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Determination of skeletal muscle architecture is important for accurately modeling muscle behavior. Current methods for 3D muscle architecture determination can be costly and time-consuming, making them prohibitive for clinical or modeling applications. Computational approaches such as Laplacian flow simulations can estimate muscle fascicle orientation based on muscle shape and aponeurosis location. The accuracy of this approach is unknown, however, since it has not been validated against other standards for muscle architecture determination. In this study, muscle architectures from the Laplacian approach were compared to those determined from diffusion tensor imaging in eight adult medial gastrocnemius muscles. The datasets were subdivided into training and validation sets, and computational fluid dynamics software was used to conduct Laplacian simulations. In training sets, inputs of muscle geometry, aponeurosis location, and geometric flow guides resulted in good agreement between methods. Application of the method to validation sets showed no significant differences in pennation angle (mean difference [Formula: see text] or fascicle length (mean difference 0.9 mm). Laplacian simulation was thus effective at predicting gastrocnemius muscle architectures in healthy volunteers using imaging-derived muscle shape and aponeurosis locations. This method may serve as a tool for determining muscle architecture in silico and as a complement to other approaches.

The Achilles is the thickest tendon in the body and is the primary elastic energy-storing component during running. The form and function of the human Achilles is complex: twisted structure, intratendinous interactions, and differential motor control from the triceps surae muscles make Achilles behavior difficult to intuit. Recent in vivo imaging of the Achilles has revealed nonuniform displacement patterns that are not fully understood and may result from complex architecture and musculotendon interactions. In order to understand which features of the Achilles tendon give rise to the nonuniform deformations observed in vivo, we used computational modeling to predict the mechanical contributions from different features of the tendon. The aims of this study are to: (i) build a novel computational model of the Achilles tendon based on ultrashort echo time MRI, (ii) compare simulated displacements with published in vivo ultrasound measures of displacement, and (iii) use the model to elucidate the effects of tendon twisting, intratendon sliding, retrocalcaneal insertion, and differential muscle forces on tendon deformation. Intratendon sliding and differential muscle forces were found to be the largest factors contributing to displacement nonuniformity between tendon regions. Elimination of intratendon sliding or muscle forces reduced displacement nonuniformity by 96% and 85%, respectively, while elimination of tendon twist and the retrocalcaneal insertion reduced displacement nonuniformity by only 35% and 3%. These results suggest that changes in the complex internal structure of the tendon alter the interaction between muscle forces and tendon behavior and therefore may have important implications on muscle function during movement., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Much debate has arisen from research on muscle synergies with respect to both limb impedance control and energy consumption. Studies of limb impedance control in the context of reaching movements and postural tasks have produced divergent findings, and this study explores whether the use of synergies by the central nervous system (CNS) can resolve these findings and also provide insights on mechanisms of energy consumption. In this study, we phrase these debates at the conceptual level of interactions between neural degrees of freedom and tasks constraints. This allows us to examine the ability of experimentally-observed synergies--correlated muscle activations--to control both energy consumption and the stiffness component of limb endpoint impedance. In our nominal 6-muscle planar arm model, muscle synergies and the desired size, shape, and orientation of endpoint stiffness ellipses, are expressed as linear constraints that define the set of feasible muscle activation patterns. Quadratic programming allows us to predict whether and how energy consumption can be minimized throughout the workspace of the limb given those linear constraints. We show that the presence of synergies drastically decreases the ability of the CNS to vary the properties of the endpoint stiffness and can even preclude the ability to minimize energy. Furthermore, the capacity to minimize energy consumption--when available--can be greatly affected by arm posture. Our computational approach helps reconcile divergent findings and conclusions about task-specific regulation of endpoint stiffness and energy consumption in the context of synergies. But more generally, these results provide further evidence that the benefits and disadvantages of muscle synergies go hand-in-hand with the structure of feasible muscle activation patterns afforded by the mechanics of the limb and task constraints. These insights will help design experiments to elucidate the interplay between synergies and the mechanisms of learning, plasticity, versatility and pathology in neuromuscular systems.

The convexity of the dorsal surface of the velum is critical for normal velopharyngeal (VP) function and is largely attributed to the levator veli palatini (LVP) and musculus uvulae (MU). Studies have correlated a concave or flat nasal velar surface to symptoms of VP dysfunction including hypernasality and nasal air emission. In the context of surgical repair of cleft palates, the MU has been given relatively little attention in the literature compared with the larger LVP. A greater understanding of the mechanics of the MU will provide insight into understanding the influence of a dysmorphic MU, as seen in cleft palate, as it relates to VP function. The purpose of this study was to quantify the contributions of the MU to VP closure in a computational model. We created a novel 3-dimensional (3D) finite element model of the VP mechanism from magnetic resonance imaging data collected from an individual with healthy noncleft VP anatomy. The model components included the velum, posterior pharyngeal wall (PPW), LVP, and MU. Simulations were based on the muscle and soft tissue mechanical properties from the literature. We found that, similar to previous hypotheses, the MU acts as (i) a space-occupying structure and (ii) a velar extensor. As a space-occupying structure, the MU helps to nearly triple the midline VP contact length. As a velar extensor, the MU acting alone without the LVP decreases the VP distance 62%. Furthermore, activation of the MU decreases the LVP activation required for closure almost 3-fold, from 20% (without MU) to 8% (with MU). Our study suggests that any possible salvaging and anatomical reconstruction of viable MU tissue in a cleft patient may improve VP closure due to its mechanical function. In the absence or dysfunction of MU tissue, implantation of autologous or engineered tissues at the velar midline, as a possible substitute for the MU, may produce a geometric convexity more favorable to VP closure. In the future, more complex models will provide further insight into optimal surgical reconstruction of the VP musculature in normal and cleft palate populations.

Purpose: This study predicted the effects of velopharyngeal (VP) anatomical parameters on VP function to provide a greater understanding of speech mechanics and aid in the treatment of speech disorders., Method: We created a computational model of the VP mechanism using dimensions obtained from magnetic resonance imaging measurements of 10 healthy adults. The model components included the levator veli palatini (LVP), the velum, and the posterior pharyngeal wall, and the simulations were based on material parameters from the literature. The outcome metrics were the VP closure force and LVP muscle activation required to achieve VP closure., Results: Our average model compared favorably with experimental data from the literature. Simulations of 1,000 random anatomies reflected the large variability in closure forces observed experimentally. VP distance had the greatest effect on both outcome metrics when considering the observed anatomic variability. Other anatomical parameters were ranked by their predicted influences on the outcome metrics., Conclusions: Our results support the implication that interventions for VP dysfunction that decrease anterior to posterior VP portal distance, increase velar length, and/or increase LVP cross-sectional area may be very effective. Future modeling studies will help to further our understanding of speech mechanics and optimize treatment of speech disorders.

The levator veli palatini (LVP) muscle has long been recognized as the muscle that contributes most to velopharyngeal (VP) closure and is therefore of principal importance for restoring normal speech in patients with a cleft palate. Different surgical reconstructive procedures can utilize varying degrees of LVP overlap, and this study developed a new finite-element model of VP closure designed to understand the biomechanical effects of LVP overlap. A three-dimensional finite-element model was created from adult anatomical dimensions and parameters taken from the literature. Velopharyngeal function was simulated and compared with experimental measurements of VP closure force from a previous study. Varying degrees of overlap and separation of the LVP were simulated, and the corresponding closure force was calculated. The computational model compares favorably with the experimental measurements of closure force from the literature. Furthermore, the model predicts that there is an optimal level of overlap that maximizes the potential for the LVP to generate closure force. The model predicts that achieving optimal overlap can increase closure force up to roughly 100% when compared with too little or too much overlap. The results of using this new model of VP closure suggest that optimizing LVP overlap may produce improved surgical outcomes due to the intrinsic properties of muscle. Future work will compare these model predictions with clinical observations and provide further insights into optimal cleft palate repair and other craniofacial surgeries.

