nils-herrmann/clean_scirepeval huggingface dataset:
Micropipette aspiration of the Pacinian corpuscle.
Venue: Journal of biomechanics

The Pacinian corpuscle (PC) is a cutaneous mechanoreceptor sensitive to high-frequency vibrations (20-1000Hz). The PC is of importance due to its integral role in somatosensation and the critical need to understand PC function for haptic feedback system development. Previous theoretical and computational studies have modeled the physiological response of the PC to sustained or vibrating mechanical stimuli, but they have used estimates of the receptor's mechanical properties, which remain largely unmeasured. In this study, we used micropipette aspiration (MPA) to determine an apparent Young's modulus for PCs isolated from a cadaveric human hand. MPA was applied in increments of 5mm H2O (49Pa), and the change in protrusion length of the PC into the pipette was recorded. The protrusion length vs. suction pressure data were used to calculate the apparent Young's modulus. Using 10 PCs with long-axis lengths of 2.99±0.41mm and short-axis lengths of 1.45±0.22mm, we calculated a Young's modulus of 1.40±0.86kPa. Our measurement is on the same order of magnitude as those approximated in previous models, which estimated the PC to be on the same order of magnitude as skin or isolated cells, so we recommend that a modulus in the kPa range be used in future studies.
Myofascial force transmission in the lower limb: An in vivo experiment.
Venue: Journal of biomechanics

Anatomical studies have shown structural continuity between the lumbopelvic region and the lower limb. The present study aimed to verify how simultaneous changes on knee/hip positions modify the ankle's resting position and passive torque. Thirty-seven subjects underwent an isokinetic assessment of ankle passive torque. The relationship between the absolute values of ankle passive resistance torque and the ankle angular position was used to calculate the dependent variables: ankle resting position (position in which the passive resistance torque is zero); and ankle passive torque at 0° (torque at the neutral position of the ankle in the sagittal plane). These measures were carried out under three test conditions: 0° at knee and 0° at hip (0°/0°); 90° at knee and 90° at hip (90°/90°); and, 135° at knee and 120° at hip (135°/120°). The results demonstrated that the ankle resting position shifted towards dorsiflexion when knee/hip position changed from 0°/0° to 90°/90° and shifted towards plantar flexion when knee/hip position changed from 90°/90° to 135°/120°, achieving values close to the ones at the position 0°/0°. Similarly, passive torque reduced when knee/hip position changed from 0°/0° to 90°/90°, but it increased when knee/hip position changed from 90°/90° to 135°/120°. The unexpected changes observed in ankle passive torque and resting position due to changes in knee and hip from 90°/90° to 135°/120°, cannot be explained exclusively by forces related to tissues crossing the knee and ankle. This result supports the existence of myofascial force transmission among lower limb joints.
Hemodynamic characteristics of flow around a deformable stenosis.
Venue: Journal of biomechanics

Clinical studies reported that some vulnerable stenoses deformed their shape in a blood vessel based on flow condition. However, the effects of shape variation on flow characteristics remain unclear. The flow characteristics are known to affect vulnerable stenosis rupture and fractional flow reserve (FFR) value which has been widely used as a diagnostic tool for stenosis. Vulnerable stenosis rupture occurs when the structural stress exerted on a fibrous cap exceeds its tolerable threshold. The stress magnitude is determined from the spatial distribution of static pressure around the stenosis. In the present study, the static pressure distribution and the FFR value in deformable stenosis were investigated with related other flow characteristics. Two phantom models were fabricated to mimic deformable and nondeformable stenoses using polydimethylsiloxane. The flow characteristics were observed under a steady-flow condition at three Reynolds numbers (Re=500, 1000, 1500) using a particle image velocimetry. The pressure drop across the stenosis models were measured using a pressure sensor to determine effects of shape deformation on FFR value. Shape variations and jet deflections were clearly observed in the deformable stenosis model, and the effective severity of the stenosis increased up to 17.2%. The shape variations of deformable stenosis model increased the static pressure difference at the upstream and downstream sides of the stenosis. The pressure drop across the deformable stenosis model was significantly higher than that of the nondeformable stenosis model. The present results substantiate that stenosis deformability should be carefully considered to diagnose the rupture of vulnerable stenosis.
Loss of ACL function leads to alterations in tibial plateau common dynamic contact stress profiles.
Venue: Journal of biomechanics

