Biorheology - Volume 44, issue 2

Authors: Fam, H. | Bryant, J.T. | Kontopoulou, M.

Article Type: Research Article

Abstract: Synovial fluid is the joint lubricant and shock absorber [Semin. Arthritis Rheum. 32 (2002), 10–37] as well as the source of nutrition for articular cartilage. The purpose of the present paper is to provide a comprehensive review of the rheological properties of synovial fluid as they relate to its chemical composition. Given its importance in the rheology of synovial fluid, an overview of the structure and rheology of HA (hyaluronic acid) is presented first. The rheology of synovial fluids is discussed in detail, with a focus on the possible diagnosis of joint pathology based on the observed differences in rheological …parameters and trends. The deterioration of viscoelastic properties of synovial fluid in pathological states due to effects of HA concentration and molecular weight is further described. Recent findings pertaining to the composition and rheology of periprosthetic fluid, the fluid that bathes prosthetic joints in vivo are reported. Show more

Keywords: Rheology, viscoelastic properties, rheumatic diseases, joint fluid, HA, periprosthetic fluid

Citation: Biorheology, vol. 44, no. 2, pp. 59-74, 2007

Authors: Gregersen, Hans | Zhao, Jingbo | Lu, Xiao | Zhou, Ji | Falk, Erling

Article Type: Research Article

Abstract: Atherosclerosis is the most frequent cause of death and severe chronic disability in North America and Europe. The atherosclerosis-prone apolipoprotein E (apoE)-deficient mice contain the entire spectrum of lesions observed during atherogenesis. Significant remodelling of the artery occurs in atherosclerosis. The aim was to study the remodelling of the zero-stress state of the aorta in apoE-deficient mice up to 56 weeks of age. Normal wild-type mice served as control groups. The mice were euthanised at ages 10, 28 and 56 weeks and tissue rings where excised from several locations along the aorta. The rings where photographed in the no-load state …(without any external forces applied), then cut radially to obtain the zero-stress state and photographed again. The cross-sectional wall area and wall thickness increased over time in apoE-deficient mice compared to controls (P<0.001). The residual strains at the inner and outer surface varied as function of aortic location both in controls and apoE-deficient mice (P<0.001). From age 28 to age 56 weeks a gradual increase in positive strain at the outer surface and negative strain at the inner surface was found in the apoE-deficient mice when compared to age-matched control mice (P<0.001). Furthermore, the inner residual strain in the plaque location was significantly smaller than in the non-plaque location in the rings with atherosclerotic plaques (P<0.001). The change over time of the opening angle was especially pronounced in the aortic arch. The opening angle increased to app. 200 degrees in the aortic arch in apoE-deficient mice at 56 weeks of age whereas it in age-matched controls was app. 125 degrees. Correspondingly, atherosclerotic plaques were prominent in the apoE-deficient mice, especially at week 56 in the ascending aorta and the aortic arch. In conclusion, a pronounced remodelling of the biomechanical properties in aorta was found in apoE-deficient mice. The stress gradient across the vessel wall in the plaque region is likely larger in vivo due to the smaller residual strain in the plaque area. Show more

Keywords: Atherosclerosis, apolipoprotein E, knockout mouse model, residual strain, opening angle, morphometry

Citation: Biorheology, vol. 44, no. 2, pp. 75-89, 2007

Authors: Banerjee, Rupak K. | Devarakonda, Surendra B. | Rajamohan, Divakar | Back, Lloyd H.

Article Type: Research Article

Abstract: The patho-physiologic process of restenosis and tissue growth may not be completely eliminated and is the primary concern of clinicians performing angioplasty and stent implantation procedures. Recent evidence suggests that the restenosis process is influenced by several factors: (1) geometry and size of vessel; (2) stent design; and (3) it's location that alter hemodynamic parameters, including local wall shear stress (WSS) distributions. The present three-dimensional (3D) analysis of pulsatile flow in a deployed coronary stent: (1) shows complex 3D variation of hemodynamic parameters; and (2) quantifies the changes in local WSS distributions for developed flow and compares with recently published …WSS data for developing flow. Higher order of magnitude of WSS of 290 dyn/cm2 is observed on the surface of cross-link intersections at the entrance of the stent for developed flow, which is about half of that for developing flow. Low WSS of 0.8 dyn/cm2 and negative WSS of −8 dyn/cm2 are seen at the immediate upstream and downstream regions of strut intersections. Persistent recirculation is observed at the downstream region of each strut cross-link and the regions of low and negative WSS may lead to patho-physiologic conditions near the stented region. The key finding of this study is that the location of stent in the coronary artery determines the developing or developed nature of the flow, which in turn, results in varied level of WSS. Show more

Keywords: Coronary artery, stent, pulsatile flow, stenosis, computational fluid dynamics, wall shear stress

Citation: Biorheology, vol. 44, no. 2, pp. 91-102, 2007

Authors: Qiao, Aike | Matsuzawa, Teruo

Article Type: Research Article

Abstract: The effectiveness of femoral bypass grafts is correlated with the geometric configuration and hemodynamics of the bypass and the arteries. As an attempt to develop a new design for femoral bypass grafts, we present a novel geometric configuration for a symmetrically implanted 2-way bypass graft. In order to investigate how the symmetric 2-way bypass grafts affect the flow patterns through the anastomosis, physiologic blood flows in 1-way and 2-way models for a fully stenosed femoral bypass were simulated with the finite element method, and the hemodynamic factors in these models were studied. The temporal and spatial distributions of flow patterns …and wall shear stresses in the vicinity of distal anastomosis during the cardiac cycle were analyzed. The results computed showed that the 2-way model has more preferable hemodynamics than the 1-way model in the distribution of flow patterns and wall shear stresses, and it may improve the flow conditions and decrease the probability of restenosis. However, the limitations of the 2-way bypass model may counteract the positive effects. More detailed hemodynamic studies are necessary to fully assess the viability of the 2-way bypass graft. Show more

Keywords: Anastomosis, intimal hyperplasia, restenosis, wall shear stress, biomechanics

Citation: Biorheology, vol. 44, no. 2, pp. 103-124, 2007

Authors: Ali, N. | Hayat, T. | Sajid, M.

Article Type: Research Article

Abstract: This paper presents an analysis of the peristaltic flow of a couple stress fluid in an asymmetric channel. The asymmetric nature of the flow is introduced through the peristaltic waves of different amplitudes and phases on the channel walls. Mathematical modelling corresponding to a two-dimensional flow has been carried out. The flow analysis is presented under long wavelength and low Reynolds number approximations. Closed form solutions for the axial velocity, stream function and the axial pressure gradient are given. Numerical computations have been carried out for the pressure rise per wavelength, friction forces and trapping. It is noted that there …is a decrease in the pressure when the couple stress fluid parameter increases. The variation of the couple stress fluid parameter with the size of the trapped bolus is also similar to that of pressure. Furthermore, the friction force on the lower channel wall is greater than that on the upper channel wall. Show more

Keywords: Asymmetric channel, peristalsis, couple stress fluid, modelling

Citation: Biorheology, vol. 44, no. 2, pp. 125-138, 2007

Authors: Boudou, Thomas | Ohayon, Jacques | Picart, Catherine | Tracqui, Phillipe

Article Type: Correction

Citation: Biorheology, vol. 44, no. 2, pp. 139-139, 2007