Analysis of the musculoskeletal movements (gait analysis) is needed in many scenarios. The in vivo method has some difficulties. For example, recruiting human subjects for the gait analysis is challenging due to many issues. In addition, when plenty of subjects are required, the follow-up experiments take a long period and the dropout of subjects always occurs. An efficient and reliable in silico simulation platform for gait analysis has been desired for a long time. Therefore, a technique using three-dimensional (3D) muscle modeling to drive the 3D musculoskeletal model was developed and the application of the technique in the simulation of lower limb movements was demonstrated. A finite element model of the lower limb with anatomically high fidelity was developed from the MRI data, where the main muscles, the bones, the subcutaneous tissues, and the skin were reconstructed. To simulate the active behavior of 3D muscles, an active, fiber-reinforced hyperelastic muscle model was developed using the user-defined material (VUMAT) model. Two typical movements, that is, hip abduction and knee lifting, were simulated by activating the responsible muscles. The results show that it is reasonable to use the improved CFD-FE method proposed in the present study to simulate the active contraction of the muscle, and it is feasible to simulate the movements by activating the relevant muscles. The results from the present technique closely match the physiological scenario and thus the technique developed has a great potential to be used in the in silico human simulation platform for many purposes. [ABSTRACT FROM AUTHOR]

Introduction: The levator veli palatini (LVP) muscle has two segments with distinct roles in velopharyngeal function. Previous research suggests longer extravelar segments with shorter intravelar segments may lead to a more advantageous mechanism for velopharyngeal closure. The purpose of this study was to examine whether the distribution of the LVP intravelar and extravelar segments differs between children with cleft palate with and without VPI and controls. Methods: The study included 97 children: 37 with cleft palate +/- lip with VPI, 37 controls, and 19 with cleft palate with normal resonance. Measures included mean LVP length, mean extravelar LVP length, and intravelar LVP length. Results: Overall mean LVP length was similar (P =.267) between controls and children with cleft palate (with and without VPI). However, there was a significant difference (P <.001) between group for both intravelar and extravelar LVP lengths: the intravelar segment was significantly longer in those with VPI compared to controls and children with cleft palate and normal resonance; and the extravelar segment was significantly shorter in those with VPI compared to controls and children with cleft palate and normal resonance. Conclusions: Results from this study demonstrate a significant difference between the distribution of the functional segments of the LVP among children with VPI, with a more disadvantageous distribution of the muscle segments among those with VPI. [ABSTRACT FROM AUTHOR]

Objectives: To establish a three-dimensional finite element model of the upper palate, pharyngeal cavity, and levator veli palatini muscle in patients with unilateral complete cleft palate, simulate two surgical procedures that the two-flap method and Furlow reverse double Z method, observe the stress distribution of the upper palate soft tissue and changes in pharyngeal cavity area after different surgical methods, and verify the accuracy of the model by reconstructing and measuring the levator veli palatini muscle., Materials and Methods: Mimics, Geomagic, Ansys, and Hypermesh were applied to establish three-dimensional finite element models of the pharyngeal cavity, upper palate, and levator veli palatini muscle in patients with unilateral complete cleft palate. The parameters including length, angle, and cross-sectional area of the levator veli palatini muscle etc. were measured in Mimics, and two surgical procedures that two-flap method and Furlow reverse double Z method were simulated in Ansys, and the area of pharyngeal cavity was measured by hypermesh., Results: A three-dimensional finite element model of the upper palate, pharyngeal cavity, and bilateral levator veli palatini muscle was established in patients with unilateral complete cleft palate ; The concept of horizontal projection characteristics of the palatal dome was applied to the finite element simulation of cleft palate surgery, vividly simulating the displacement and elastic stretching of the two flap method and Furlow reverse double Z method during the surgical process; The areas with the highest stress in the two-flap method and Furlow reverse double Z method both occur in the hard soft palate junction area; In resting state, as measured, the two flap method can narrow the pharyngeal cavity area by 50.9%, while the Furlow reverse double Z method can narrow the pharyngeal cavity area by 65.4%; The measurement results of the levator veli palatini muscle showed no significant difference compared to previous studies, confirming the accuracy of the model., Conclusions: The finite element method was used to establish a model to simulate the surgical procedure, which is effective and reliable. The area with the highest postoperative stress for both methods is the hard soft palate junction area, and the stress of the Furlow reverse double Z method is lower than that of the two-flap method. The anatomical conditions of pharyngeal cavity of Furlow reverse double Z method are better than that of two-flap method in the resting state., Clinical Relevance: This article uses three-dimensional finite element method to simulate the commonly used two-flap method and Furlow reverse double Z method in clinical cleft palate surgery, and analyzes the stress distribution characteristics and changes in pharyngeal cavity area of the two surgical methods, in order to provide a theoretical basis for the surgeon to choose the surgical method and reduce the occurrence of complications., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In this narrative review, we explore developments in the field of computational musculoskeletal model personalization using the Physiome and Musculoskeletal Atlas Projects. Model geometry personalization; statistical shape modeling; and its impact on segmentation, classification, and model creation are explored. Examples include the trapeziometacarpal and tibiofemoral joints, Achilles tendon, gastrocnemius muscle, and pediatric lower limb bones. Finally, a more general approach to model personalization is discussed based on the idea of multiscale personalization called scaffolds. [ABSTRACT FROM AUTHOR]

This clinical report describes the implementation of magnetic resonance imaging (MRI) to evaluate a patient with long-standing velopharyngeal dysfunction. She was referred to the craniofacial clinic at age 10 with no prior surgical history and subsequently completed a Furlow palatoplasty due to a suspected submucous cleft palate. However, results were unfavorable with minimal improvement in speech or resonance. The clinical presentation, treatment, outcomes, and contributions from MRI for secondary surgical planning are described. Addition of MRI into the clinical workflow provided insights into the anatomy and physiology of the velopharyngeal mechanism that were unable to be obtained from nasendoscopy and speech evaluation alone. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the superficial anatomy, kinesiology, and functions of the hand to reveal its morphometry and apply the findings in various fields such as prosthetic hand and protective hand support product design. We examined 51 young adults (32 females, 19 males) aged between 18–30. Hand photographs were taken, and measurements were conducted using ImageJ software. Pearson correlation analysis was performed to determine the relationship between personal information and the parameters. The results of the measurements showed the average lengths of finger segments: thumb (49.5±5.5 mm), index finger (63.9±4.1 mm), middle finger (70.7±5.2 mm), ring finger (65.5±4.8 mm), and little finger (53.3±4.3 mm). Both females and males, the left index finger was measured longer than the right index finger. The right ring finger was found to be longer than the left in both sexes. Additionally, length differences between fingers in extended and maximally adducted positions were determined: thumb-index finger (56.1±6.2 mm), index-middle finger (10.7±4.1 mm), middle-ring finger (10.8±1.4 mm), and ring-little finger (25.6±2.7 mm). Other findings included the average radial natural angle (56.4°±10.5°), ulnar natural angle (23.4°±7.1°), radial deviation angle (65.2°±8.2°), ulnar deviation angle (51.2°±9.6°), and grasping/gripping angle (49.1°±5.8°). The average angles between fingers in maximum abduction positions were also measured: thumb-index finger (53.4°±6.5°), index-middle finger (17.2°±2.6°), middle-ring finger (14.3°±2.3°), and ring-little finger (32.1°±7.0°). The study examined the variability in the positioning of proximal interphalangeal joints during maximum metacarpophalangeal and proximal interphalangeal flexion, coinciding with maximum distal interphalangeal extension movements. The focal points of our observations were the asymmetrical and symmetrical arches formed by these joints. This study provides valuable hand parameters in young adults, which can be utilized in various applications such as prosthetic design, ergonomic product development, and hand-related research. The results highlight the significance of considering individual factors when assessing hand morphology and function. [ABSTRACT FROM AUTHOR]

