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AbstractThe meniscus plays a crucial role in the proper functioning of the knee joint, and when it becomes damaged, partial removal or replacement is necessary to restore proper function. Understanding the stress and deformation of the meniscus during various movements is essential for developing effective materials for meniscus repair. However, accurately estimating the contact mechanics of the knee joint can be challenging due to its complex shape and the dynamic changes it undergoes during movement. To address this issue, the open-source software SCONE can be used to establish a kinematics model that monitors the different states of the knee joint during human motion and obtains relevant gait kinematics data. To evaluate the stress and deformation of the meniscus during normal human movement, values of different states in the movement gait can be selected for finite element analysis (FEA) of the knee joint. This analysis enables researchers to assess changes in the meniscus. To evaluate meniscus damage, it is necessary to obtain changes in its mechanical behavior during abnormal movements. This information can serve as a reference for designing and optimizing the mechanical performance of materials used in meniscus repair and replacement. [ABSTRACT FROM AUTHOR]

AbstractThis study investigated whether modes of variance in trial-to-trial whole-body kinematic variability identified by principal component analysis (PCA) were consistent across data pre-processing conditions generated from a common dataset. Comparisons made included 1) when trajectory data was expressed in a global vs. local reference frame; 2) when the number of landmarks used to represent whole-body motion differed, and; 3) whether input trajectory data were normalized to participant stature. Varying data pre-processing conditions prior to PCA does not bias the total variance identified. However, it can influence how modes of variance are dispersed across PCs, which in turn, can influence interpretation. [ABSTRACT FROM AUTHOR]

Kinematic reconstruction of lower-limb movements using electroencephalography (EEG) has been used in several rehabilitation systems. However, the nonlinear relationship between neural activity and limb movement may challenge decoders in real-time Brain-Computer Interface (BCI) applications. This paper proposes a nonlinear neural decoder using an Unscented Kalman Filter (UKF) to infer lower-limb kinematics from EEG signals during pedaling. The results demonstrated maximum decoding accuracy using slow cortical potentials in the delta band (0.1-4 Hz) of 0.33 for Pearson's r-value and 8 for the signal-to-noise ratio (SNR). This leaves an open door to the development of closed-loop EEG-based BCI systems for kinematic monitoring during pedaling rehabilitation tasks. [ABSTRACT FROM AUTHOR]

Despite availability of in vivo knee loads and kinematics data, conventional load- and displacement-controlled configurations still can't accurately predict tibiofemoral loads from kinematics or vice versa. We propose a combined load- and displacement-control method for joint-level simulations of the knee to reliably reproduce in vivo contact mechanics. Prediction errors of the new approach were compared to those of conventional purely load- or displacement-controlled models using in vivo implant loads and kinematics for multiple subjects and activities (CAMS-Knee dataset). Our method reproduced both loads and kinematics more closely than conventional models and thus demonstrates clear advantages for investigating tibiofemoral contact or wear. [ABSTRACT FROM AUTHOR]

AbstractIndustrial back support exoskeletons are a promising solution to alleviate lumbar musculoskeletal strain. Due to the complexity of spinal loading, evaluation of EMG data alone has been considered insufficient to assess their support effects, and complementary kinematic and dynamic data are required. However, the acquisition of marker-based kinematics is challenging with exoskeletons, as anatomical reference points, particularly on the pelvis, are occluded by exoskeleton structures. The aim of this study was therefore to develop and validate a method to reliably reconstruct the occluded pelvic markers. The movement data of six subjects, for whom pelvic markers could be placed while wearing an exoskeleton, were used to test the reconstructions and compare them to anatomical landmarks during lifting, holding and walking. Two separate approaches were used for the reconstruction. One used a reference coordinate system based on only exoskeleton markers (EXO), as has been suggested in the literature, while our proposed method adds a technical marker in the lumbar region (LUMB) to compensate for any shifting between exoskeleton and pelvis. Reconstruction with EXO yielded on average an absolute linear deviation of 54 mm ± 16 mm (mean ± 1SD) compared to anatomical markers. The additional marker in LUMB reduced mean deviations to 14 mm ± 7 mm (mean ± 1SD). Both methods were compared to reference values from the literature for expected variances due to marker placement and soft tissue artifacts. For LUMB 99% of reconstructions were within the defined threshold of 24 mm ±9 mm while for EXO 91% were outside. [ABSTRACT FROM AUTHOR]

