nils-herrmann/clean_scirepeval huggingface dataset:
Time dependent degradation of vitreous gel under enzymatic reaction: Polymeric network role in fluid properties.
Venue: Journal of biomechanics

The viscoelastic behavior of vitreous gel is due to the presence of biopolymers in its structure. Fluid properties of the vitreous is mainly the result of interactions between the characteristics of collagen type II and Hyaluronic Acid networks. Having a better understanding of the structure of each component and their changes during aging and various diseases such as diabetes can lead to better monitoring and treatment options. We study the effects of collagenase type II on 44 samples of porcine vitreous using an in situ rheological experiment in comparison with 18 eyes in a control group injected with Phosphate Buffered Saline Solution. We analyze the behavior of each component over time in both groups. We focus on the changes of viscosity and elasticity of the collagen network within the vitreous. The results of the analysis in this study show that the changes in the fluid properties of the vitreous after collagenase injection is driven by the structural alterations of the collagen network. Creep compliance values of the collagen network are significantly higher in the first group compared to the control group one hour and twenty-four hours after the injection. In contrast, creep compliance of the HA network shows no statistically significant change one hour after the injection in both groups. The results of the reported analysis of individual components in this study support the previous findings on the alterations within the vitreous structure in its entirety.
Mechanobiological based long bone growth model for the design of limb deformities correction devices.
Venue: Journal of biomechanics

A mechanobiological model of bone growth aimed for the design of medical devices for the treatment of limb deformities during childhood and adolescence was developed. Dimensional analysis was introduced as a tool for the systematic evaluation of the influence attributed to different factors that might modify the bone growth process. Simplifications were proposed, allowing the reduction of bone growth relevant parameters to four non-dimensional numbers, representing the chondrocyte sensitivity to stress, the epiphyseal plate geometry, the bone rigidity and the time. Benchmark situations considered for model validation were bone growth under normal conditions and an epiphyseal stapling treatment. A finite elements approach was used to analyze bone growth in the distal portion of the femur. Results are shown to be consistent with corresponding clinical data published in the literature, which indicates the potential of the here proposed method for the design of specific devices and treatments.
Alterations with age in the biomechanical behavior of human ureteral wall: Microstructure-based modeling.
Venue: Journal of biomechanics

The human ureters have not been thoroughly explored from the biomechanics perspective, despite the wealth of such data for other soft-tissue types. This study was motivated by the need to use relevant biomechanical data from human ureters and microstructure-based material formulations for simulations of ureteral peristalsis and stenting. Our starting choice was the four-fiber family model that has proven its validity as a descriptor of the multiaxial response of cardiovascular tissues. The degree of model complexity, required for rigorous fits to passive quasi-static pressure-diameter-force data at several axial stretches, was systematically investigated. Ureteral segments from sixteen human autopsy subjects were evaluated. A diagonal and axial family model allowed equally-good fits as the full model for all age groups and ureteral regions; considerably better than those allowed by the phenomenological Fung-type model whose root-mean-square error of fitting was three-fold greater. This reduced model mimicked the structure seen in histologic sections, namely plentiful diagonal collagen fibers in the lamina propria and axial fibers in the muscle and adventitia. The paucity of elastin fibers and mixed muscle orientation justified the use of isotropic muscle-dominated matrix with small neo-Hookean parameter values. The significantly thicker lamina propria in the lower than the upper ureter of young subjects (312 ± 27 vs. 232 ± 26 μm; mean ± standard error) corroborated the significant regional differences in diagonal-fiber family parameter values. The significant muscle thickening with age (upper ureter: 373 ± 48 vs. 527 ± 67 μm; middle: 388 ± 29 vs. 575 ± 69 μm; lower: 440 ± 21 vs. 602 ± 71 μm) corroborated the significant age-related increase in axial-fiber family parameter values.
The effect of coordinate system selection on wrist kinematics.
Venue: Journal of biomechanics

Three-dimensional motion analysis of the hand and wrist is common in in-vitro and in-vivo biomechanical research. However, all studies rely on post testing analysis, where anatomical joint coordinate systems (JCS) are created to generate clinically relevant data to describe wrist motion. The purpose of this study was to present a comparison of four JCS that have been previously described in literature. Five cadaveric upper limbs were passively cycled through a flexion-extension and radial-ulnar deviation motion pathways using a wrist motion simulator. During testing, clinical wrist angle was measured using a goniometer. Following testing, wrist angle was calculated using four previously described methods of generating wrist coordinate systems, to facilitate their comparison. For flexion-extension wrist motion, only subtle difference between JCSs were detected. When comparing the performance of each JCS to the measured wrist angle during flexion-extension wrist motion, the RMSE for all three analyzed axes were all within 6.6°. For radial-ulnar deviation wrist motion, again only subtle difference between JCSs were detected. When comparing the performance of each JCS to the measured wrist angle during radial-ulnar deviation wrist motion, the RMSE for all three analyzed axes were all within 7.1°. The results of this coordinate system comparison do not favor one JCS generation method over another, as all were found to be similar and the small differences that were found are likely not clinically significant. We support using any of the analyzed coordinate system generation methods; however, a practical advantage of using certain methods is that the required digitized points to form the coordinate systems are palpable on the skin's surface.
Rearfoot-forefoot profile defined by vertical ground reaction forces during gait is altered in patients with unilateral intermittent claudication.
Venue: Journal of biomechanics