Presbyopia is an age-related ocular disorder where accommodative ability declines so that an individual's focusing range is insufficient to provide visual clarity for near and distance vision tasks without corrective measures. With age, the eye exhibits changes in biomechanical properties of many components involved in accommodation, including the lens, sclera, and ciliary muscle. Changes occur at different rates, affecting accommodative biomechanics differently, but individual contributions to presbyopia are unknown. We used a finite element model (FEM) of the accommodative mechanism to simulate age-related changes in lens stiffness, scleral stiffness, and ciliary contraction to predict differences in accommodative function. The FEM predicts how ciliary muscle action leads to lens displacement by initializing a tensioned unaccommodated lens (Phase 0) then simulating ciliary muscle contraction in accommodation (Phase 1). Model inputs were calibrated to replicate experimentally measured lens and ciliary muscle in 30-year-old eyes. Predictions of accommodative lens deformation were verified with additional imaging studies. Model variations were created with altered lens component stiffnesses, scleral stiffness, or ciliary muscle section activations, representing fifteen-year incremental age-related changes. Model variations predict significant changes in accommodative function with age-related biomechanical property changes. Lens changes only significantly altered lens thickening with advanced age (46% decrease at 75 years old) while sclera changes produced progressive dysfunction with increasing age (23%, 36%, 49% decrease at 45, 60, and 75 years old). Ciliary muscle changes effected lens position modulation. Model predictions identified potential mechanisms of presbyopia that likely work in combination to reduce accommodative function and could indicate effectiveness of treatment strategies and their dependency on patient age or relative ocular mechanical properties. [ABSTRACT FROM AUTHOR]

The purpose of this study was to develop a framework for 3D subject-specific computational models capable of simulating velopharyngeal biomechanics for anatomic changes that occur following pharyngoplasty and to gain insight into biomechanical factors that may lead to different speech/surgical outcomes. Patient-specific models for two, matched participants with differing speech/surgical outcomes were developed: one with a successful pharyngoplasty outcome and one with a failed pharyngoplasty outcome. Surgical scenarios were simulated to model pharyngoplasty location, identify LVP muscle biomechanics, and identify an optimal pharyngoplasty location for each participant. These simulations illustrate the potential for optimizing pharyngoplasties based on patient-specific geometry. [ABSTRACT FROM AUTHOR]

Background: Postpalatoplasty velopharyngeal function needs to be evaluated through long-term follow-up, but such reports are limited in the literature, and there has been no consensus as to which surgical technique yields optimal velopharyngeal function with minimum complication rate. This study aimed to evaluate the long-term outcome of the modified Furlow palatoplasty using small double-opposing Z-plasty (small-DOZ)., Methods: A retrospective review was conducted of consecutive patients who underwent palatoplasty performed by the senior author (L.J.L.) between January of 2000 and March of 2014. Nonsyndromic patients who underwent palatoplasty before the age of 18 months and followed up until at least 9 years of age were included. Comparisons between the small-DOZ and 2-flap methods for soft palate repair were made., Results: A total of 196 small-DOZ and 167 2-flap palatoplasty patients were eligible in the study. Among the small-DOZ palatoplasty patients, 1 patient (0.5%) developed oronasal fistula and 18 patients (9.2%) developed velopharyngeal insufficiency (VPI) surgery (10 patients at preschool age, and 8 at 9 years of age). Compared with the small-DOZ palatoplasty, the oronasal fistula rate, VPI surgery rate, and the need for myringotomy tube insertion were significantly higher in the 2-flap group (P = 0.01, P < 0.01, and P < 0.01, respectively). Patients who developed oronasal fistula had significantly higher likelihood of having VPI (P < 0.01)., Conclusions: The small-DOZ provided successful palatal repair with low rates of oronasal fistula and VPI in the long term. Wound closure under minimal tension facilitated avoiding oronasal fistula. Reconstruction of the functional muscle sling enabled the authors to achieve normal velopharyngeal function with favorable speech outcome and middle ear function., Clinical Question/level of Evidence: Therapeutic, III., (Copyright © 2023 by the American Society of Plastic Surgeons.)

To elucidate the underlying physiological mechanisms of muscle synergies, we investigated long-range functional connectivity by cortico-muscular (CMC), intermuscular (IMC) and cortico-synergy (CSC) coherence. Fourteen healthy participants executed an isometric upper limb task in synergy-tuned directions. Cortical activity was recorded using 32-channel electroencephalography (EEG) and muscle activity using 16-channel electromyography (EMG). Using non-negative matrix factorisation (NMF), we calculated muscle synergies from two different tasks. A preliminary multidirectional task was used to identify synergy-preferred directions (PDs). A subsequent coherence task, consisting of generating forces isometrically in the synergy PDs, was used to assess the functional connectivity properties of synergies. Overall, we were able to identify four different synergies from the multidirectional task. A significant alpha band IMC was consistently present in all extracted synergies. Moreover, IMC alpha band was higher between muscles with higher weights within a synergy. Interestingly, CSC alpha band was also significantly higher across muscles with higher weights within a synergy. In contrast, no significant CMC was found between the motor cortex area and synergy muscles. The presence of a shared input onto synergistic muscles within a synergy supports the idea of neurally derived muscle synergies that build human movement. Our findings suggest cortical modulation of some of the synergies and the consequential existence of shared input between muscles within cortically modulated synergies. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to investigate the individual triceps surae muscle forces during the execution of six different functional movements and rehabilitation exercises in patients with Achilles tendinopathy compared to a control group. Methods: Triceps surae muscle forces of 15 participants with Achilles tendinopathy (AT) and 15 healthy controls were estimated through a combination of experimental data and musculo‐skeletal modeling. Three‐dimensional motion capture and force plates were used to collect the ankle and knee joint angles and moments during three functional movements (walking, heel walking, and toe walking) and three rehabilitation exercises (bilateral heel drop, unilateral heel drop with extended knee and with flexed knee). A dynamic optimization method was used to obtain the modeled triceps surae muscle forces. Force‐sharing strategies were calculated at the peak triceps surae muscle force and compared between groups. Results: Lower peak triceps surae forces were obtained for the AT group during dynamic exercises. Across all exercises, the average contribution of the soleus (SOL) to the total triceps surae muscle force was the largest (60.83 ± 13.89% [AT] > 56.90 ± 16.18% [healthy]), followed by the gastrocnemius medialis (29.87 ± 10.67% [AT] < 32.19 ± 12.90% [healthy]) and the gastrocnemius lateralis (9.30 ± 4.31% [AT] < 10.91 ± 4.66% [healthy]). The triceps surae force‐sharing strategy was different for the toe walking, heel walking, and the bilateral and unilateral heel drop with extended knee. Conclusion: This study provides evidence for altered triceps surae muscle force‐sharing strategies during dynamic tasks in patients with AT. The influence of altered muscle force‐sharing on the subtendon nonuniformity and/or the tendon loading should be explored in future work. [ABSTRACT FROM AUTHOR]

