by the interaction of mechanically and/or hydrolytically induced bond failure of the metal-cement interface. In this work, an improvement of the hydrolysis resistance of the titanium-bone cement interface was obtained by cement modification with a bifunctional coupling agent combined with a tribochemical TiO2-modification of the metal surface. Methacryloxypropyl-trimethoxysilane was added as coupling agent to the PMMA monomer in concentrations between 5 and 20 wt.% followed by the testing the shear bond strength of PMMA/titanium joints before and after ageing in physiological saline solution. It was found that the hydrolysis resistance of the metal-PMMA interface could be significantly improved by the modification of the cement. At the same time, the mechanical properties (compressive and bending strength) of the modified cement were not altered by the addition of the coupling agent. The advantage of the modification of the cement matrix is an easy clinical applicability of the procedure maintaining the processing and implantation techniques of the cement material.