Abstract
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
Correspondence should be addressed to Ms Larissa Welti, Scientific Secretary, EFORT Central Office, Technoparkstrasse 1, CH-8005 Zürich, Switzerland
