nils-herrmann/clean_scirepeval huggingface dataset:
Fluid-structure interaction modeling of lactating breast: Newtonian vs. non-Newtonian milk.
Venue: Journal of biomechanics

Breastfeeding is a highly dynamic and complex mechanism. The suckling process by the infant involves compression and intra-oral vacuum pressure, leading to milk expression from breast. The accumulated milk from the nipple varies depending on the milk properties and transient flow rate during the suckling cycle. Rheological studies on raw human milk indicate that milk has a non-Newtonian shear-thinning flow behavior. This study aims to investigate the effect of non-Newtonian milk on flow behavior through the breast ductal system using fluid-structure interaction (FSI) simulation. The results of the non-Newtonian effects on flow velocity and the volumetric flow rate of expressed milk are presented. The results show that non-Newtonian Carreau model is promising for the simulation of human milk flow through the breast ductal systems. Also, the results show that the non-Newtonian effects on the milk flow behavior appear for 30-35% of the suckling cycle. Therefore, the Newtonian model is acceptable for the purpose of numerical simulation.
Effect of the underlying cadaver data and patient-specific adaptation of the femur and pelvis on the prediction of the hip joint force estimated using static models.
Venue: Journal of biomechanics

The prediction of the hip joint force (HJF) is a fundamental factor for the prevention of edge loading in total hip arthroplasty. Naturally, the loading of the liner of the acetabular component depends on the HJF acting on the artificial joint. In contrast to dynamic musculoskeletal models, static models for HJF prediction do not require motion analysis of the patient. However, patient-specific adaptability and validity of static models have to be scrutinized. In this study, a modular framework for HJF prediction using static models is introduced to compare the results of different cadaver templates that are the basis of most static and dynamic models, and different scaling laws for the patient-specific adaptation with in vivo HJF of ten patients for one-leg stance and level walking. The results revealed the significant effect of the underlying cadaver template used for the prediction of the HJF (p < 0.01). A higher degree of patient-specific scaling of the cadaver template often did not significantly reduce the prediction error. Three static models with the lowest prediction errors were compared to results of dynamic models from literature. The prediction error of the peak HJF of the static models (median absolute errors below 15% body weight in magnitude and below 5° in direction) was similar in magnitude and even smaller in direction compared to dynamic models. The necessary reduction of a load-based target zone for the prevention of edge loading due to the uncertainty of the HJF prediction has to be considered in the preoperative planning. The framework for HJF prediction is openly accessible at https://github.com/RWTHmediTEC/HipJointForceModel.
Importance of the cervical capsular joint cartilage geometry on head and facet joint kinematics assessed in a Finite element neck model.
Venue: Journal of biomechanics

Finite element human neck models (NMs) aim to predict neck response and injury at the tissue level; however, contemporary models are most often assessed using global response such as head kinematics. Additionally, many NMs are developed from subject-specific imaging with limited soft tissue resolution in small structures such as the facet joints in the neck. Such details may be critical to enable NMs to predict tissue-level response. In the present study, the capsular joint cartilage (CJC) geometry in a contemporary NM was enhanced (M50-CJC) based on literature data. The M50-CJC was validated at the segment and full neck levels and assessed using relative facet joint kinematics (FJK), capsular ligament (CL) and intervertebral disc (IVD) strains, a relative vertebral rotation assessment (IV-NIC) and head kinematics in frontal and rear impact. The validation ratings at the segment level increased from 0.60 to 0.64, with improvements for modes of deformation associated with the facet joints, while no difference was noted at the head kinematic level. The improved CJC led to increased FJK rotation (188%) and IVD strain (152.2%,) attributed to the reduced facet joint gap. Further enhancements of the capsular joint representation or a link between the FJK and CL injury risk are recommended. Enhancements at the tissue level demonstrated a large effect on the IVD strain, but were not apparent in global metrics such as head kinematics. This study demonstrated that a biofidelic and detailed geometrical representation of the CJC contributes significantly to the predicted joint response, which is critical to investigate neck injury risk at the tissue level.
Increasing the stability of the spring loaded inverted pendulum model of running with a wobbling mass.
Venue: Journal of biomechanics

