nils-herrmann/clean_scirepeval huggingface dataset:
Effect of chronic idiopathic low back pain on the kinetic gait characteristics in different foot masks.
Venue: Journal of biomechanics

Identification of kinetic variables in different masks of foot is important for the evaluation and treatment of chronic low back pain. The aim of this study was to investigate the effect of chronic idiopathic low back pain on kinetic variables of gait in different foot masks. 11 idiopathic chronic low back pain patients and 13 healthy matched controls participated in this study. Using Emed foot-scanner system, the ground reaction force and impulse were measured during barefoot normal walking. Then, the average footprints were divided into 10 masks using the Automask program and the data were extracted using Multimask Evaluation programs. The low back pain disability was measured by Quebec questionnaire. Our results revealed that the ground reaction force and impulse in medial and lateral midfoot and hallux masks of patients were significantly lower than controls. Furthermore, these patients demonstrated greater ground reaction force and impulse in 3-5th metatarsals mask than control group. There was a significant interaction between the low back pain and the foot masks factors. In conclusion, the ground reaction forces and impulses in different areas of foot are affected by low back pain. Therefore, the kinetic gait analysis should be considered as an appropriate tool in evaluation and prescribing proper treatment program in low back pain patients.
The mechanics of agonistic muscles.
Venue: Journal of biomechanics

In this study, we tested two assumptions that have been made in experimental studies on muscle mechanics: (i) that the torque-angle properties are similar among agonistic muscles crossing a joint, and (ii) that the sum of the torque capacity of individual muscles adds up to the torque capacity of the agonist group.



Maximum isometric torque measurements were made using a specifically designed animal knee extension dynamometer for the intact rabbit quadriceps muscles (n = 10) for knee angles between 60 and 120°. The nerve branches of the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) muscles were carefully dissected, and a custom made nerve cuff electrode was implanted on each branch. Knee extensor torques were measured for four maximal activation conditions at each knee angle: VL activation, VM activation, RF activation, and activation of all three muscles together.



With the exception of VL, the torque-angle relationships of the individual muscles did not have the shape of the torque-angle relationship obtained when all muscles were activated simultaneously. Furthermore, the maximum torque capacity obtained by adding the individual torque capacities of VL, VM and RF was approximately 20% higher than the torques produced when the three muscles were activated simultaneously.



These results bring into question our understanding of in-vivo muscle contraction and challenge assumptions that are sometimes made in human and animal muscle force analyses.
Comparison of NOCSAE head kinematics using the Hybrid III and EuroSID-2 necks.
Venue: Journal of biomechanics

Anthropomorphic test devices (ATDs) are designed for specific loading scenarios and possess uniquely designed individual components including the neck. The purpose of this study was to determine the influence of the neck surrogate on head kinematics. Inertial loads were generated using a pendulum system with an anthropomorphic head attached to a Hybrid III (HIII) or EuroSID-2 (ES-2) neck. The ATD head-neck assemblies were tested under extension, flexion, lateral bending, oblique extension, and oblique flexion at 3.4 m/s. Peak head kinematics were found to be statistically different with the ES-2 versus HIII neck under certain cases. For extension, the resultant peak linear acceleration (PLA) and resultant peak angular acceleration (PAA) were statistically higher with the ES-2 versus HIII neck. For flexion and lateral bending, there were no statistical differences in the resultant PLA based on neck selection although the resultant PAA was statistically higher with the ES-2 versus HIII neck. For oblique extension, the resultant PLA and PAA statistically increased with the ES-2 versus HIII neck. Furthermore, the acceleration components ax, αx, and αy were statistically higher with the ES-2 neck while ay showed no statistical difference due to neck selection. For oblique flexion, the resultant PLA and PAA were statistically higher with the ES-2 versus HIII neck. Additionally, the acceleration components ax, ay, αx, and αy were statistically higher with the ES-2 versus HIII neck. These findings indicate that for certain loading directions and acceleration components, head kinematics were influenced by the neck surrogate used.
Numerical simulation of aneurysmal haemodynamics with calibrated porous-medium models of flow-diverting stents.
Venue: Journal of biomechanics

