Single-Slice XRF Mapping of Light Elements in Frozen-Hydrated Allium schoenoprasum via a Self-Absorption-Corrected Hyperspectral Tomographic Reconstruction Approach.

3D and 2D-cross-sectional X-ray fluorescence analysis of biological material is a powerful tool to image the distribution of elements and to understand and quantify metal homeostasis and the distribution of anthropogenic metals and nanoparticles with minimal preparation artifacts. Using tomograms recorded on cryogenically prepared leaves of Allium schoenoprasum, the cross-sectional distribution of physiologically relevant elements like calcium, potassium, manganese, and zinc could be tomographically reconstructed by peak fitting followed by a conventional maximum-likelihood algorithm with self-absorption correction to reveal the quantitative cross-sectional element distribution. If light elements such as S and P are located deep in the sample compared to the escape depth of their characteristic X-ray fluorescence lines, the quantitative reconstruction becomes inaccurate. As a consequence, noise is amplified to a magnitude where it might be misinterpreted as actual concentration. We show that a tomographic MCA hyperspectral reconstruction in combination with a self-absorption correction allows for fitting of the XRF spectra directly in real space, which significantly improves the qualitative and quantitative analysis of the light elements compared to the conventional method as noise and artifacts in the tomographic reconstruction are reduced. This reconstruction approach can substantially improve the quantitative analysis of trace elements as it allows the fitting of summed voxel spectra in anatomical regions of interest. The presented method can be applied to XRF 2D single-slice tomography data and 3D tomograms and is particularly relevant for, but not limited to, biological material in order to help retrieve self-absorption corrected quantitative reconstructions of the spatial distribution of light elements and ultra-trace-elements.

X-ray fluorescence analysis of metal distributions in cryogenic biological samples using large-acceptance-angle SDD detection and continuous scanning at the Hard X-ray Micro/Nano-Probe beamline P06 at PETRA III.

A new Rococo 2 X-ray fluorescence detector was implemented into the cryogenic sample environment at the Hard X-ray Micro/Nano-Probe beamline P06 at PETRA III, DESY, Hamburg, Germany. A four sensor-field cloverleaf design is optimized for the investigation of planar samples and operates in a backscattering geometry resulting in a large solid angle of up to 1.1 steradian. The detector, coupled with the Xspress 3 pulse processor, enables measurements at high count rates of up to 106 counts per second per sensor. The measured energy resolution of ∼129 eV (Mn Kα at 10000 counts s-1) is only minimally impaired at the highest count rates. The resulting high detection sensitivity allows for an accurate determination of trace element distributions such as in thin frozen hydrated biological specimens. First proof-of-principle measurements using continuous-movement 2D scans of frozen hydrated HeLa cells as a model system are reported to demonstrate the potential of the new detection system.

Biomechanical analysis of polyaxial locking vs. non-locking plate fixation of unstable fractures of the distal fibula: A cadaver study with a bone only model.

BACKGROUND: Open reduction and internal fixation is the current standard of treatment of displaced distal fibula fractures, whereupon using a lag screw often is impossible because of a multifragmantary fracturezone. This study investigates in what extend polyaxial-locking plating is superior to non-locking constructs in unstable distal fibula fractures. METHODS: Seven pairs of human cadaver fibulae were double osteotomized in standardized fashion with a 5mm gap. This gap simulated an area of comminution, where both main fragments were no longer in direct contact. One fibula of the pair was managed using a 3.5-mm screw in a polyaxial-locking construct and the other fibula in a non-locking construct.

Does a polyaxial-locking system confer benefits for osteosynthesis of the distal fibula: A cadaver study.

BACKGROUND: In plate osteosynthesis involving the distal fibula, antiglide plating is superior to lateral plating in terms of the biomechanical properties. The goal of this study was to examine whether polyaxial-locking implants confer additional benefits in terms of biomechanical stability. METHODS: Seven pairs of human cadaveric fibulae were subjected to osteotomy in a standardized manner to simulate an uncomplicated Weber B fracture. The generated fractures were managed with a dorsolateral antiglide plate. To this end, one fibula of the pair was subjected to non-locking plating and the other to polyaxial-locking plating. Biomechanical tests included quantification of the primary bending and torsional stiffness. In addition, the number of cycles to failure in cyclic bending loading were determined and compared. Bone mineral density was measured in all specimens. RESULTS: Bone mineral density was comparable in both groups. Primary stability was higher in the polyaxial-locking group under torsional loading, and higher in the non-locking group under bending loading. The differences, however, were not statistically significant. All specimens except for one fixed-angle construct failed the cyclic loading test. The number of cycles to failure did not differ significantly between polyaxial-locking and non-locking fixation. CONCLUSION: In a cadaveric Weber B fracture model, we observed no differences in biomechanical properties between polyaxial-locking and non-locking fixation using an antiglide plate. Based on the biomechanical considerations, no recommendation can be made regarding the choice of the implant. Further biomechanical and clinical studies are required. CLINICAL RELEVANCE: Information on the behavior of polyaxial-locking plates is relevant to surgeons performing internal fixation of distal fibula fractures.