nils-herrmann/clean_scirepeval huggingface dataset:
Plantarflexor fiber and tendon slack length are strong determinates of simulated single-leg heel raise height.
Venue: Journal of biomechanics

Achilles tendon ruptures have been linked with detrimental changes in muscle-tendon structure, which may help explain long-term functional deficits. However, the causal effects of muscle-tendon structure on joint function have not been tested in a controlled setting. Therefore, the purpose of this study was to test the implications of muscle-tendon unit parameters on simulated single-leg heel raise height. We hypothesized that muscle fiber length and resting ankle angle - a clinical surrogate measure of tendon slack length - would predict single-leg heel raise height more strongly than other parameters. To test this hypothesis, we developed a two-part simulation paradigm that recreated clinically relevant muscle-tendon scenarios and then tested these parameters on single-leg heel raise height. We found that longer muscle fibers had the greatest positive effect on single-leg heel raise height. However, tendon slack length, determined by simulating resting ankle angles in a secondary analysis, revealed a stronger negative correlation with heel raise height. Our findings support previous clinical observations that both muscle fascicle length and resting tendon length are important muscle-tendon parameters for patient function. In addition to minimizing tendon elongation following rupture, treatment plans should focus on preserving plantarflexor muscle structure to mitigate functional loses following Achilles tendon ruptures.
Computational analysis of knee joint stability following total knee arthroplasty.
Venue: Journal of biomechanics

The overall objective of this study was to introduce knee joint power as a potential measure to investigate knee joint stability following total knee arthroplasty (TKA). Specific aims were to investigate whether weakened knee joint stabilizers cause abnormal kinematics and how it influences the knee joint kinetic (i.e., power) in response to perturbation. Patient-specific musculoskeletal models were simulated with experimental gait data from six TKA patients (baseline models). Muscle strength and ligament force parameter were reduced by up to 30% to simulate weak knee joint stabilizers (weak models). Two different muscle recruitment criteria were tested to examine whether altered muscle recruitment pattern can mask the influence of weakened stabilizers on the knee joint kinematics and kinetics. Level-walking knee joint kinematics and kinetics were calculated though force-dependent kinematic and inverse dynamic analyses. Bode analysis was then recruited to estimate the knee joint power in response to a simulated perturbation. Weak models resulted in larger anterior-posterior (A-P) displacement and internal-external (I-E) rotation compared to baseline (I-E: 18.4 ± 8.5 vs. 11.6 ± 5.7 (deg), A-P: 9.7 ± 5.6 vs. 5.5 ± 4.1 (mm)). Changes in muscle recruitment criterion however altered the results such that A-P and I-E were not notably different from baseline models. In response to the simulated perturbation, weak models versus baseline models generated a delayed power response with unbounded magnitudes. Perturbed power behavior of the knee remained unaltered regardless of the muscle recruitment criteria. In conclusion, impairment at the knee joint stabilizers may or may not lead to excessive joint motions but it notably affects the knee joint power in response to a perturbation. Whether perturbed knee joint power is associated with the patient-reported outcome requires further investigation.
Recommendation for the minimum number of steps to analyze when performing the uncontrolled manifold analysis on walking data.
Venue: Journal of biomechanics