Calculated intersegmental moments are commonly used in analyzing throwing movements. The inverse dynamics (ID) results can vary due to the chosen set of body segment inertia parameters (BSIP). A multitude of methods to determine BSIP sets are available. The purpose of this study was to clarify the influence of different estimation methods on the BSIPs and the respective impact on the ID results in javelin throwing. Movement kinematics were recorded for ten male javelin throwers. Six different methods were used to estimate BSIP sets for the upper extremities of each thrower. Subsequently, ID results were obtained for each thrower and BSIP set. Results show variations between 8% and 120% between the BSIP sets, and maximum intersegmental moments varied between 6% and 21%, respectively. Joint-specific variations of intersegmental moments were observed as well as movement-specific variations within a joint related to the different BSIP sets. Furthermore, the influence of BSIP sets appears to be subject-specific as well, with observed variations between 9% and 18% – some athletes are better represented by the chosen methods than others. Hence, our study results suggest that the method to determine BSIP sets needs to be carefully chosen for calculating joint kinetics in throwing movements. [ABSTRACT FROM AUTHOR]

Ligament properties in the literature are variable, yet scarce, but needed to calibrate computational models for spine clinical research applications. A comparison of ligament stiffness properties and their effect on the kinematic behavior of a thoracic functional spinal unit (FSU) is examined in this paper. Six unique ligament property sets were utilized within a volumetric T7–T8 finite element (FE) model developed using computer-aided design (CAD) spinal geometry. A 7.5 Nm moment was applied along three anatomical planes both with and without costovertebral (CV) joints present. Range of Motion (RoM) was assessed for each property set and compared to published experimental data. Intact and serial ligament removal procedures were implemented in accordance with experimental protocol. The variance in both kinematic behavior and comparability with experimental data among property sets emphasizes the role nonlinear characterization plays in determining proper kinematic behavior in spinal FE models. Additionally, a decrease in RoM variation among property sets was exhibited when the model setup incorporated the CV joint. With proper assessment of the source and size of each ligament, the material properties considered here could be expanded and justified for implementation into thoracic spine clinical studies. [ABSTRACT FROM AUTHOR]

Abstract Total knee arthroplasty (TKA) is an end-stage treatment for knee osteoarthritis that relieves pain and loss of mobility, but patient satisfaction and revision rates require improvement. One cause for TKA revision is joint instability, which may be due to improper ligament balancing. A better understanding of the relationship between prosthesis design, alignment, and ligament engagement is necessary to improve component designs and surgical techniques to achieve better outcomes. We investigated the biomechanical effects of ligament model complexity and ligament wrapping during laxity tests using a virtual joint motion simulator. There was little difference in kinematics due to ligament complexity or ligament wrapping. [ABSTRACT FROM AUTHOR]

This work presents Motion Envelopes (ME), a simple method to estimate the missing longitudinal rotations of minimal stick figures, which is based on the spatial-temporal surface traced by line segments that connect contiguous pairs of joints. We validate ME by analyzing the gait patterns of 6 healthy subjects, comprising a total of 18 gait cycles. A strong correlation between experimental and estimated data was obtained for lower limbs and upper arms, indicating that ME can predict their longitudinal orientation in normal gait, hence, ME can be used to complement the kinematic information of stick figures whenever it is incomplete. [ABSTRACT FROM AUTHOR]

Accurate in vivo measurement of finger joint kinematics is important for evaluation of treatment methods, implant designs, and for the development and validation of computer models of the hand. The main objective of this project was to develop a standardized finger kinematic measurement system employing electromagnetic (EM) tracking to measure in vivo finger motion pathways. A landmark digitization protocol was developed and used in vivo, in a biomechanical study using EM trackers secured to the finger segments. In vivo results for finger flexion/extension showed no significant differences between EM and goniometer results, 5°±3°; p = 0.735. [ABSTRACT FROM AUTHOR]

Morphing can be used to alter human body models (HBMs) to represent a diverse population of occupants in car crashes. The mid-sized male SAFER HBM v9 was parametrically morphed to match 22 Post Mortem Human Subjects, loaded in different configurations. Kinetics and kinematics were compared for the morphed and baseline HBMs. In frontal impacts, the morphed HBMs correlated closer with the kinematics of obese subjects, but lower to small females. In lateral impacts HBM responses were too stiff. This study outlines a necessary evaluation of all HBMs that should be morphed to represent the diverse population in vehicle safety evaluations. [ABSTRACT FROM AUTHOR]

Various neurological and musculoskeletal disorders can induce pathologic toe walking and lead to changes in foot kinematics. In this study, we analyzed the differences in foot kinematics between toe walking and heel-toe walking (HW) in able-bodied individuals. Twenty young healthy adults performed three gaits: HW, comfortable-height toe walking (CTW), and maximum-height toe walking (MTW). Oxford Foot Model was used for gait analysis. Toe walking showed increase of forefoot plantarflexion and hindfoot internal rotation compared to HW. Thus, our results may help distinguish the pathologic mechanism of the equinus gait in various disorders from the kinematic change of toe walking itself. [ABSTRACT FROM AUTHOR]