Intermittent Claudication due to Peripheral Arterial Disease (PAD-IC) induces ischemic pain in exercising muscles, and therefore impaired gait. In a pathological context, the analysis of the Vertical component of Ground Reaction Force (VGRF) is frequently used to describe gait pattern. This paper aims to define gait profiles according to the relative difference between peaks of VGRF; a Rearfoot and a Forefoot profile revealing a more loading or push-off strategy. We evaluated 70 participants (24 with unilateral disease (Unilat-IC), 22 with bilateral disease (Bilat-IC) and 24 Controls) during a walk test on an instrumented treadmill. Results indicate that Unilat-IC patients present a Rearfoot-profile in both legs during the pain-free gait period, likely to stabilize their gait. With the onset and increase of pain, the asymptomatic leg changes for a Forefoot-profile. This asymmetrical pattern suggests that a compensatory mechanism occurred to unload the symptomatic (painful) leg, possibly creating an imbalance. In Bilat-IC and Controls subjects, a Forefoot-profile is found, with a symmetrical pattern. However, there is a trend for lower propulsive capacity in case of Bilat-IC due to ischemic pain, but patients did not have the ability to compensate as in Unilat-IC. Therefore, Bilat-IC should not be considered as a "double" Unilat-IC. This study highlights the existence of gait profiles based on VGRF in PAD-IC patients. These profiles are dependent on the type of disease. Analysis of these gait profiles can 1) provide a simple way to identify gait alterations and 2) participate in improving physical rehabilitation strategies in PAD-IC patients.
Achilles tendon moment arms are similar when computed using a single fixed axis versus a moving instantaneous helical axis.
Venue: Journal of biomechanics

Accurate location of the axis of ankle rotation is critical to in vivo estimates of Achilles tendon moment arm. Here we investigated how the plantarflexion moment arm of the Achilles tendon is affected by using an instantaneous helical axis that moves with ankle motion as opposed to a single fixed joint axis that approximates the average axis of rotation. Twenty young healthy adults performed a series of weightbearing cyclical plantar- and dorsi-flexion motions. Motion analysis tracked the motions of markers placed on the foot and shank and also tracked an ultrasound probe imaging the Achilles tendon. Differences in ATma between the methods were investigated using a two-way repeated-measures ANOVA with factors of joint angle (+5°, 0°, -5°, -10°, -15°) and method (instantaneous helical axes, fixed axis). Moment arms computed between the two methods were moderately to strongly correlated, especially in the mid-range of motion (for 0° to 10° plantarflexion, all r2 > 0.619 and all p < 0.004). The two methods produced Achilles tendon moment arms that were comparable and not significantly different except in the most dorsiflexed position, when they differed on average by 9.35 ± 3.23 mm (p = 0.001). Our results suggest that either approach for locating the axis of ankle rotation would be appropriate for the purpose of estimating ATma, but that a fixed axis may be preferable because it is applicable over a greater range of ankle motion.
Computational modeling of a right-sided Fontan assist device: Effectiveness across patient anatomies and cannulations.
Venue: Journal of biomechanics

The use of mechanical circulatory support for failing Fontan patients is an area of growing interest, as the increased life expectancy of these patients continues to be accompanied by numerous end-organ complications. In vitro work has shown positive results using the CentriMag device for right-sided Fontan support, however the generalizability across various patient anatomies and cannulations is unknown. Computational simulations are first validated against in vitro modeling, then used to assess generalizability and further explore hemodynamic metrics including relative pressure changes, hepatic flow distribution, wall shear stress and power added. Computational modeling matched previous in vitro work very well, with vessel flow rates and relative average pressure change each within 1%. Positive results were seen across all patient anatomies and cannulations. On average, pressure from the vena cava to pulmonary arteries increased by 5.4 mmHg corresponding to 32 mW of power added. Hepatic flow distribution and wall shear stress were within acceptable ranges, with an average hepatic flow distribution of 47% and all patients showing ≤ 1% of the total Fontan connection surface area at a wall shear stress above 150 Pa. The positive results previously seen using CentriMag as a right-sided Fontan support device were found to be repeatable across multiple patient anatomies and cannulations. While animal models and eventual patient studies will provide further insight into the efficacy of this support strategy, our findings here suggest this method may reproduce right heart function.
Theoretical justification for distal foot power equation.
Venue: Journal of biomechanics