Human running can be simulated using a simple model called the spring-loaded inverted pendulum (SLIP). The SLIP model predicts some aspects of running including the self-stabilizing properties of running. In human locomotion energy is dissipated due to the passive motion of the soft tissue. However, little is known about the effects of this energy dissipation on the dynamics of running. This study utilizes a SLIP model with an additional spring-mass-damper system to study the effects of energy dissipation due to an additional wobbling mass on the self-stabilizing properties of human running. It was found that the additional spring-mass-damper system increased the self-stabilizing properties of the SLIP model and increased its robustness to perturbations. This suggests that increasing stability is one of the effects of energy dissipation due to the passive motion of a wobbling mass during human running.
Experimental study on the influence of model variations on the airway occlusion of an obstructive sleep apnea patient.
Venue: Journal of biomechanics

This study deals with the analysis of model parameters to mimic the airway collapse of an obstructive sleep apnea patient during nasal breathing. Different material properties and geometry variations of a patient-specific airway model are analyzed in detail. The patient-specific airway geometry is obtained from MRI data. A completely rigid model is compared to two partly elastic variations with different elasticities. Furthermore, the influence of the nasal cavities and the treatment effect of a mandibular protrusion are studied. Rigid model parts are 3D-printed and elastic parts cast from silicone. The models are analyzed under the impact of a transient airflow which is realized through a computer controlled piston pump. The results suggest, that, for moderate deformations, the elasticity of the soft tissue replicate influences rather the level of the pressure drop inside the airway than the shape of the pressure curve. The same suggestion can be made for the influence of the nasal cavities. Often, the spatial location of the minimum pressure is taken as the collapse site of the airway geometry. This study demonstrates, that the spatial locations of the minimum pressure and the maximum deformation do not match. This reveals the importance of a coupled approach of soft tissue and airflow analysis in the search of the collapse site and therefore the best treatment option. A treatment effect of the mandibular protrusion can be anticipated with an accurate patient-specific airway model.
Anthropometric scaling of musculoskeletal models of the hand captures age-dependent differences in lateral pinch force.
Venue: Journal of biomechanics

Musculoskeletal models and computer simulations enable non-invasive study of muscle function and contact forces. Hand models are useful for understanding the complexities of hand strength, precision movement, and the dexterity required during daily activities. Yet, generic models fail to accurately represent the entire scope of the population, while subject-specific models are labor-intensive to create. The objective of this study was to assess the efficacy of scaled generic models to represent the broad spectrum of strength profiles across the lifespan. We examined one hundred lateral pinch simulations using a generic model of the wrist and thumb anthropometrically scaled to represent the full range of heights reported for four ages across childhood, puberty, older adolescence, and adulthood. We evaluated maximum lateral pinch force produced, muscle control strategies, and the effect of linearly scaling the maximum isometric force. Our simulations demonstrated three main concepts. First, anthropometric scaling could capture age-dependent differences in pinch strength. Second, a generic muscle control strategy is not representative of all populations. Lastly, simulations do not employ optimal fiber length to complete a lateral pinch task. These results demonstrate the potential of anthropometrically-scaled models to study hand strength across the lifespan, while also highlighting that muscle control strategies may adapt as we age. The results also provide insight to the force-length relationship of thumb muscles during lateral pinch. We conclude that anthropometric scaling can accurately represent age characteristics of the population, but subject-specific models are still necessary to represent individuals.
Moment arm of the knee-extensor mechanism measured in vivo across a range of daily activities.
Venue: Journal of biomechanics

