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Pain is the most significant symptom of knee osteoarthritis (OA), which seriously affects the quality of life of patients. However, the cause of pain, pain relief, and targeted treatment methods are still unclear. Based on the diversified characteristics of knee pain location, this study was aimed to explore the associations between knee pain location and the mechanical properties of soft tissues in patients with knee OA. Fifteen healthy participants and 55 patients with knee OA were recruited and divided into five groups: no pain, anterior superior pain, anterior inferior pain, medial pain, and lateral pain. The Young’s moduli of the muscles, tendons, and ligaments around the knee joint were measured by shear wave elastography (SWE), and the differences between the five groups of soft tissue material properties were compared in this study. The Young’s moduli of the quadriceps tendon (QT), patellar tendon (PT), medial collateral ligament (MCL), and lateral patellar retinaculum (LPR) were strongly associated with pain location and were significantly increased compared with the other four groups, respectively. In addition, the Young’s moduli of the remaining soft tissue were not associated with pain location, and did not change significantly compared with the other four groups. This study provides data reference for the mechanical properties of soft tissue of healthy people and patients with knee OA, and provides a theoretical basis for more targeted pain relief, treatment, and rehabilitation in knee OA.

This study aims to explore the possibility of assessing muscle stress state using shear wave elastography (SWE). Eight healthy males participated in the measurements, and the Young's modulus of 10 leg muscles of each participant were measured in six standard positions: lying, sitting, and four quasi-static walking postures. The contributions of each muscle in the four quasi-static walking postures were examined, and the relationship between the Young's modulus and simultaneously recorded plantar pressure was preliminarily explored for the most significant muscles. Results indicate that ICC3,1 ranges from 0.941 to 0.998, and 95% CI is in the range 0.909-0.999, CV ranges from 1.45% to 9.5%, and SEM ranges from 0.026 kPa to 0.824 kPa for all the tested muscles. This indicates that the Young's modulus of the muscles, measured by SWE, showed excellent retest reliability. In the lying and sitting positions, significant differences were observed in Young's modulus of 9 muscles with the only exception of biceps femoris (BF). In the heel strike and push off positions, strong linear relationships were found between the plantar pressure and Young's modulus of gastrocnemius medialis (GM) suggesting that muscle SWE measurement may be a good indicator of ground reaction forces. This study demonstrates that the SWE measures of the muscle Young's modulus can be used to reliably reflect the quantitative change in the stiffness of a muscle at different positions, and may also be employed to estimate the ground reaction forces and muscle stress state. Although this is a great progress in studying muscle force, it is still a great challenge to measure the Young's modulus of muscle and noninvasively evaluate the muscle force in vivo using SWE.

The necks of birds that possess complex structures, graceful curves, and flexible movements are perfect natural motion actuators. Studying their structural features, mechanic characteristics, and motion rules can provide valuable references for imitating such actuators and motion functions artificially. Previous studies have analyzed the influence of two-dimensional motion geometric features and anatomical structure of the neck on motion efficiency and motion stability. However, the mechanism of motion flexibility from the perspective of neck structure has not been investigated. This study investigates the general law of the relationship between the structural parameters and motion characteristics of birds’ necks using tomography technology and 3D reconstruction technology. The results show that the structural characteristics of geese and ducks are similar, and there are significant differences in joint motion characteristics. Geese obtains complex neck postures through active intervertebral joints and highly flexible facet joints and possesses higher neck flexibility than ducks. This study provides a generic measuring method for obtaining birds’ cervical spinal vertebral structural dimensional parameters and offers a new theoretical concept for bionic robotic structural design and manufacture.