The uncontrolled manifold (UCM) analysis quantifies the extent to which co-variation among a set of variables facilitates consistent performance by partitioning variance in those variables into two components then calculating their normalized difference (i.e., the synergy index). Although UCM-derived measures are thought to depend on the number of data points analyzed, the minimum number needed to reasonably approximate true values of these measures is unknown. For each of two performance variables related to mechanical stability of gait, we evaluated changes in UCM-derived measures when increasing the number of analyzed points, here steps. Fourteen older adults walked on a treadmill while motion capture tracked movement. For each subject, n steps (where n = 2-99) were randomly sampled from the first 100, then used to calculate UCM-derived variables. For each subject, variables were expressed as a percent of the subject-specific value with n = 100 and averaged across 50 simulations. For each n, 95% confidence intervals (CIs) were calculated from group data. The minimum number of steps to "reasonably approximate" a variables was defined as the value of n for which the lower CI was >90% of the value with n = 100. Regardless of performance variable, reasonable approximations of the synergy index were attained with n = 16 steps, whereas n = 50 steps were needed for each of the variance components However, the differences between using 16 steps and 50 steps were small. Collecting 15-20 steps is recommended for a reasonable approximation of the synergy indices considered herein, particularly when data collection is constrained to a limited number of steps.
A coupled framework of in situ and in silico analysis reveals the role of lateral force transmission in force production in volumetric muscle loss injuries.
Venue: Journal of biomechanics

Volumetric muscle loss injuries (VML) are challenging to treat because of the variability in wound location. Regenerative medicine offers promising alternative treatments, but there is little understanding of the correlation between magnitude of VML injuries and corresponding functional deficits that must be addressed. There is a need for a tool that can elucidate the relationship between VML injury and force loss, as well as the impact on specific mechanisms responsible for force production. The purpose of this study was to develop a novel coupled framework of in situ and in silico methods to more precisely understand the relationship between injury location and force production deficits. We created a three-dimensional finite-element model of the pennate latissimus dorsi (LD) muscle in the rat and validated the model experimentally. We found that the model's prediction (2.6 N/g Model I, 2.1 N/g Model V) compared favorably to in situ testing of isometric force generation of the injured rat LD muscle (2.8 ± 0.3 N/g Experimental I, 2.0 ± 0.2 N/g Experimental V). Further model analysis revealed that the contribution from lateral and longitudinal force transmission to the total force varied with injury location and led to a greater understanding of the mechanisms responsible for VML-related force deficits. In the future, the coupled computational and experimental framework can be used to inform development of preclinical VML injury models that better recapitulate the spectrum of VML injuries observed in affected patients, and the mechanistic insight can accelerate the creation of improved regenerative therapeutics for VML injuries.
Relation between the ankle joint angle and the maximum isometric force of the toe flexor muscles.
Venue: Journal of biomechanics

The purpose of this study was to investigate the relationships between the ankle joint angle and maximum isometric force of the toe flexor muscles. Toe flexor strength and electromyography activity of the foot muscles were measured in 12 healthy men at 6 different ankle joint angles with the knee joint at 90 deg in the sitting position. To measure the maximum isometric force of the toe flexor muscles, subjects exerted maximum force on a toe grip dynamometer while the activity levels of the intrinsic and extrinsic plantar muscles were measured. The relation between ankle joint angle and maximum isometric force of the toe flexor muscles was determined, and the isometric force exhibited a peak when the ankle joint was at 70-90 deg on average. From this optimal neutral position, the isometric force gradually decreased and reached its nadir in the plantar flexion position (i.e., 120 deg). The EMG activity of the abductor hallucis (intrinsic plantar muscle) and peroneus longus (extrinsic plantar muscle) did not differ at any ankle joint angles. The results of this study suggest that the force generation of toe flexor muscles is regulated at the ankle joint and that changes in the length-tension relations of the extrinsic plantar muscle could be a reason for the force-generating capacity at the metatarsophalangeal joint when the ankle joint angle is changed.
Including surrounding tissue improves ultrasound-based 3D mechanical characterization of abdominal aortic aneurysms.
Venue: Journal of biomechanics

In this study the influence of surrounding tissues including the presence of the spine on wall stress analysis and mechanical characterization of abdominal aortic aneurysms using ultrasound imaging has been investigated.



Geometries of 7 AAA patients and 11 healthy volunteers were acquired using 3-D ultrasound and converted to finite element based models. Model complexity of externally unsupported (aorta-only) models was complemented with inclusion of both soft tissue around the aorta and a spine support dorsal to the aorta. Computed 3-D motion of the aortic wall was verified by means of ultrasound speckle tracking. Resulting stress, strain, and estimated shear moduli were analyzed to quantify the effect of adding surrounding material supports.