It has been suggested that the repetitive nature of altered joint tissue loading which occurs after anterior cruciate ligament (ACL) rupture can contribute to the development of osteoarthritis (OA). However, changes in dynamic knee joint contact stresses after ACL rupture have not been quantified for activities of daily living. Our objective was to characterize changes in dynamic contact stress profiles that occur across the tibial plateau immediately after ACL transection. By subjecting sensor-augmented cadaveric knees to simulated gait, and analyzing the resulting contact stress profiles using a normalized cross-correlation algorithm, we tested the hypothesis that common changes in dynamic contact stress profiles exist after ACL injury. Three common profiles were identified in intact knees, occurring on the: (I) posterior lateral plateau, (II) posterior medial plateau, and (III) central region of the medial plateau. In ACL-transected knees, the magnitude and shape of the common dynamic stress profiles did not change, but their locations on the tibial plateau and the number of knees identified for each profile changed. Furthermore, in the ACL transected knees, a unique common contact stress profile was identified in the posterior region of the lateral plateau near the tibial spine. This framework can be used to understand the regional and temporal changes in joint mechanics after injury.
Nodal cilia-driven flow: Development of a computational model of the nodal cilia axoneme.
Venue: Journal of biomechanics

Cilia-driven nodal flow is important in the determination of left-right asymmetry in the body. Several theoretical and computational models have been proposed to explain the mechanics of ciliary motion, although the full mechanism remains unknown. Here, we developed a three-dimensional nodal cilia axoneme model using a finite element-boundary element coupling method, and investigated the mechanics of nodal ciliary motion. We found that the rotational orbit was strongly dependent on the dynein activation frequency. We also investigated flow field generated by the ciliary rotation, and the flow strength decayed as r-3 at the far field from the cilium. Our numerical results also suggest that experimentally observed tilt angle θ=2π/9 is sufficiently large to make a leftward flow. These findings are helpful in better understanding ciliary motion and nodal flow.
Quantification of bladder wall biomechanics during urodynamics: A methodologic investigation using ultrasound.
Venue: Journal of biomechanics

Overactive bladder is often characterized by biomechanical changes in the bladder wall, but there is no established method to measure these changes in vivo. The goal of this study was to develop a novel method to determine detrusor wall biomechanical parameters during urodynamics through the incorporation of transabdominal ultrasound imaging. Individuals with overactive bladder (OAB) underwent ultrasound imaging during filling. The fill rate was 10% of the cystometric capacity per minute as determined by an initial fill. Transabdominal ultrasound images were captured in the midsagittal and transverse planes at 1min intervals. Using image data and Pves, detrusor wall tension, stress, and compliance were calculated. From each cross-sectional image, luminal and wall areas along with inner perimeters were measured. In the sagittal and transverse planes, wall tension was calculated as Pves∗luminal area, wall stress as tension/wall area, and strain as the change in perimeter normalized to the perimeter at 10% capacity. Elastic modulus was calculated as stress/strain in the medial-lateral and cranial-caudal directions. Patient-reported fullness sensation was continuously recorded. Data from five individuals with OAB showed that detrusor wall tension, volume, and strain had the highest correlations to continuous bladder sensation of all quantities measured. This study demonstrates how detrusor wall tension, stress, strain, and elastic modulus can be quantified by adding ultrasound imaging to standard urodynamics. This technique may be useful in diagnosing and better understanding the biomechanics involved in OAB and other bladder disorders.
Consistent trilayer biomechanical modeling of aortic valve leaflet tissue.
Venue: Journal of biomechanics