Objective: Velopharyngeal dysfunction (VPD) associated with 22q11.2 deletion syndrome (22q11.2DS) has a complex etiology. This study had 3 aims: (1) assess differences in velopharyngeal and levator muscle configuration during rest versus sustained speech production (2) compare differences in velopharyngeal changes between children with and without 22q11.2DS (3) examine the relationship between adenoid thickness, pharyngeal depth, and velopharyngeal changes. Design: Cross-sectional. Methods: A total of 22 participants, 11 with 22q11.2DS and 11 controls with normal speech and velopharyngeal anatomy (ages 4-12 years), underwent nonsedated MRI at rest and during sustained /i/. Differences in velar and levator muscle contraction across the 2 different conditions were analyzed, using matched paired t -tests. Mean differences across participant groups were examined. Correlation analyses were also conducted. Results: When comparing differences between rest and sustained phoneme production (aim 1), significant (P <.05) differences were noted for all velar and levator muscle variables. For differences in velopharyngeal changes between children with and without 22q11.2DS (aim 2), VP ratio and effective VP ratio were noted to be significantly different. Pharyngeal depth and adenoid thickness were correlated with velar and levator muscle change measures and ratios (aim 3). Conclusion: Results from this study provide quantitative in vivo measurements of the contracted levator muscle and velum in young children with 22q11.2DS. Results demonstrated that VP ratio and EVP ratio are significantly different between children with and without 22q11.2DS and that pharyngeal depth is a strong clinical determinant of VPD in children with 22q11.2DS. [ABSTRACT FROM AUTHOR]

The eye's accommodative mechanism changes optical power for near vision. In accommodation, ciliary muscle excursion relieves lens tension, allowing it to return to its more convex shape. Lens deformation alters its refractive properties, but the mechanics of ciliary muscle actions are difficult to intuit due to the complex architecture of the tissues involved. The muscle itself comprises three sections of dissimilarly oriented cells. These cells contract, transmitting forces through the zonule fibers and extralenticular structures. This study aims to create a finite element model (FEM) to predict how the action of the ciliary muscle sections leads to lens displacement. The FEM incorporates initialization of the disaccommodated lens state and ciliary muscle contraction, with three muscle sections capable of independent activation, to drive accommodative movement. Model inputs were calibrated to replicate experimentally measured disaccommodated lens and accommodated ciliary muscle shape changes. Additional imaging studies were used to validate model predictions of accommodative lens deformation. Models were analyzed to quantify mechanical actions of ciliary muscle sections in lens deformation and position modulation. Analyses revealed that ciliary muscle sections act synergistically: the circular section contributes most to increasing lens thickness, while longitudinal and radial sections can oppose this action. Conversely, longitudinal and radial sections act to translate the lens anteriorly with opposition from the circular section. This FEM demonstrates the complex interplay of the three sections of ciliary muscle in deforming and translating the lens during accommodation, providing a useful framework for future investigations of accommodative dysfunction that occurs with age in presbyopia.

Computational models have been used extensively to assess diseases and disabilities effects on musculoskeletal system dysfunction. In the current study, we developed a two degree-of-freedom subject-specific second-order task-specific arm model for characterizing upper-extremity function (UEF) to assess muscle dysfunction due to chronic obstructive pulmonary disease (COPD). Older adults (65 years or older) with and without COPD and healthy young control participants (18 to 30 years) were recruited. First, we evaluated the musculoskeletal arm model using electromyography (EMG) data. Second, we compared the computational musculoskeletal arm model parameters along with EMG-based time lag and kinematics parameters (such as elbow angular velocity) between participants. The developed model showed strong cross-correlation with EMG data for biceps (0.905, 0.915) and moderate cross-correlation for triceps (0.717, 0.672) within both fast and normal pace tasks among older adults with COPD. We also showed that parameters obtained from the musculoskeletal model were significantly different between COPD and healthy participants. On average, higher effect sizes were achieved for parameters obtained from the musculoskeletal model, especially for co-contraction measures (effect size = 1.650 ± 0.606, p < 0.001), which was the only parameter that showed significant differences between all pairwise comparisons across the three groups. These findings suggest that studying the muscle performance and co-contraction, may provide better information regarding neuromuscular deficiencies compared to kinematics data. The presented model has potential for assessing functional capacity and studying longitudinal outcomes in COPD. [ABSTRACT FROM AUTHOR]

Diffusion tensor imaging (DTI) may allow the determination of new threshold values, based on water anisotropy, to differentiate between healthy muscle and various pathological processes. Additionally, it may quantify treatment monitoring or training effects. Most current studies have evaluated the potential of DTI of skeletal muscle to assess sports-related injuries or therapy, and training monitoring. Another critical area of application of this technique is the characterization and monitoring of primary and secondary myopathies. In this manuscript, we review the application of DTI in the evaluation of skeletal muscle in these and other novel clinical scenarios, with emphasis on the use of quantitative imaging–derived biomarkers. Finally, the main limitations of the introduction of DTI in the clinical setting and potential areas of future use are discussed. [ABSTRACT FROM AUTHOR]

Posterior pharyngeal flap palatoplasty is used to restore the function of velopharyngeal (VP) closure, after which 2 ports remain between the nasal and oral cavity. The authors hypothesized that the airflow dynamics of the upper airway is different in PPF patients compared to health subjects, who only has 1 movable port. Twenty adults who have multislice spiral computed tomography scan were included in this study. Two cylinders (radius, 2.00 mm; height, 4.5 mm) were used to recapitulate the 2-port VP structure after PPF palatoplasty. The areas of ports were modified by changing the radius of 2 cylinders. Real-time computational fluid dynamics simulation was used to capture the airflow velocity and pressures through the 2 ports. The airflow velocity and pressure of upper airway were recorded as the total areas of 2 VP ports increased. The total orifice areas of the 2-port VP closure for 4 VP conditions, including adequate closure, adequate/borderline closure, borderline/inadequate closure, and inadequate closure, were demonstrated. Significant differences between the 2-port VP function for demonstrating PPF reconstruction and the 1-port VP function were found. Airflow dynamics is dependent on the VP structure. The 2-port airflow model for mimicking VP closure after PPF palatoplasty demonstrated airflow characteristics that were significantly different from the 1-port model in normal VP closure.

