Journal of Biomechanical Engineering

Development of patient specific models of LV-MV interactions in ischemic mitral regurgitation (IMR) are complicated by the substantial variability and complex etiologies, making it difficult to extract underlying mechanisms. We thus developed a detailed ovine LV-MV finite element model based for the normal and acute post-MI states. The ovine LV FEM model was first extended to incorporate a detailed MV leaflet sub-model with a functionally-equivalent CT structure. The resulting complete LV-MV model was first used to simulate the full cardiac cycle in the normal state to establish baseline responses...

Penn State University is developing a pediatric total artificial heart (pTAH) as a bridge-to-transplant device that supports infants and small children with single ventricle anomalies or biventricular heart failure to address high waitlist mortality rates for patients with severe congenital heart disease. Two issues with mechanical circulatory support devices are thrombus formation and thromboembolic events. This in vitro study characterizes flow within Penn State's pTAH under physiological operating conditions...

Ballistic shields protect users from a variety of threats, including projectiles. Shield back-face deformation (BFD) is the result of the shield deflecting or absorbing a projectile and deforming towards the user. Back-face deformation can result in localized blunt loading to the upper extremity, where the shield is supported by the user. Two vulnerable locations along the upper extremity were investigated - the wrist and elbow - on eight post-mortem human subjects (PMHS) using a pneumatic impacting apparatus for investigating the fracture threshold as a result of behind shield blunt trauma (BSBT)...

Vaginal childbirth is the final phase of pregnancy when one or more fetuses pass through the birth canal from the uterus, and it is a biomechanical process. The uterine active contraction, causing the pushing force on the fetus, plays a vital role in regulating the fetus delivery process. In this project, the active contraction behaviors of muscle tissue were first modeled and investigated. After that, a Finite Element Method (FEM) model to simulate the uterine cyclic active contraction and delivery of a fetus was developed in LS-DYNA...

This erratum corrects a mistake in a sub-component of the numerical algorithm proposed in our recent study for modeling anisotropic reactive nonlinear viscoelasticity (doi:10.1115/1.4054983), for the special case where multiple weak bond families may be recruited with loading. This correction overcomes a non-physical response noted under uniaxial cyclical loading.

The ASME Journal of Biomechanical Engineering presents a Special Section dedicated to promoting inclusivity within the field of biomechanical engineering. This collection showcases diverse research articles and reviews that emphasize the importance of considering different backgrounds, experiences, and perspectives in biomechanics research. By amplifying underrepresented voices and broadening perspectives, this collection advances our understanding of biomechanical principles and fosters a more inclusive and equitable approach to research and development in engineering for human health...

The objective of this study was to investigate whether the two most common growth mechanics modeling frameworks, the constrained-mixture growth model and the kinematic growth model, could be reconciled mathematically. The purpose of this effort was to provide practical guidelines for potential users of these modeling frameworks. Results showed that the kinematic growth model is mathematically consistent with a special form of the constrained-mixture growth model, where only one generation of a growing solid exists at any given time, overturning its entire solid mass at each instant of growth in order to adopt the reference configuration dictated by the growth deformation...

Aging is a primary risk factor for degenerative tendon injuries, yet the etiology and progression of this degeneration is poorly understood. While aged tendons have innate cellular differences that support a reduced ability to maintain mechanical tissue homeostasis, the response of aged tendons to altered levels of mechanical loading has not yet been studied. To address this question, we subjected young and aged murine flexor tendon explants to various levels of in vitro tensile strain. We first compared the effect of static and cyclic strain on matrix remodeling in young tendons, finding that cyclic strain is optimal for studying remodeling in vitro...

Wildland firefighters (WLFFs) experience lung function decline due to occupational exposure to fire smoke. To pinpoint the biological underpinnings of abnormal respiratory function following 3-7 years of WLFF service, we exposed mice to Douglas Fir Smoke (DFS) over 8 weeks. Following exposure, we assessed changes in lung structure through Magnetic Resonance Imaging (MRI) and histological analysis, which was supported by immunohistochemistry staining. With MRI, we assessed the signal decay time, T2*, from ultrashort echo time images and utilized this metric as a measure of airspace enlargement...

The continuous softening behaviour of the brain tissue, i.e., the softening in the primary loading path with increase in deformation, is modelled in this work as a state of hyperelasticity, up to the onset of failure. That is, the softening behaviour is captured via a core hyperleastic model, without the addition of damage variables and/or functions. Examples of the application of the model will be provided to extant datasets of uniaxial tension and simple shear deformations, demonstrating the capability of the model to capture the whole-range deformation of the brain tissue specimens, including their softening behaviour...

