Comparative Functional Morphology of Human and Chimpanzee Feet Based on Three-Dimensional Finite Element Analysis

To comparatively investigate the morphological adaptation of the human foot for achieving robust and efficient bipedal locomotion, we develop three-dimensional finite element models of the human and chimpanzee feet. Foot bones and the outer surface of the foot are extracted from computer tomography images and meshed with tetrahedral elements. The ligaments and plantar fascia are represented by tension-only spring elements. The contacts between the bones and between the foot and ground are solved using frictionless and Coulomb friction contact algorithms, respectively. Physiologically realistic loading conditions of the feet during quiet bipedal standing are simulated. Our results indicate that the center of pressure (COP) is located more anteriorly in the human foot than in the chimpanzee foot, indicating a larger stability margin in bipedal posture in humans. Furthermore, the vertical free moment generated by the coupling motion of the calcaneus and tibia during axial loading is larger in the human foot, which can facilitate the compensation of the net yaw moment of the body around the COP during bipedal locomotion. Furthermore, the human foot can store elastic energy more effectively during axial loading for the effective generation of propulsive force in the late stance phase. This computational framework for a comparative investigation of the causal relationship among the morphology, kinematics, and kinetics of the foot may provide a better understanding regarding the functional significance of the morphological features of the human foot.

Structural FEA-Based Design and Functionality Verification Methodology of Energy-Storing-and-Releasing Prosthetic Feet

The prosthetic feet that are most often prescribed to individuals with K3/K4 levels of ambulation are the ESR feet. ESR stands for energy-storing and -releasing. The elastic energy is stored by the elastic elements in composite materials (carbon fiber or glass fiber). ESR feet must be developed and optimized in terms of stiffness, taking into account the loads that a healthy human foot undergoes and its kinematics while walking. So far, state-of-the-art analyses show that the literature approaches for prosthetic foot design are not based on a systematic methodology. With the aim of optimizing the stiffness of ESR feet following a methodological procedure, a methodology based on finite element structural analysis, standard static testing (ISO 10328) and functional verification was optimized and it is presented in this paper. During the path of optimization of the foot prototypes, this methodology was validated experimentally. It includes the following: (i) geometry optimization through two-dimensional finite element analysis; (ii) material properties optimization through three-dimensional finite element analysis; (iii) validation test on physical prototypes; (iv) functionality verification through dynamic finite element analysis. The design and functional verification of MyFlex-γ, a three-blade ESR foot prosthesis, is presented to describe the methodology and demonstrate its usability.

Reconstruction of a 3D Human Foot Shape Model Based on a Video Stream Using Photogrammetry and Deep Neural Networks

Reconstructed 3D foot models can be used for 3D printing and further manufacturing of individual orthopedic shoes, as well as in medical research and for online shoe shopping. This study presents a technique based on the approach and algorithms of photogrammetry. The presented technique was used to reconstruct a 3D model of the foot shape, including the lower arch, using smartphone images. The technique is based on modern computer vision and artificial intelligence algorithms designed for image processing, obtaining sparse and dense point clouds, depth maps, and a final 3D model. For the segmentation of foot images, the Mask R-CNN neural network was used, which was trained on foot data from a set of 40 people. The obtained accuracy was 97.88%. The result of the study was a high-quality reconstructed 3D model. The standard deviation of linear indicators in length and width was 0.95 mm, with an average creation time of 1 min 35 s recorded. Integration of this technique into the business models of orthopedic enterprises, Internet stores, and medical organizations will allow basic manufacturing and shoe-fitting services to be carried out and will help medical research to be performed via the Internet.

Design and Manufacturing of a New Prosthetic Foot

All prosthetic foot designs, adapted in common use, don't imitate the specific qualities of a typical human foot. The premise of this task is to explore current prosthetics so as to plan and assemble a more human like prosthesis. In attempted such a structure, the new prosthesis will show a more extensive scope of qualities than those showed in current prosthetic feet. In doing as such, the new prosthesis will give a closer portrayal of the capacities inalienable to an ordinary human foot. The qualities associated with ordinary strolling incorporate dorsiflexion foot test. The qualities showed in the produced new foot tried are contrasted with those of" SACH foot". The qualities showed by prostheses which compared well with those of a human foot were researched further. Another prosthetic foot is structured and made from composite random E-glass-polyester. The premise of the new prosthetic plan consolidates current prosthetic structure components, such as, prosthetic materials and segments. The scientific part presents the aftereffects of the static investigation by techniques, such as, mathematical strategies (Finite Element method FEM) and experimental methods. Thus the new foot was designed and dorsiflexion were measured. The new prosthetic foot has a good characteristics when compared with the SACH foot, such as good dorsiflexion (7°-6.4°) respectively.Prosthetic foot

Stiffening the human foot with a biomimetic exotendon

Shoes are generally designed protect the feet against repetitive collisions with the ground, often using thick viscoelastic midsoles to add in-series compliance under the human. Recent footwear design developments have shown that this approach may also produce metabolic energy savings. Here we test an alternative approach to modify the foot–ground interface by adding additional stiffness in parallel to the plantar aponeurosis, targeting the windlass mechanism. Stiffening the windlass mechanism by about 9% led to decreases in peak activation of the ankle plantarflexors soleus (~ 5%, p < 0.001) and medial gastrocnemius (~ 4%, p < 0.001), as well as a ~ 6% decrease in positive ankle work (p < 0.001) during fixed-frequency bilateral hopping (2.33 Hz). These results suggest that stiffening the foot may reduce cost in dynamic tasks primarily by reducing the effort required to plantarflex the ankle, since peak activation of the intrinsic foot muscle abductor hallucis was unchanged (p = 0.31). Because the novel exotendon design does not operate via the compression or bending of a bulky midsole, the device is light (55 g) and its profile is low enough that it can be worn within an existing shoe.