An improved agreement was shown between the ultrasound measurements and the finite element tissue and spine models compared to the aorta-only models. Peak and 99-percentile Von Mises stress showed an overall decrease of 23-30%, while estimated shear modulus decreased with 12-20% after addition of the soft tissue. Shear strains in the aortic wall were higher in areas close to the spine compared to the anterior region.



Improving model complexity with surrounding tissue and spine showed a homogenization of wall stresses, reduction in homogeneity of shear strain at the posterior side of the AAA, and a decrease in estimated aortic wall shear modulus. Future research will focus on the importance of a patient-specific spine geometry and location.
Stiffness modulation of redundant musculoskeletal systems.
Venue: Journal of biomechanics

This work presents a framework for computing the limbs' stiffness using inverse methods that account for the musculoskeletal redundancy effects. The musculoskeletal task, joint and muscle stiffness are regulated by the central nervous system towards improving stability and interaction with the environment during movement. Many pathological conditions, such as Parkinson's disease, result in increased rigidity due to elevated muscle tone in antagonist muscle pairs, therefore the stiffness is an important quantity that can provide valuable information during the analysis phase. Musculoskeletal redundancy poses significant challenges in obtaining accurate stiffness results without introducing critical modeling assumptions. Currently, model-based estimation of stiffness relies on some objective criterion to deal with muscle redundancy, which, however, cannot be assumed to hold in every context. To alleviate this source of error, our approach explores the entire space of possible solutions that satisfy the action and the physiological muscle constraints. Using the notion of null space, the proposed framework rigorously accounts for the effect of muscle redundancy in the computation of the feasible stiffness characteristics. To confirm this, comprehensive case studies on hand movement and gait are provided, where the feasible endpoint and joint stiffness is evaluated. Notably, this process enables the estimation of stiffness distribution over the range of motion and aids in further investigation of factors affecting the capacity of the system to modulate its stiffness. Such knowledge can significantly improve modeling by providing a holistic overview of dynamic quantities related to the human musculoskeletal system, despite its inherent redundancy.
Hemodynamic analysis of a novel stent graft design with slit perforations in thoracic aortic aneurysm.
Venue: Journal of biomechanics

Thoracic endovascular aortic repair (TEVAR) has been introduced as a less invasive approach to the treatment of thoracic aortic aneurysm (TAA). However, the effectiveness of TEVAR in the treatment of TAA is often limited due to the complex anatomy of aortic arch. Flow preservation at the three supra-aortic branches further increases the overall technical difficulty. This study proposes a novel stent graft design with slit perforations that can positively alter the hemodynamics at the aortic arch while maintaining blood flow to supra-aortic branches. We carried out a computational fluid dynamic (CFD) analysis to evaluate flow characteristics near stented aortic arch in simplified TAA models, followed by in-vitro experiments using particle image velocimetry (PIV) in a mock circulatory loop. The hemodynamics result was studied in terms of time-averaged wall shear stress (TAWSS), oscillating shear index (OSI), and endothelial cell action potential (ECAP). The results showed that the stent graft with slit perforations can reduce the disturbed flow region considerably. Furthermore, the effect of the slits on flow preservation to the supra-aortic branches was simulated and compared with experimental results. The effectiveness of the stent graft with slit perforations in preserving flow to the branches was demonstrated by both simulated and experimental results. Low TAWSS and elevated ECAP were observed in the aortic arch aneurysm after the placement of the stent graft with slits, implying the potential of thrombus formation in the aneurysm. On the other hand, the effects of the stent grafts with full-slit design and half-slit design on the shear stress did not differ significantly. The present analysis indicated that not only could the stent graft with slit perforations shield the aneurysm from rupture, but also it resulted in a favorable environment for thrombus that can contribute to the shrinkage of the aneurysm.
Characterization and estimation of turbulence-related wall shear stress in patient-specific pulsatile blood flow.
Venue: Journal of biomechanics