We developed and validated a multi-segment foot and ankle model for human walking and running. The model has 6-segments, and 7 degrees of freedom; motion between foot segments were constrained with a single oblique axis to enable triplanar motion [Joint Constrained (JC) model]. The accuracy of the JC model and that of a conventional model using a 6 degrees of freedom approach were assessed by comparison to segment motion determined with biplanar videoradiography. Compared to the 6-DoF model, our JC model demonstrated significantly smaller RMS differences [JC: 2.19° (1.43–2.73); 6-DoF: 3.25° (1.37–5.89)] across walking and running. The JC model is thus capable of more accurate musculoskeletal analyses and is also well suited for predictive simulations. [ABSTRACT FROM AUTHOR]

Marker-based clinical gait analysis and multi-segment foot models (MSFM) have been successfully used for the diagnosis and clinical management of various lower limb disorders. The accuracy and validity of the kinematics measured depend on the design of the model, as well as on the adherence to its inherent rigid body assumption. This study applies a Monte-Carlo based global sensitivity analysis to evaluate the efficacy of using 'rigid body error ( σ RBE )' in quantifying the rigidity of a MSFM marker-cluster. A regression model is proposed. It is concluded that σ RBE is effective in quantifying rigidity. [ABSTRACT FROM AUTHOR]

Estimating the motion between two bones is crucial for understanding their biomechanical function. The vertebral column is particularly challenging because the vertebrae articulate at more than one surface. This paper proposes a method to estimate 3D motion between two avian vertebrae, by bones surface reconstruction and contact modeling. The neck of birds was selected as a case study because it is a functionally highly versatile structure combining dexterity and strength. As such, it has great potential to serve as a source for bioinspired design, for robotic manipulators for instance. First, 3D models of the vertebrae are obtained by computed tomography (CT). Next, joint surfaces of contact are approximated with polynomial surfaces, and a system of equations derived from contact modeling between surfaces is established. A constrained optimization problem is defined in order to find the best position of the vertebrae for a set of given orientations in space. As a result, the possible intervertebral range of motion is estimated. [ABSTRACT FROM AUTHOR]

The effects of robotic-assisted gait training on upper and lower body strategy during gait in diplegic children with Cerebral Palsy (CP) were quantified using summary parameters (Upper Body Profile Score (UBPS) and Gait Profile Score (GPS)). Firstly, the upper body strategy during gait was assessed in 73 children with CP and 15 healthy children (Control Group: CG): patients with CP exhibited higher values of most of the summary parameters of the upper body position than the CG. Then, the effects of a robotic-assisted gait training in a sub-group of 35 children by means of UBPS were evaluated. After robotic-assisted gait training program, no significant differences as for the summary parameters (UBPS and GPS). However, considering the specific variables scores, significant improvements are displayed as for the upper body parameter on the sagittal plane (Upper Body Ant/Pst index) and the lower limbs, in particular pelvis (Pelvic Ant/Pst and Pelvic Int/Ext indices) and as for walking velocity. A sort of reorganization of full-body kinematics, especially at upper body and proximal level (pelvis) seems to appear, with a new gait approach, characterised by a better strategy of the upper body associated with a significant improvement of the pelvis movement. [ABSTRACT FROM AUTHOR]

Advanced SSAs (e.g., the Mark III (MKIII)) were designed to increase mobility by eliminating the volume change associated with bending joints by using constant-volume rigid components with bearings connecting these components. Even with these changes, there are added torques required by the operator to drive the motion, which increases the energy expenditure with respect to unsuited motion. Part of the added effort stems from the mass and inertia of the suit, as well as frictional resistances to motion. This research considers the relationship between joint torques that an operator must generate and the resulting flexion/extension of the hip bearing assembly. A computational dynamics model of the MKIII inclusive of inertial and bearing friction properties was created and sensitivities of the model to input parameters (e.g., applied force, direction of gravity, bearing friction magnitude, knee angle) were investigated. The model was configured to match previously collected benchtop experimental suit data without a human that was externally forced. The model captured the hysteretic behaviour and estimated about 80% of the mean hip angle range as compared to the experimental data. Decreasing bearing resistance increased alignment with the experimental data. The torque due to inertia and friction each had periods where they dominated the total torque, supporting the importance of minimizing both mass and bearing friction. The present effort also highlighted how external forces and boundary conditions affected peak hip flexion/extension. Future efforts can use these types of dynamics models to examine motions driven internally by a person to achieve specific motions. [ABSTRACT FROM AUTHOR]