We measured the moment arm of the knee-extensor mechanism as ten healthy young individuals performed six functional activities: level walking, downhill walking, stair ascent, stair descent, open-chain (non-weight-bearing) knee flexion, and open-chain knee extension. The moment arm of the knee-extensor mechanism was described by the moment arm of the patellar-tendon force, which acts to rotate the tibia about the instantaneous axis of rotation (screw axis) of the knee. A mobile biplane X-ray imaging system enabled simultaneous measurements of the three-dimensional movements of the femur, tibia and patella during each activity, from which the position and orientation of the screw axis and the patellar-tendon moment arm (PTMA) were determined. Mean PTMA across all activities and all participants remained nearly constant (~46 mm) from 0° to 70° of knee flexion and decreased by no more than 20% at higher flexion angles. The magnitude of the PTMA varied more substantially across individuals than across activities, indicating that the moment arm is more heavily influenced by differences in knee-joint geometry than muscle loading. Hence, PTMA measurements obtained for a given activity performed by one individual may be used with good confidence to describe the PTMA for any other activity performed by the same individual. Caution is advised when using PTMA measurements obtained from one individual to describe the moment arm in another individual even once the data are normalized by knee bone size, as the PTMA varied by as much as 13% from the mean across individuals.
Topographic features of nano-pores within the osteochondral interface and their effects on transport properties -a 3D imaging and modeling study.
Venue: Journal of biomechanics

Recent insights suggest that the osteochondral interface plays a central role in maintaining healthy articulating joints. Uncovering the underlying transport mechanisms is key to the understanding of the cross-talk between articular cartilage and subchondral bone. Here, we describe the mechanisms that facilitate transport at the osteochondral interface. Using scanning electron microscopy (SEM), we found a continuous transition of mineralization architecture from the non-calcified cartilage towards the calcified cartilage. This refurbishes the classical picture of the so-called tidemark; a well-defined discontinuity at the osteochondral interface. Using focused-ion-beam SEM (FIB-SEM) on one osteochondral plug derived from a human cadaveric knee, we elucidated that the pore structure gradually varies from the calcified cartilage towards the subchondral bone plate. We identified nano-pores with radius of 10.71 ± 6.45 nm in calcified cartilage to 39.1 ± 26.17 nm in the subchondral bone plate. The extracted pore sizes were used to construct 3D pore-scale numerical models to explore the effect of pore sizes and connectivity among different pores. Results indicated that connectivity of nano-pores in calcified cartilage is highly compromised compared to the subchondral bone plate. Flow simulations showed a permeability decrease by about 2000-fold and solute transport simulations using a tracer (iodixanol, 1.5 kDa with a free diffusivity of 2.5 × 10-10 m2/s) showed diffusivity decrease by a factor of 1.5. Taken together, architecture of the nano-pores and the complex mineralization pattern in the osteochondral interface considerably impacts the cross-talk between cartilage and bone.
Shear-mediated platelet activation in the free flow II: Evolving mechanobiological mechanisms reveal an identifiable signature of activation and a bi-directional platelet dyscrasia with thrombotic and bleeding features.
Venue: Journal of biomechanics

