Focal osteoporosis defects play a key role in hip fracture

$\textbf{BACKGROUND}$: Hip fractures are mainly caused by accidental falls and trips, which magnify forces in well-defined areas of the proximal femur. Unfortunately, the same areas are at risk of rapid bone loss with ageing, since they are relatively stress-shielded during walking and sitting. Focal osteoporosis in those areas may contribute to fracture, and targeted 3D measurements might enhance hip fracture prediction. In the FEMCO case-control clinical study, Cortical Bone Mapping (CBM) was applied to clinical computed tomography (CT) scans to define 3D cortical and trabecular bone defects in patients with acute hip fracture compared to controls. Direct measurements of trabecular bone volume were then made in biopsies of target regions removed at operation. $\textbf{METHODS}$: The sample consisted of CT scans from 313 female and 40 male volunteers (158 with proximal femoral fracture, 145 age-matched controls and 50 fallers without hip fracture). Detailed Cortical Bone Maps (c.5580 measurement points on the unfractured hip) were created before registering each hip to an average femur shape to facilitate statistical parametric mapping (SPM). Areas where cortical and trabecular bone differed from controls were visualised in 3D for location, magnitude and statistical significance. Measures from the novel regions created by the SPM process were then tested for their ability to classify fracture versus control by comparison with traditional CT measures of areal Bone Mineral Density (aBMD). In women we used the surgical classification of fracture location ('femoral neck' or 'trochanteric') to discover whether focal osteoporosis was specific to fracture type. To explore whether the focal areas were osteoporotic by histological criteria, we used micro CT to measure trabecular bone parameters in targeted biopsies taken from the femoral heads of 14 cases. $\textbf{RESULTS}$: Hip fracture patients had distinct patterns of focal osteoporosis that determined fracture type, and CBM measures classified fracture type better than aBMD parameters. CBM measures however improved only minimally on aBMD for predicting any hip fracture and depended on the inclusion of trabecular bone measures alongside cortical regions. Focal osteoporosis was confirmed on biopsy as reduced sub-cortical trabecular bone volume. $\textbf{CONCLUSION}$: Using 3D imaging methods and targeted bone biopsy, we discovered focal osteoporosis affecting trabecular and cortical bone of the proximal femur, among men and women with hip fracture.Arthritis Research UK (grant no. ARC17822) and Cambridge National Institute for Health Research (NIHR) Biomedical Research Centre

IgM Promotes the Clearance of Small Particles and Apoptotic Microparticles by Macrophages

Background: Antibodies are often involved in enhancing particle clearance by macrophages. Although the mechanisms of antibody-dependent phagocytosis have been studied for IgG in greater detail, very little is known about IgM-mediated clearance. It has been generally considered that IgM does not support phagocytosis. Recent studies indicate that natural IgM is important to clear microbes and other bioparticles, and that shape is critical to particle uptake by macrophages; however, the relevance of IgM and particle size in their clearance remains unclear. Here we show that IgM has a sizedependent effect on clearance. Methodology/Principal Findings: We used antibody-opsonized sheep red blood cells, different size beads and apoptotic cells to determine the effect of human and mouse IgM on phagocytosis by mouse alveolar macrophages. Our microscopy (light, epifluorescence, confocal) and flow cytometry data show that IgM greatly enhances the clearance of small particles (about 1–2 micron) by these macrophages. There is an inverse relationship between IgM-mediated clearance by macrophages and the particle size; however, macrophages bind and internalize many different size particles coated with IgG. We also show that IgM avidly binds to small size late apoptotic cells or bodies (2–5 micron) and apoptotic microparticles (,2 mm) released from dying cells. IgM also promotes the binding and uptake of microparticle-coated beads. Conclusions/Significance: Therefore, while the shape of the particles is important for non-opsonized particle uptake, th

Control of the IAQ conditions in office buildings by general ventilation - a simple guide

Peer reviewed: YesNRC publication: Ye

Simple guide to ventilating buildings for contaminant control

Peer reviewed: NoNRC publication: Ye

Maintaining indoor air quality through the use of HVAC systems

Aussi disponible en fran\ue7ais: Maintien de la qualit\ue9 de l'air int\ue9rieur au moyen des syst\ue8mes CVCAPeer reviewed: NoNRC publication: Ye

In-situ testing of the shear strength of masonry joints – proposal for a new simplified testing approach and comparison to existing techniques

For other than minor modifications or additions to existing masonry structures, an understanding of the in-situ mechanical properties of the masonry is required. Estimation of shear strength of the masonry bond is often made using the in-plane shove test as it only requires access from one side of the masonry being tested, and is therefore considered to be only mildly invasive. In-situ and laboratory simulations of the shove tests have however shown that a number of site-specific problems can arise. These include: preparation of the test area which can damage the mortar joints resulting in loss of cohesion, imprecise alignment of both the loading system and instrumentation leading to complications with data interpretation, and without an adequately long section of wall to be tested, flexural cracking and lateral displacement of large wall sections. In an attempt to address these issues, in this paper, an alternative in-situ test is proposed. This new ‘pull test’ measures shear strength by extracting a single brick orthogonally in the wall’s out-of-plane direction. A laboratory investigation is performed to compare the two types of in-situ test (shove and pull) using plain and frogged units, as well as lime and cement mortars, and both tests are further benchmarked using the standard laboratory couplet test. It is demonstrated that for regular (rectangular), plain units with weak mortar, the two in-situ tests produce strength measurements that are statistically equivalent, indicating that under this specific scenario the out-of-plane shear strength can be used as a proxy for the in-plane shear strength, and that the pull test could be used as an alternative to the shove test. In addition, the new pull test is shown to perform with demonstrated repeatability, requires minimal instrumentation, and is particularly relevant for design of anchorages under out-of-plane loading.C. Burton, J. Vaculik, M.C. Griffith, P. Visinti

Out-of-Plane Shaketable Testing of Unreinforced Masonry Walls in Two-Way Bending: Supplementary Material

This data set contains supplementary material for Vaculik and Griffith (2017) [full reference below].<br><br>Included are:<br>- Supplementary Material pdf document (120 pages)<br>- zip file containing time-domain data, both processed and unprocessed<br><br>Vaculik, J., and Griffith, M. C. (2017), Out-of-plane shaketable testing of unreinforced masonry walls in two-way bending, Bulletin of Earthquake Engineering, doi: 10.1007/s10518-017-0282-8<br