Videogrammetry is commonly used to record upper limb motions. However, it cannot track the glenohumeral joint center (GH). GH is required to reconstruct upper limb motions. Therefore, it is often estimated by separately measuring scapular motions using scapular kinematics measurements devices (SKMD). Applications of SKMD are neither straightforward nor always noninvasive. Therefore, this work investigates the feasibility of an alternative method to estimate GH from videogrammetry using a CT/MRI image of subject's glenohumeral joint and without requiring SKMD. In order to evaluate the method's accuracy, its GH estimations were compared to reference GH trajectories. The method was also applied to estimate scapular configurations and reconstruct an abduction motion measured by videogrammetry. The accuracy of GH estimations were within 5 mm, and the reconstructed motion was in good agreement with reported in vivo measurements. [ABSTRACT FROM AUTHOR]

Marker-based motion capture presents the problem of gaps, which are traditionally processed using motion capture software, requiring intensive manual input. We propose and study an automated method of gap-filling that uses inverse kinematics (IK) to close the loop of an iterative process to minimize error, while nearly eliminating user input. Comparing our method to manual gap-filling, we observe a 21% reduction in the worst-case gap-filling error (p < 0.05), and an 80% reduction in completion time (p < 0.01). Our contribution encompasses the release of an open-source repository of the method and interaction with OpenSim. [ABSTRACT FROM AUTHOR]

Subject-specific musculoskeletal model use in clinical settings is limited due to development-associated time and effort burdens together with potential medical imaging unavailability. As an alternative, this study investigated consistency in estimating longitudinal changes in joint contact forces (JCF) between scaled generic and subject-specific models. For 11 children, joint kinematics and JCF were calculated using subject-specific and scaled generic models. JCF changes estimated by both models were strongly correlated for the hip and knee although JCF estimates varied between models. Findings suggest that within specified limits of accuracy, scaled generic models are sensitive enough to detect JCF changes consistent with subject-specific models. [ABSTRACT FROM AUTHOR]

A major source of error in reliability of gait analysis arises from the palpation of anatomical landmarks (ALs). The purpose of this study was to investigate whether less reliance on manually identifying ALs could improve inter-assessor reliability of joint kinematics compared to two anatomical models. It was hypothesised that the Strathclyde functional cluster model (SFCM), in which the hip, knee and ankle joint centres and knee and ankle flexion axes were determined by functional methods, would obtain greater inter-assessor reliability. Ten able-bodied participants and seven assessors were recruited. Each participant completed three trials conducted by different assessors on non-consecutive days. Agreement and inter-assessor reliability between the models were compared and analysed, whilst factor effects of assessor experience and body mass index (BMI) were investigated. The SFCM obtained excellent agreement with anatomical models for all sagittal angles and hip ab/adduction angle, and it showed slightly higher inter-assessor reliability with smaller variations in the knee and ankle. The assessor experience was not a significant factor, but the BMI had a significant effect on the inter-assessor reliability. The results demonstrate that the SFCM may be more beneficial for less experienced assessors. [ABSTRACT FROM AUTHOR]

Populations with lower extremity muscle weakness have difficulty performing the sit-to-stand (STS) transfer. The degree of weakness that can be tolerated before compromising the ability to perform this task is unknown. Using dynamic simulations, we investigated the effects of weakness before changes in kinematics/kinetics would be required. Lower extremity muscles were weakened globally and individually and muscle forces were re-estimated as the model tracked original task kinematics/kinetics. The STS transfer was sensitive to quadriceps and plantarflexor weakness, suggesting that strengthening these muscles or changing kinematics are essential for populations who have difficulty rising from a chair independently. [ABSTRACT FROM AUTHOR]

Despite recent advances in algorithms for estimating muscle activities, static optimization remains the most used. Static optimization estimates muscle activations required to obtain a particular set of estimated kinematics. Although fast, static optimization may require considerable time for long trials. Improvements have been proposed in the past, but the current implementations are either accurate and slow (such as the most traditional implementation) or fast but less accurate (such as the linearized at maximal activations method used by OpenSim). Two innovative algorithms are proposed to improve both optimization time and accuracy of the static optimization. The first, designed to be fast, linearizes the constraint—i.e., constructing a constant constraint Jacobian—at the activations of the previous frame. The second, designed to be as accurate as possible, approaches the constraint Jacobian by cubic splines. Their performance and accuracy are compared to the traditional and OpenSim implementations. The linearized method performed as fast as the OpenSim implementation and was more accurate (0.3% of RMSE versus 5.9%). The spline method had excellent accuracy (0.1% of RMSE), but was 2X slower than the linearized approaches. Nevertheless, it was 100X faster than the traditional implementation. Our linearized method is therefore recommended when fast computation is needed, such as real-time applications, while the spline method is recommended otherwise. [ABSTRACT FROM AUTHOR]

