Specific deformation behavior of isotactic polypropylene films under a multiaxial stress field.

The specific deformation behavior of crystalline polymer films, namely unoriented crystallized isotactic polypropylene (it PP) films, was investigated under a multiaxial stress field. Changes in the aggregation structure of the films were investigated during the bulge deformation process using in situ small-angle X-ray scattering, wide-angle X-ray diffraction (WAXD) measurements, and polarized high-speed-camera observations. The films had a thickness of approximately 10 µm. The it PP films were fixed at the hole of a plate, then bulge deformation was applied using N2 or He gas pressure, and stress-strain curves were then calculated from the applied pressure and bulge height. Yielding was observed in the stress-strain curves. Below the yield point, in situ WAXD measurements revealed that the crystal lattice expanded isotropically at the center, edge, and bottom of the bulge hole. Above the yield point, a craze started to form slightly near the center, and crazes formed in various directions with a further increase in strain, while the crystal lattice expanded uniaxially along the circumference at the edge and bottom. Crazes oriented in various directions merged and lost birefringence, indicating a change to the isotropic orientation. The different directions of the crazes indicated several directions of stress. In other words, even if multiaxial deformation is applied to a crystalline it PP film, the string-shaped crystalline polymer chain structure produces local anisotropic uniaxial stress.

Morphological variations of the human talus investigated using three-dimensional geometric morphometrics.

INTRODUCTION: The shape of the talus determines the positional and kinematic features of the subtalar, talonavicular, and talocrural joints during walking. Thus, detailed knowledge of the pattern of sexual dimorphism of the human talus may be useful for revealing the pathogenetic mechanism of foot and knee disorders, which are more prevalent in females. The aim of this study was to characterize and visualize the three-dimensional shape variations of the talus in relation to sex and age using geometric morphometrics. MATERIALS AND METHODS: Computed tomography images of 56 feet without talar injuries or disorders were used in this study. Thirty-seven anatomical landmarks were identified on a bone model of the talus to calculate principal components (PCs) of shape variations among specimens. PC scores were compared between sexes, and their correlations with age were also investigated. RESULTS: The female talus had a longer neck and narrower head width than the male talus. The superior trochlea was tilted more laterally in the frontal plane in females. Furthermore, the female talar head was more twisted and was more elongated in the dorsoplantar direction. CONCLUSIONS: Morphological features of the talus in females could alter the subtalar and talonavicular joint kinematics during walking and could be a structural factor in the pathogenetic mechanism underlying foot and knee disorders. This study contributes to the comprehensive understanding of shape variations in the human talus.

Three-Dimensional Morphological Variations of the Human Calcaneus Investigated Using Geometric Morphometrics.

The shape of the calcaneus determines the mechanical interaction of the foot with the ground during the heel-strike in human walking. Detailed knowledge of the pattern of sexual dimorphism of the human calcaneus could help to clarify the pathogenetic mechanism of foot and knee disorders, which are more prevalent in females. Therefore, the aim of this study was to characterize and visualize the three-dimensional shape variations of the calcaneus in relation to sex and age using geometric morphometrics. Computed tomography images of 56 feet without subtalar injuries or disorders were used in this study. Thirty-seven anatomical landmarks were identified on the bone model of the calcaneus to calculate principal components (PCs) of shape variations among specimens. The PC scores were compared between males and females, and their correlations with age were also analyzed. The female calcaneus was longer in length and shorter in height than that of males. The medial process of the calcaneal tuberosity in females was more inferiorly projected and the tuberosity was shifted more laterally. Also, the calcaneus was wider and the sustentaculum tali thickened with aging. Female structural features of the calcaneus alter the kinematics of the foot during walking and could be a structural factor in foot and knee disorders. This study contributes to a comprehensive understanding of shape variations in the human calcaneus. Clin. Anat., 33:751-758, 2020. © 2019 Wiley Periodicals, Inc.

Radius of curvature at the talocrural joint surface: inference of subject-specific kinematics.