Plantar fascia plays an important role in human foot biomechanics; however, the morphology and mechanical properties of plantar fascia in patients with flexible flatfoot are unknown. In this study, 15 flexible flatfeet were studied, each plantar fascia was divided into 12 positions, and the morphologies and mechanical properties in the 12 positions were measured in vivo with B-mode ultrasound and shear wave elastography (SWE). Peak pressures under the first to fifth metatarsal heads (MH) were measured with FreeStep. Statistical analysis included 95% confidence interval, intragroup correlation coefficient (ICC1,1), one-way analysis of variance (one-way ANOVA), and least significant difference. The results showed that thickness and Young’s modulus of plantar fascia were the largest at the proximal fascia (PF) and decreased gradually from the proximal end to the distal end. Among the five distal branches (DB) of the fascia, the thickness and Young’s modulus of the second and third DB were larger. The peak pressures were also higher under the second and third MH. This study found a gradient distribution in that the thickness and Young’s modulus gradient decreased from the proximal end to the distal end of plantar fascia in the longitudinal arch of flexible flatfeet. In the transverse arch, the thickness and Young’s modulus under the second and third DB were larger than those under the other three DB in flexible flatfoot, and the peak pressures under the second and third MH were also larger than those under the other three MH in patients with flexible flatfoot. These findings deepen our understanding of the changes of biomechanical properties and may be meaningful for the study of pathological mechanisms and therapy for flexible flatfoot.

BACKGROUND The fifth and sixth cervical vertebrae (C5-C6) represent the high-risk segment requiring surgical correction in cervical spondylosis. Anterior cervical discectomy and fusion (ACDF) of C5-C6 includes an intervertebral fusion cage to maintain foraminal height and is combined with anterior plate fixation. The shape of the intervertebral cage can affect the postoperative outcome, including the rates of fusion, subsidence, and neck pain. This study aimed to use finite element (FE) parametric analysis to compare biomechanical properties of changes in intervertebral cage shape for C5-C6 cervical fusion using the anterior cervical plate and cage (ACPC) fixation system. MATERIAL AND METHODS Five shapes were designed for cervical intervertebral cages, square, oval, kidney-shaped, clover-shaped, and 12-leaf-shaped. The performance was evaluated following implantation into the validated normal C5-C6 FE model using simulation with five physiological conditions. The indicators included the maximum von Mises stress of the endplates, the fusion cages, and the cervical vertebrae. The postoperative subsidence-resistance properties were determined, including the interior stress responses of the intervertebral cages and the surrounding tissues. The fusion-promoting properties were evaluated by the interior stress responses of the bone grafts. RESULTS The optimal shape of the cervical intervertebral cage was the 12-leaf-shape for postoperative subsidence resistance. The kidney shape for the cervical intervertebral cage was optimal for postoperative fusion. CONCLUSIONS FE analysis identified the optimal cervical intervertebral cage design for ACPC fixation of C5-C6. This method may be useful for future developments in the design of spinal implants.

The overall distributions of the plantar fascia thickness and Young’s modulus in the ten subjects were systematically investigated in this paper using two-dimensional ultrasound and shear wave elastography (SWE). The statistical analyses showed that ICC1,1 of the plantar fascia thickness and Young’s modulus ranged from 0.950 to 0.991, with the 95% CI in the range of 0.953–0.996. This result indicated that the thickness and Young’s modulus exhibited excellent retest reliability. The conclusion that both the thickness, $d$ , and Young’s modulus, $E$ , of the plantar fascia showed a simple and specific spatial dependence on the characteristics of the gradient distribution can be drawn. As the plantar fascia extends from the calcaneus to the five toes, both the thickness, $d$ , and Young’s modulus, $E$ , of the five bundles of plantar fascia showed a downward trend of a negative exponential function, and the thickness, $d$ , and Young’s modulus, $E$ , were the largest at the tubercle of the calcaneus and closest to the lowest value at the tubercles of the five metatarsal bones. The coefficient of determination (R2) of the fitting curve of thickness, $d$ , and Young’s modulus, $E$ , was higher than 0.959 in all ten subjects. The distribution characteristics of the plantar fascia thickness, $d$ , and Young’s modulus, $E$ , showed good consistency in the healthy subjects in this paper. The conclusions of this paper may provide more accurate references and a basis for material mechanics data for plantar fascia diseases (such as fasciitis) and foot mechanical models (such as finite element models).