Substantial research on complete Achilles tendon ruptures is available, but guidance on partial ruptures is comparatively sparse. Conservative management is considered acceptable in partial tendon ruptures affecting less than 50% of the tendon's width, but supporting experimental evidence is currently lacking. Using a previously validated finite element model of the Achilles tendon, this study aimed to assess whether loading conditions simulating an early functional rehabilitation protocol could elicit progression to a complete rupture in partial ruptures of varying severity. In silico tendon rupture simulations were performed to locate the most likely rupture site for least, moderate, and extreme subtendon twist configurations. These three models were split at the corresponding rupture site and two sets of partial ruptures were created for each, starting from the medial and lateral sides, and ranging from 10% to 50% loss of continuity. Simulations were conducted with material parameters from healthy and tendinopathic tendons. Partial ruptures were considered to progress if the volume of elements showing a maximum principal strain above 10% exceeded 3 mm 3 . To assess whether the tendinopathic tendons typical geometric characteristics could compensate for the inferior material properties found in tendinopathy, an additional model with increased cross-sectional area in the free tendon region was developed. Progression to complete ruptures occurred even with less than a 50% loss of continuity, regardless of subtendon twisting, and material parameters. The tendinopathic tendon model with increased cross-sectional area showed similar results. These findings suggest the current criteria for surgical treatment of partial ruptures should be reconsidered. Statement of clinical significance: The clinical significance and most appropriate treatment of partial ruptures of the Achilles tendon is unclear. Despite the widespread use of the "50% rule" in treatment decisions of partial tendon ruptures, experimental evidence supporting it is missing. The present study provides new data, from a validated aponeurotic and free Achilles tendon finite element model, showing that partial ruptures may progress to complete ruptures under loading conditions elicited from functional rehabilitation protocols, even for partial ruptures affecting less than 50% of the tendon's width. Under these novel findings, the current criteria for surgical treatment of partial ruptures should be reconsidered., (© 2024 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals LLC on behalf of Orthopaedic Research Society.)

The Achilles tendon (AT) is a common injury site. Ruptures are usually located in the free tendon but may cross the myotendinous junction into the aponeurotic region. Considering the possibility of aponeurotic region involvement in AT ruptures, a novel three dimensional (3D) finite element (FE) model that includes both the aponeurotic and free AT regions and features subtendon twisting and sliding was developed. It was hypothesized that the model would be able to predict in vivo data collected from the literature, thus being considered valid, and that model outputs would be most sensitive to subtendon twist configurations. The 3D model was constructed using magnetic resonance images. The model was divided into soleus and gastrocnemius subtendons. In addition to a frictionless contact condition, the interaction between subtendons was modeled using two contact formulations: sliding with anisotropic friction and no sliding. Loads were applied on the tendon's most proximal cross‐section and anterior surface, with magnitudes estimated from in vivo studies. Model outputs were compared with experimental data regarding 3D deformation, transverse plane rotation, and nodal displacements in the free tendon. The FE model adequately simulated the free tendon behavior regarding longitudinal strain, cross‐section area variation, transverse plane rotation, and sagittal nodal displacements, provided that subtendon sliding was allowed. The frictionless model exhibited noticeable medial transverse sliding of the soleus subtendon, which was present to a much lesser degree in the anisotropic friction model. Model outputs were most sensitive to variations in subtendon twist and dispersion of the collagen fiber orientations. Clinical Significance: This Achilles tendon finite element model, validated using in vivo experimental data, may be used to study its mechanical behavior, injury mechanisms, and rupture risk factors. [ABSTRACT FROM AUTHOR]

The subject-specific range of motion (RoM) of a musculoskeletal joint system is balanced by pre-tension levels of individual muscles, which affects their contraction capability. Such an inherent pre-tension or pre-stretch of muscles is not measureable with in vivo experiments. Using a 3D continuum mechanical forward simulation approach for motion analysis of the musculoskeletal system of the forearm with 3 flexor and 2 extensor muscles, we developed an optimization process to determine the muscle fibre pre-stretches for an initial arm position, which is given human dataset. We used RoM values of a healthy person to balance the motion in extension and flexion. The performed sensitivity study shows that the fibre pre-stretches of the m. brachialis, m. biceps brachii and m. triceps brachii with 91 % dominate the objective flexion ratio, while m. brachiradialis and m. anconeus amount 7.8 % and 1.2 % . Within the multi-dimensional space of the surrogate model, 3D sub-spaces of primary variables, namely the dominant muscles and the global objective, flexion ratio, exhibit a path of optimal solutions. Within this optimal path, the muscle fibre pre-stretch of two flexors demonstrate a negative correlation, while, in contrast, the primary extensor, m. triceps brachii correlates positively to each of the flexors. Comparing the global optimum with four other designs along the optimal path, we saw large deviations, e.g., up to 15 ∘ in motion and up to 40% in muscle force. This underlines the importance of accurate determination of fibre pre-stretch in muscles, especially, their role in pathological muscular disorders and surgical applications such as free muscle or tendon transfer., (© 2024. The Author(s).)

Objective : Sphincter pharyngoplasty is a surgical method to treat velopharyngeal dysfunction. However, surgical failure is often noted and postoperative assessment frequently reveals low-set pharyngoplasties. Past studies have not quantified pharyngoplasty tissue changes that occur postoperatively and gaps remain related to the patient-specific variables that influence postoperative change. The purpose of this study was to utilize advanced three-dimensional imaging and volumetric magnetic resonance imaging (MRI) data to visualize and quantify pharyngoplasty insertion site and postsurgical tissue changes over time. Design : A prospective, repeated measures design was used for the assessment of craniometric and velopharyngeal variables postsurgically. Imaging was completed across two postoperative time points. Tissue migration, pharyngoplasty dimensions, and predictors of change were analyzed across imaging time points. Results : Significant differences were present between the initial location of pharyngoplasty tissue and the pharyngoplasty location 2 to 4 months postoperatively. The average postoperative inferior movement of pharyngoplasty tissue was 6.82 mm, although notable variability was present across participants. The pharyngoplasty volume decreased by 30%, on average. Conclusions : Inferior migration of the pharyngoplasty tissue was present in all patients. Gravity, scar contracture, and patient-specific variables likely interact, impacting final postoperative pharyngoplasty location. The use of advanced imaging modalities, such as 3D MRI, allows for the quantification and visualization of tissue change. There is a need for continued identification of patient-specific factors that may impact the amount of inferior tissue migration and scar contracture postoperatively. [ABSTRACT FROM AUTHOR]

Magnetic resonance imaging (MRI) of skeletal muscle is routinely performed using morphological sequences to acquire anatomical information. Recently, there is an increasing interest in applying advanced MRI techniques that provide pathophysiologic information for skeletal muscle evaluation to complement standard morphologic information. Among these advanced techniques, diffusion tensor imaging (DTI) has emerged as a potential tool to explore muscle microstructure. DTI can noninvasively assess the movement of water molecules in well-organized tissues with anisotropic diffusion, such as skeletal muscle. The acquisition of DTI studies for skeletal muscle assessment requires specific technical adjustments. Besides, knowledge of DTI physical basis and skeletal muscle physiopathology facilitates the evaluation of this advanced sequence and both image and parameter interpretation. Parameters derived from DTI provide a quantitative assessment of muscle microstructure with potential to become imaging biomarkers of normal and pathological skeletal muscle. Key Points: • Diffusion tensor imaging (DTI) allows to evaluate the three-dimensional movement of water molecules inside biological tissues. • The skeletal muscle structure makes it suitable for being evaluated with DTI. • Several technical adjustments have to be considered for obtaining robust and reproducible DTI studies for skeletal muscle assessment, minimizing potential artifacts. [ABSTRACT FROM AUTHOR]