PURPOSE: The coupled behavior of talocrural joint motion is primarily determined by the morphological features of the talar trochlea and tibiofibular mortise. Features of the radius of curvature of the talocrural joint, however, remain unclear. The objectives of this study were to evaluate the radius of curvature at the mid, medial, and lateral regions of both the talar trochlea and the tibial plafond, and to estimate subject-specific kinematics of the talocrural joint. METHODS: Computed tomography images of 44 subjects with healthy talocrural joints were assessed by creating three-dimensional bone models. The radii of curvature of the anterior and posterior regions at the mid, medial, and lateral regions of both the talar trochlea and the tibial plafond were calculated. Hypothetical dorsiflexion and plantarflexion axes of the talocrural joint were estimated from the shape of the talar trochlea. Orientations and distances of these axes were calculated. RESULTS: At both the talar trochlea and the tibial plafond, the anteromedial and posteromedial radii exhibited the largest coefficients of variation. The anterior-to-posterior radius ratio (APRR) of the medial talar trochlea significantly correlated with the mid APRR, anterior medial-to-lateral radius ratio (MLRR), and posterior MLRR of the trochlea (r = 0.45, 0.52, - 0.60, respectively, and all P < 0.01). CONCLUSIONS: The asymmetric shape of the medial talar trochlea seems to determine a fixed or changing axis of rotation at the talocrural joint. This subject-specific rotational axis of the talocrural joint should be considered in the management of patients with ankle injuries.

In situ synchrotron radiation X-ray diffraction studies on molecular aggregation structure of nylon 12 films during bulge testing.

It is desirable to establish a method for evaluating mechanical properties, such as modulus and strength, of micrometer and sub-micrometer thick polymer films. Bulge tests, where bulge deformation is imposed on films by the pressure of an inert gas, are suitable for satisfying this demand. However, very few studies on polymer films exist in the literature. In this study, bulge testing equipment for in situ synchrotron radiation wide-angle X-ray diffraction (WAXD) measurements is designed and used to study the relationship between the molecular aggregation structure and the mechanical properties of a crystalline nylon 12 (Ny12) film during bulge testing. Isothermally crystallized and quenched Ny12 films exhibited stress-strain curves similar to those obtained by conventional uniaxial elongation. In situ WAXD measurements during bulge testing revealed that the lattice extension of the crystallites is clearly dependent on crystallinity. Concretely, crystallites in the isothermally crystallized film show higher elastic properties than those in the quenched one. The results of the molecular aggregation structure, including the crystal structure and the amorphous chain surrounding the crystallites, of the films during bulge deformation firstly obtained in this study must be useful for designing toughened polymer films.

Selectivity of Ca2+ channel blockers for dilator actions on the isolated lower esophageal sphincter and aorta from rats.

We compared dilator actions of representative four Ca2+ channel blockers on the isolated lower esophagus sphincter (LES) and thoracic aorta from rats. Verapamil, diltiazem, nifedipine and cilnidipine suppressed KCl-induced contractions of LES and thoracic aorta in a concentration-dependent manner. The order of selectivity for LES, which was calculated as ratio of IC50 value for thoracic aorta divided by that for LES, was diltiazem > verapamil > nifedipine > cilnidipine. These results suggest that diltiazem more preferentially dilates the LES whereas cilnidipine is expected to have lower potential risk of gastroesophageal dysfunction during the antihypertensive therapy.

Three-dimensional morphometric analysis of the talus: implication for variations in kinematics of the subtalar joint.

PURPOSE: Three-dimensional (3D) movement of the clinical subtalar joint (CSTJ) is primarily determined by the morphology of the articular surfaces of the talus. The purposes of this study were to assess the 3D orientation of the CSTJ facets of the talus and the talar head and to determine the tri-axial angular relationship. METHODS: Fifty dry tali were scanned using computed tomography to create a 3D bone model of the talus. The tri-axial angles of the anterior, middle, and posterior facets and the talar head were calculated. A correlation analysis between the angles of the posterior facet and the talar head was also performed. RESULTS: The transverse angle at both the posterior facet and the talar head was significantly correlated with the sagittal angle (r = -0.441, p < 0.001; and r = -0.694, p < 0.001, respectively). The sagittal angle of the posterior facet was significantly correlated with that of the talar head (r = 0.478, p < 0.001). CONCLUSIONS: When the posterior facet of the talus and the talar head exhibits a greater downward and lesser medial orientation, a greater inversion/eversion at the CSTJ should be induced, while an opposite orientation should induce greater plantarflexion/dorsiflexion and medial/lateral rotation at the CSTJ. Our findings will be useful for planning rehabilitation programs and surgical interventions to correct the subtalar joint orientation in clinical settings.