Modelling flow-diverting (FD) stents as porous media (PM) markedly improves the efficiency of computational fluid dynamics (CFD) simulations in the study of intracranial aneurysm treatment. Nonetheless, the parameters of PM models adopted for simulations up until now were rarely calibrated to match the represented FD structure. We therefore sought to evaluate the PM parameters for a representative variety of commercially available stents, so characterising the flow-diversion behaviours of different FD devices on the market. We generated fully-resolved geometries for treatments using PED, Silk+, FRED, and dual PED stents. We then correspondingly derived the calibrated PM parameters-permeability (k) and inertial resistance factor (C2)-for each stent design from CFD simulations, to ensure the calibrated PM model has identical flow resistance to the FD stent it represents. With each of the calibrated PM models respectively deployed in two aneurysms, we studied the flow-diversion effects of these stent configurations. This work for the first time reported several sets of parameters for PM models, which is vital to address the current knowledge gap and rectify the errors in PM model simulations, thereby setting right the modelling protocol for future studies using PM models. The flow resistance parameters were strongly affected by porosity and effective thickness of the commercial stents, and thus accounted for in the PM models. Flow simulations using the PM stent models revealed differences in aneurysmal mass flowrate (MFR) and energy loss (EL) between various stent designs. This study improves the practicability of FD simulation by using calibrated PM models, providing an individualised method with improved simulation efficiency and accuracy.
Repetitive trunk loading leads to faster trunk movement in response to external perturbation.
Venue: Journal of biomechanics

The purpose of the present study was to examine trunk movement pattern responses to mechanical perturbation before and after two different repetitive trunk flexion-extension loading schemes. Spatial and temporal parameters were studied to understand the trunk recovery from an anteriorly directed perturbation. Eighteen male and female subjects (18-27 yrs) participated in active and passive trunk flexion-extension, performed seven days apart. Subjects performed 60 trunk flexion-extension repetitions in each condition. Subjects either volitionally moved their trunks (active condition) or relaxed while a dynamometer controlled the movements (passive condition). Trunk perturbations occurred before and immediately after two 30 repetition sessions. Initial responses included latency measures of trunk displacement and peak trunk velocity (VP). Temporal measures included perturbation onset to initial trunk movement (TD), movement initiation to VP (TMIPV), and perturbation onset to VP (TPPV). Recovery measures included peak recovery velocity (VPR), recovery time (TR), velocity slope (VS), and recovery slope (RS). Differences between loading sessions were present for TPPV (p < .05), TR (p < .05), and RS (p < .05). Overall, the results indicate repetitive loading leads to lower resistance to perturbation, but faster recovery from perturbation although no differences to active or passive repetitive loading was observed.
Modelling of the forces acting on the human stomatognathic system during dynamic symmetric incisal biting of foodstuffs.
Venue: Journal of biomechanics

A major stage in the preparation of a computational model of the human stomatognathic system is the determination of the values of the forces for the adopted loading configuration. In physiological conditions, food is a factor having a significant effect on the values of the loads acting on the stomatognathic system. Considering that the act of mastication is a complex process, this research undertook to determine the forces (bite forces, muscular forces and temporomandibular joint reaction forces) acting on the stomatognathic system during the dynamic symmetric incisal biting of selected foodstuffs. The investigations were divided into two stages: (1) experimental tests and (2) numerical simulations. In the first stage, classic force-displacement characteristic curves (Fi-Δh) were determined for the food while in the second stage, the curves were used as a dynamic stomatognathic system model load function. One of the most important results of this research is that the food characteristic in the form of a force-displacement function has been shown to have a significant effect not only on the values of the muscular forces and the temporomandibular joint reaction forces, but also on their curves during the dynamic loading of the stomatognathic system. The analysis of the results indicates that Fi-Δh has an effect on not only the (active and passive) forces, but also on other parameters, such as stress, deformation, displacement, and probably the rigidity of the muscles.
Assessment of vertebral wedge strength using cancellous textural properties derived from digital tomosynthesis and density properties from dual energy X-ray absorptiometry and high resolution computed tomography.
Venue: Journal of biomechanics

