Computation of physiological loading induced interstitial fluid motion in muscle standardized femur: Healthy vs. osteoporotic bone.

BACKGROUND AND OBJECTIVES: Physiological loading-induced mechanical environments regulate bone modeling and remodeling. Thus, loading-induced normal strain is typically considered a stimulus to osteogenesis. However, several studies noticed new bone formation near the sites of minimal normal strain, e.g., the neutral axis of bending in long bones, which raises a question on how bone mass is maintained near these sites. Secondary mechanical components such as shear strain and interstitial fluid flow also stimulate bone cells and regulate bone mass. However, the osteogenic potential of these components is not well established. Accordingly, the present study estimates the distribution of physiological muscle loading-induced mechanical environments such as normal strain, shear strain, pore pressure, and interstitial fluid flow in long bones. METHODS: A poroelastic finite element muscle standardized femur (MuscleSF) model is developed to compute the distribution of the mechanical environment as a function of bone porosities associated with osteoporotic and disuse bone loss. RESULTS: The results indicate the presence of higher shear strain and interstitial fluid motion near the minimal strain sites, i.e., the neutral axis of bending of femoral cross-sections. This suggests that secondary stimuli may maintain the bone mass at these locations. Pore pressure and interstitial fluid motion reduce with the increased porosity associated with bone disorders, possibly resulting in diminished skeletal mechano-sensitivity to exogenous loading. CONCLUSIONS: These outcomes present a better understanding of mechanical environment-mediated regulation of site-specific bone mass, which can be beneficial in developing prophylactic exercise to prevent bone loss in osteoporosis and muscle disuse.

Applications of Healthcare Robots in Combating the COVID-19 Pandemic.

Due to the increasing number of COVID-19 cases, there is a remarkable demand for robots, especially in the clinical sector. SARS-CoV-2 mainly propagates due to close human interactions and contaminated surfaces, and hence, maintaining social distancing has become a mandatory preventive measure. This generates the need to treat patients with minimal doctor-patient interaction. Introducing robots in the healthcare sector protects the frontline healthcare workers from getting exposed to the coronavirus as well as decreases the need for medical personnel as robots can partially take over some medical roles. The aim of this paper is to highlight the emerging role of robotic applications in the healthcare sector and allied areas. To this end, a systematic review was conducted regarding the various robots that have been implemented worldwide during the COVID-19 pandemic to attenuate and contain the virus. The results obtained from this study reveal that the implementation of robotics into the healthcare field has a substantial effect in controlling the spread of SARS-CoV-2, as it blocks coronavirus propagation between patients and healthcare workers, along with other advantages such as disinfection or cleaning.

Physiological Loading-Induced Interstitial Fluid Dynamics in Osteon of Osteogenesis Imperfecta Bone.

Osteogenesis imperfecta (OI), also known as "brittle bone disease," is a genetic bone disorder. OI bones experience frequent fractures. Surgical procedures are usually followed by clinicians in the management of OI. It has been observed physical activity is equally beneficial in reducing OI bone fractures in both children and adults as mechanical stimulation improves bone mass and strength. Loading-induced mechanical strain and interstitial fluid flow stimulate bone remodeling activities. Several studies have characterized strain environment in OI bones, whereas very few studies attempted to characterize the interstitial fluid flow. OI significantly affects bone micro-architecture. Thus, this study anticipates that canalicular fluid flow reduces in OI bone in comparison to the healthy bone in response to physiological loading due to altered poromechanical properties. This work attempts to understand the canalicular fluid distribution in single osteon models of OI and healthy bone. A poromechanical model of osteon is developed to compute pore-pressure and interstitial fluid flow as a function of gait loading pattern reported for OI and healthy subjects. Fluid distribution patterns are compared at different time-points of the stance phase of the gait cycle. It is observed that fluid flow significantly reduces in OI bone. Additionally, flow is more static than dynamic in OI osteon in comparison to healthy subjects. This work attempts to identify the plausible explanation behind the diminished mechanotransduction capability of OI bone. This work may further be extended for designing better biomechanical therapies to enhance the fluid flow in order to improve osteogenic activities in OI bone.

Canalicular fluid flow induced by loading waveforms: A comparative analysis.

Dynamic loading on the bone is beneficial in prevention and cure of bone loss as it encourages osteogenesis (i.e., new bone formation). Loading parameters such as strain magnitude, frequency, cycles, and strain rate (depending on loading waveform) affect the new bone formation. In-vivo studies suggested an optimal and osteogenic range of strain magnitude, frequency, and cycles to elicit the maximum new bone response. Still, there is no consensus on the selection of loading waveform. Animal studies on bone adaptation considered sinusoidal, and non-sinusoidal (e.g., trapezoidal, sawtooth, and triangular) loading waveforms according to physiological loadings (e.g., walking, running, and jumping etc.) without considering the relative effect of these waveforms on the loading-induced mechanical environment. The present study attempts to bridge this gap. Accordingly, this work hypothesizes that bone being a biphasic material (solid and fluid phases) experiences the same strain distribution for the different loading waves of the same amplitude, however, other components of the mechanical environment such as pore-pressure and interstitial fluid motion regulating the bone adaptation may differ. An in-vivo cantilever bending study is selected to substantiate the hypothesis. A poroelastic model is used to estimate the pore pressure and fluid motion developed in mouse tibia subjected to the: (i) trapezoidal, (ii) sawtooth, and (iii) triangular bending waves. Furthermore, poroelastic response of pore-pressure and fluid motion induced by these loading waveforms are compared and analyzed. This work also investigates how bone loss associated alterations in the microstructural environment of cortical bone affect the canalicular fluid motion induced by these waveforms. Overall results may be useful in designing optimal biomechanical interventions such as physical exercises to improve the bone health.