The objective of this paper is to quantitatively evaluate the effects of rotator cuff tear propagation on glenohumeral joint stability in a previously constructed and validated finite element shoulder model. Rotator cuff tears with a sequence of increasing sizes were created from the anterior portion of the supraspinatus osseous insertion site and propagated posteriorly through the infraspinatus tendon until a complete tear extended through the entire teres minor tendon. Finite element simulations were performed in the same physiological loading and boundary conditions as in the original model. A novel integrative stability index was proposed and used for quantitative analysis of the simulated results. By defining the healthy condition as the baseline (100%), the stability index decreased slightly with small tear sizes but declined suddenly after half tear of the infraspinatus accompanied by a complete tear of the supraspinatus tendon until the full tear condition, when the index reached 0.41%. These results confirm the clinical and cadaveric findings that glenohumeral joint stability generally decreases as the size of the rotator cuff tear increases and that the critical tear size which leads to the loss of normal shoulder biomechanics was half tear of the infraspinatus accompanied by a complete tear of the supraspinatus tendon. It is concluded that the finite element shoulder model and the proposed novel stability ratio can accurately predict shoulder biomechanics in the investigated rotator cuff condition. Both the model and ratio may have the potential to be used to improve diagnostic and therapeutic strategies for clinicians.

This paper presents the design, analysis, and development of an anthropomorphic robotic hand coined MCR-hand II. This hand takes the advantages of both the tendon-driven and linkage-driven systems, leading to a compact mechanical structure that aims to imitate the mobility of a human hand. Based on the investigation of the human hand anatomical structure and the related existing robotic hands, mechanical design of the MCR-hand II is presented. Then, using D-H convention, kinematics of this hand is formulated and illustrated with numerical simulations. Furthermore, fingertip force is deduced and analyzed, and mechatronic system integration and control strategy are addressed. Subsequently, a prototype of the proposed robotic hand is developed, integrated with low-level control system, and following which empirical study is carried out, which demonstrates that the proposed hand is capable of implementing the grasp and manipulation of most of the objects used in daily life. In addition, the three widely used tools, i.e., the Kapandji score test, Cutkosky taxonomy, and Kamakura taxonomy, are used to evaluate the performance of the hand, which evidences that the MCR-hand II possesses high dexterity and excellent grasping capability; object manipulation performance is also demonstrated. This paper hence presents the design and development of a type of novel tendon–linkage-integrated anthropomorphic robotic hand, laying broader background for the development of low-cost robotic hands for both industrial and prosthetic use.

AIMS The purpose of this study was to detect and compare the surface temperature of plantar vessels in mild diabetic peripheral neuropathy (DPN) patients and healthy controls, to explore a simple, convenient and reliable method for early diagnosis of DPN, and to explore the influence of sex and age on vascular surface temperature. MATERIALS AND METHODS In this study, 60 mild DPN patients (30 males and 30 females) and 60 healthy volunteers were randomly recruited according to their age and sex. Intra-class correlation coefficient was used to evaluate the repeatability of skin temperature measurement in the vascular area. A general linear model was used to analyse the difference of skin temperature between mild DPN patients and healthy controls. RESULTS The infrared detection results of skin temperature corresponding to blood vessels showed excellent test-retest reliability. There was no significant difference in skin temperature between sex and age. But there were significant differences in skin temperature between mild DPN patients and healthy controls, except for the posterior tibial artery. CONCLUSIONS For mild DNP patients, in case of no obvious abnormality in the infrared detection of lower extremity arterial surface temperature, the small vessels have shown early abnormal body surface temperature, that is, the surface temperature of related vessels increased. The research conclusions of this article not only enable us to better understand the correlation between body surface temperature and hemodynamic parameters, but also provide an in vivo, non-invasive, and convenient way of thinking and methods for early diagnosis of DPN.