The soft palate is the only structure that reversibly separates the respiratory and gastrointestinal systems. Most species can eat and breathe at the same time. Humans cannot do this and malfunction of the soft palate may allow food to enter the lungs and cause fatal aspiration pneumonia. Speech is the most defining characteristic of humans and the soft palate, along with the larynx and tongue, plays the key roles. In addition, palatal muscles are involved in snoring and obstructive sleep apnea. Considering the significance of the soft palate, its function is insufficiently understood. The objectives of this study were to document morphometric and immunohistochemical characteristics of adult human soft palate muscles, including fiber size, the fiber type, and myosin heavy chain (MyHC) composition for better understanding muscle functions. In this study, 15 soft palates were obtained from human autopsies. The palatal muscles were separated, cryosectioned, and stained using histological and immunohistochemical techniques. The results showed that there was a fast type II predominance in the musculus uvulae and palatopharyngeus and a slow type I predominance in the levator veli palatine. Approximately equal proportions of type I and type II fibers existed in both the palatoglossus and tensor veli palatine. Soft palate muscles also contained hybrid fibers and some specialized myofibers expressing slow-tonic and embryonic MyHC isoforms. These findings would help better understand muscle functions. [ABSTRACT FROM AUTHOR]

Real‐time magnetic resonance imaging (RT‐MRI) allows for imaging dynamic processes as they occur, without relying on any repetition or synchronization. This is made possible by modern MRI technology such as fast‐switching gradients and parallel imaging. It is compatible with many (but not all) MRI sequences, including spoiled gradient echo, balanced steady‐state free precession, and single‐shot rapid acquisition with relaxation enhancement. RT‐MRI has earned an important role in both diagnostic imaging and image guidance of invasive procedures. Its unique diagnostic value is prominent in areas of the body that undergo substantial and often irregular motion, such as the heart, gastrointestinal system, upper airway vocal tract, and joints. Its value in interventional procedure guidance is prominent for procedures that require multiple forms of soft‐tissue contrast, as well as flow information. In this review, we discuss the history of RT‐MRI, fundamental tradeoffs, enabling technology, established applications, and current trends. Level of Evidence: 5 Technical Efficacy Stage: 1 [ABSTRACT FROM AUTHOR]

Robotic hands perform several amazing functions similar to the human hands, thereby offering high flexibility in terms of the tasks performed. However, developing integrated hands without additional actuation parts while maintaining important functions such as human-level dexterity and grasping force is challenging. The actuation parts make it difficult to integrate these hands into existing robotic arms, thus limiting their applicability. Based on a linkage-driven mechanism, an integrated linkage-driven dexterous anthropomorphic robotic hand called ILDA hand, which integrates all the components required for actuation and sensing and possesses high dexterity, is developed. It has the following features: 15-degree-of-freedom (20 joints), a fingertip force of 34N, compact size (maximum length: 218 mm) without additional parts, low weight of 1.1 kg, and tactile sensing capabilities. Actual manipulation tasks involving tools used in everyday life are performed with the hand mounted on a commercial robot arm. Though robotic hands capable of adaptive grasping have been developed, realizing integrated hands with higher degree of freedom (DOF) movement and technology compatibility remains a challenge. Here, the authors report integrated linkage-driven robotic hand with improved design and performance. [ABSTRACT FROM AUTHOR]

Knowledge of skeletal muscle fiber orientations is important for modeling mechanical properties and behavior of muscle tissue. Diffusion tensor imaging (DTI) may be used to define fiber architecture in vivo but can be expensive and time‐consuming and thus impractical for biomechanical modeling applications. Muscle tractography using computational fluid dynamics (CFD) has been shown to determine muscle fiber directions for finite element models in which aponeuroses serve as inlet and outlet boundaries. While the technique is simple to implement, it is unclear which flow simulations and constraints achieve fiber architectures similar to DTI and whether FE simulations based on CFD versus DTI fiber directions produce similar results. Here, we implement CFD tractography on the gastrocnemius muscle using a novel boundary condition method that we developed based on specified inflow direction. We compared results from incompressible potential flow and nondimensionalized incompressible Stokes flow. Comparisons were made between flow methods and results from DTI. Mechanical finite element simulations were subsequently performed on muscle models with fiber directions defined by CFD tractography and DTI. Using our boundary condition method, fiber directions modeled from CFD simulations were similar to DTI. Strain distributions from mechanical simulations were similar between Stokes flow and DTI fiber models. This study demonstrates a new method for specifying inlet boundary conditions that generates physiologically reasonable fiber directions in skeletal muscle. Finite element simulations based on this method are similar to those from DTI, illustrating the ability of CFD to determine muscle fiber architecture for modeling purposes when DTI is not available. [ABSTRACT FROM AUTHOR]

The superficial digital flexor tendon (SDFT) is considered functionally equivalent to the human Achilles tendon. Circular chondroid depositions scattered amongst the fascicles of the equine SDFT are rarely reported. The purpose of this study was the detailed characterization of intrafascicular chondroid‐like bodies (ICBs) in the equine SDFT, and the assessment of the effect of ageing on the presence and distribution of these structures. Ultrahigh field magnetic resonance imaging (9.4T) series of SDFT samples of young (1–9 years) and aged (17–25 years) horses were obtained, and three‐dimensional reconstruction of ICBs was performed. Morphological evaluation of the ICBs included histology, immunohistochemistry and transmission electron microscopy. The number, size, and position of ICBs was determined and compared between age groups. There was a significant difference (p =.008) in the ICB count between young and old horses with ICBs present in varying number (13–467; median = 47, mean = 132.6), size and distribution in the SDFT of aged horses only. There were significantly more ICBs in the tendon periphery when compared with the tendon core region (p =.010). Histological characterization identified distinctive cells associated with increased glycosaminoglycan and type II collagen extracellular matrix content. Ageing and repetitive strain frequently cause tendon micro‐damage before the development of clinical tendinopathy. Documentation of the presence and distribution of ICBs is a first step towards improving our understanding of the impact of these structures on the viscoelastic properties, and ultimately their effect on the risk of age‐related tendinopathy in energy‐storing tendons. [ABSTRACT FROM AUTHOR]

Learning Objectives: After studying this article, the participant should be able to: 1. Describe the incidence of cleft palate and risk factors associated with development of an orofacial cleft. 2. Understand differences among several techniques to repair clefts of both the hard and soft palates. 3. Discuss risk factors for development of postoperative fistulas, velopharyngeal insufficiency, and facial growth problems. 4. Establish a treatment plan for individualized care of a cleft palate patient., Summary: Orofacial clefts are the most common congenital malformations of the head and neck region, and approximately three-quarters of these patients have some form of cleft palate deformity. Cleft palate repair is generally performed in children between 6 and 12 months of age. The goals of palate repair are to minimize the occurrence of fistulas, establish a normal velopharyngeal mechanism, and optimize facial growth. This Maintenance of Certification review discusses the incidence and epidemiology associated with cleft palate deformity and specifics associated with patient care, including analgesia, surgical repair techniques, and complications associated with repair of the cleft palate.

