Analytic guidelines for optimal stem designs of custom-made joint prostheses

Functional reconstruction of bones and joints by total joint replacement has become an attractive alternative to limb amputation. This paper addresses design of the stem to establish an optimal stem shape for a specific bone when its dimensions are known from x-rays, and to establish an optimal dimensional classification system. [2 Refs

Untersuchung des Einflusses von iatrogenen Schädigungen auf Marknägel

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Marknägel werden zur internen Fixierung von Brüchen der langen Röhrenknochen benutzt. Dabei muß der Nagel physiologische Lasten durch Biegung, Druck (d.h. Verkürzung) und Verdrehung aufnehmen. Der Rotationsschutz zur notwendigen Drehmomentübertragung, sowie auch die Längenkontrolle, wird üblicherweise durch eine Verriegelung des Nagels mit Schrauben oder Bolzen erreicht, die in proximalen und distalen Querbohrungen des Marknagels sitzen

A spatia-temporal mechanobiological model to inversigate the heteroneneity of perisprosthetic tissue healing

Non renseign

High resolution magnetic resonance flow imaging in a model of porous bone-implant interface

PURPOSE: To evaluate the application of high-resolution MRI methodology for characterizing the fluid velocity field and evaluate fluid shear field within a simplified in vitro model of a bone-implant interface. MATERIALS AND METHODS: The study used a specific micromotion canine bone implant that has been used for over a decade in the experimental evaluation of anatomical, biomaterial, mechanical and surgical factors influencing the quality of the implant interface. To allow its implementation in an MR coil, a nonmagnetic model of the micromotion implant was fabricated. The model consisted of a cylinder of polymethylmethacrylate (PMMA) representing the implant, located within an annular controlled gap into a block of coralline-derived bulk porous hydroxyapatite (HA; Interpore Cross International, Irvine, CA, USA). The assembly was potted in a polycarbonate shell and connected to a gravity-feed flow system consisting of a water fluid reservoir and peristaltic pump. Cross-sectional fluid velocity images through the principal axis of the implant were generated using a phase-encoding MR imaging technique; axial fluid flow was derived, and fluid shear was evaluated using a Newtonian fluid model. RESULTS: Due to the nonuniform gap of the actual experimental construct, a highly nonuniform flow through the annular gap and a secondary flow through the porous HA block were observed. Axial velocity magnitudes in the range 0.04 to 14 mm/s were measured, and the flow velocities within the annular gap and the surrounding bone differed by nearly two orders of magnitude. Image analysis showed that 95% of total flow passed through the annular gap and 5% was transported through the porous HA block. Fluid shear was computed within the porous structure and the annular gap, and they differed by one order of magnitude. CONCLUSION: We demonstrated that high-resolution MR flow imaging has the resolution to measure fluid transport processes noninvasively through a nonmagnetic model bone implant. Gap fluid flow and fluid flow into the permeable skeleton (HA block) were quantified, and these data allowed the noninvasive determination of fluid shear. These promising results are encouraging for applications in biological tissue, artificial bone substitutes, tissue engineering and clinically relevant studies concerning implant fixation

Time-series transcriptomics reveals that AGAMOUS-LIKE22 affects primary metabolism and developmental processes in drought-stressed arabidopsis

This is the author accepted manuscript. The final version is available from the American Society of Plant Biologists via the DOI in this record.In Arabidopsis thaliana, changes in metabolism and gene expression drive increased drought tolerance and initiate diverse drought avoidance and escape responses. To address regulatory processes that link these responses, we set out to identify genes that govern early responses to drought. To do this, a high-resolution time series transcriptomics data set was produced, coupled with detailed physiological and metabolic analyses of plants subjected to a slow transition from well-watered to drought conditions. A total of 1815 drought-responsive differentially expressed genes were identified. The early changes in gene expression coincided with a drop in carbon assimilation, and only in the late stages with an increase in foliar abscisic acid content. To identify gene regulatory networks (GRNs) mediating the transition between the early and late stages of drought, we used Bayesian network modeling of differentially expressed transcription factor (TF) genes. This approach identified AGAMOUS-LIKE22 (AGL22), as key hub gene in a TF GRN. It has previously been shown that AGL22 is involved in the transition from vegetative state to flowering but here we show that AGL22 expression influences steady state photosynthetic rates and lifetime water use. This suggests that AGL22 uniquely regulates a transcriptional network during drought stress, linking changes in primary metabolism and the initiation of stress responses.The authors acknowledge the support of the UK Biotechnology and Biological Science Research Council (BBSRC; Grant BB/F005806/1). S.S. was supported by a University of Essex PhD studentship. J.S.A.M. is supported by an NERC-CASE award (ENV-EATR-DTP: NE/L002582/1), and S.R.M.V-C. is supported by the BBSRC (BB/1001187_1). R.F. and J.E.L. are supported by the Max Planck Society. N.S. and H.F. are supported by Exeter Science Strategy funding, and C.S. is supported by the BBSRC and the Department for Environment, Food, and Rural Affairs through the NORNEX project. D.L.S was supported by a Wellcome Trust Institutional Strategic Support Fund. We thank Susan Corbett and Phillip A. Davey for help with the drought experiments and gas exchange measurements