Introduction: It is well known that foot massage is a very prevalent stress relief method in China. Literatures have reported various massage-inducted peripheral nerve injuries. However, massage-inducted lateral plantar nerve (LPN) injury is very rare. Here, we represent an unusual case of massage-inducted LPN damage, and we also report the diagnostic method of this patient using musculoskeletal ultrasonography combined with electromyography (EMG). Patient concerns: A 21-year-old woman presented symptoms of redness, swelling, pain and numbness in the medial right ankle joint for 2 days. Diagnosis: The results of musculoskeletal ultrasonography and EMG provide great help for doctors to make accurate diagnosis. The patient was eventually diagnosed with LPN injury. Interventions: No further foot massage was allowed. Vitamin B12 was taken orally for 2 months. Conservative therapy, including electrical stimulation therapy and infrared therapy, was conducted. Besides, active rehabilitation training was also performed. Outcomes: The discomfort symptoms were relieved significantly after 2 months conservative treatment. Clinical symptoms and EMG examination illustrated satisfactory result during follow up time. Conclusion: The report showed that the masseur should be very careful when doing foot massage to prevent nerve damage. Besides, musculoskeletal ultrasonography combined with EMG can provide important evidence for accurate and effective diagnosis of LPN injury.

Biological muscles exhibit a high level of integration, in which actuators, sensors and transmission elements can be included in one component. Artificial muscles or actuators refer to intelligent stimuli-responsive materials that could reversibly deform with the trigger of various external stimuli. These materials, which have attracted tremendous attention, produce natural muscle-like actuation performance and show promising applications in robotics. After an introduction of various actuator technologies that contribute to robotic applications, a comparative analysis of the main actuation parameter is provided. The comprehensive comparisons of each kind of artificial muscle are summarised, and the promising properties that are required in robotics are presented, which highlight the development of their actuation performances and the challenges that limit their further employments. Future developmental prospects and perspectives of artificial actuators are discussed.

This paper aims to develop and validate a subject-specific framework for modelling the human hand. This was achieved by combining medical image-based finite element modelling, individualized muscle force and kinematic measurements. Firstly, a subject-specific human hand finite element (FE) model was developed. The geometries of the phalanges, carpal bones, wrist bones, ligaments, tendons, subcutaneous tissue and skin were all included. The material properties were derived from in-vivo and in-vitro experiment results available in the literature. The boundary and loading conditions were defined based on the kinematic data and muscle forces of a specific subject captured from the in-vivo grasping tests. The predicted contact pressure and contact area were in good agreement with the in-vivo test results of the same subject, with the relative errors for the contact pressures all being below 20%. Finally, sensitivity analysis was performed to investigate the effects of important modelling parameters on the predictions. The results showed that contact pressure and area were sensitive to the material properties and muscle forces. This FE human hand model can be used to make a detailed and quantitative evaluation into biomechanical and neurophysiological aspects of human hand contact during daily perception and manipulation. The findings can be applied to the design of the bionic hands or neuro-prosthetics in the future. Electronic supplementary material The online version of this article (10.1007/s10439-019-02439-2) contains supplementary material, which is available to authorized users.

Vertebral fractures associated with the loss of structural integrity of neoplastic vertebrae are common, and determined to the deterioration of the bone quality in the lesion area. The prediction of the fracture risk in metastatically involved spines can guide in deciding if preventive solutions, such as medical prophylaxis, bracing, or surgery are indicated for the patient. In this study, finite element models of 22 thoracolumbar vertebrae were built based on CT scans of three spines, covering a wide spectrum of possible clinical scenarios in terms of age, bone quality and degenerative features, taking into account the local material properties of bone tissue. Simulations were performed in order to investigate the effect of the size and location of the tumoral lesion, the bone quality and the vertebral level in determining the structural stability of the neoplastic vertebrae. Tumors with random size and positions were added to the models, for a total of 660 simulations in which a compressive load was simulated. Results highlighted the fundamental role of the tumor size, whereas the other parameters had a lower, but non-negligible impact on the axial collapse of the vertebra, the vertebral bulge in the transverse plane and the canal narrowing under the application of the load. All the considered parameters are radiologically measurable, and can therefore be translated in a straightforward way to the clinical practice to support decisions about preventive treatment of metastatic fractures.