Aortic valve tissue exhibits highly nonlinear, anisotropic, and heterogeneous material behavior due to its complex microstructure. A thorough understanding of these characteristics permits us to develop numerical models that can shed insight on the function of the aortic valve in health and disease. Herein, we take a closer look at consistently capturing the observed physical response of aortic valve tissue in a continuum mechanics framework. Such a treatment is the first step in developing comprehensive multiscale and multiphysics models. We highlight two important aspects of aortic valve tissue behavior: the role of the collagen fiber microstructure and the native prestressing. We propose a model that captures these two features as well as the heterogeneous layer-scale topology of the tissue. We find the model can reproduce the experimentally observed multiscale mechanical behavior in a manner that provides intuition on the underlying mechanics.
The use of a single inertial sensor to estimate 3-dimensional ground reaction force during accelerative running tasks.
Venue: Journal of biomechanics

The purpose of this investigation was to determine the feasibility of using a single inertial measurement unit (IMU) placed on the sacrum to estimate 3-dimensional ground reaction force (F) during linear acceleration and change of direction tasks. Force plate measurements of F and estimates from the proposed IMU method were collected while subjects (n=15) performed a standing sprint start (SS) and a 45° change of direction task (COD). Error in the IMU estimate of step-averaged component and resultant F was quantified by comparison to estimates from the force plate using Bland-Altman 95% limits of agreement (LOA), root mean square error (RMSE), Pearson's product-moment correlation coefficient (r), and the effect size (ES) of the differences between the two systems. RMSE of the IMU estimate of step-average F ranged from 37.70 N to 77.05 N with ES between 0.04 and 0.47 for SS while for COD, RMSE was between 54.19 N to 182.92 N with ES between 0.08 and 1.69. Correlation coefficients between the IMU and force plate measurements were significant (p≤0.05) for all values (r=0.53 to 0.95) except the medio-lateral component of step-average F. The average angular error in the IMU estimate of the orientation of step-average F was ≤10° for all tasks. The results of this study suggest the proposed IMU method may be used to estimate sagittal plane components and magnitude of step-average F during a linear standing sprint start as well as the vertical component and magnitude of step-average F during a 45° change of direction task.
A comparison of two non-invasive methods for measuring scapular orientation in functional positions.
Venue: Journal of biomechanics

Identification of scapular dyskinesis and evaluation of interventions depend on the ability to properly measure scapulothoracic (ST) motion. The most widely used measurement approach is the acromion marker cluster (AMC), which can yield large errors in extreme humeral elevation and can be inaccurate in children and patient populations. Recently, an individualized regression approach has been proposed as an alternative to the AMC. This technique utilizes the relationship between ST orientation, humerothoracic orientation and acromion process position derived from calibration positions to predict dynamic ST orientations from humerothoracic and acromion process measures during motion. These individualized regressions demonstrated promising results for healthy adults; however, this method had not yet been compared to the more conventional AMC. This study compared ST orientation estimates by the AMC and regression approaches to static ST angles determined by surface markers placed on palpated landmarks in typically developing adolescents performing functional tasks. Both approaches produced errors within the range reported in the literature for skin-based scapular measurement techniques. The performance of the regression approach suffered when applied to positions outside of the range of motion in the set of calibration positions. The AMC significantly underestimated ST internal rotation across all positions and overestimated posterior tilt in some positions. Overall, root mean square errors for the regression approach were smaller than the AMC for every position across all axes of ST motion. Accordingly, we recommend the regression approach as a suitable technique for measuring ST kinematics in functional motion.
Does a micro-grooved trunnion stem surface finish improve fixation and reduce fretting wear at the taper junction of total hip replacements? A finite element evaluation.
Venue: Journal of biomechanics