Purpose: The goal of this study is to determine the typical range of asymmetry between the length and thickness of the levator veli palatini muscle and to explore the impact of the observed asymmetry on velopharyngeal closure. A second objective is to report normative length and thickness of the levator veli palatini muscle among adults with typical velopharyngeal anatomy. Method: Magnetic resonance imaging (MRI) data and Amira 5.5 Visualization software were used to evaluate the levator veli palatini muscle among 89 participants with typical velopharyngeal anatomy. Flexible nasopharyngoscopy was used to determine the function of velopharyngeal closure among 39 of the 89 participants with typical velopharyngeal anatomy to examine the functional impact of observed asymmetry. Results: Matched paired t tests demonstrated a nonsignificant difference between the length and thickness of the right and left levator muscle. The mean difference between the right and left length of the levator muscle was 2.28 mm but ranged from 0.09 mm to 10.37 mm. In all cases where individuals displayed asymmetry in the levator muscle through MRI, there was no observed impact on the symmetry of velopharyngeal closure. Discussion: This study suggest that differences in the right and left levator veli palatini muscle are not significant among individuals without cleft palate. However, among individual cases where asymmetry was sizeable, there was no direct impact on the closure pattern. This may suggest there are multiple factors that contribute to asymmetrical velopharyngeal closure that are beyond the level of the levator veli palatini muscle. [ABSTRACT FROM AUTHOR]

Numerous studies have been conducted on three-finger robot hands, which are widely used in industries. These studies led to the development of motorized prosthetic hands for amputees. Although many developers have focused on the functionality of motorized prosthetic hands, prosthetic users place more importance on the human-like motion of the device owing to social implications. Therefore, this study aims to achieve human-like flexion of a three-finger robot hand. Each finger contains three phalanges joined by pivots and torsional return springs. A tendon wire runs through guide pins inside the phalanges up to the linear actuator located in the forearm. When the tendon wire is pulled, the finger is flexed. The return springs are optimally selected based on ADAMS simulations and kinesiology of the human hand. The selection is then verified by experiments [ABSTRACT FROM AUTHOR]

Objective: To identify quantitative and qualitative differences in the velopharyngeal musculature and surrounding structures between children with submucous cleft palate (SMCP) and velopharyngeal insufficiency (VPI) and noncleft controls with normal anatomy and normal speech. Methods: Magnetic resonance imaging was used to evaluate the velopharyngeal mechanism in 20 children between 4 and 9 years of age; 5 with unrepaired SMCP and VPI. Quantitative and qualitative measures of the velum and levator veli palatini in participants with symptomatic SMCP were compared to noncleft controls with normal velopharyngeal anatomy and normal speech. Results: Analysis of covariance revealed that children with symptomatic SMCP demonstrated increased velar genu angle (15.6°, P =.004), decreased α angle (13.2°, P =.37), and longer (5.1 mm, P =.32) and thinner (4 mm, P =.005) levator veli palatini muscles compared to noncleft controls. Qualitative comparisons revealed discontinuity of the levator muscle through the velar midline and absence of a musculus uvulae in children with symptomatic SMCP compared to noncleft controls. Conclusions: The levator veli palatini muscle is longer, thinner, and discontinuous through the velar midline, and the musculus uvulae is absent in children with SMCP and VPI compared to noncleft controls. The overall velar configuration in children with SMCP and VPI is disadvantageous for achieving adequate velopharyngeal closure necessary for nonnasal speech compared to noncleft controls. These findings add to the body of literature documenting levator muscle, musculus uvulae, and velar and craniometric parameters in children with SMCP. [ABSTRACT FROM AUTHOR]

Forward propulsion during the push-off phase of walking is largely governed at the ankle by differential neuromechanical contributions from the biarticular medial (MG) and lateral gastrocnemii (LG) and the uniarticular soleus (SOL). However, the relative contribution of these individual muscles to forward propulsion is equivocal, with important implications for the design and control of wearable assistive devices and for targeted therapeutics. The aim of this study was to evaluate the agreement between empirical and model-predicted triceps surae (i.e., MG, LG, and SOL) contributions to forward propulsion during walking using conditions that systematically manipulated both walking speed and the mechanical demand for forward propulsion at a fixed speed—through the use of aiding and impeding forces. Ten young adults (age: 24.1 ± 3.6 years, 6M/4F) participated. We found that muscle-specific responses derived from experimental measurements (i.e., activation and fascicle behavior) were consistent with those derived from musculoskeletal simulations (i.e., muscle force and positive mechanical work) within the same subjects. In vivo, compared to walking normally, only LG muscle activation was affected by both aiding and impeding forces. Similarly, increased propulsive demand elicited greater relative fascicle shortening in the MG but not the SOL. In silico, only MG and LG force and positive mechanical work increased significantly to meet the increased demands for forward propulsion. By combining electromyography, ultrasound imaging, and musculoskeletal modeling in the same subjects, our cumulative findings suggest that the biarticular gastrocnemius muscles play a more significant role than the uniarticular soleus in governing changes in forward propulsion during the mid to late stance phase of walking. [ABSTRACT FROM AUTHOR]

Introduction: Previous research has shown that altering the nasal signal level auditory feedback changed the control of oral-nasal balance in normal speakers. The present study investigated whether knowledge of the task and the instruction not to compensate would change the participants' response to the manipulation. Methods: Twenty participants (10 females) in 2 groups continuously repeated a sentence while their nasal signal level was increased or decreased and fed back to them via headphones, so the speakers heard themselves as more or less nasal, respectively. After the first recording session, participants were debriefed about the true nature of the experiment. They were instructed not to compensate in the second recording session. The outcome measures were the percentage changes of nasalance scores from the first baseline. Results: Statistical analysis using a repeated measures analysis of variance showed an effect of the nasal signal level, F(5,80) = 2.51, p = 0.049, and a nasal signal level by knowledge of task interaction effect, F(5,80) = 3.25, p = 0.019. Post hoc tests showed that the maximum nasal signal level auditory feedback resulted in a significant decrease of nasality from the initial baseline. Conclusion: Despite knowledge of the task, speakers were unable to resist compensating. As found in previous research, there was a numerically higher compensation response at the maximum than at the minimum nasal signal level auditory feedback condition. [ABSTRACT FROM AUTHOR]

Objectives: To provide detailed descriptions of contraction-induced morphometric changes in the extravelar segments of the levator veli palatini (LVP) muscle using 3-dimensional (3-D) magnetic resonance imaging (MRI). Design: Three-dimensional MRI data were acquired at rest and during "silent /i/" from 4 singers. During silent /i/, participants voluntarily sustained velar elevation while breathing orally for the entire scan time. Focusing on the extravelar segments, LVP length, angle of the muscle origin, and cross-sectional area (CSA), measurements were obtained and compared between tasks. Results: Three of the 4 participants exhibited the expected patterns of change following concentric contraction of the LVP muscle. Consistent changes from the resting to the contracted state included reductions in LVP length by 13.5% and angle of the muscle origin by 9.8%, as well as increases in CSAs by 22.1%, on average. Conclusions: This study presented high-resolution data of the LVP muscle behavior with the first in vivo 3-D measurements of the contracted LVP muscle, which can be useful for the validation of computational models that aim at describing biomechanical properties of the LVP muscle in future research. The active behavior of the extravelar LVP muscle also provides some insight on optimal LVP muscle geometry to consider during cleft palate repair. [ABSTRACT FROM AUTHOR]

Diffusion tensor imaging (DTI) has been widely used to characterise the 3D fascicle architecture in muscle mechanics. However, the computational expense associated with continuum models make their use in graphics and medical visualisation intractable. This study presents an integration of continuum muscle mechanics with partial least-squares regression to create a fast mechanostatistical model. We use the human gastrocnemius muscle (medial and lateral heads) as an example informed though DTI. Our statistical models predicted muscle shape (within 0.063 mm root-mean-square (RMS) error), musculotendon force (within 1% error), and tissue strain (within 8% max error during muscle contraction), compared to a finite-element model simulation. The technique presented here is a step towards integrating expensive continuum mechanics with fast rigid body solutions in biomechanics. While muscle force is a primary objective in rigid body solvers the additional information including 3D muscle shape and stress/strain fields may now be integrated. One of the key benefits is that muscle interaction with other soft tissues is accounted for, muscle moment arms are not estimated, and the detailed rich 3D continuum fascicle architecture is no longer simplified but plays a full role in biomechanics simulation. This has implications for musculoskeletal biomechanics, orthopaedics and medical visualisation. [ABSTRACT FROM AUTHOR]