Summary Humans and animals can achieve agile and efficient movements because the muscle can operate in different modes depending on its intrinsic mechanical properties. For bioinspired robotics and prosthetics, it is highly desirable to have artificial actuators with muscle-like properties. However, it still remains a challenge to realize both intrinsic muscle-like force-velocity and force-length properties in one single actuator simultaneously. This study presents a bioinspired soft actuator, named HimiSK (highly imitating skeletal muscle), designed by spatially arranging a set of synergistically contractile units in a flexible matrix similar to skeletal musculature. We have demonstrated that the actuator presents both intrinsic force-velocity and force-length characteristics that are very close to biological muscle with inherent self-stability and robustness in response to external perturbations. These outstanding properties result from the bioinspired architecture and the adaptive morphing of the flexible matrix material, which adapts automatically to mechanically diverse tasks without reliance on sensors and controllers., Graphical abstract, Highlights • The actuators present intrinsic force-length and force-velocity properties • The actuators provide a variable gearing mechanism to regulate load and velocity • The actuators enable a robotic system in response to external perturbations stably, Biotechnology; Biomechanical engineering; Mechanical systems; Materials mechanics

The simulated calculation is carried out on the ultrasonic detection process for stainless steel resistance spot welding by the finite element technology. It reveals the ultrasonic propagation characteristics and regularity in the inner of the spot welds, and provides a theoretical basis for selecting the Am as a characteristic parameter to represent the fusion state of the spot weld in the actual ultrasonic detection. Then the ultrasonic detection of spot welds with the presence of the porosity defect which easily appears is simulated, and the effect of the porosity on the ultrasonic propagation characteristics is studied. It is found that the ultrasonic reflection and transmission occur at the porosity defect, and finally the correctness and validity of the simulation and the model are verified by the experimental method.

Although the hydraulic transmission system in spider legs is well known, the spider’s mechanism of locomotion during different terrain conditions still need to be explored further. In this study, spider locomotion was observed in detail on three pavement test platforms: horizontal hard pavement, horizontal soft pavement, and sloped soft pavement. The movement characteristics and joint kinematics of Grammostola rosea legs were captured by high-speed cameras and Simi Motion 3D tracking software. These observations showed that the gait pattern was basically consistent with an alternating tetrapod gait; however, the pattern observed on the sloped soft pavement was slightly different from that of the two horizontal pavements. In particular, the duty factor of the spiders was 0.683 when walking on the horizontal hard pavement, 0.668 on the horizontal soft pavement, and 0.630 on the sloped soft pavement. The duty factor was greater than 60% in all three pavement environments, which was minimal when walking on the sloped soft pavement. This pattern showed that spiders might have superior stability when walking, but their stability decreased in the sloped soft pavement environment. The ranges of joint angles through the spiders’ gait cycles in every pavement environment were also analysed and compared. The findings showed that the hydraulically driven femur-patella and tibia-metatarsal joint angles varied widely, which confirmed that hydraulically driven joints had major functions and obvious effects on the walking process. The kinematic patterns identified in this study provide improved understanding of the hydraulic transmission mechanisms, the factors that affect motion stability, and the design of biomimetic systems.