Three-dimensional analysis of talar trochlea morphology: Implications for subject-specific kinematics of the talocrural joint.

Three-dimensional (3D) behavior of the talocrural joint is primarily determined by the articular surface morphology of the talar trochlea and tibiofibular mortise. However, morphological features of the anterior and posterior regions of the talar trochlea remain unclear. The objectives of this study were to evaluate anterior and posterior radii of the medial and lateral talar trochlea and to estimate subject-specific kinematics of the talocrural joint. Fifty dry tali were scanned using computed tomography to create 3D bone models. Radii of curvature of the anterior and posterior region at both the medial and lateral trochlea were calculated. Orientations of the dorsiflexion and plantarflexion axis passing through the centers of the circles fitted to the anterior region of the medial and lateral trochlea and through the centers of the circles fitted to the posterior region of the medial and lateral trochlea were evaluated, respectively. The anterior radius of the medial trochlea was significantly smaller than that of the lateral trochlea by a mean of 7.8 mm (P < 0.001). The posterior radius of the medial trochlea was larger than that of lateral trochlea in 30 samples (60%) and vice versa in 20 samples (40%). Unilateral asymmetric shape of anterior trochlea would induce external rotation of the talus during ankle dorsiflexion, whereas bilateral asymmetric shape of posterior trochlea would induce opposite axial rotations among subjects during ankle plantarflexion, which would help the physical therapists to restore talocrural joint motions to ideal state for patients with ankle injuries. Clin. Anat. 29:1066-1074, 2016. © 2016 Wiley Periodicals, Inc.

Morphological features of the non-affected side of the hindfoot in patients with unilateral varus ankle osteoarthritis.

BACKGROUND: The innate shape characteristics of the hindfoot bones alter the loading conditions of the foot and thus may be associated with an increased risk of developing varus ankle osteoarthritis (OA). This study aimed to clarify the innate morphological patterns of the hindfoot bones that may be associated with ankle OA by analyzing the differences between the bone morphology of the non-affected side of patients with unilateral varus ankle OA and that of healthy participants. METHODS: In this case-control study, computed tomography images were used to develop three-dimensional models of three hindfoot bones (distal tibia with fibula, talus, and calcaneus) from 23 non-affected sides of patients with radiography-diagnosed unilateral ankle OA and 22 healthy control participants. Anatomical and sliding landmarks were placed on the surface of each bone, and the principal components (PCs) of shape variation among specimens were independently calculated for each bone, preserving homology between individuals. The PC modes representing 5% or more of the overall variation were statistically compared between the ankle OA and control groups. RESULTS: Significant differences were identified between the OA and control groups in the fifth PC mode for the tibia with fibula (proportion of variance, 5.1%; p =.025), fifth PC mode for the talus (6.7%, p =.031), and third PC mode for the calcaneus (7.4%, p =.001). The hindfoot bones of the participants who developed ankle OA had the following innate morphological characteristics: the lateral malleolar articular surface of the fibula was shifted superiorly, tibial plafond was enlarged posteroinferiorly, posterior width of the talar trochlea was narrower, talonavicular articular surface of the talus was oriented more frontally, anterior-middle talocalcaneal articular surfaces of the talus were more medially shifted and those of the calcaneus were flatter, calcaneal sustentaculum tali was less protruding, and lateral plantar process of the calcaneus was more superiorly positioned. CONCLUSIONS: These distinctive morphological alterations may increase the incidence and progression of varus ankle OA through aberrant anterior translation, internal rotation, and varus tilting of the talus.

Robot-assisted nephroureterectomy using the GelPoint Platform with a focus on optimizing the port position and specimen retrieval.