Disturbed, turbulent-like blood flow promotes chaotic wall shear stress (WSS) environments, impairing essential endothelial functions and increasing the susceptibility and progression of vascular diseases. These flow characteristics are today frequently detected at various anatomical, lesion and intervention-related sites, while their role as a pathological determinant is less understood. To present-day, numerous WSS-based descriptors have been proposed to characterize the spatiotemporal nature of the WSS disturbances, however, without differentiation between physiological laminar oscillations and turbulence-related WSS (tWSS) fluctuations. Also, much attention has been focused on magnetic resonance (MR) WSS estimations, so far with limited success; promoting the need of a near-wall surrogate marker. In this study, a new approach is explored to characterize the tWSS, by taking advantage of the tensor characteristics of the fluctuating WSS correlations, providing both a magnitude and an anisotropy measure of the disturbances. These parameters were studied in two patient-specific coarctation models (sever and mild), using large eddy simulations, and correlated against near-wall reciprocal Reynolds stress parameters. Collectively, results showed distinct regions of differing tWSS characteristics, features which were sensitive to changes in flow conditions. Generally, the post-stenotic tWSS was governed by near axisymmetric fluctuations, findings that where not consistent with conventional WSS disturbance predictors. At the 2-3 mm wall-offset range, a strong linear correlation was found between tWSS magnitude and near-wall turbulence kinetic energy (TKE), in contrast to the anisotropy indices, suggesting that MR-measured TKE can be used to assess elevated tWSS regions while tWSS anisotropy estimates request well-resolved simulation methods.
An image-based kinematic model of the tibiotalar and subtalar joints and its application to gait analysis in children with Juvenile Idiopathic Arthritis.
Venue: Journal of biomechanics

In vivo estimates of tibiotalar and the subtalar joint kinematics can unveil unique information about gait biomechanics, especially in the presence of musculoskeletal disorders affecting the foot and ankle complex. Previous literature investigated the ankle kinematics on ex vivo data sets, but little has been reported for natural walking, and even less for pathological and juvenile populations. This paper proposes an MRI-based morphological fitting methodology for the personalised definition of the tibiotalar and the subtalar joint axes during gait, and investigated its application to characterise the ankle kinematics in twenty patients affected by Juvenile Idiopathic Arthritis (JIA). The estimated joint axes were in line with in vivo and ex vivo literature data and joint kinematics variation subsequent to inter-operator variability was in the order of 1°. The model allowed to investigate, for the first time in patients with JIA, the functional response to joint impairment. The joint kinematics highlighted changes over time that were consistent with changes in the patient's clinical pattern and notably varied from patient to patient. The heterogeneous and patient-specific nature of the effects of JIA was confirmed by the absence of a correlation between a semi-quantitative MRI-based impairment score and a variety of investigated joint kinematics indexes. In conclusion, this study showed the feasibility of using MRI and morphological fitting to identify the tibiotalar and subtalar joint axes in a non-invasive patient-specific manner. The proposed methodology represents an innovative and reliable approach to the analysis of the ankle joint kinematics in pathological juvenile populations.
Cervical spine morphology and ligament property variations: A finite element study of their influence on sagittal bending characteristics.
Venue: Journal of biomechanics