Patellar tendinopathy is among the most widespread patellar tendon diseases in athletes that participate in activities involving running and jumping. Although their symptoms can be detected, especially at the inferior pole of the patella, their biomechanical cause remains unknown. In this study, a three-dimensional finite element model of knee complex was developed to investigate principal stress and strain distributions in the patellar tendon during 0° to 90° knee flexion and slow and fast level-ground walking. Results indicate that the patellar tendon is subjected to tensile stress and strains during all three activities. During flexion, its central proximal posterior region exhibited highest peak stress and strain, followed by central distal posterior, central distal anterior and central proximal anterior region. Similar trends and magnitudes were reported during slow and fast walking. The region with highest principal stresses and strains, central proximal anterior region, also corresponds to the most commonly reported patellar tendinopathy lesion site, suggesting that principal stress and strain are good indicators of lesion site location. Additional factors such as regional variations in material properties and frequency and duration of cyclic loading also need to be considered when determining the biomechanical aetiology of patellar tendinopathy.

In this paper, ultrasonic echo signals of four kinds of stainless steel resistance spot welds, namely failed weld, stick weld, good weld, and defective weld with gas pore, are analyzed in the time domain, frequency domain, and time-frequency domain based on wavelet packet transform. Fourteen ultrasonic characteristic signals which can reflect the different kinds of spot welds are extracted and can be automatically identified and classified by back-propagation (BP) neural network. The method of this paper can realize the intelligent identification of resistance spot welding defects, and the feasibility of this method has been verified in the experiment.

Previous studies on knee biomechanics have mainly focused on the joint structure itself, largely neglecting the material properties of the muscles and connective tissues around the knee joint. Therefore, this study was purposed to conduct a systematic in vivo examination of the material properties of muscles, tendons, and ligaments, and investigated the respective influences of gender and age on the material properties. The participants were 50 healthy males and females within the following four age groups: 21-30 years, 31-40 years, 41-50 years, and above 51 years. The Young's moduli of the muscles, tendons, and ligaments around the knee joint were measured by shear wave elastography (SWE). Analysis of the Young's modulus results showed that excellent repeatability could be achieved by using SWE. For muscles, the intraclass correlation coefficient (ICC) and 95% confidence interval (CI) ranged between 0.952 and 0.987, and 0.923 and 0.992, respectively. The ICC ranged from 0.920 to 0.941, and the 95% CI was between 0.872 and 0.969 for tendons and ligaments. Additionally, the Young's moduli of the muscles, tendons, and ligaments of males were greater than those of females. With the exception for medial patellar retinaculum (MPR), the Young's moduli of other observed tissues decreased with age for both males and females, indicating that age has a significant impact on the Young's moduli of muscles, tendons, and ligaments. Hence, SWE is a reliable and repeatable technique that can be used to assess the Young's moduli of the muscles, tendons, and ligaments around the knee joint. Furthermore, gender and age affects the material properties. The results of this study provide an in vivo database of the material properties of muscles and connective tissues, and thus may prove useful for the prevention and treatment of knee joint injuries and diseases.

Important aspects of spider locomotion rely on a hydraulic mechanism. So far, this has not been theoretically analysed. In this work, the flow mechanism of a main hydraulic joint in a spider leg was studied. The purpose is to gain insight into a biohydraulic mechanism using an engineering approach to improve our understanding of the hemolymph flow path in the spider’s legs and to contribute to the theoretical analysis of the spider’s hydraulic transmission mechanism, thereby providing an inspiration for advanced biomimetic hydraulic systems. During the study, Micro-CT results were used to reconstruct the detailed flow channel. The high-pressure areas (inlet, joint, and closed leg end) and low pressures in between are also identified. Then, the internal flow field was investigated using computational fluid dynamics. At the same time, the method of dynamic mesh regeneration, elastic smoothing, is used to simulate muscle contraction and joint extension. The different functions of the channels are substantiated by the velocity profiles. Finally, a bionic hydraulic system was designed according to the trajectory of haemolymph in the flow channel.