The generation of particulate debris at the taper junction of total hip replacements (THRs), can cause failure of the artificial hip. The taper surfaces of femoral heads and trunnions of femoral stems are generally machined to a certain roughness to enhance fixation. However, the effect of the surface roughness of these surfaces on the fixation, wear and consequently clinical outcomes of the design is largely unknown. In this study, we asked whether a micro-grooved trunnion surface finish (1) improves the fixation and (2) reduces the wear rate at the taper junction of THRs. We used 3D finite element (FE) models of THRs to, firstly, investigate the effect of initial fixation of a Cobalt-Chromium femoral head with a smooth taper surface mated with a Titanium (1) micro-grooved and (2) smooth, trunnion surface finishes. Secondly, we used a computational FE wear model to compare the wear evolution between the models, which was then validated against wear measurements of the taper surface of explanted femoral heads. The fixation at the taper junction was found to be better for the smooth couplings. Over a 7 million load cycle analysis in-silico, the linear wear depth and the total material loss was around 3.2 and 1.4 times higher for the femoral heads mated with micro-grooved trunnions. It was therefore concluded that smooth taper and trunnion surfaces will provide better fixation at the taper junction and reduce the volumetric wear rates.
Quantifying differences in the material properties of the fiber regions of the pectoralis major using ultrasound shear wave elastography.
Venue: Journal of biomechanics

The sternocostal and clavicular regions of the pectoralis major are independently harvested to provide shoulder stability, but surgical decision making does not consider the biomechanical consequences that disinsertion of one fiber region over the other has on shoulder function. Differences in material properties between the fiber regions could influence which tissue is more optimal for surgical harvesting. The current study utilized ultrasound shear wave elastography (SWE) to investigate whether the in vivo material properties differ between the fiber regions. Shear wave velocities (SWVs) were collected from the sternocostal and clavicular fiber regions of the pectoralis major from ten healthy young male participants. Participants produced isometric shoulder torques of varying magnitudes (passive, 15%, and 30% MVC) and directions (horizontal and vertical adduction). Four shoulder positions encompassing different vertical abduction and external rotation angles were examined. One-way ANOVAs tested the hypotheses that differences in SWVs during rest existed between the fiber regions asa function of shoulder position, and differences in SWVs during contraction existed asa function of shoulder position and torque direction. In all shoulder positions, the clavicular region exhibited greater SWVs during rest than the sternocostal region (P<0.001). In shoulder positions that did not include external rotation, the clavicular region exhibited greater SWVs during contraction when producing horizontal adduction torques (P<0.001), while the sternocostal region exhibited greater SWVs during contraction when producing vertical adduction torques at 30% MVC (P<0.01). Our results suggest that each fiber region of the pectoralis major provides unique contributions to passive and active shoulder function.
The effect of finger spreading on drag of the hand in human swimming.
Venue: Journal of biomechanics

The effect of finger spread on overall drag on a swimmer's hand is relatively small, but could be relevant for elite swimmers. There are many sensitivities in measuring this effect. A comparison between numerical simulations, experiments and theory is urgently required to observe whether the effect is significant. In this study, the beneficial effect of a small finger spread in swimming is confirmed using three different but complementary methods. For the first time numerical simulations and laboratory experiments are conducted on the exact same 3D model of the hand with attached forearm. The virtual version of the hand with forearm was implemented in a numerical code by means of an immersed boundary method and the 3D printed physical version was studied in a wind tunnel experiment. An enhancement of the drag coefficient of 2% and 5% compared to the case with closed fingers was found for the numerical simulation and experiment, respectively. A 5% and 8% favorable effect on the (dimensionless) force moment at an optimal finger spreading of 10° was found, which indicates that the difference is more outspoken in the force moment. Moreover, an analytical model is proposed, using scaling arguments similar to the Betz actuator disk model, to explain the drag coefficient as a function of finger spacing.
Multi-sensor assessment of dynamic balance during gait in patients with subacute stroke.
Venue: Journal of biomechanics

