Antimicrobial silver-coating for locking plates shows uneventful osteotomy healing and good biocompatibility results of an experimental study in rabbits.

Infections after internal fixation of fractures remain a challenge. Silver is known for its antimicrobial activity, including activity against multi-resistant strains. The aim of the current study was to analyze the biocompatibility and potential influence on the osteotomy healing process of a silver-coating technology for locking plates compared to silver-free locking plates in an established rabbit model. The implants used in this study were 7-hole titanium locking plates, and plasma electrolytic oxidation (PEO) silver-coated equivalents. A total of 24 rabbits were used in this study (12 coated, 12 non-coated). An osteotomy of the midshaft of the humerus was created and the humerus stabilized with the 7-hole locking plates with a total of 6 screws. Radiographs were taken on day 0, week 2, 4, 6, 8, and 10 for continuous radiographical evaluation. All animals were euthanized after 10 weeks and further assessment was performed using X-rays, micro-CT, non-destructive four-point bending biomechanical testing and semi-quantitative histopathological evaluation. Furthermore, silver concentration was measured in the blood, kidney, liver, spleen, brain, feces and soft tissue around the plate. Radiographs showed normal undisturbed and completed healing of the osteotomy in all animals without any differences between the two groups over the entire observation period. Micro-CT analysis revealed overall tissue volume as well as tissue density to be comparable between the two groups. Mechanical testing showed comparable stiffness with an average stiffness relative to contralateral bones of 75.7 ±â€¯16.1% in the silver-free control group compared to 69.7 ±â€¯18.5% (p-value: 0.46). Semi-quantitative histopathological evaluation showed no remarkable difference in the analysis of the osteotomy gap healing or in the surrounding soft tissue area. There were detectable silver concentrations in the soft tissue around the plate after 10 weeks. Silver in the blood was only found in 3 animals within the first two weeks and all animals were free of silver afterwards. There were no detectable silver concentrations in the brain, liver, spleen, axillary lymph nodes and kidney. This study shows undisturbed osteotomy healing of the presented antimicrobial silver surface coating and a good biocompatibility in this rabbit model.

Stability of two angular stable locking plates for open wedge high tibial osteotomy (HTO): TomoFix™ versus LOQTEQ® HTO plate.

INTRODUCTION: The aim of this study was to test the mechanical stability of LOQTEQ® HTO plate in comparison to the TomoFix™ internal plate fixator. MATERIALS AND METHODS: An unstable fracture gap model with two standardized polyoxymethylene (POM) cylinders was used for this study. With this model 5 LOQTEQ® HTO plates and 5 TomoFix™ were cyclically loaded. The start load was 100 N and increased by 50 N after each successful completed cycle. Each load step included 250,000 cycles. All tests were performed in accordance with the American Society for Testing and Materials (ASTM) Standard Specification and Test Method for Metallic Bone Plates F382-99(2003)e1. RESULTS: The mean fatigue strength of the LOQTEQ® HTO Plate was 155 % of the value gained by the TomoFix™ implant. This difference was statistically significant (t test <0.001). There was also a significant difference in the cycles but both implants survived. The LOQTEQ® HTO Plate system survived 1,520,336.8 (±121,687.7) cycles, whereas the TomoFix™ group passed on average 847,802,600 (±134,660.7) cycles. In both groups, the only failure mode was plate breakage in a shaft hole. CONCLUSIONS: The results of the present study showed that fatigue strength of the LOQTEQ® HTO plate was significantly higher in comparison to TomoFix™. These results justify the clinical use of the LOQTEQ® HTO plate.