The objective of this study was to develop a probabilistic representation of the hip capsule, which is calibrated to experimental capsular torque-rotation behavior and captures the observed variability for use in population-based studies. A finite element model of the hip capsule was developed with structures composed of a fiber-reinforced membrane, represented by 2D quadrilateral elements embedded with tension-only non-linear spring. An average capsule representation was developed by calibrating ligament properties (linear stiffness, reference strain) so that torque-rotation behavior matched mean cadaveric data. A probabilistic capsule was produced by determining the ligament property variability which represented ±2 SD measured in the experiment. Differences between experimental and model kinematics across all positions had RMS error of 4.7°. Output bounds from the optimized probabilistic capsule representation were consistent with ±2 SD of experimental data; the overall RMS error was 5.1°. This model can be employed in population-based finite element studies of THA to assess mechanics in realistic scenarios considering implant design, as well as surgical and patient factors. [ABSTRACT FROM AUTHOR]

Joint-level rigid body dynamics simulations, when coupled with tissue-level finite element analyses, can simultaneously provide movement and tissue deformation metrics to understand mechanical interactions within the joint on a multi-scale level. In this study, a co-simulation workflow of a joint-level rigid body model that predicts the relative motion as a function of the non-linear cartilage response predicted by a non-linear implicit finite element solver is presented. Predictions are compared to in-vitro measurements (The Open Knee(s) project) in terms of the mean error and level-of-agreement: pressureerror = 0.46 MPa (level-of-agreement, −0.23 – 1.1 MPa); areaerror = −89 mm2 (level-of-agreement, −280 – 98 mm2) and contact forceerror = 93 N (level-of-agreement, 7.8 – 180 N). The automated co-simulation control algorithm enables multiscale coupling between joint and tissue-level models with real-time two-way communication as opposed to the traditional feed-forward approach of multi-scale models. [ABSTRACT FROM AUTHOR]

Most of musculoskeletal models (MSKM) estimate the tibiofemoral joint reaction load at a single point or do not support large lower-limb ranges. This study aimed to adapt a generic MSKM that allows large knee and hip flexions to compute medial and lateral tibiofemoral contact forces (TFCF) during gait and squat tasks. The updated model includes medial and lateral knee compartment geometries that allow computing the vertical TFCF. The updated MSKM does not affect kinematics and kinetics outputs in both of the tasks, and the sum of the medial and lateral TFCF was equivalent to the net TFCF of the original MSKM. [ABSTRACT FROM AUTHOR]

Lumbar total disc arthroplasty (TDA) is an attractive option for the treatment of spinal disorders. However, post-operative complications may cause revision surgery. In this study, an in-depth biomechanical analysis was performed to test how sensitive post-operative spinal responses in sagittal bending were to design parameters of a widely used ball-in-socket TDA design. Our simulation results revealed that lowering the intervertebral distraction, posteriorly positioning the implant, or decreasing the radius of curvature of the metal-on-polyethylene bearing surface could result in spinal responses which better matched normal spinal kinematics, but deviated further from the normal spinal tissue load-sharing pattern. [ABSTRACT FROM AUTHOR]

Compared to adults, it has been documented that children are at elevated risk for concussion, repeated concussions, and experience longer recovery times. What is unknown, is whether the developing brain may be injured at differing strain levels. This study examined peak and cumulative brain strain from 20 cases of concussion in both young children and adults using physical reconstructions and finite element modelling of the brain response to impacts. The child group showed lower impact kinematics as well as strain metrics. Results suggest children may suffer concussive injuries with lower brain strains compared to adults. [ABSTRACT FROM AUTHOR]

The location of the terminal hinge axis of the temporomandibular joint is still a very wide-spread procedure in dentistry in order to replicate the movement in various articulator devices. Especially pantographic methods are claimed to provide accurate measurements and, additionally, are seen to be able to separate a pure rotation of the joint from a movement with an arbitrary combined shift and rotation. In the latter application, these methods were used in a lot of studies as a reference standard. The aim of this study was to analyze, whether common pantographic methods in general are able to distinguish between a pure rotation and a movement with rotational and translational portions. The mathematical proof of this analysis was done with theoretical kinematic considerations and compared with computer simulations. The results show for the first time that there exist combinations of rotational and translational movements of the temporomandibular joint which cannot be separated from pure rotational movements using actual pantographic methods. Even more, the consequence is a shifted location of the (combined) finite center (axis) of rotation in comparison to the true center (axis) of rotation: in case of a translational portion of only 1 mm, this is a displacement of around ±6 mm and, in case of 2 mm translation, a displacement of ±12 mm. This finding necessitates a critical reinterpretation of former studies using pantographic methods as a reference standard. Further, under some circumstances it may also affect the applicability of articulator concepts and the interpretation of functional signs. [ABSTRACT FROM AUTHOR]