Muscle fascicle structure characterises muscle function, which in turn plays a key role in computer simulation of muscle shape. In this study, we use 3D ultrasound from the human medial gastrocnemius muscle to identify and map the muscle fascicle orientation and deformation during passive motion in four subjects. This muscle fascicle description is integrated into a representative muscle volume element using a free-form deformation technique to create a muscle primitive building block that deforms according to the embedded muscle fascicles within. For each subject computed passive tensile force was used to optimise the constitutive behaviour so that the known deformation matched this load. Each subject was fit to match deformation at 25, 50, 75 and 100% of muscle stretch. The subjects that exhibited a larger muscle fascicle pennation angle change during passive stretch were characterised best by a less stiff constitutive law. In contrast, subjects that had a more parallel muscle fascicle deformation, showed stiffer behaviour. The medial gastrocnemius muscle built from these muscle primitives exhibited a contractile shape that is consistent to that observed in human gastrocnemius contraction. This shape was evaluated against the same muscle embedded with muscle fascicles derived from diffusion tensor magnetic resonance imaging and was in good qualitative agreement. Muscle principal strain was shown to align with muscle fascicle direction and was spatially non-uniform. Muscle primitives may be used as building blocks to build large muscle volumes for mechanics simulation, visualisation and medical education. [ABSTRACT FROM AUTHOR]

Joint stiffness is often measured to make inferences about the stiffness of muscle groups, but little can be gleaned about individual muscles. Decomposing the muscular origins of joint stiffness may inform treatment targets for conditions like spasticity. To complement joint stiffness, shear wave ultrasound elastography has been used to estimate the material properties of individual muscles. If shear wave measures are to be used to assess the muscular origins of joint stiffness, then changes in shear wave velocity should strongly relate to changes in joint stiffness. Here, we estimated the relationships between shear wave velocity in the primary plantar flexors [soleus (SOL) and medial gastrocnemius (MG)] and ankle joint stiffness. Participants performed isometric plantar flexion tasks at a range of activations (0-40%), while joint stiffness and muscle shear wave velocities were obtained. We observed a strong, linear relationship between plantar flexor shear wave velocities and joint stiffness. Remarkably, the parameter estimates of this stiffness-shear wave relationship strongly agreed with theoretical and literature-based estimates [SOL:MG parameter ratios = 2.83 (observed) vs. 2.85 (expected from theoretical stiffness ratio)]. Finally, a musculoskeletal model of the plantar flexors was able to accurately reproduce joint stiffness estimates, and shear wave velocities could explain 80-95% of the variance in modeled muscle stiffness. These findings suggest that shear wave velocity may be used to infer the muscular origins of changes in joint stiffness. [ABSTRACT FROM AUTHOR]

Objective: To investigate the efficiency of diffusion tensor imaging (DTI) fiber-tracking based neuronavigation and assess its usefulness in the preoperative surgical planning, prognostic prediction, intraoperative course and outcome improvement. Methods: Seventeen patients with cerebral masses adjacent to corticospinal tract (CST) were given standard magnetic resonance imaging and DTI examination. By incorporation of DTI data, the relation between tumor and adjacent white matter tracts was reconstructed and assessed in the neuronavigation system. Distance from tumor border to CST was measured. Results: The sub-portion of CST in closest proximity to tumor was found displaced in all patients. The chief disruptive changes were classified as follows: complete interruption, partial interruption, or simple displacement. Partial interruption was evident in seven patients (41.2%) whose lesions were close to cortex. In the other 10 patients (58.8%), delineated CSTs were intact but distorted. No complete CST interruption was identified. Overall, the mean distance from resection border to CST was 6.12 mm (range, 0-21), as opposed to 8.18 mm (range, 2-21) with simple displacement and 2.33 mm (range, 0-5) with partial interruption. The clinical outcomes were analyzed in groups stratified by intervening distances (close, <5 mm; moderated, 5-10 mm; far, >10 mm). For the primary brain tumor patients, the proportion of completely resected tumors increased progressively from close to far grouping (42.9%, 50%, and 100%, respectively). Five patients out of seven (71.4%) experienced new neurologic deficits postoperatively in the close group. At meantime, motor deterioration was found in six cases in the close group. All patients in the far and moderate groups received excellent (modified Rankin Scale [mRS] score, 0-1) or good (mRS score, 2-3) rankings, but only 57.1% of patients in the close group earned good outcome scores. Conclusion: DTI fiber tracking based neuronavigation has merit in assessing the relation between lesions and adjacent white matter tracts, allowing prediction of patient outcomes based on lesion-CST distance. It has also proven beneficial in formulating surgical strategies. [ABSTRACT FROM AUTHOR]

Understanding how dexterity improves with practice is a fundamental challenge of motor control and neurorehabilitation. Here we investigate a ball and beam implementation of a dexterity puzzle in which subjects stabilize a ball at the mid-point of a beam by manipulating the angular position of the beam. Stabilizability analysis of different biomechanical models for the ball and beam task with time-delayed proportional-derivative feedback identified the angular position of the beam as the manipulated variable. Consequently, we monitored the changes in the dynamics with learning by measuring changes in the control parameters. Two types of stable motion are possible: node type (nonoscillatory) and spiral type (oscillatory). Both types of motion are observed experimentally and correspond to well-defined regions in the parameter space of the control gains. With practice the control gains for each subject move close to or on the portion of the boundary which separates the node-type and spiral-type solutions and which is associated with the rightmost characteristic exponent of smallest real part. These observations suggest that with learning the control gains for ball and beam balancing change in such a way that minimizes overshoot and the settling time. This study provides an example of how mathematical analysis together with careful experimental observations can shed light onto the early stages of skill acquisition. Since the difficulty of this task depends on the length of the beam, ball and beam balancing tasks may be useful for the rehabilitation of children with dyspraxia and those recovering from a stroke. [ABSTRACT FROM AUTHOR]

Objective: Velopharyngeal (VP) closure has high impact on the quality of life, especially in patients with cleft palate. For better understanding the VP closure, it is important to understand the airflow dynamics of different closure patterns, including circular, coronal, sagittal, and circular with a Passavant's ridge. The purpose of this study was to demonstrate the airflow characteristics of different velopharyngeal closure patterns. Methods: Sixteen adults with no notable upper airway abnormality who needed multislice spiral computed tomography scans as part of their clinical care. Airways were reconstructed. A cylinder and a cuboid were used to replace the VP port in three models of VP port patterns. Flow simulations were carried using computational fluid dynamics. Airflow pressures in the VP orifice, oral cavity and nasal cavity, as well as airflow velocity through the velopharyngeal orifice, were calculated. Results: The airflow dynamics at the velopharynx were different among different velopharyngeal patterns as the area of the velopharyngeal port increased from 0 to 25 mm2. The orifice areas of different closure conditions in four velopharyngeal closure patterns were significantly different. The maximal orifice area for adequate velopharyngeal closure was 7.57 mm2 in the coronal pattern and 6.21 mm2 in the sagittal pattern. Conclusions: Airflow dynamics of the velopharynx were correlated to the velopharyngeal closure patterns. Different closure patterns had different largest permitted orifice areas for getting the appropriate oral pressures for normal speech. [ABSTRACT FROM AUTHOR]