The distal foot power equation is a simple yet powerful tool for estimating the power dissipation or generation within the foot even while modeling it as a rigid body. It was introduced over two decades ago, but has seen a resurgence of use in recent years. Nevertheless, the theoretical justification for this formula has thus far been limited. It is difficult to properly use any equation and interpret the results from analyses using it without a solid understanding of how it is derived as well as its underlying assumptions. In this communication, a thorough derivation of the distal foot power equation is provided first for the case where the foot is interacting with a rigid ground without sliding and then second generalized for situations when the foot may slide relative to a deformable ground surface. For the first case, the derivation makes clear that distal foot power represents the power due to the deviation of the foot from a rigid body state for the portion of the foot between its mass center (or other point of reference) and the center of pressure. For the second case, distal foot power represents not only the internal deformation power of the foot, but also the power due to sliding of the foot on the ground and the power due to deformation of the ground near the point of contact.
Instrumented immobilizing boot paradigm quantifies reduced Achilles tendon loading during gait.
Venue: Journal of biomechanics

Achilles tendon ruptures are common injuries that lead to functional deficits in two-thirds of patients. Progressively loading the healing tendon has been associated with superior outcomes, but the loading profiles that patients experience throughout rehabilitation have not yet been established. In this study, we developed and calibrated an instrumented immobilizing boot paradigm that is aimed at longitudinally quantifying patient loading biomechanics to develop personalized rehabilitation protocols. We used a 3-part instrumented insole to quantify the ankle loads generated by the Achilles tendon and secured a load cell inline with the posterior strut of the immobilizing boot to quantify boot loading. We then collected gait data from five healthy young adults to demonstrate the validity of this instrumented immobilizing boot paradigm to assess Achilles tendon loading during ambulation. We developed a simple calibration procedure to improve the measurement fidelity of the instrumented insole needed to quantify Achilles tendon loading while ambulating with an immobilizing boot. By assessing Achilles tendon loading with the ankle constrained to 0 degrees and 30 degrees plantar flexion, we confirmed that walking with the foot supported in plantar flexion decreased Achilles tendon loading by 60% (P < 0.001). This instrumented immobilizing boot paradigm leverages commercially available sensors and logs data using a small microcontroller secured to the boot and a handheld device, making our paradigm capable of continuously monitoring biomechanical loading outside of the lab or clinic.
Modeling the initial-volume dependent approximate compressibility of porcine liver tissues using a novel volumetric strain energy model.
Venue: Journal of biomechanics

Experimental observations in the open literature indicate that soft tissues are slightly compressible, and this characteristic affects not only their overall elastic response but also their damage evolution and failure mechanism. In this study, we find that the compressibility of liver tissues is also closely related to the initial specimen volume according to the confined compression tests: the samples with smaller initial volume exhibit more compressible behavior compared to the larger ones. To include this initial-volume dependent effect, we developed a novel volumetric strain energy model with two variables, i.e., the bulk modulus and the compressibility factor. A detailed scheme was proposed as well to identify these two parameters, and the relationship between the bulk modulus and the initial volume was clarified. Findings from this study will help to deepen the understanding of the biomechanical properties of soft tissues.  Liver is a highly vascular organ and traditionally assumed to be an incompressible medium. However, through the confined compression tests, we found that the samples with smaller initial volumes exhibit more compressible behavior. Hence, we developed a novel strain energy density model to characterize the initial-volume dependent hyperelastic response, and found that the bulk modulus of liver tissues is positively related to the initial volume. Our results suggest that the compressibility of liver tissues should be considered in the future study of liver biomechanics.
Instantaneous helical axis estimation of glenohumeral kinematics: The impact of rotator cuff pathology.
Venue: Journal of biomechanics

The rotator cuff is theorized to contribute to force couples required to produce glenohumeral kinematics. Impairment in these force couples would theoretically result in impaired ball-and-socket kinematics. Although less frequently used than traditional kinematic descriptors (e.g., Euler angles, joint translations), helical axes are capable of identifying alterations in ball-and-socket kinematics by quantifying the variability (i.e., dispersion) in axis orientation and position during motion. Consequently, assessing glenohumeral helical dispersion may provide indirect evidence of rotator cuff function. The purpose of this exploratory study was to determine the extent to which rotator cuff pathology is associated with alterations in ball-and-socket kinematics. Fifty-one participants were classified into one of five groups based on an assessment of the supraspinatus using diagnostic imaging: asymptomatic healthy, asymptomatic tendinosis, asymptomatic partial-thickness tear, asymptomatic full-thickness tear, symptomatic full-thickness tear. Glenohumeral kinematics were quantified during coronal plane abduction using a biplane x-ray system and described using instantaneous helical axes. The degree to which glenohumeral motion coincided with ball-and-socket kinematics was described using the angular and positional dispersion about the optimal helical axis and pivot, respectively. No statistically significant difference was observed between groups in angular dispersion. However, symptomatic individuals with a full-thickness supraspinatus tear had significantly more positional dispersion than asymptomatic individuals with a healthy supraspinatus or tendinosis. These findings suggest that symptomatic individuals with a full-thickness supraspinatus tear exhibit impaired ball-and-socket kinematics, which is believed to be associated with a disruption of the glenohumeral force couples.
Site dependent elastic property of human iliotibial band and the effect of hip and knee joint angle configuration.
Venue: Journal of biomechanics