In a highly autonomous vehicle (HAV), the rotatable seat is likely to be designed to facilitate ease of communication between the occupants. We hypothesize that the protective effects of current restraint systems vary among different seating configurations and that by using the rotational seat to alter the occupant's orientation in accordance with the direction of impact, occupants will be better protected. Moreover, in HAVs, it's likely that an imminent impact could be detected at a time of 200 ms, or even longer, prior to the initial contact. The availability of this additional time could be used strategically to actively position the occupants into a safer position for impact. Finite element simulations were performed using the THUMS model to test the hypothesis. The simulation results indicated that during a frontal impact, the backward-facing occupant is safer than occupants in other seating orientations. Moreover, 200 ms is sufficient to rotate the occupant by ±45° and ±90° without introducing additional injuries. Finally, the timing of the post-rotation impact also plays a role in injury risk of the rear-facing impact. Further studies are needed to optimize the rotating seat parameters in order to maintain occupant posture and improve crash safety in HAVs. [ABSTRACT FROM AUTHOR]

Medical images are not typically included in protocol of motion laboratories. Thus, accurate scaling of musculoskeletal models from optoelectronic data are important for any biomechanical analysis. The aim of the current study was to identify a scaling method based on optoelectronic data, inspired from literature, which could offer the best trade-off between accurate geometrical parameters (segment lengths, orientation of joint axes, marker coordinates) and consistent inverse kinematics outputs (kinematic error, joint angles). The methods were applied on 26 subjects and assessed with medical imagery building EOS-based models, considered as a reference. The main contribution of this paper is to show that the marker-based scaling followed by an optimisation of orientation joint axes and markers local coordinates, gives the most consistent scaling and joint angles with EOS-based models. Thus, when a non-invasive mean with an optoelectronic system is considered, a marker-based scaling is preliminary needed to get accurate segment lengths and to optimise joint axes and marker local coordinates to reduce kinematic errors. AJC Ankle joint centre CKE cumulative kinematic error DoF degree of freedom EB EOS-based HB height-based HJC hip joint centre KJC knee joint centre MB marker-based MSM musculoskeletal models SPM statistical parametric mapping STA soft tissue artifact EBa.m∗ EOS-based with optimised joint axes, and all model markers coordinates MBa.m∗ marker-based with optimised joint axes, and all model markers coordinates MBl.a.m marker-based with optimised segment lengths, joint axes, and selected model markers coordinates ASIS anterior superior illiac spine PSIS posterior superior illiac spine [ABSTRACT FROM AUTHOR]

Background: Closely approximating the functional flexion-extension (FE) axis of the tibiofemoral joint in 3D models of the femur is important when computing joint motions which are physiologic. The objectives were to 1) develop methods to approximate the functional FE axis based on fitting circles, a tapered cylinder, and spheres to the posterior condyles, 2) determine the repeatability and reproducibility of each method, and 3) determine limits of agreement between pairs of axes. Methods: For each method, the respective axis was determined in forty 3D bone models of the distal femur. Varus-valgus angles and internal-external axial angles were computed relative to standard planes. Results: Repeatability and reproducibility were comparable for the tapered cylinder-based and sphere-based methods and better than that for the circle-based method. Limits of agreement were tightest when comparing the sphere-based and tapered cylinder-based axes. However, limits of agreement for the internal-external axial angle were wide at +3.6° to −3.9° whereas limits of agreement were tighter at +1.4° to −0.7° for the varus-valgus angle. Conclusion: The tapered cylinder-based and sphere-based methods offer advantages of better repeatability and reproducibility over the circle-based method. However, the sphere-based and tapered cylinder-based axes are not interchangeable owing to wide limits of agreement for the internal-external axial angle. The tapered cylinder-based axis is preferred intuitively over the sphere-based axis because the spheres require fitting in both the sagittal and coronal planes whereas the tapered cylinder requires fitting in the sagittal plane only which is the plane of motion in flexion-extension. [ABSTRACT FROM AUTHOR]

The study presents a screening method used to identify the influential parameters of a lower limb model including ligaments, at low numerical cost. Concerning multibody kinematics optimisation, the ligament parameters (isometric length) were found the most influential ones in a previous study. The screening method tested if they remain influential with minimised length variations. The most important parameters for tibiofemoral kinematics were the skin markers, segment lengths and joint parameters, including two ligaments. This was confirmed by a quantitative sensitivity analysis. The screening method has the potential to be used as a stand-alone procedure for a sensitivity analysis. [ABSTRACT FROM AUTHOR]

