Is the pull-out force of the Meniscus Arrow in bone affected by the inward curling of the barbs during biodegradation? An in vitro study

Background: Inward curling of the barbs of Meniscus Arrows during degradation was observed in a previous study, in which swelling, distention, and water uptake by Meniscus Arrows was evaluated. This change of configuration could have consequences with respect to anchorage capacity in bone. Material/Methods: Eight non-degraded Meniscus Arrows in the original configuration were pulled out of thawed, fresh-frozen human femoral condyle, and pull-out force was measured and compared with that of 6 Meniscus Arrows after 31 days of degradation under controlled conditions. Results: No significant difference was found between the 2 groups with respect to the required pull-out force (t test), the distribution of the data, or the interaction between degradation and location, as evaluated by mann-Whitney test, and no significant difference was found between the 2 groups with respect to the degradation state or position in the coudyles, as evaluated by 2-way analysis of variance. Conclusions: Our results indicate that the decrease in barb-barb diameter during the first month of degradation of the Meniscus Arrows has no significant effect on the tensile pull-out force required for removal from human femur condyle. Further research should be undertaken to examine whether the same is true for other biodegradable devices with barbs

Reactive wetting of liquid metals on ceramic substrates

This paper deals with a well known puzzling observation that sometimes the wetting is improved by a chemical reaction between a liquid and a solid substrate and sometimes just the opposite effect takes place. Here, contact angles of liquid Al on SiO2 and liquid Ti on Al2O3 have been measured. The surface and interface structures have been explored by scanning electron microscopy and energy dispersive X-ray spectrometry. According to the experimental observations, it turns out that the volume change of ceramic substrates during reaction plays a key role in the effect of chemical reaction on wetting. If the volume of ceramic substrate decreases after reaction, the wettability is not improved by the chemical reaction. This is the case of liquid Al wetting on SiO2. If the volume of ceramic substrate increases after reaction, the wettability is improved by the chemical reaction. This is the case of liquid Ti wetting on Al2O3. Besides our experimental observations, results from literature have been reviewed as well, which are in good agreement with the predictions based on the volume change criterion of ceramic substrate proposed in this paper

In-situ TEM analysis of the reduction of nanometre-sized Mn3O4 precipitates in a metal matrix

The objective of the present work is the in-situ study of the transformation of small oxide precipitates in a metal matrix by conventional and high-resolution transmission electron microscopy (HRTEM). As an example the reduction of Mn3O4 into MnO for nano-sized oxide precipitates in a silver matrix was studied in detail. A convenient method for monitoring the reduction process is shown for a large number of precipitates simultaneously. It is based on two-beam dark-field images showing distinct Moiré patterns for the MnO and the various types of Mn3O4 precipitates embedded within an Ag matrix. A controlling factor of the transformation kinetics appeared to be the rate in which the system can relax the strains due to the accompanying volume reduction of the precipitates. Other interesting aspects of the Mn3O4 to MnO transformation scrutinized and explained were the shape change of the precipitates upon reduction and the fact that mixed Mn3O4/MnO precipitates were only detected within a small temperature/time interval. Ostwald ripening of the MnO precipitates was observed as well.