Narrow Results

Introduction: The purpose of this study was to ascertain the primary ex vivo biomechanical stability of a novel bioabsorbable magnesium alloy (ZX00: Mg–Zn–Ca) bone anchor in human cadaveric proximal humeri, indicated in the reconstruction of the rotator cuff.

Methods: Twenty human Thiel-embalmed cadaveric humeri were prepared and freed from soft tissue. One $\varnothing$5.7 × 20.5-mm ZX00 anchor and one $\varnothing$5.5 mm × 16.3 mm Arthrex Titanium FT Corkscrew (ATC) control anchor were inserted into the footprint of the supraspinatus tendon, 15 mm apart. The humeri were mounted onto a material testing machine and following a 40 N preload, cyclic loading was performed over 400 cycles. If the construct remained intact, ultimate load to failure (ULTF) was measured using an increasing axial load of 1 mm/s, ULTF and mode of failure were recorded.

Results: No difference was found in the ability to withstand cyclic loading, mode or load-to-failure strengths between ZX00 and control anchors. The maximum tractional force loaded for the ZX00 anchors had a median of 257.4 N (range 165.3–328.2). The corresponding value for the ATC anchors averaged 239.9 N (range 118.9–306.7).

Conclusion: ZX00 alloy anchors appear to provide adequate initial biomechanical stability when compared to an industry-standard control in a cadaveric rotator cuff repair model.

This paper presents a theoretical model for describing the thermodynamic properties of doped ferroelectric crystals based on a modified Weiss mean-field approach. Accounting for quadrupole and octupole terms in the expression for the effective field within the Weiss model makes it possible to move from the Langevin equation to the Landau–Ginzburg equation. Furthermore, the coefficients of the Landau–Ginzburg equation can be expressed in terms of the physical parameters of the crystal lattice. For these parameters, analytical expressions are proposed that describe their change when adding dopants in ceramic matrix composites. Perovskite barium titanate ceramics with a variety of inclusions is considered as an application example of the developed method. The obtained agreement between the analytical and experimental results for barium titanate ceramics with lanthanum/magnesium/zirconium dopants gives us hope of the applicability of the present theory to the calculation of other doped ferroelectrics as well.

The teeth of Evenchinus chloroticus are not only vital tools for their survival but also have fascinating structures in the world of science and engineering. Despite being compositionally similar to rocks, these teeth are still able to scrape along the hard surfaces of rocks for food, while having the unique ability to self-sharpen. Yet these abilities arise from the properties of the teeth, which are in turn dependent on their design and composition. Nanoindentation was used in this study to characterise the hardness across the sea urchin tooth in detail. It focuses on the chewing tip since the main grinding function is performed by this region. In addition, SEM and EDS were used to explore any correlations between the mechanical properties of the tooth and its composition. It was found that there were two main relatively hard regions (stone part in the centre of the top flange part and another similar region in the centre of the bottom keel zone). These regions are similar in structure, consisting of thin needles and matrix and have a higher magnesium content compared to other areas of the tooth, which is attributed to the greater proportion of matrix present. Furthermore, the regions below the stone part and at the start of the keel zone appear to be weaker, which might be due to the significant amount of pores in these areas. The sharp tip is maintained by shedding of the primary plates surrounding the stone part and the keel fibres, leaving only the stone part at the chewing tip.