Statistical shape models (SSM) of bony surfaces have been widely proposed in orthopedics, especially for anatomical bone modeling, joint kinematic analysis, staging of morphological abnormality, and pre- and intra-operative shape reconstruction. In the SSM computation, reference shape selection, shape registration and point correspondence computation are fundamental aspects determining the quality (generality, specificity and compactness) of the SSM. Such procedures can be made critical by the presence of large morphological dissimilarities within the surfaces, not only because of anthropometrical variability but also mainly due to pathological abnormalities. In this work, we proposed a SW pipeline for SSM construction based on pair-wise (PW) shape registration, which requires the a-priori selection of the reference shape, and on a custom iterative point correspondence algorithm. We addressed large morphological deformations in five different bony surface sets, namely proximal femur, distal femur, patella, proximal fibula and proximal tibia, extracted from a retrospective patient dataset. The technique was compared to a method from the literature, based on group-wise (GW) shape registration. As a main finding, the proposed technique provided generalization and specificity median errors, for all the five bony regions, lower than 2 mm. The comparative analysis provided basically similar results. Particularly, for the distal femur that was the shape affected by the largest pathological deformations, the differences in generalization, specificity and compactness were lower than 0.5 mm, 0.5 mm, and 1%, respectively. We can argue the proposed pipeline, along with the robust correspondence algorithm, is able to compute high-quality SSM of bony shapes, even affected by large morphological variability. [ABSTRACT FROM AUTHOR]

The gleno-humeral (GH) rotation centre is typically estimated using predictive or functional methods, however these methods may lead to location errors. This study aimed at determining a location error threshold above which statistically significant changes in the values of kinematic and kinetic GH parameters occur. The secondary aims were to quantify the effects of the direction of mislocation (X, Y or Z axis) of the GH rotation centre on GH kinematic and kinetic parameters. Shoulder flexion and abduction movements of 11 healthy volunteers were recorded using a standard motion capture system (Vicon, Oxford Metrics Ltd, Oxford, UK), then GH kinematic and kinetic parameters were computed. The true position of the GH rotation centre was determined using a low dose x-ray scanner (EOS™ imaging, France) and this position was transferred to the motion data. GH angles and moments were re-computed for each position of the GH rotation centre after errors of up to ± 20 mm were added in increments of ± 5 mm to each axis. The three-dimensional error range was 5 mm to 34.65 mm. GH joint angle and moment values were significantly altered from 10 mm of three-dimensional error, and from 5 mm of error on individual axes. However, errors on the longitudinal and antero-posterior axes only caused very small alterations of GH joint angle and moment values respectively. Future research should develop methods of GH rotation centre estimation that produce three-dimensional location errors of less than 10 mm to reduce error propagation on GH kinematics and kinetics. [ABSTRACT FROM AUTHOR]

Concussion can occur from a variety of events (falls to ice, collisions etc) in ice hockey, and as a result it is important to identify how these different impact sources affect the relationship between impact kinematics and strain that has been found to be associated to this injury. The purpose of this research was to examine the relationship between kinematic variables and strain in the brain for impact sources that led to concussion in ice hockey. Video of professional ice hockey games was analyzed for impacts that resulted in reported clinically diagnosed concussions. The impacts were reconstructed using physical models/ATDs to determine the impact kinematics and then simulated using finite element modelling to determine maximum principal strain and cumulative strain damage measure. A stepwise linear regression was conducted between linear acceleration, change in linear velocity, rotational acceleration, rotational velocity, and strain response in the brain. The results for the entire dataset was that rotational acceleration had the highest r2 value for MPS (r2 = 0.581) and change in rotational velocity for cumulative strain damage measure (r2 = 450). When the impact source (shoulder, elbow, boards, or ice impacts) was isolated the rotational velocity and acceleration r2 value increased, indicating that when evaluating the relationships between kinematics and strain based metrics the characteristics of the impact is an important factor. These results suggest that rotational measures should be included in future standard methods and helmet innovation and design in ice hockey as they have the highest association with strain in the brain tissues. [ABSTRACT FROM AUTHOR]

Neuromusculoskeletal models provide a mathematical tool for understanding and simulating human motor control and neuromechanics. In this work, we propose a combined computational model for the musculotendon paths and muscle-joint kinematics for the human hand, including all extrinsic and intrinsic muscles. This model is implemented based on the anatomical descriptions and a human hand dissection study. The model takes joint angles as input and estimates the musculotendon lengths, length change rates, and excursion moment arms. The proposed model is simulated to generate according moment arms, which are compared with cadaver measurements available from literature in terms of similarity coefficient s. For most muscles compared, high similarity with for 92% of cases is achieved between the modeled and the measured moment arms. These results suggest the correctness of modeled moment arms and imply the feasibility of modeled musculotendon paths, lengths, and length change rates. [ABSTRACT FROM AUTHOR]