Adeno-associated virus (AAV) has been demonstrated to be a clinically useful gene delivery vehicle for treating neurological diseases. To deliver AAV to focal targets, direct infusion into brain tissue by convection-enhanced delivery (CED) is often needed due to AAV's limited penetration across the blood-brain-barrier and its low tissue diffusivity. In this study, computational models that predict the spatial distribution of AAV in brain tissue during CED were developed to guide surgical placement of infusion catheters in recurrent brain tumors following primary tumor resection...

Understanding the natural biomechanics of walking at different speeds and activities is crucial to develop effective assistive devices for persons with lower-limb impairments. While continuous measures such as joint angle and moment are well-suited for biomimetic control of robotic systems, whole-stride summary metrics are useful for describing changes across behaviors and for designing and controlling passive and semi-active devices. Dynamic mean ankle moment arm (DMAMA) is a whole-stride measure representing the moment arm of the ground reaction impulse about the ankle joint - effectively, how "forefoot-dominated" or "hindfoot-dominated" a movement is...

State-of-the-art participant-specific finite element models require advanced medical imaging to quantify bone geometry and density distribution; access to and cost of imaging is prohibitive to the use of this approach. Statistical appearance models may enable estimation of participants' geometry and density in the absence of medical imaging. The purpose of this study was to: (1) quantify errors associated with predicting tibia-fibula geometry and density distribution from skin-mounted landmarks using a statistical appearance model and (2) quantify how those errors propagate to finite element-calculated bone strain...

A previously developed model of a lymphatic vessel as a chain of lymphangions was investigated to determine whether lymphangions of unequal length reduce pumping relative to a similar chain of equal-length ones. The model incorporates passive elastic and active contractile properties taken from ex vivo measurements, and intravascular lymphatic valves as transvalvular pressure-dependent resistances to flow with hysteresis and transmural pressure dependent bias to the open state as observed experimentally. Coordination of lymphangion contractions is managed by marrying an autonomous transmural pressure-dependent pacemaker for each lymphangion with bidirectional transmission of activation signals between lymphangions, qualitatively matching empirical observations...

Development of respiratory tissue constructs is challenging due to the complex structure of native respiratory tissue and the unique biomechanical conditions induced by breathing. While studies have shown that the inclusion of biomechanical stimulus mimicking physiological conditions greatly benefits the development of engineered tissues, to our knowledge no studies investigating the influence of biomechanical stimulus on the development of respiratory tissue models produced through three-dimensional (3D) bioprinting have been reported...

To facilitate smooth and pain-free joint motion, articular cartilage (AC) relies on the health of its resident cells (chondrocytes). However, the factors governing the vulnerability of chondrocytes to mechanically-induced death or injury are not fully understood. Thus, the objective of this study was to determine whether tissue deformation or load magnitude drives chondrocyte death under sub-impact (negligible kinetic energy) loading conditions. We hypothesized that there is a critical tissue deformation at which chondrocytes are killed...

Tendinopathy is a leading cause of mobility issues. Currently, the cell-matrix interactions involved in the development of tendinopathy are not fully understood. In vitro tendon models provide a unique tool for addressing this knowledge gap as they permit fine control over biochemical, micromechanical, and structural aspects of the local environment to explore cell-matrix interactions. In this study, direct-write, near-field electrospinning of gelatin solution was implemented to fabricate micron-scale fibrous scaffolds that mimic native collagen fiber size and orientation...

PURPOSE: We present an unsupervised deep learning method to perform flow denoising and super-resolution without high resolution labels. We demonstrate the ability of this model to reconstruct 3D stenosis and aneurysm flows, with varying geometries, orientations, and boundary conditions. METHODS: Ground truth data was generated using computational fluid dynamics, and then corrupted with multiplicative Gaussian noise. Autoencoders were used to compress the representations of the flow domain geometry and the (possibly noisy and low-resolution) flow field...

Murine models are commonly used to study glaucoma, the leading cause of irreversible blind-ness. Glaucoma is associated with elevated intraocular pressure (IOP), which is regulated by the tissues of the aqueous outflow pathway. In particular, pectinate ligaments (PLs) connect the iris and trabecular meshwork (TM) at the anterior chamber angle, with an unkown role in maintenance of the biomechanical stability of the aqueous outflow pathway, thus motivating this study. We conducted histomorphometric analysis and optical coherence tomography-based finite element (FE) modeling on three cohorts of C57BL/6 mice: 'young' (2-6 months), 'middle-aged' (11-16 months), and 'elderly' (25-32 months)...

Lowery urinary tract symptoms (LUTS) affect a large majority of the aging population. 3D Dynamic MRI shows promise as a noninvasive diagnostic tool that can assess bladder anatomy and function (urodynamics) while overcoming challenges associated with current urodynamic assessment methods. However, validation of this technique remains an unmet need. In this study, an anatomically realistic, bladder mimicking in-vitro flow model was created and used to systematically benchmark 3D dynamic MRI performance using a highly controllable syringe pump...