The objective of this study was to develop and validate\ud a subject-specific framework for modelling the human\ud foot. This was achieved by integrating medical image-based\ud finite element modelling, individualised multi-body musculoskeletal\ud modelling and 3D gait measurements. A 3D\ud ankle–foot finite element model comprising all major foot\ud structures was constructed based on MRI of one individual.\ud A multi-body musculoskeletal model and 3D gait measurements\ud for the same subject were used to define loading and\ud boundary conditions. Sensitivity analyses were used to investigate\ud the effects of key modelling parameters on model\ud predictions. Prediction errors of average and peak plantar\ud pressures were below 10% in all ten plantar regions at five\ud key gait events with only one exception (lateral heel, in early\ud stance, error of 14.44%). The sensitivity analyses results suggest\ud that predictions of peak plantar pressures are moderately\ud sensitive to material properties, ground reaction forces and\ud muscle forces, and significantly sensitive to foot orientation.\ud The maximum region-specific percentage change ratios\ud (peak stress percentage change over parameter percentage\ud change) were 1.935–2.258 for ground reaction forces, 1.528–\ud 2.727 for plantar flexor muscles and 4.84–11.37 for foot\ud orientations. This strongly suggests that loading and boundary conditions need to be very carefully defined based on\ud personalised measurement data.

Biological musculoskeletal system (MSK), composed of numerous bones, cartilages, skeletal muscles, tendons, ligaments etc., provides form, support, movement and stability for human or animal body. As the result of million years of selection and evolution, the biological MSK evolves to be a nearly perfect mechanical mechanism to support and transport the human or animal body, and would provide enormously rich resources to inspire engineers to innovate new technology and methodology to develop robots and mechanisms as effective and economical as the biological systems. This paper provides a general review of the current status of musculoskeletal biomechanics studies using both experimental and computational methods. This includes the use of the latest three-dimensional motion analysis systems, various medical imaging modalities, and also the advanced rigid-body and continuum mechanics musculoskeletal modelling techniques. Afterwards, several representative biomimetic studies based on ideas and concepts inspired from the structures and biomechanical functions of the biological MSK are discussed. Finally, the major challenges and also the future research directions in musculoskeletal biomechanics and its biomimetic studies are proposed.

In the panorama of available musculoskeletal modeling software, AnyBody software is a commercial tool that provides a full body musculoskeletal model which is increasingly exploited by numerous researchers worldwide. In this regard, model validation becomes essential to guarantee the suitability of the model in representing the simulated system. When focusing on lumbar spine, the previous works aimed at validating the AnyBody model in computing the intervertebral loads held several limitations, and a comprehensive validation is to be considered as lacking. The present study was aimed at extensively validating the suitability of the AnyBody model in computing lumbar spine loads at L4L5 level. The intersegmental loads were calculated during twelve specific exercise tasks designed to accurately replicate the conditions during which Wilke et al. (2001) measured in vivo the L4L5 intradiscal pressure. Motion capture data of one volunteer subject were acquired during the execution of the tasks and then imported into AnyBody to set model kinematics. Two different approaches in computing intradiscal pressure from the intersegmental load were evaluated. Lumbopelvic rhythm was compared with reference in vivo measurements to assess the accuracy of the lumbopelvic kinematics. Positive agreement was confirmed between the calculated pressures and the in vivo measurements, thus demonstrating the suitability of the AnyBody model. Specific caution needs to be taken only when considering postures characterized by large lateral displacements. Minor discrepancy was found assessing lumbopelvic rhythm. The present findings promote the AnyBody model as an appropriate tool to non-invasively evaluate the lumbar loads at L4L5 in physiological activities.