INTRODUCTION: One of the factors that makes robot-assisted nephroureterectomy difficult is that the optimal port position differs between nephrectomy and bladder cuff excision. In addition, how best to retrieve the specimen after resection while minimizing the size of the wound is a challenge in robot-assisted surgery. To solve these problems, we designed a surgical technique for robot-assisted nephroureterectomy using the GelPoint Platform with a focus on port position optimization and specimen retrieval. This study describes the surgical technique of GelPoint robot-assisted nephroureterectomy and reports our initial experience with this technique. METHODS: Between January 2023 and May 2024, seven patients underwent robot-assisted nephroureterectomy using the GelPoint Platform and 11 underwent conventional robot-assisted nephroureterectomy. We compared the patients' characteristics and surgical outcomes between the two groups. RESULTS: Compared with the conventional robot-assisted nephroureterectomy group, the median operative time tended to be shorter in the GelPoint robot-assisted nephroureterectomy group (280 vs. 357 min, respectively; p = .135). The maximum incision length tended to be longer in the GelPoint robot-assisted nephroureterectomy group (7.0 vs. 6.0 cm, respectively; p = .078). The incidence of 30-day complications was similar between the two groups (28.5% vs. 18.2%, respectively; p = 1.000). No complications were associated with the use of the GelPoint Platform. CONCLUSION: The surgical outcomes of GelPoint robot-assisted nephroureterectomy are comparable to those of conventional robot-assisted nephroureterectomy, and it can be performed safely and effectively. GelPoint robot-assisted nephroureterectomy can be considered a feasible alternative for selected patients with upper tract urothelial carcinoma.

Electrophysiological effects of an anti-influenza drug oseltamivir on the guinea-pig atrium: comparison with those of pilsicainide.

We assessed the effects of oseltamivir on the conduction velocity and effective refractory period in the guinea-pig atrium in comparison with those of a class Ic antiarrhythmic drug pilsicainide. The recording and stimulating electrodes were attached on the epicardium close to the sinus nodal region and on the left atrial appendage. Oseltamivir (10-100 µM) as well as pilsicainide (1-10 µM) decreased the atrial conduction velocity in a frequency-dependent manner. Both drugs also increased the effective refractory period in both atria; but the frequency-dependent property of oseltamivir was lacking in the left atrium, and it was less obvious in the right atrium compared with that of pilsicainide. These results suggest that oseltamivir can directly modify the electrophysiological functions in the guinea-pig atrium possibly via combination of Na(+) and K(+) channel-blocking actions.

Three-dimensional morphological variations in the calcaneus and talus in relation to the hallux valgus angle.

BACKGROUND: The present study aimed to clarify the morphological patterns of the calcaneus and talus that are associated with hallux valgus angle (HVA) by quantifying the differences in the hindfoot bone morphology between left and right sides in HV patients with clear bilateral difference of HVA. METHODS: Three-dimensional (3D) computed tomography scans of 32 feet of 16 patients with HV who had right-to-left HVA differences of more than 5 degrees (68.8 ± 8.6 years) were enrolled, and 3D surface models of the calcaneus and talus were generated. A total of 556 and 430 landmarks were placed on the calcaneal and talar surfaces, respectively, to calculate the principal components (PCs) of shape variations. The PC scores were compared between the small and large HVA sides within an individual. RESULTS: The calcaneus in patients with a larger HVA (mean, 43.2 degrees) possessed slender calcaneal tuberosity, more medially oriented posterior articular surface in the coronal plane, and narrower and more concave anterior-middle articular surfaces compared to those with a small HVA (mean, 33.7 degrees). The talus with a larger HVA exhibited more medially oriented talar head in the transverse plane and more anteriorly protruded lateral region of the talar head compared to the small HVA. CONCLUSIONS: The morphological patterns of the calcaneus in patients with a larger HVA allows the hindfoot bones to easily rotate in the everting direction, while those of the talus could induce a larger internal rotation of the first metatarsal. These morphological patterns of the calcaneus and talus could be structural factors affecting the HV.

Quantification of the in vivo stiffness and natural length of the human plantar aponeurosis during quiet standing using ultrasound elastography.

This study aimed to identify the stiffness and natural length of the human plantar aponeurosis (PA) during quiet standing using ultrasound shear wave elastography. The shear wave velocity (SWV) of the PA in young healthy males and females (10 participants each) was measured by placing a probe in a hole in the floor plate. The change in the SWV with the passive dorsiflexion of the metatarsophalangeal (MP) joint was measured. The Young's modulus of the PA was estimated to be 64.7 ± 9.4 kPa, which exponentially increased with MP joint dorsiflexion. The PA was estimated to have the natural length when the MP joint was plantarflexed by 13.8°, indicating that the PA is stretched by arch compression during standing. However, the present study demonstrated that the estimated stiffness for the natural length in quiet standing was significantly larger than that in the unloaded condition, revealing that the PA during standing is stiffened by elongation and through the possible activation of intrinsic muscles. Such quantitative information possibly contributes to the detailed biomechanical modeling of the human foot, facilitating an improved understanding of the mechanical functions and pathogenetic mechanisms of the PA during movements.

