Insertions of orthopedic implants are traumatic procedures that trigger an inflammatory response. Macrophages have been shown to liberate gold ions from metallic gold. Gold ions are known to act in an antiinflammatory manner by inhibiting cellular NF-κB–DNA binding and suppressing I-κ B-kinase activation. The present study investigated whether gilding implant surfaces augmented early implant osseointegration and implant fixation by its modulatory effect on the local inflammatory response. Ion release was traced by autometallographic silver enhancement. Gold-coated cylindrical porous coated Ti6Al4V implants were inserted press-fit in the proximal part of tibiae in nine canines and control implants without gold inserted contralateral. Observation time was 4 weeks. Biomechanical push-out tests showed that implants with gold coating had ~50% decrease in mechanical strength and stiffness. Histomorphometrical analyses showed gold-coated implants had a decrease in overall total bone-to-implant contact of 35%. Autometallographic analysis revealed few cells loaded with gold close to the gilded implant surface. The findings demonstrate that gilding of implants negatively affects mechanical strength and osseointegration because of a significant effect of the released gold ions on the local inflammatory process around the implant. The possibility that a partial metallic gold coating could prolong the period of satisfactory mechanical strength, however, cannot be excluded.
Morselized allograft is widely used when increased bone stock is needed in implant surgery. Gold ions liberated from metallic gold surfaces act in an anti-inflammatory manner by inhibiting cellular NF-κB-DNA binding and suppressing I-κ B-kinase activation. This study investigated the effect of 45-63 μm sized gold particles mixed in morselized allograft. It was hypothesized that bio-released gold ions would influence allograft reabsorption, increase mechanical stability, and further stimulate osseointegration. A pair of 10 mm long implants surrounded by a 2.5-mm gap was inserted in proximal part of each humerus in 10 sheep. Each gap was filled with morselized allograft with 1.29 mg gold particles or nothing. Observation time was 12 weeks. The gold ion liberation was visualized by autometallographic tracing and showed liberation of gold ions. Biomechanical push-out tests and stereological histomorphometric analyses showed no statistically significant differences in the two groups. Although particulate gold was primarily observed surrounded by bone marrow tissue, no obvious clinically relevant short-term effects could be measured using gold as an anti-inflammatory mediator. These findings show that the released gold ions have only influenced cells adjacent to the particles without influencing the fixation and illustrates gold ions' limited field of effect. We suggest a new design for orthopedic implants by introducing gold dots on the prosthesis surface. This aims at suppressing the inflammatory foci along the implant-bone zone and reduces the risk of chronic inflammation before aseptic loosening without affecting bone remodeling. This implant model will be investigated in further studies.
Noncemented implants are the primary choice for younger patients undergoing total hip replacements. However, the major concern in this group of patients regarding revision is the concern from wear particles, periimplant inflammation, and subsequently aseptic implant loosening. Macrophages have been shown to liberate gold ions through the process termed dissolucytosis. Furthermore, gold ions are known to act in an anti-inflammatory manner by inhibiting cellular NF-κB-DNA binding. The present study investigated whether partial coating of titanium implants could augment early osseointegration and increase mechanical fixation. Cylindrical porous coated Ti-6Al-4V implants partially coated with metallic gold were inserted in the proximal region of the humerus in ten canines and control implants without gold were inserted in contralateral humerus. Observation time was 4 weeks. Biomechanical push out tests and stereological histomorphometrical analyses showed no statistically significant differences in the two groups. The unchanged parameters are considered an improvement of the coating properties, as a previous complete gold-coated implant showed inferior mechanical fixation and reduced osseointegration compared to control titanium implants in a similar model. Since sufficient early mechanical fixation is achieved with this new coating, it is reasonable to investigate the implant further in long-term studies.
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