The study of three-dimensional human kinematics has significant impacts on medical and healthcare technology innovations. As a non-invasive technology, optoelectronic stereophotogrammetry is widely used for in-vivo locomotor evaluations. However, relatively high testing difficulties, poor testing accuracies, and high analysis complexities prohibit its further employment. The objective of this study is to explore an improved modeling technique for quantitative measurement and analysis of human locomotion. Firstly, a 3D whole body model of 17 rigid segments was developed to describe human locomotion. Subsequently, a novel infrared reflective marker cluster for 17 body segments was constructed to calibrate and record the 3D segmental position and orientation of each functional body region simultaneously with high spatial accuracy. In addition, the novel calibration procedure and the conception of kinematic coupling of human locomotion were proposed to investigate the segmental functional characteristics of human motion. Eight healthy male subjects were evaluated with walking and running experiments using the Qualisys motion capture system. The experimental results demonstrated the followings: (i) The kinematic coupling of the upper limbs and the lower limbs both showed the significant characteristics of joint motion, while the torso motion of human possessed remarkable features of segmental motion; (ii) flexion/extension was the main motion feature in sagittal plane, while the lateral bending in coronal plane and the axial rotation in transverse plane were subsidiary motions during an entire walking cycle regarding to all the segments of the human body; (iii) compared with conventional methods, the improved techniques have a competitive advantage in the convenient measurement and accurate analysis of the segmental dynamic functional characteristics during human locomotion. The modeling technique proposed in this paper has great potentials in rehabilitation engineering as well as ergonomics and biomimetic engineering.

Extenics is a newly developed interdisciplinary subject combining mathematics, philosophy and engineering. It provides useful formalized qualitative tools and quantitative tools for solving contradictory problems. In this paper, extension theory is introduced briefly and the primary applications of this theory and methods in bionic engineering research are discussed. The extension model of biological coupling functional system is established. In order to identify the primary and secondary sequencing of coupling elements, the Extension Analytic Hierarchy Process (EAHP) was adopted to analyze the contribution of each coupling element to the coupling functional system. Thus, the influence weight factor of each coupling element can be determined, so as to provide a new approach for solving primary and secondary sequencing problem of coupling elements in a quantitative way, and facilitate the subsequent bionic coupling study.

The corresponding author of the article was not correctly indicated. The correct corresponding author is not the last author, but instead the second author, Lei Ren. The corresponding author's email address is: lei.ren@manchester.ac.uk. In addition, two grant numbers from the Key Project of the National Science Foundation of China were incorrectly listed in the Funding Statement. The Funding Statement should read: "This work was supported by the International Cooperation Project of National Natural Science Foundation of China (No. 50920105504), a Biotechnology and Biological Sciences Research Council Grant (No.BB/H002782/1), the Project of National Natural Science Foundation of China (No. 51105167), the Fundamental Research Founds of China (No. Z201105), the Key project of National Science Foundation of China (No, 51290290 & 51290292), the postdoctoral project (No, 2013M530985) and the scientific and technological development planning project of Jilin Province (No, 20130522187JH). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript."

The objective of this study is to develop a computational framework for investigating the dynamic behavior and the internal loading conditions of the human foot complex during locomotion. A subject-specific dynamic finite element model in the sagittal plane was constructed based on anatomical structures segmented from medical CT scan images. Three-dimensional gait measurements were conducted to support and validate the model. Ankle joint forces and moment derived from gait measurements were used to drive the model. Explicit finite element simulations were conducted, covering the entire stance phase from heel-strike impact to toe-off. The predicted ground reaction forces, center of pressure, foot bone motions and plantar surface pressure showed reasonably good agreement with the gait measurement data over most of the stance phase. The prediction discrepancies can be explained by the assumptions and limitations of the model. Our analysis showed that a dynamic FE simulation can improve the prediction accuracy in the peak plantar pressures at some parts of the foot complex by 10%-33% compared to a quasi-static FE simulation. However, to simplify the costly explicit FE simulation, the proposed model is confined only to the sagittal plane and has a simplified representation of foot structure. The dynamic finite element foot model proposed in this study would provide a useful tool for future extension to a fully muscle-driven dynamic three-dimensional model with detailed representation of all major anatomical structures, in order to investigate the structural dynamics of the human foot musculoskeletal system during normal or even pathological functioning.