Biomechanical Response of the Human Foot Model Exposed to Vibrations: A Finite Element Analysis

Prolonged exposure to mechanical vibration has been associated with many musculoskeletal, vascular and sensorineural disorders of the foot from simple Plantar fasciitis and Achilles Tendonitis to complex ones as Tarsal tunnel syndrome (TTS) and Vibration white feet/toes. Foot-transmitted vibrations (FTV) are exposed to the occupants using vibrating equipment’s or standing on vibrating platforms. Prolonged exposure to foot-transmitted vibrations (FTV) can lead to syndromes like vibration white feet/toes may result in tingling sensation, blanching of the toes and even numbness in the feet and toes. A multi-layered two dimensional, plane strain finite element model is developed from the actual cross-section of the human foot to study the stresses and strains developed in the skin and soft tissues. The foot is assumed to be in contact with a steel plate, mimicking the interaction between the foot and the work platform. The skin and the subcutaneous tissue are considered as hyperelastic and viscoelastic. The effects of loading in the form of displacements and the frequency of sinusoidal vibration on a time-dependent stress/strain distribution at various depths in the subcutaneous tissue of the foot are investigated. The simulations indicate that lower frequency vibrations penetrate deep into the subcutaneous tissue while higher frequencies are concentrated in the outer skin layer. The present biomechanical model may serve as a valuable tool to study the response of foot of those who work on a vibrating platform.

Comparative radiographic analysis of three-dimensional innate mobility of the foot bones under axial loading of humans and African great apes

The human foot is considered to be morphologically adapted for habitual bipedal locomotion. However, how the mobility and mechanical interaction of the human foot with the ground under a weight-bearing condition differ from those of African great apes is not well understood. We compared three-dimensional (3D) bone kinematics of cadaver feet under axial loading of humans and African great apes using a biplanar X-ray fluoroscopy system. The calcaneus was everted and the talus and tibia were internally rotated in the human foot, but such coupling motion was much smaller in the feet of African great apes, possibly due to the difference in morphology of the foot bones and articular surfaces. This study also found that the changes in the length of the longitudinal arch were larger in the human foot than in the feet of chimpanzees and gorillas, indicating that the human foot is more deformable, possibly to allow storage and release of the elastic energy during locomotion. The coupling motion of the calcaneus and the tibia, and the larger capacity to be flattened due to axial loading observed in the human foot are possibly morphological adaptations for habitual bipedal locomotion that has evolved in the human lineage.

Morphometric relationships between dimensions the anterior talofibular ligament and calcaneofibular ligament in routine magnetic resonance imaging

Purpose This study aimed to test the hypothesis that routine MRI ankle can be used to evaluate dimensions and correlations between dimensions of single and double fascicular variants of the ATFL and the CFL. Methods We reviewed ankle MRIs for 251 patients. Differences between the length, thickness, width, and length of the bony attachments were evaluated twice. P < .05 was considered as significant. Results For the ATFL, we observed a negative correlation between thickness and width, with a positive correlation between thickness and length (p < 0.001). The average values for the ATFL were thickness, 2.2 ± 0.05 mm; length, 21.5 ± 0.5 mm; and width, 7.6 ± 0.6 mm. The average values for the CFL were thickness, 2.1 ± 0.04 mm; length, 27.5 ± 0.5 mm; and width, 5.6 ± 0.3 mm. A negative correlation was found between length and width for the CFL (p < 0.001). Conclusions Routine MRI showed that most dimensions of the ATFL and CFL correlate with each other, which should be considered when planning new reconstruction techniques and developing a virtual biomechanical model of the human foot. Level of evidence III

Design of 3D printable prosthetic foot to implement nonlinear stiffness behavior of human toe joint based on finite element analysis

Toe joint is known as one of the critical factors in designing a prosthetic foot due to its nonlinear stiffness characteristic. This stiffness characteristic provides a general feeling of springiness in the toe-off and it also affects the ankle kinetics. In this study, the toe part of the prosthetic foot was designed to improve walking performance. The toe joint was implemented as a single part suitable for 3D printing. The various shape factors such as curved shape, bending space, auxetic structure, and bending zone were applied to mimic human foot characteristics. The finite element analysis (FEA) was conducted to simulate terminal stance (from heel-off to toe-off) using the designed prosthetic foot. To find the structure with characteristics similar to the human foot, the optimization was performed based on the toe joint geometries. As a result, the optimized foot showed good agreement with human foot behavior in the toe torque-angle curve. Finally, the simulation conditions were validated by comparing with human walking data and it was confirmed that the designed prosthetic foot structure can implement the human foot function.