Three-Dimensional Innate Mobility of the Human Foot on Coronally-Wedged Surfaces Using a Biplane X-Ray Fluoroscopy.

Improving our understanding on how the foot and ankle joints kinematically adapt to coronally wedged surfaces is important for clarifying the pathogenetic mechanism and possible interventions for the treatment and prevention of foot and lower leg injuries. It is also crucial to interpret the basic biomechanics and functions of the human foot that evolved as an adaptation to obligatory bipedal locomotion. Therefore, we investigated the three-dimensional (3D) bone kinematics of human cadaver feet on level (0°, LS), medially wedged (-10°, MWS), and laterally wedged (+10°, LWS) surfaces under axial loading using a biplanar X-ray fluoroscopy system. Five healthy cadaver feet were axially loaded up to 60 kg (588N) and biplanar fluoroscopic images of the foot and ankle were acquired during axial loading. For the 3D visualization and quantification of detailed foot bony movements, a model-based registration method was employed. The results indicated that the human foot was more largely deformed from the natural posture when the foot was placed on the MWS than on the LWS. During the process of human evolution, the human foot may have retained the ability to more flexibly invert as in African apes to better conform to MWS, possibly because this ability was more adaptive even for terrestrial locomotion on uneven terrains. Moreover, the talus and tibia were externally rotated when the foot was placed on the MWS due to the inversion of the calcaneus, and they were internally rotated when the foot was placed on the LWS due to the eversion of the calcaneus, owing to the structurally embedded mobility of the human talocalcaneal joint. Deformation of the foot during axial loading was relatively smaller on the MWS due to restricted eversion of the calcaneus. The present study provided new insights about kinematic adaptation of the human foot to coronally wedged surfaces that is inherently embedded and prescribed in its anatomical structure. Such detailed descriptions may increase our understanding of the pathogenetic mechanism and possible interventions for the treatment and prevention of foot and lower leg injuries, as well as the evolution of the human foot.

Talar trochlear morphology may not be a good skeletal indicator of locomotor behavior in humans and great apes.

To reconstruct locomotor behaviors of fossil hominins and understand the evolution of bipedal locomotion in the human lineage, it is important to clarify the functional morphology of the talar trochlea in humans and extant great apes. Therefore, the present study aimed to investigate the interspecific-differences of the talar trochlear morphology among humans, chimpanzees, gorillas, and orangutans by means of cone frustum approximation to calculate an apical angle and geometric morphometrics for detailed variability in the shape of the talar trochlea. The apical angles in gorillas and orangutans were significantly greater than those in humans and chimpanzees, but no statistical difference was observed between humans and chimpanzees, indicating that the apical angle did not necessarily correspond with the degree of arboreality in hominoids. The geometric morphometrics revealed clear interspecific differences in the trochlear morphology, but no clear association between the morphological characteristics of the trochlea and locomotor behavior was observed. The morphology of the trochlea may not be a distinct skeletal correlate of locomotor behavior, possibly because the morphology is determined not only by locomotor behavior, but also by other factors such as phylogeny and body size.

Morphological differences in the calcaneus among extant great apes investigated by three-dimensional geometric morphometrics.

Investigating the morphological differences of the calcaneus in humans and great apes is crucial for reconstructing locomotor repertories of fossil hominins. However, morphological variations in the calcaneus of the great apes (chimpanzees, gorillas, and orangutans) have not been sufficiently studied. This study aims to clarify variations in calcaneal morphology among great apes based on three-dimensional geometric morphometrics. A total of 556 landmarks and semilandmarks were placed on the calcaneal surface to calculate the principal components of shape variations among specimens. Clear interspecific differences in calcaneal morphology were extracted, corresponding to the degree of arboreality of the three species. The most arboreal orangutans possessed comparatively more slender calcaneal tuberosity and deeper pivot region of the cuboid articular surface than chimpanzees and gorillas. However, the most terrestrial gorillas exhibited longer lever arm of the triceps surae muscle, larger peroneal trochlea, more concave plantar surface, more inverted calcaneal tuberosity, more everted cuboid articular surface, and more prominent plantar process than the orangutans and chimpanzees. These interspecific differences possibly reflect the functional adaptation of the calcaneus to locomotor behavior in great apes. Such information might be useful for inferring foot functions and reconstructing the locomotion of fossil hominoids and hominids.