Motion analysis (MA) hardware has recently become more accessible; however, protocols have not developed in conjunction. Routine clinical assessment mostly relies on unreliable observational methods. This study aimed to develop an MA protocol for routine clinical use and compare kinematics and reliability to the gold-standard. Ten participants completed 10 over ground walks with a comprehensive marker set (bespoke and gold-standard). Inter/intra-assessor reliability was also compared. Results demonstrated comparable kinematics. Reliability of the bespoke model was lower than the gold standard but higher than observational methods. The bespoke model can be recommended for routine clinical use to assess patient progress and function. [ABSTRACT FROM AUTHOR]

Computed tomography is used more routinely to design patient-specific instrumentation for knee replacement surgery. Its moderate imaging cost and simplified segmentation reduce design costs compared with magnetic resonance (MR) imaging, but it cannot provide the necessary cartilage information. Our method based on statistical shape modelling proved to be successful in predicting tibiofemoral cartilage in leave-one-out experiments. The obtained accuracy of 0.54 mm for femur and 0.49 mm for tibia outperforms the average cartilage thickness distribution and reported inter-observer MR segmentation variability. These results suggest that shape modelling is able to predict tibiofemoral cartilage with sufficient accuracy to design patient-specific instrumentation. [ABSTRACT FROM AUTHOR]

C has a typical crouch gait characterized by excessive hip and knee flexion and ankle dorsiflexion, especially in the stance phase. The hip orientation is expressed w.r.t. the pelvis and the anterior pelvis tilt of C was around 20° more than the one of H. Hip and knee flexions of C are stiffer (H-C - average ROM: 8.74°). The right hip adduction and internal rotation behaviour of C in the stance phase can be influenced by the higher right ankle eversion that pushes the leg inward. [Extracted from the article]

Keywords: Nonlinear optimization; gait simulation; kinematics; gait modeling EN Nonlinear optimization gait simulation kinematics gait modeling S136 S138 3 11/26/20 20200902 NES 200902 1. The optimization problem becomes: Graph HT ht Graph HT ht where I F i SB r sb and I F i SB l sb are, respectively, the next right and left footprints, and Graph HT ht a function computing the angular momentum of the gait cycle modelled with CP. Correlation (mean Graph HT ht between simulated and target angular trajectories. [Extracted from the article]

Keywords: Multibody kinematics optimisation; kinematic constraint; contact point trajectory; slip velocity; level walking EN Multibody kinematics optimisation kinematic constraint contact point trajectory slip velocity level walking S91 S93 3 11/26/20 20200902 NES 200902 1. Multibody kinematics optimisation Joint kinematics during gait is estimated by multibody kinematics optimisation, formulated as: Graph HT ht The lower limb model is parameterised with natural coordinates B Q b I SB i sb i (i.e., I i i = 1, 2, 3, 4 for foot, shank, thigh, and pelvis, respectively) (Dumas and Chèze [3]). [Extracted from the article]

Keywords: Gymnastics; full-body model; kinematics; lumbar lordosis; hip extension EN Gymnastics full-body model kinematics lumbar lordosis hip extension S101 S103 3 11/26/20 20200902 NES 200902 1. However, during the bridge posture, GR002 showed a higher lumbar lordosis contribution to total extension (sum of the hip extension, knee flexion and lumbar lordosis angles) than GR001 and GAF01 (59% vs 55% and 53%). [Extracted from the article]

Keywords: Posture; center of mass; kinematics; dancing EN Posture center of mass kinematics dancing S362 S364 3 01/29/21 20191002 NES 191002 1. Regarding the mean coordinates of the bCOM (X, Y, Z), no significant difference is observed, suggesting that neither vision nor dance practice have any influence on the mean body posture (also referred to as the "internal model"). Eyes closed, several parameters were significantly higher in ND (AP r, area, g v, AP v), suggesting that dance practice reduces postural sway in more challenging activities. Posture, center of mass, kinematics, dancing. [Extracted from the article]

Keywords: Human; ergometer; sports; constraint EN Human ergometer sports constraint S345 S347 3 01/29/21 20191002 NES 191002 1. To confirm or refute this hypothesis, the pelvis tilt values computed with OPENSIM I i i ) were used as input data with ROBOTRAN, I ii i ) were compared with the absolute pelvis orientation computed with cardan angles from the reflective markers. [Extracted from the article]

Keywords: Mechanical energy; pole vaulting; kinematics; motion capture EN Mechanical energy pole vaulting kinematics motion capture S326 S328 3 01/29/21 20191002 NES 191002 1. Also, distributions of performances (in m), TO I SB S sb i , SD I SB ff sb i of the last foot support, I SB SL sb i , and E I SB gain sb i were compared between the regulator and non-regulator pole vaulters by means of U Mann-Whitney tests (significance: I p i < 0.05). [Extracted from the article]