The iliotibial band (ITB) is the lateral thickening of the fascia lata. The ITB has been extensively studied for its relevance to injury, but not much is known about its elastic properties. We aimed to investigate the site- and joint angle-dependence of ITB elasticity. We tested twelve healthy males (22-30 years; in vivo) and twelve male cadavers (69-93 years; cadaver). The Young's modulus of the ITB was measured in the longitudinal direction at five sites (over the proximal, middle, and distal bellies of the vastus lateralis (VL), superior border of the patella, and between femur and tibia) of the right limb, by ultrasound shear wave elastography (in vivo) and the tensile test (cadaver). Joint angle-dependence was also studied for nine different positions (knee angles at 0, 25, 90˚ x hip angles at 0, 40, 90˚) (in vivo). Over VL, the ITB was more compliant at the distal (17.6-190.1 kPa; in vivo, 219.4 ± 68.8 MPa; cadaver, mean ± SD) than other sites (24.2-221.4 kPa, 337.9-362.7 MPa). The ITB at the superior border of the patella and between femur and tibia was stiffer in vivo (31.8-271.8 and 50.9-208.8 kPa), while it was more compliant in cadavers (113.4 ± 63.7 and 130.4 ± 73.7 MPa), compared to other sites. The ITB became stiffer associated with increasing hip extension angle and knee flexion angle, and the hip remarkably affecting the values regardless of site (in vivo). Our findings have clinical significance with respect to the site- and joint angle-dependence of ITB-related overuse injury.
Residual and passive force enhancement in skinned cardiac fibre bundles.
Venue: Journal of biomechanics

In skeletal muscle, steady-state force is consistently greater following active stretch than during a purely isometric contraction at the same length (residual force enhancement; RFE). Similarly, when deactivated, the force remains higher following active stretch than following an isometric condition (passive force enhancement; PFE). RFE and PFE have been associated with the sarcomere protein titin, but skeletal and cardiac titin have different structures, and results regarding RFE in cardiac muscle have been inconsistent and contradictory. Therefore, the purpose of this study was to determine if cardiac muscle exhibits RFE and PFE. Skinned fibre bundles (n = 10) were activated isometrically at a sarcomere length of 2.2 μm and actively stretched by 15% of their length. The resultant active and passive forces were compared to the corresponding forces obtained for purely isometric contractions at the long length. RFE was observed in all fibre bundles, averaging 5.5 ± 2.5% (ranging from 2.3 to 9.4%). PFE was observed in nine of the ten bundles, averaging 11.1 ± 6.5% (ranging from -2.1 to 18.7%). Stiffness was not different between the active isometric and the force enhanced conditions, but was higher following deactivation from the force-enhanced compared to the isometric reference state. We conclude that there is RFE and PFE in cardiac muscle. We speculate that cardiac muscle has the same RFE capability as skeletal muscle, and that the most likely mechanism for the RFE and PFE is the engagement of a passive structural element during active stretching.
Correlation between running asymmetry, mechanical efficiency, and performance during a 10 km run.
Venue: Journal of biomechanics

Running asymmetry is considered a matter of concern for performance and injury, but the association between asymmetry and performance remain unclear. There are different strategies to address asymmetries and its relationship with performance. Here we investigated the correlation between global symmetry index and mechanical efficiency during 10 km running. Thirteen amateur trained athletes (8 men and 5 women) performed a 10 km running at a fixed pace while a 3D accelerometer attached to the pelvic region recorded position data throughout the course of the run and gas exchanges were monitored breath by breath. Global symmetry index was determined for 3 directions, and mechanical efficiency was calculated as the ratio of external work output to energy expenditure determined from gas analysis. Global Symmetry Index and mechanical efficiency decreased (-55.5% and -44.8%, respectively) during the course of the 10 km run (p < 0.01). A positive correlation was observed between global symmetry index and efficiency (r = 0.66, p = 0.01). Asymmetry in the vertical direction had a relatively higher impact on the global symmetry index. The global symmetry index accounted for 43.1% of the variance in mechanical efficiency (p = 0.015). Symmetry, evaluated by the global symmetry index, directly correlates with mechanical efficiency during a 10 km run.