Orientation and end zone of the osteotomy cut for high tibial osteotomy: Influence on the risk of lateral hinge fracture. A finite element analysis.

Place: FranceInternational audienceINTRODUCTION: the hinge plays a fundamental role in the support and consolidation of a high tibial osteotomy. The objective of this work was to analyse the influence of the end zone of the osteotomy cut and its orientation in relation to the articular joint line (JL) on the risk of hinge fracture. HYPOTHESIS: a specific orientation and end zone of the osteotomy cut can be utilised to decrease the risk of hinge fracture.MATERIAL AND METHOD: a finite element (FE) model was used to reproduce the proximal portion of the tibia and the proximal tibiofibular joint with transverse isotropic elastic bone properties. A 1.27mm thick, complete, anteroposterior saw cut was made with a U-shaped saw blade. Five proximal and lateral tibial zones were used according to Nakamura et al corresponding to the end zones of the osteotomy cut. Three angulations of the cut relative to the JL were defined: 10°, 15°, 20°. The tests consisted of simulating 15 possible situations (3 angulations for each of the 5 end zones) on this model. These simulations made it possible to identify the existence of a local stress concentration (von Mises, in MPa) at the level of the hinge, corresponding to the main judgment criterion.RESULTS: If we consider only the end zones of the osteotomy cut, regardless of its angulation with respect to the JL, the zone which presents, on average, the lowest local stress concentration is the AM zone (40.3MPa). If we consider only the angulation of the osteotomy cut, with respect to the JL, regardless of the end zone of the cut, the angulation that locally concentrates, on average, the least stress is an angulation at 10° (147.7MPa). Finally, it is important to define the best end zone of the osteotomy cut for each angulation value in relation to the JL: for an angulation of 10°, the end zone must be in AM (38MPa), but also for an angulation of 15° (45MPa), and for an angulation of 20° (38MPa). DISCUSSION-CONCLUSION: With the inherent caveats of the experimental conditions, the hypothesis is confirmed. An end zone of the osteotomy cut exists (AM) and an orientation (10°) that induces the lowest local stress concentration and therefore the least likely to induce lateral hinge fracture. However, the orientation of the osteotomy cut is also a matter of surgical habit, especially regarding complementary osteotomy of the tibial tuberosity that some may want to avoid. Thus, it is equally important to know the best end zone associated with a given angulation of the cut in relation to the JL, which according to these results is the AM zone for each angulation. This information helps guide the operator in their surgical practices according to their habits.LEVEL OF EVIDENCE: V, expert opinion

Effect of saw blade geometry on crack initiation and propagation on the lateral cortical hinge for HTO: Finite element analysis.

Place: FranceInternational audienceINTRODUCTION: The hinge plays a primary role in the hold and healing of a high tibial osteotomy (HTO). Weakening of the hinge is a risk factor for failure. The aim of our study was to determine whether the geometry of the saw blade's cutting edge impacts crack initiation or propagation on the hinge. HYPOTHESIS: A certain cutting edge geometry exists that will reduce this risk. MATERIALS AND METHODS: A finite element model with transverse isotropic elastic bone properties was created. A 1.27-mm thick saw cut (full thickness in anteroposterior direction) was made leaving a 1cm lateral cortical hinge. Three different cutting edge geometries were compared: rectangular, U-shaped, V-shaped. Opening of the osteotomy was done over 1mm for 1 s by a load applied distally with the proximal portion fixed. In the first simulation, no crack was initiated at the hinge, while in the second simulation, the beginnings of a 2mm crack angled upward at 15° was added. These two simulations were used to identify whether a local stress riser was present at the hinge. This information was used to calculate the energy release rate to the hinge, which corresponds to the energy needed to initiate and propagate a crack on the hinge. RESULTS: In the first simulation (no crack initiation), a rectangular saw blade geometry resulted in the lowest local stress concentration. In the second simulation (with crack initiation), the U-shaped geometry resulted in the lowest local stress concentration. The U-shaped geometry had the lowest energy release rate, meaning that it was the least likely to initiate and propagate a crack on the lateral cortical hinge. DISCUSSION/CONCLUSION: Keeping the inherent limitations related to computer modelling in mind, our findings show that a U-shaped cutting edge is least likely to initiate or propagate a crack since it has the lowest energy release rate. This confirms our hypothesis. LEVEL OF EVIDENCE: V, expert opinion