Shear-mediated platelet activation (SMPA) in the "free flow" is the net result of a range of cell mechanobiological mechanisms. Previously, we outlined three main groups of mechanisms including: 1) mechano-destruction - i.e. additive platelet (membrane) damage; 2) mechano-activation - i.e. activation of shear-sensitive ion channels and pores; and 3) mechano-transduction - i.e. "outside-in" signaling via a range of transducers. Here, we report on recent advances since our original report which describes additional features of SMPA. A clear "signature" of SMPA has been defined, allowing differentiation from biochemically-mediated activation. Notably, SMPA is characterized by mitochondrial dysfunction, platelet membrane eversion, externalization of anionic phospholipids, and increased thrombin generation on the platelet surface. However, SMPA does not lead to integrin αIIbβ3 activation or P-selectin exposure due to platelet degranulation, as is commonly observed in biochemical activation. Rather, downregulation of GPIb, αIIbβ3, and P-selectin surface expression is evident. Furthermore, SMPA is accompanied by a decrease in overall platelet size coupled with a concomitant, progressive increase in microparticle generation. Shear-ejected microparticles are highly enriched in GPIb and αIIbβ3. These observations indicate the enhanced diffusion, migration, or otherwise dispersion of platelet adhesion receptors to membrane zones, which are ultimately shed as receptor-rich PDMPs. The pathophysiological consequence of this progressive shear accumulation phenomenon is an associated dyscrasia of remaining platelets - being both reduced in size and less activatable via biochemical means - a tendency to favor bleeding, while concomitantly shed microparticles are highly prothrombotic and increase the tendency for thrombosis in both local and systemic milieu. These mechanisms and observations offer direct clinical utility in allowing measurement and guidance of the net balance of platelet driven events in patients with implanted cardiovascular therapeutic devices.
Modeling of bending and torsional stiffnesses of bone at sub-microscale: Effect of curved mineral lamellae.
Venue: Journal of biomechanics

Recent transmission electron microscopy images of transverse sections of human cortical bone showed that mineral lamellae (polycrystalline sheets of apatite crystals) form arcuate multi-radius patterns around collagen fibrils. The 3-6 nm thick mineral lamellae are arranged in stacks of 3-20 layers and curve around individual fibrils, few fibrils, and higher numbers of collagen fibrils. We evaluate the effect of these stacked mineral lamellae with various radius of curvature patterns on the elastic bending and torsional responses of bone at the sub-microscale using a finite element method. We find that the curved multi-radius stack patterns increased the bending and torsional stiffnesses by 7% and 23%, respectively, compared to when the stacks of mineral lamellae only encircle individual fibrils for the idealized geometric models considered. This study provides new insights into the structure-property relations for the bone ultrastructure.
Development and analytical validation of a finite element model of fluid transport through osteochondral tissue.
Venue: Journal of biomechanics

Fluid transport is critical to joint health. In this study we evaluate an unexplored component of joint fluid transport -fluid transport between cartilage and bone. Such transport across the cartilage-bone interface could potentially provide chondrocytes with an additional source of nutrients and signaling molecules. A biphasic viscoelastic model using an ellipsoidal fiber distribution was created with three distinct layers of cartilage (superficial zone, middle zone, and deep zone) along with a layer of subchondral bone. For stress-relaxation in unconfined compression, our results for compressive stress, radial stress, and effective fluid pressure were compared with established biphasic analytical solutions. Our model also shows the development of fluid pressure gradients at the cartilage-bone interface during loading. Fluid pressure gradients that develop at the cartilage-bone interface show consistently higher pressures in cartilage following the initial loading to 10% stain, followed by convergence of the pressures in cartilage and bone during the 400 s relaxation period. These results provide additional evidence that fluid is transported between cartilage and bone during loading and improves upon estimates of the magnitude of this effect through incorporating a realistic distribution and estimate of the collagen ultrastructure. Understanding fluid transport between cartilage and bone may be key to new insights about the mechanical and biological environment of both tissues in health and disease.
Spinal segment ranges of motion, movement coordination, and three-dimensional kinematics during occupational activities in normal-weight and obese individuals.
Venue: Journal of biomechanics

