Journal of the Royal Society, Interface
-
Haemodynamics and morphology play an important role in the genesis, growth and rupture of cerebral aneurysms. The goal of this study was to generate and analyse statistical wall shear stress (WSS) distributions and shapes in middle cerebral artery (MCA) saccular aneurysms. Unsteady flow was simulated in seven ruptured and 15 unruptured MCA aneurysms. ⋯ In ruptured aneurysms, we found significantly lower WSS. The averaged aneurysm surface of unruptured aneurysms is round shaped, whereas the averaged surface of ruptured cases is multi-lobular. Our results confirm the hypothesis of low WSS and irregular shape as the essential rupture risk parameters.
-
Finite element modelling is well entrenched in comparative vertebrate biomechanics as a tool to assess the mechanical design of skeletal structures and to better comprehend the complex interaction of their form-function relationships. But what makes a reliable subject-specific finite element model? To approach this question, we here present a set of convergence and sensitivity analyses and a validation study as an example, for finite element analysis (FEA) in general, of ways to ensure a reliable model. We detail how choices of element size, type and material properties in FEA influence the results of simulations. ⋯ We then use an ex vivo experimental validation test of a cadaveric femur to check our FEA results and find that the heterogeneous model matches the experimental results extremely well, and far better than the homogeneous model. We emphasize how considering heterogeneous material properties in FEA may be critical, so this should become standard practice in comparative FEA studies along with convergence analyses, consideration of element size, type and experimental validation. These steps may be required to obtain accurate models and derive reliable conclusions from them.
-
By revisiting the air distribution and bioaerosol dispersion in Ward 8A where the largest nosocomial severe acute respiratory syndrome (SARS) outbreak occurred in Hong Kong in 2003, we found an interesting phenomenon. Although all the cubicles were in 'positive pressure' towards the corridor, the virus-containing bioaerosols generated from the index patient's cubicle were still transmitted to other cubicles, which cannot be explained in a traditional manner. A multi-zone model combining the two-way airflow effect was used to analyse this phenomenon. ⋯ Comparing with the previous computational fluid dynamic simulation results, we found that the air exchange owing to the small temperature differences between cubicles played a major role in SARS transmission. Additionally, the validated multi-zone model combining the two-way airflow effect could simulate the pollutant transport with reasonable accuracy but much less computational time. A probable improvement in general ward design was also proposed.
-
Improved protective measures and medical care has increased the survivability from battlefield injuries. In an attempt to reduce the debilitating consequences of blast injury, understanding and mitigating the effects of explosion on the extremities is key. In this study, forensic biomechanical analyses have been applied to determine mechanisms of injury after the traumatic event. ⋯ However, tertiary blast effects were the predominant mechanism of injury, with severe axial loading to the lower extremity being a characteristic of the fractures seen. The development of future mitigation strategies must focus on reducing all explosion-related injury mechanisms. Integral to this process is an urgent requirement to better understand the behaviour of bone in this unique environment.
-
The aims of this study were (i) to quantify chondrocyte mechanics in fully intact articular cartilage attached to its native bone and (ii) to compare the chondrocyte mechanics for cells in healthy and early osteoarthritis (OA) tissue. We hypothesized that cells in the healthy tissue would deform less for given articular surface pressures than cells in the early OA tissue because of a loss of matrix integrity in early OA and the associated loss of structural integrity that is thought to protect chondrocytes. Chondrocyte dynamics were quantified by measuring the deformation response of the cells to controlled loading of fully intact cartilage using a custom-designed confocal indentation system. ⋯ On average, chondrocyte volume increased with indentation loading in the early OA cartilage (8 +/- 3%, p = 0.001), while it decreased for the two control groups (-8 +/- 2%, p = 0.002 for contralateral and -8 +/- 1%, p = 0.004 for normal controls). We conclude from these results that our hypothesis of cell deformations in the early OA tissue was only partially supported: specifically, changes in chondrocyte mechanics in early OA were direction-specific with the primary axial deformations remaining unaffected despite vastly increased average axial matrix deformations. Surprisingly, chondrocyte deformations increased in early OA in specific transverse directions which have received little attention to date but might be crucial to chondrocyte signalling in early OA.