The purpose of this study was to examine the potential of digital tomosynthesis (DTS) derived cancellous bone textural measures to predict vertebral strength under conditions simulating a wedge fracture. 40 vertebral bodies (T6, T8, T11, and L3 levels) from 5 male and 5 female cadaveric donors were utilized. The specimens were scanned using dual energy X-ray absorptiometry (DXA) and high resolution computed tomography (HRCT) to obtain measures of bone mineral density (BMD) and content (BMC), and DTS to obtain measures of bone texture. Using a custom loading apparatus designed to deliver a nonuniform displacement resulting in a wedge deformity similar to those observed clinically, the specimens were loaded to fracture and their fracture strength was recorded. Mixed model regressions were used to determine the associations between wedge strength and DTS derived textural variables, alone and in the presence of BMD or BMC information. DTS derived fractal, lacunarity and mean intercept length variables correlated with wedge strength, and individually explained up to 53% variability. DTS derived textural variables, notably fractal dimension and lacunarity, contributed to multiple regression models of wedge strength independently from BMC and BMD. The model from a scan orientation transverse to the spine axis and in the anterior-posterior view resulted in highest explanatory capability (R2adj = 0.91), with a scan orientation parallel to the spine axis and in the lateral view offering an alternative (R2adj = 0.88). In conclusion, DTS can be used to examine cancellous texture relevant to vertebral wedge strength, and potentially complement BMD in assessment of vertebral fracture risk.
The effect of glenohumeral plane of elevation on supraspinatus subacromial proximity.
Venue: Journal of biomechanics

Shoulder pain is a common clinical problem affecting most individuals in their lifetime. Despite the high prevalence of rotator cuff pathology in these individuals, the pathogenesis of rotator cuff disease remains unclear. Position and motion related mechanisms of rotator cuff disease are often proposed, but poorly understood. The purpose of this study was to determine the impact of systematically altering glenohumeral plane on subacromial proximities across arm elevation as measures of tendon compression risk. Three-dimensional models of the humerus, scapula, coracoacromial ligament, and supraspinatus were reconstructed from MRIs in 20 subjects. Glenohumeral elevation was imposed on the humeral and supraspinatus tendon models for three glenohumeral planes, which were chosen to represent flexion, scapular plane abduction, and abduction based on average values from a previous study of asymptomatic individuals. Subacromial proximity was quantified as the minimum distance between the supraspinatus tendon and coracoacromial arch (acromion and coracoacromial ligament), the surface area of the supraspinatus tendon within 2 mm proximity to the coracoacromial arch, and the volume of intersection between the supraspinatus tendon and coracoacromial arch. The lowest modeled subacromial supraspinatus compression measures occurred during flexion at lower angles of elevation. This finding was consistent across all three measures of subacromial proximity. Knowledge of this range of reduced risk may be useful to inform future studies related to patient education and ergonomic design to prevent the development of shoulder pain and dysfunction.
Micropipette aspiration method for characterizing biological materials with surface energy.
Venue: Journal of biomechanics