The capacity to maintain upright balance by minimising upper body oscillations during walking, also referred to as gait stability, has been associated with a decreased risk of fall. Although it is well known that fall is a common complication after stroke, no study considered the role of both trunk and head when assessing gait stability in this population. The primary aim of this study was to propose a multi-sensor protocol to quantify gait stability in patients with subacute stroke using gait quality indices derived from pelvis, sternum, and head accelerations. Second, the association of these indices with the level of walking ability, with traditional clinical scale scores, and with fall events occurring within the six months after patients' dismissal was investigated. The accelerations corresponding to the three abovementioned body levels were measured using inertial sensors during a 10-Meter Walk Test performed by 45 inpatients and 25 control healthy subjects. A set of indices related to gait stability were estimated and clinical performance scales were administered to each patient. The amplitude of the accelerations, the way it is attenuated/amplified from lower to upper body levels, and the gait symmetry provide valuable information about subject-specific motor strategies, discriminate between different levels of walking ability, and correlate with clinical scales. In conclusion, the proposed multi-sensor protocol could represent a useful tool to quantify gait stability, support clinicians in the identification of patients potentially exposed to a high risk of falling, and assess the effectiveness of rehabilitation protocols in the clinical routine.
A novel surrogate lung material for impact studies: Development and testing procedures.
Venue: Journal of biomechanics

This work focuses on the development of a surrogate lung material (SLM) that reproduces the dynamic response of a human lung under various loading conditions and also allows for the analysis of the extent and distribution of damage. The SLM consists of polyurethane foam used to mimic the spongy lung tissue and fluid-filled gelatine microcapsules used to simulate the damage of alveoli. The bursting pressure of the microcapsules was investigated by conducting low and high rate compression tests on single microcapsules. A bursting pressure of around 5bar was measured which is comparable to the reported lung overpressure at injury level. Low and high rate compression tests were conducted on the SLMs. From the measured mechanical properties and mass density, the stress wave speed was calculated and found to be well in the range of the reported values for human lungs (16-70m/s). In order to study the extent and distribution of damage in the SLMs, as represented by burst microcapsules, a CT scan analysis was carried out before and after the impacts. The CT scan results clearly demonstrated the magnitude and distribution of damage within the specimen. The results are then compared to the Bowen curves, the most often used criteria for predicting blast injuries in humans. An excellent agreement was found between the observed damage in the surrogate lungs and the expected damage in real human lungs. In general, the SLM showed similar stress wave speed, bursting pressure and damage to that of the real lungs.
Scapular kinematics in adolescent idiopathic scoliosis: A three-dimensional motion analysis during multiplanar humeral elevation.
Venue: Journal of biomechanics

The scapula plays a critical role in supporting shoulder function. Considering the closed anatomical relationship between the scapula and the thoracic cage, the presence of postural disturbances could be linked to alterations in the scapular position and orientation in adolescent idiopathic scoliosis (AIS). However, currently there is a lack of descriptive research and detailed assessment of scapular kinematics in AIS. The aim of this study was to investigate the three-dimensional scapular kinematics in AIS. Nineteen AIS patients and fourteen healthy controls participated in this study. Bilateral shoulder kinematics were measured with an electromagnetic tracking device during shoulder elevation in the sagittal, scapular, and frontal planes. Data for the scapular orientation were analyzed in the resting position and at 30°, 60°, 90°, and 120° of humerothoracic elevation. Scapular behavior was different in participants with AIS, compared to healthy controls, with different patterns observed on convex and concave sides. While examining all three planes of elevation, the scapula was more internally and anteriorly tilted on the convex side, while the scapula was more externally, downwardly rotated, and posteriorly tilted on the concave side in participants with AIS. Furthermore, there was a decreased peak humerothoracic elevation and altered scapular posterior tilt in participants with AIS in the resting position. These findings increase our knowledge and understanding of scapular alterations and the reported scapular alterations can be considered as adaptive compensation strategies in AIS.