World Scientific Annual Review of Biomechanics

The biomechanical properties of arteries play a crucial role in governing the overall hemodynamic function of the circulatory system. The nonuniformity in elastic and geometric structures of the blood vessels adds on to the complexity in dealing with pulsatile natures of blood pressure and flow. Short-term or chronic changes in arterial wall properties subjecting to distending pressure and perfusing flow make quantification of arterial compliance especially important in its use in describing the overall arterial function. This paper will first review the methodologies of determining arterial compliance in systole, in diastole and varying throughout the entire cardiac cycle. The stroke volume-to-pulse pressure method, the linear Windkessel model-based approaches and the nonlinear pressure-dependent compliance model method to derive arterial compliance are presented. The clinical relevance and implications are highlighted accordingly, in particular, the consequences of hypertension and aging.

It has been recognized that endothelial dysfunction is an early indication of Arterial disease. Endothelial function can be noninvasively evaluated by Inducing a temporary increase in blood flow and then observing the degree of vasodilation response or flow-mediated dilation. Impaired flow mediated vasodilation is then an indication of impaired endothelium. Vascular ultrasound Imaging has been the typical approach to access vasodilation by flow-mediated dilation most often at the brachial artery. Together with other measures of cardiovascular risk, the flow-mediated dilation response provides a very early noninvasive screen for cardiovascular disease. The skill and equipment required for brachial artery ultrasound imaging have limited the use of flow-mediated dilation as a routine medical test. Moreover, it has been recognized that other vascular parameters such as vessel size and blood pressure may influence the test itself.

We have introduced a potential solution to the routine measurement of flow-mediated dilation by Analyzing the response of a simple occlusive arm cuff to obtain the Brachial Artery diameter in a noninvasive way. The analysis for occlusive cuff Plethysmography was provided here in a calibrated manner. This approach is an alternative to ultrasound flow-mediated dilation testing. It requires no special operator skills and may be automated for precision.

Two experimental evaluations of the proposed cuff method are provided. First, The cuff- based brachial diameters were compared to Ultrasound obtained diameters. Second, as a sensitivity test, the cuff-based dilation test was used to measure the dilation response of several subjects to blood sugar loading. For further evaluation, the cuff-based measurements were applied to a mechanical model of the brachial artery to reveal a standard error of estimate less than 5%. The results show that the cuff-based diameters compare well to those obtained via ultrasound imaging. Moreover, the cuff-based dilation testing showed the expected reduction in endothelial function response due to a blood sugar load. Additionally, cuff-based flow-mediated dilation testing provides measurements as a function of the subject blood pressure, which Ultrasound generally cannot.

Investigators collect data and present them in a way that offers the best insight regarding the questions at hand. To facilitate understanding of certain aspects, it may occasionally be useful to rearrange primary data and formulate them as derived variables. For example, the travel distance divided by the invested time yields average velocity (as m/s). Problems may arise when interpreting ratios that fail to have a physical dimension. For example, current TV-sets have a fixed ratio for height and width, implying that we need an additional detail to define its size. Size then is determined by the diagonal, which can be calculated from the two sides using the Pythagorean theorem. Similarly, paired hemodynamic variables may be expressed as ratios. Again, a fixed ratio may refer to a variety of underlying primary data which require consideration if the ratio is unitless. In this survey, we evaluate several derived metrics commonly used in cardiovascular studies, and offer comprehensive analysis strategies.

Synovial fluid functions as a biological lubricant and lubricates articular cartilage to reduce friction and wear. Lubricin and hyaluronic acid are the primary components of synovial fluid responsible for its lubricating properties. The loss of properties in synovial fluid and articular cartilage due to aging and activities can restrict mobility in synovial joints, resulting in the degradation of articular cartilage and ultimately leading to pathological synovial joints, which is a major cause of disability. Thus, research on synovial joints remains crucial, and despite previous investigations on synovial joint lubrication, there are several issues related to squeeze film lubrication that require further attention. The Newtonian model of squeeze film lubrication in synovial joints needs to be extensively studied. In this study, lubrication and other related properties of synovial fluid are studied theoretically. In this paper, we have studied the flow of synovial fluid in the diseased synovial joint. Further, we have studied the effect of the viscosity of the synovial fluid, the permeability of articular cartilage, thickness of articular cartilage, and fluid film thickness on the characteristic of the squeeze film formed between the articular cartilages of the diseased human knee joint. The flow of synovial fluid is modeled by considering it as a viscous, incompressible and Newtonian fluid. We have derived the modified Reynolds equation using the principle of hydrodynamic lubrication and continuum mechanics theory and solved it by applying the suitable boundary conditions according to the physical considerations. Subsequently, we obtained the expression for pressure distribution in fluid film, load-bearing capacity, and squeeze time and have done the theoretical analysis on these properties for different parameters. Pressure increases with squeeze velocity and viscosity of the synovial fluid and decreases with permeability and fluid film thickness. Human knee joint becomes diseased due to excessive pressure, and the mobility of the knee joint decreases. The load capacity increases with viscosity and squeeze velocity and decreases with permeability resulting in the reduction of the load-carrying capacity of the knee joint in diseased conditions. Moreover, the squeeze time also increased in the diseased state of the joint.

Recently, scientists have utilized a range of techniques in the attempt to model ligamentous structures, which play a vital role in the functioning of the human body. Therefore, our objective is to conduct a systematic scoping review that evaluates the scope of 163 journals pertaining to computational modeling of ligaments, while also assessing the limitations associated with each method. These limitations encompass various aspects, including anatomical considerations, subject specificity, viscoelasticity, mechanical properties, model-specific factors, and limitations related to medical imaging. The guiding question for this review is: What are the existing limitations in the surveyed literature regarding ligament modeling and methods, specifically with regard to time variance and environmental hazards? A search of PubMed/MEDLINE, Web of Science (WoS), and ScienceDirect was conducted following the scoping review methodology recommended by the Joanna Briggs Institute (JBI) for evidence-based healthcare. After applying the inclusion and exclusion criteria, 74 full-text articles were analyzed, revealing that each method possesses its own set of limitations and may not comprehensively encompass all aspects of ligament properties. Nevertheless, despite these limitations, the majority of these methods exhibit the ability to produce reliable outcomes.

This narrative review examines the use of inertial measurement units (IMUs) for assessing gait balance control. Impaired gait balance control is associated with an increased risk of falls and reduced mobility, particularly in older adults. Traditional methods of assessing gait balance control, such as clinical balance assessments and camera-based motion analysis, have limitations in terms of reliability, cost, and practicality. Wearable sensor technology, including IMUs, offers a more accessible and cost-effective alternative for assessing gait and balance performance in real-world settings. IMUs, equipped with tri-axial accelerometers, gyroscopes, and magnetometers, can directly measure body movement and provide quantifiable data. This review explores the advantages and limitations of using IMUs for assessing gait balance control, including the measurement of anticipatory postural adjustments (APAs) for gait initiation, spatiotemporal gait parameters, center of mass (COM) motion during walking, and data-driven machine learning models. IMUs have shown promise in quantifying APAs, estimating gait spatiotemporal parameters, assessing COM motion, and using machine learning algorithms to classify and predict balance-related outcomes. However, further research is needed to establish standardized protocols, validate IMU-based measurements, and determine the specific IMU parameters that correlate with balance control ability. Overall, IMUs have the potential to be a valuable tool for assessing gait balance control, monitoring changes over time, and tracking interventions to improve balance control in both clinical and research settings.