A highly-sensitive microplate fluorimetric method for the high-throughput determination of nitrate ion in aqueous compost extracts

International audience9 In this paper, a new spectrofluorimetric method for the determination of nitrate in aqueous 10 compost extracts is presented. The microplate procedure is based on the reduction of nitrate 11 to ammonium by means of Zn powder under acidic conditions and the following derivatization 12 of ammonium with o-phtaladehyde (OPA) and N-acetylcysteine (NAC) to give a fluorescent 13 derivative. Optimization work allowed performing the reduction in 30 min on a small sample 14 volume (150 µL) and using a little quantity of metal (20 mg). The use of strong acids is also 15 avoided. Excellent limit of detection was achieved (1.3 µM = 0.08 mg.L-1 NO3-) along with good 16 precision levels (4.2 and 14.3 % for 50 and 5 µM, respectively) and a satisfactory linear 17 dynamic range (4-100 µM). A good agreement between data coming from our method and 18 from ion-exchange chromatography was found on real compost samples, indicating a good 19 level of accuracy. 20 21 2

Anaerobic Oxidation of Fatty Acids and Alkenes by the Hyperthermophilic Sulfate-Reducing Archaeon Archaeoglobus fulgidus▿ †

Archaeoglobus fulgidus oxidizes fatty acids (C4 to C18) and n-alk-1-enes (C12:1 to C21:1) in the presence of thiosulfate as a terminal electron acceptor. End products of metabolism were CO2 and sulfide. Growth on perdeuterated hexadecene yielded C15- to C17-labeled fatty acids as metabolites, thus confirming the ability of A. fulgidus to oxidize alkyl chains

Archaeoglobus fulgidus and Thermotoga elfii, Thermophilic Isolates from Deep Geothermal Water of the Paris Basin

International audienceThermophilic anaerobic microorganisms with the ability to reduce sulfur compounds (e.g., sulfate and/or thiosulfate) were isolated from water samples collected from about 2000 meters depth at in situ temperatures of 70°C in a geothermal well from the Paris Basin (France). Chemical and isotopic analyses show that microbial sulfate reduction occurred in the samples. Two strains were characterized by both DNA/DNA hybridization and 16S rRNA gene sequence analysis, which indicated that they are most closely related to Thermotoga elfii, a thiosulfate-reducing bacterium, and Archaeoglobus fulgidus, a sulfate- and thiosulfate-reducing archaeon. Besides thiosulfate reduction using H2 as energy source, both isolates are shown to be able to retrieve energy from H2/Fe(III), a metabolic capability of importance in a deep biosphere context. It is suggested that T. elfii and A. fulgidus could be used, either as pure culture or as a consortium, in future laboratory studies aiming at better understanding microbial iron (III) and sulfate/thiosulfate reduction, hydrogen production/consumption, as well as the effect of microorganisms on the evolution of CO2 in deep aquifers. The present work examines numerous culture conditions and demonstrates that in spite of similarities in phylogenetic/genetic characteristics and in growth conditions, there are significant phenotypic differences between the isolated archaeal strain and the type strain of A. fulgidus. These differences, evidenced by a proteomic study, should be taken into account and could be useful parameters to be studied in the deep aquifers by geomicrobiological laboratories

Adding a protective screw improves hinge's axial and torsional stability in High Tibial Osteotomy

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Modified 3D-printed device for mercury determination in waters

3D printing technology is increasingly used in flow analysis, to develop low cost and tailor-made devices. The possibility of grafting specific molecules onto 3D printed parts offers new perspectives for the development of flow systems. In this study, a MPFS system including a dicarboxylate 1,5-diphenyl-3-thiocarbazone grafted 3D-printed device has been developed for mercury determination. For this purpose, the surface of 3D-printed cuboids was first modified with amine functional groups and then grafted with dicarboxylate 1,5-diphenyl-3-thiocarbazone. This new grafted device resulted in selective mercury preconcentration with extraction and elution yields higher than 90% even at high sampling flow rates. The detection can then be carried out in two ways: a direct detection of mercury extracted onto 3D-printed grafted cuboids by atomic absorption spectrophotometry after amalgam on gold or a detection of mercury in solution after elution with L-cysteine by spectrophotometry or cold vapor atomic absorption spectrometry