Sex- and age-related variations in the three-dimensional orientations and curvatures of the articular surfaces of the human talus.

The high prevalence of foot pathologies in women and the elderly could be associated with gender and age difference in the morphology of the foot, particularly the morphology of the keystone of the foot, the talus. The present study investigated the orientation and curvature of the three articular surfaces of the talus in relation to sex and age based on computer tomography (CT), to identify possible morphological factors of the higher prevalence of foot disorders in women and elderly. Fifty-six participants were included in this study. The orientations of the talocrural, subtalar, and talonavicular joints were quantified three-dimensionally by calculating normal and principal axes of the articular surfaces defined by planar approximation. The curvature radii of the articular surfaces were quantified by cylindrical and spherical approximations. The talonavicular surface was significantly more twisted in the frontal plane and less adducted in the transverse plane in females than in males. With aging, the subtalar articular surface was significantly facing more posteriorly. Moreover, it was found that the curvature radii of the trochlea and navicular articular surfaces significantly increased with aging, indicating a flattening of these surfaces. The identified changes in the talar morphology with aging could potentially lead to a higher prevalence of foot disorders in the elderly.

Sex- and age-related morphological variations in the talar articular surfaces of the calcaneus.

BACKGROUND: The prevalence of foot pathologies, such as flatfoot deformity and hallux valgus, is higher in women and increases with age. It has been reported that these types of foot disorders may also be linked to excessive mobility of the subtalar joint to the eversion direction during weight bearing. Given that the mobility of the joint is determined by its articular morphology, sex- and age-related variations in the subtalar articular surface morphology are possible. The purpose of this study was to investigate the orientation and the curvature radii of the talar articular facets of the calcaneus in relation to age and sex using three-dimensional computer tomography. METHODS: Fifty-six feet without subtalar injuries or disorders were included in this study. The orientations of the talar articular surfaces of the calcaneus were quantified in the sagittal and coronal planes. The curvature radii of the articular surfaces of the calcaneus were also assessed based on the approximations of the sphere surfaces. RESULTS: The talar articular surface was oriented more anteriorly and medially in the females than in the males. The curvature radius of the calcaneal posterior facet in the females exhibited a positive correlation with age, indicative of increased articular surface flattening. CONCLUSIONS: The morphological features of the female calcaneus could induce excessive eversion and could lead to a higher prevalence of foot disorders, including flatfoot and hallux valgus, in elderly females. This study contributes to an understanding of the sexual dimorphism of the articular surfaces of the calcaneus and provides insight into the mechanisms that underline various foot disorders.

Direct Evaluation of Local Dynamic Viscoelastic Properties of Isotactic Polypropylene Films Based on a Dynamic µ-Beam X-ray Diffraction Method.

The local mechanical properties of crystalline polymer were evaluated using synchrotron radiation X-ray diffraction with 10 µm lateral resolution. A nonoriented isotactic polypropylene (iPP) film with isolated spherulites in a crystallized matrix was used as a model sample. In situ wide-angle X-ray diffraction (WAXD) measurement was performed on the iPP film using a microbeam synchrotron radiation X-ray under sinusoidal strain. The lattice spacing of the crystal planes increased and decreased in response to the applied sinusoidal strain. Local dynamic viscoelastic functions (dynamic storage and loss moduli (E' and E″)) were calculated at room temperature from the relationship between the calculated applied stress and the response strain obtained by dynamic µ-beam WAXD measurement inside and outside of the spherulites. The E' values inside and outside of spherulite obtained from the change in spacing of the (110) plane were 1.8 and 1.1 GPa, respectively. Furthermore, the E' value inside of spherulite obtained from the change in spacing of the (1̅13) plane was 6.0 GPa. These values can be explained by the deformation of crystallite, which depends on the direction of crystal planes. The results obtained here revealed that synchrotron radiation X-ray diffraction measurement gives not only structural information but also the local mechanical properties of the materials E'.