Many soft biological tissues possess a considerable surface stress, which plays a significant role in their biophysical functions, but most previous methods for characterizing their mechanical properties have neglected the effects of surface stress. In this work, we investigate the micropipette aspiration method to measure the mechanical properties of soft tissues and cells with surface effects. The neo-Hookean constitutive model is adopted to describe the hyperelasticity of the measured biological material, and the surface effect is taken into account by the finite element method. It is found that when the pipette radius or aspiration length is comparable to the elastocapillary length, surface energy may distinctly alter the aspiration response. Generally, both the aspiration length and the bulk normal stress decrease with increasing surface energy, and thus neglecting the surface energy would lead to an overestimation of elastic modulus. Through dimensional analysis and numerical simulations, we provide an explicit relation between the imposed pressure and the aspiration length. This method can be applied to determine the mechanical properties of soft biological tissues and organs, e.g., livers, tumors and embryos.
The neutral posture of the cervical spine is not unique in human subjects.
Venue: Journal of biomechanics

Cervical spine injuries often happen in dynamic environments (e.g., sports and motor vehicle crashes) where individuals may be moving their head and neck immediately prior to impact. This motion may reposition the cervical vertebrae in a way that is dissimilar to the upright resting posture that is often used as the initial position in cadaveric studies of catastrophic neck injury. Therefore our aim was to compare the "neutral" cervical alignment measured using fluoroscopy of 11 human subjects while resting in a neutral posture and as their neck passed through neutral during the four combinations of active flexion and extension movements in both an upright and inverted posture. Muscle activation patterns were also measured unilaterally using surface and indwelling electromyography in 8 muscles and then compared between the different conditions. Overall, the head posture, cervical spine alignment and muscle activation levels were significantly different while moving compared to resting upright. Compared to the resting upright condition, average head postures were 6-13° more extended, average vertebral angles varied from 11° more extended to 10° more flexed, and average muscle activation levels varied from unchanged to 10% MVC more active, although the exact differences varied with both direction of motion and orientation. These findings are important for ex vivo testing where the head and neck are statically positioned prior to impact - often in an upright neutral posture with negligible muscle forces - and suggest that current cadaveric head-first impact tests may not reflect many dynamic injury environments.
Effect of guided bone regeneration on bone quality surrounding dental implants.
Venue: Journal of biomechanics

Bone quality as well as its quantity at the implant interface is responsible for determining stability of the implant system. The objective of this study is to examine the nanoindentation based elastic modulus (E) at different bone regions adjacent to titanium dental implants with guided bone regeneration (GBR) treated with DBM and BMP-2 during different post-implantation periods. Six adult male beagle dogs were used to create circumferential defects with buccal bone removal at each implantation site of mandibles. The implant systems were randomly assigned to only GBR (control), GBR with demineralized bone matrix (DBM), and GBR with DBM + recombinant human bone morphogenetic protein-2 (rhBMP-2) (BMP) groups. Three animals were sacrificed at each 4 and 8 weeks of post-implantation healing periods. Following buccolingual dissection, the E values were assessed at the defects (Defect), interfacial bone tissue adjacent to the implant (Interface), and pre-existing bone tissue away from the implant (Pre-existing). The E values of BMP group had significantly higher than control and DBM groups for interface and defect regions at 4 weeks of post-implantation period and for the defect region at 8 weeks (p < 0.043). DBM group had higher E values than control group only for the defect region at 4 weeks (p < 0.001). The current results indicate that treatment of rhBMP-2 with GBR accelerates bone tissue mineralization for longer healing period because the GBR likely facilitates a microenvironment to provide more metabolites with open space of the defect region surrounding the implant.
Three-dimensional temporomandibular joint muscle attachment morphometry and its impacts on musculoskeletal modeling.
Venue: Journal of biomechanics