Measurements of spinal segment ranges of motion (RoMs), movement coordination, and three-dimensional kinematics during occupational activities have implications in occupational/clinical biomechanics. Due to the large amount of adipose tissues, obese individuals may have different RoMs, lumbopelvic coordination, and kinematics than normal-weight ones. We aimed to measure/compare trunk, lumbar, and pelvis primary RoMs in all anatomical planes/directions, lumbopelvic ratios (lumbar to pelvis rotations at different trunk angles) in all anatomical planes/directions and three-dimensional spine kinematics during twelve symmetric/asymmetric statics load-handling activities in healthy normal-weight and obese individuals. Kinematics/motion data were collected from nine healthy young male normal-weight and nine age/height/sex matched obese individuals via a ten-camera Vicon motion capture system. Obese individuals had significantly smaller (p < 0.05) lumbar flexion (~9° in average) and larger pelvis right lateral bending (~5°) RoMs as well as smaller lumbopelvic ratios (~37%) in lateral bending and axial rotation movements as compared to normal-weight individuals. Moreover, the two groups had generally non-significant different segmental orientations (<20° and in most cases < 10°) in load-handling tasks that depended on the magnitude of load asymmetry angle (p < 0.05). Differences were larger for tasks performed near the floor, away from body, and at larger load asymmetry angles. Biomechanical models simulating pure lateral bending, axial rotation, or tasks involving large load asymmetry may therefore need subject-specific, rather than population-based, motion analysis due to the effects from body weight. In clinical applications, it should be noted that healthy obese individuals may have different RoMs and lumbopelvic rhythms than healthy normal-weight individuals in some anatomical planes/directions.
In vivo primary and coupled segmental motions of the healthy female head-neck complex during dynamic head axial rotation.
Venue: Journal of biomechanics

While previous studies have greatly improved our knowledge on the motion capability of the cervical spine, few reported on the kinematics of the entire head-neck complex (C0-T1) during dynamic activities of the head in the upright posture. This study investigated in vivo kinematics of the entire head-neck complex (C0-T1) of eight female asymptomatic subjects during dynamic left-right head axial rotation using a dual fluoroscopic imaging system and 3D-to-2D registration techniques. During one-sided head rotation (i.e., left or right head rotation), the primary rotation of the overall head-neck complex (C0-T1) reached 55.5 ± 10.8°, the upper cervical spine region (C0-2) had a primary axial rotation of 39.7 ± 9.6° (71.3 ± 8.5% of the overall C0-T1 axial rotation), and the lower cervical spine region (C2-T1) had a primary rotation of 10.0 ± 3.7° (18.6 ± 7.2% of the overall C0-T1 axial rotation). Coupled bending rotations occurred in the upper and lower cervical spine regions in similar magnitude but opposite directions (upper: contralateral bending of 18.2 ± 5.9° versus lower: ipsilateral bending of 21.4 ± 5.1°), resulting in a compensatory cervical lateral curvature that balances the head to rotate horizontally. Furthermore, upper cervical segments (C0-1 or C1-2) provided main mobility in different rotational degrees of freedom needed for head axial rotations. Additionally, we quantitatively described both coupled segmental motions (flexion-extension and lateral bending) by correlation with the overall primary axial rotation of the head-neck complex. This investigation offers comprehensive baseline data regarding primary and coupled motions of craniocervical segments during head axial rotation.
A novel posture control device to induce high-rate complex loads for spine biomechanical studies.
Venue: Journal of biomechanics

Modern environmental scenarios such as autonomous vehicles, aircrafts, and military vehicles position the human body in a nonstandard posture and induce multiplanar loads; however, current spine alignment methods and loading are based on sagittal and planar loads. The objective of this study is to develop a posture control device and demonstrate its ability to induce multiplanar loads to the human cadaver spinal columns. The inferior end of the device was designed to allow a full six degree-of-freedom control for positioning the specimen via a coupled x-y cross table, vertical lift platform, and triaxial rotation mechanism. The superior end of the device was designed such that the cranial fixation of the specimen could be attached to the piston of the electrohydraulic testing apparatus directly or via a rotary disc through a slider-crank mechanism. The former attachment induces complex forces and moments, while the latter induces controlled moments with minimal forces. The usability of the posture control device was demonstrated by conducting experiments with a thoracolumbar spinal column for combined forces and moments, and with a head-neck column for complex moments, and in both cases, the uniaxial travel of the piston was at a dynamic rate. The posture control device can be used to study the biomechanics of the spine under complex loads and with different postures and develop injury criteria for different field environments.