Cervical spine finite element models reported in biomechanical literature usually represent a static morphology. Not considering morphology as a model parameter limits the predictive capabilities for applications in personalized medicine, a growing trend in modern clinical practice. The objective of the study was to investigate the influence of variations in spinal morphology on the flexion-extension responses, utilizing mesh-morphing-based parametrization and metamodel-based sensitivity analysis. A C5-C6 segment was used as the baseline model. Variations of intervertebral disc height, facet joint slope, facet joint articular processes height, vertebral body anterior-posterior depth, and segment size were parametrized. In addition, material property variations of ligaments were considered for sensitivity analysis. The influence of these variations on vertebral rotation and forces in the ligaments were analyzed. The disc height, segmental size, and body depth were found to be the most influential (in the cited order) morphology variations; while among the ligament material property variations, capsular ligament and ligamentum flavum influenced vertebral rotation the most. Changes in disc height influenced forces in the posterior ligaments, indicating that changes in the anterior load-bearing column of the spine could have consequences on the posterior column. A method to identify influential morphology variations is presented in this work, which will help automation efforts in modeling to focus on variations that matter. This study underscores the importance of incorporating influential morphology parameters, easily obtained through computed tomography/magnetic resonance images, to better predict subject-specific biomechanical responses for applications in personalized medicine.
The effect of subscapularis muscle contraction on coaptation of anteroinferior glenohumeral ligament-labrum complex after Bankart repair.
Venue: Journal of biomechanics

Facilitation of healing is important for the anteroinferior glenohumeral ligament-labrum complex (AIGHL-LC) after Bankart repair in shoulder dislocation. The purpose of this study was to investigate the effect of subscapularis muscle loading on contact area and contact pressure between the subscapularis and AIGHL-LC and between the glenoid bone and the AIGHL-LC following Bankart repair. Twenty-two fresh-frozen cadaveric shoulders were used. They were attached to a shoulder-positioning device to which a compression force was applied. Loads applied to the supraspinatus, infraspinatus, and teres minor tendons were held constant. The loads applied to the subscapularis tendon were set at 0, 10, 20, and 30 Newton (N). Contact pressure and area between the subscapularis and the AIGHL-LC were measured with the arm at 4 rotational positions: 60° and 30° internal, neutral, and 30° external. After the Bankart lesion was created, the contact area and pressure between the AIGHL-LC and glenoid bone were measured while Bankart repair was performed with or without loading of the subscapularis. The contact area and pressures with 10, 20, and 30 N of subscapularis loadings were significantly greater than with 0 N of subscapularis loading at 60° internal rotation and 30° external rotation (P < .05). After Bankart repair, contact area and pressure with subscapularis loading between the AIGHL-LC and glenoid bone were significantly greater than without subscapularis loading (P < .01). We conclude that isometric contraction exercises of the subscapularis might facilitate healing of the AIGHL-LC after Bankart repair.
Reliability of ultrasound speckle tracking with singular value decomposition for quantifying displacement in the carpal tunnel.
Venue: Journal of biomechanics

Inhibited movement patterns of carpal tunnel structures have been found in carpal tunnel syndrome (CTS) patients. Motion analysis on ultrasound images allows us to non-invasively study the (relative) movement of carpal tunnel structures and recently a speckle tracking method using singular value decomposition (SVD) has been proposed to optimize this tracking. This study aims to assess the reliability of longitudinal speckle tracking with SVD in both healthy volunteers and patients with CTS. Images from sixteen healthy volunteers and twenty-two CTS patients were used. Ultrasound clips of the third superficial flexor tendon and surrounding subsynovial connective tissue (SSCT) were acquired during finger flexion-extension. A custom made tracking algorithm was used for the analysis. Intra-class correlation coefficients (ICCs) were calculated using a single measure, two-way random model with absolute agreement and Bland-Altman plots were added for graphical representation. ICC values varied between 0.73 and 0.95 in the control group and 0.66-0.98 in the CTS patients, with the majority of the results classified as good to excellent. Tendon tracking showed higher reliability values compared to the SSCT, but values between the control and CTS groups were comparable. Speckle tracking with SVD can reliably be used to analyze longitudinal movement of anatomical structures with different sizes and compositions within the context of the carpal tunnel in both a healthy as well as a pathological state. Based on these results, this technique also holds relevant potential for areas where ultrasound based dynamic imaging requires quantification of motion.