In musculoskeletal models of the human temporomandibular joint (TMJ), muscles are typically represented by force vectors that connect approximate muscle origin and insertion centroids (centroid-to-centroid force vectors). This simplification assumes equivalent moment arms and muscle lengths for all fibers within a muscle even with complex geometry and may result in inaccurate estimations of muscle force and joint loading. The objectives of this study were to quantify the three-dimensional (3D) human TMJ muscle attachment morphometry and examine its impact on TMJ mechanics. 3D muscle attachment surfaces of temporalis, masseter, lateral pterygoid, and medial pterygoid muscles of human cadaveric heads were generated by co-registering measured attachment boundaries with underlying skull models created from cone-beam computerized tomography (CBCT) images. A bounding box technique was used to quantify 3D muscle attachment size, shape, location, and orientation. Musculoskeletal models of the mandible were then developed and validated to assess the impact of 3D muscle attachment morphometry on joint loading during jaw maximal open-close. The 3D morphometry revealed that muscle lengths and moment arms of temporalis and masseter muscles varied substantially among muscle fibers. The values calculated from the centroid-to-centroid model were significantly different from those calculated using the 'Distributed model', which considered crucial 3D muscle attachment morphometry. Consequently, joint loading was underestimated by more than 50% in the centroid-to-centroid model. Therefore, it is necessary to consider 3D muscle attachment morphometry, especially for muscles with broad attachments, in TMJ musculoskeletal models to precisely quantify the joint mechanical environment critical for understanding TMJ function and mechanobiology.
Functional deficits may be explained by plantarflexor remodeling following Achilles tendon rupture repair: Preliminary findings.
Venue: Journal of biomechanics

Achilles tendon ruptures are common injuries that often lead to long-term functional deficits. Despite the prevalence of these injuries, the mechanism responsible for limited function has not yet been established. Therefore, the purpose of this study was to present preliminary findings that support a hypothesis that skeletal muscle remodeling is the driving factor of poor outcomes in some patients. Biomechanical and ultrasonography assessments were performed on a patient that presented with poor functional outcomes 2.5 years after a surgically-repaired acute Achilles tendon rupture. Single-leg heel raise height was decreased by 75% in the affected limb (3.0 cm compared to 11.9 cm) while walking mechanics showed no deficits. Ultrasonography revealed that the affected medial gastrocnemius muscle was less thick and had shorter, more pennate fascicles compared to the unaffected limb. A simple computational model of a maximal-effort plantarflexion contraction was employed to test the implications of changes in muscle architecture on single-leg heel raise function. Subject-specific measurements of fascicle length and pennation were input into the model, which supported these architectural parameters as being drivers of heel raise function. These preliminary findings support the hypothesis that an Achilles tendon rupture elicits changes in skeletal muscle architecture, which reduces the amount of work and power the joint can generate. This multidisciplinary framework of biomechanical, imaging, and computational modeling provides a unique platform for studying the complex interactions between structure and function in patients recovering from Achilles tendon injuries.
Individual muscle contributions to tibiofemoral compressive articular loading during walking, running and sidestepping.
Venue: Journal of biomechanics

The tibiofemoral joint (TFJ) experiences large compressive articular contact loads during activities of daily living, caused by inertial, ligamentous, capsular, and most significantly musculotendon loads. Comparisons of relative contributions of individual muscles to TFJ contact loading between walking and sporting movements have not been previously examined. The purpose of this study was to determine relative contributions of individual lower-limb muscles to compressive articular loading of the medial and lateral TFJ during walking, running, and sidestepping. The medial and lateral compartments of the TFJ were loaded by a combination of medial and lateral muscles. During all gait tasks, the primary muscles loading the medial and lateral TFJ were the vastus medialis (VM) and vastus lateralis (VL) respectively during weight acceptance, while typically the medial gastrocnemii (MG) and lateral gastrocnemii (LG) dominated medial and lateral TFJ loading respectively during midstance and push off. Generally, the contribution of the quadriceps muscles were higher in running compared to walking, whereas gastrocnemii contributions were higher in walking compared to running. When comparing running and sidestepping, contributions to medial TFJ contact loading were generally higher during sidestepping while contributions to lateral TFJ contact loading were generally lower. These results suggests that after orthopaedic procedures, the VM, VL, MG and LG should be of particular rehabilitation focus to restore TFJ stability during dynamic gait tasks.