Introduction: Similar local infection prophylaxis as in cemented total joint by antibiotic-loaded bone cement has not been possible yet for cementless prostheses. In this study, a gentamicin-coating which can be brought additionally onto standard hydroxyapatite (HA) coatings of cementless prostheses is presented. It was tested whether this gentamicin-coating can reduce infection rates in a rabbit infection model with Staphylococcus aureus compared to compared to standard-HA coating. Furthermore, the biocompatibility of this gentamicin coating was investigated.

Materials and Methods: Staphylococcus aureus with a dose of 10(7) CFUs was inoculated into the intramedullary canal of the tibia of 30 rabbits followed by the implantation of standard hydroxyapatite (HA) K-wires, K-wires coated with a HA--gentamicin combination, and K-wires coated with a HA-RGD-gentamicin combination, respectively. The animals were sacrificed after 28 days and clinical, histological and microbiological assessment on the bone and on the removed K-wire itself by agar plating and DNA-pulse field gel electrophoresis were carried out to detect infection. Infection was defined as positive culture growth from the bone and/or cement samples. In another study with 40 rabbits biocompatibility of the two gentamicin-coating types was assessed after an implantation time of 12 weeks and compared to pure HA-coating and uncoated implants.

Results: Infection rates were 88% (7 of 8 animals) for the standard HA, 0% (0 of 9 animals) for the HA-gentamicin and 0% (0 of 10 animals) for the HA-RGD-gentamicin group. There was a statistically highly significant reduction of infection rates by both gentamicin-coating types compared to standard HA-coating (p < 0.001). The animals that were identified to have positive culture growth corresponded to the animals that showed clinical signs of infection. An excellent correlation between agar plating testing results of the K-wires and of the bone samples was found. Detailed histology showed cortical lysis, abcess and sequester formation in the infected animals. There were no major differences in the biocompatibility between the different groups. There were only a few giant cells and regions of bone marrow necrosis in the gentamicin-groups which was comparable to the control implants. There was a very similar histologic appearance of the gentamicin coatings and the standard HA coating.

Conclusion: Both gentamicin-coating types showed significant improvement of infection prophylaxis compared to standard HA coating. Furthermore, both gentamicin coating types revealed good biocompatibility after 12 weeks. Therefore, HA-gentamicin and HA-RGD-gentamicin coatings could help to reduce infection rates in cementless arthroplasty in all day clinical use

Infections in total joint arthroplasty, particularly with multiresistant bacteria, are a serious problem. A new nanoparticulate silver cement had previously shown good biocompatibility combined with good in vitro antimicrobial activity against multiresistant bacteria.

The purpose of the current study was to evaluate the antibacterial activity of nanoparticulate silver cement against biofilm-building methicillin-resistant S. aureus (MRSA) in a rabbit model and to compare it to that of gentamicin-loaded cement.

Gentamicin cement or nanoparticulate silver bone cement was injected into the proximal half of one femur in 10 animals, respectively. Before hardening of the cement 10⁷ or 10⁸ colony forming units of MRSA with high gentamicin resistance were inoculated at the cement bone interface in 5 rabbits of each group. The animals were euthanized after 14 days and both the cement adjacent bone and the cement itself were studied using microbiological and histological methods. Infection was defined as positive culture growth from the bone and/or cement samples.

Infections rates were 100% for the gentamicin group (10 of 10 animals had infection) and 30% for the NanoSilver group (3 of 10 animals). Thus, nanoparticulate silver bone cement significantly reduced infection rates by 70%.

Nanoparticulate silver cement exhibited good antimicrobial activity in the prophylaxis of cement-related infections with MRSA and is therefore a promising alternative in total joint arthroplasty.

Introduction: Deep periprosthetic infections are infrequent but devastating situations in total joint arthroplasty. During the last years the total number and the percentage of total joint infections with multiresistant bacteria has increased. The aim of this study was to investigate the antimicrobial activity of a new bone cement loaded with nanoparticulate silver against bacteria with different antibiotic resistance.

Material and Methods: An in vitro proliferation test was used to test antimicrobial properties of 1% nanoparticulate silver bone cement, gentamicin-loaded, tobramycin-loaded and plain bone cement. This in vitro testing method consisted of two incubation steps. During the first step the tested bacteria could adhere to the bone cement surface. In the second step bacteria either seeded out of vital daughter cells in case of no antimicrobial effect of the cement or were killed by the antibacterial properties of the cement. Seeding out of daughter cells was detected by a microplate reading system resulting in specific time proliferation curves. Several staphylococci and gram-negative strains with different resistance profiles against methicillin, tobramycin, and gentamicin were tested including MRSA and MRSE.

Results: 1% nanoparticulate silver bone cement showed bactericidal effect against all tested strains, including MRSA and MRSE. Gentamicin and tobramycin cement was not effective against bacteria with high resistance level against the respective antibiotic. Plain bone cement was not effective against any strain.

Conclusion: 1% nanoparticulate silver bone cement exhibited excellent antibacterial properties that could not be reached by gentamicin or tobramycin-loaded cement. Good activity against MRSA could also already be shown in a first animal trial. If further in vivo investigations confirm these promising results nanoparticulate silver bone cement is a new alternative for prophylaxis in total joint arthroplasty.