The use of polymethyl methacrylate based cement for the fixation of joint replacements although commonly applied, is still limited by interfacial weakness. This study aims to document the effects of a variety of surface treatments on implant/cement bonding and link them to their surface properties. Thirty seven femoral implant analogues of Ti6Al4V rods were given one of six different surface treatments: traditional grit blasting, wet and dry Vaquasheening, acid etching in concentrated sulphuric and hydrochloric acid, anodisation at 150V, and a combination of acid etching and anodisation, before being embedded into a commercially available poly(methyl methacrylate) bone cement. The interfacial strength, energy and stiffness were measured through pushout testing. Surface analysis included examination with scanning electron microscopy, wettability tests and roughness analysis. Results were analysed with a one-way ANOVA with post hoc tests. Overall, the coarse blasted surface created the strongest interface, followed by both etched then anodised, acid etched only, wet Vaquasheened, anodised only and finally dry vaquasheened. While anodised samples showed a weaker bond than etched samples, the combination of etching and anodisation was not different to etching alone. In addition, six different types of interface failure modes were observed, and theories as to explain their mechanism, using experimental evidence were outlined. Coarse blasted surfaces showed the strongest bonding, while other surface modifications may encourage tissue ingrowth and other biological responses, these surface treatments do not strengthen bonding for cemented fixation.
Implant contamination prior to cement application has the potential to affect the cement-implant bond. the consequences of implant contamination were investigated Fifty Titanium alloy (Ti-6Al-4V) dowels were prepared with two surface finishes comparable to existing stems. The roughness (Ra and Rq) of the dowel surface was measured before and after the pushout test. Four contaminants (Phosphate Buffered Saline (PBS), ovine marrow, ovine blood, olive oil) were prepared and heated to 37°C. Each contaminant was smeared on the dowel surface completely and uniformly approximately 4 minutes prior to implantation. Samples were separated into ten groups (n=5 per group) based on surface roughness and contaminant. Titanium alloy dowels was placed in the center of Polyvinyl chloride (PVC) tubes with bone cement, and equilibrated at 37°C in PBS for 7 days prior to mechanical testing. The push out test was performed at 1 mm per minute. The dowel surface and cement mantel were analyzed using a Scanning Electron Microscopy (SEM) to determine the distribution and composition of any debris and contaminates on the surface.Introduction
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