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Purpose : Toe flexor strength (TFS) has been determined to evaluate the toe flexor muscle function. However, it is unclear how strength and size relationships of toe flexor muscles vary depending on the toes intended for force production. We aimed to clarify this by examining the relationship between TFS and toe flexor muscle size, and hypothesized TFS produced by all toes (TFS-All), the great toe (TFS-Great) and lesser toes (TFS-Lesser) would be specifically associated with the size of the muscles specialized in each corresponding toe flexion. Methods : The maximal anatomical cross-sectional area (ACSA max ) of each toe flexor muscle was measured by magnetic resonance imaging in twenty healthy young men. The three types of TFS were measured using a custom-made toe push dynamometer. Results : TFS-All was significantly associated with ACSA max of the adductor hallucis transverse head (ADDH-TH) ( r = 0.58, P = 0.01) and flexor hallucis brevis (FHB) ( r = 0.56, P = 0.01). TFS-Great and TFS-Lesser were not significantly correlated with ACSA max of any analyzed muscles, except for a significant correlation between TFS-Lesser and dorsal/plantar interosseous muscle ( r = 0.48, P = 0.03). Conclusions : The size of two plantar intrinsic foot muscles, FHB, anatomically specialized for the great toe flexion, and ADDH-TH, supplementary flex the great toe, may be the determinant for TFS-All. However, TFS-Great and TFS-Lesser are not associated with the size of the muscles anatomically specialized in each corresponding toe flexion, perhaps due to difficulty in maximally and separately activating individual muscles (i.e., neural/anatomical reasons) during the TFS-Great and TFS-Lesser production., (© 2024 Yuki Kusagawa et al., published by Sciendo.)

For over a century researchers have marveled at the square-shaped toe tips of several species of climbing salamanders (genus Aneides), speculating about the function of large blood sinuses therein. Wandering salamanders (Aneides vagrans) have been reported to exhibit exquisite locomotor control while climbing, jumping, and gliding high (88 m) within the redwood canopy; however, a detailed investigation of their digital vascular system has yet to be conducted. Here, we describe the vascular and osteological structure of, and blood circulation through, the distal regions of the toes of A. vagrans using histology in tandem with live-animal videos. Specifically, we sectioned a toe of A. vagrans at 0.90 μm, embedded it in Spurrs resin, and stained the tissue with toluidine blue. An additional three toes were sectioned at 10 μm, embedded in paraffin, and after sectioning and mounting, treated with Verhoeff and Quad stains. For living salamanders, we recorded real-time videos of blood flowing within individual toes upon a translucent surface oriented both horizontally (0°) and vertically (90°) to simulate both prostrate and vertical clinging scenarios, then analyzed the image sequences using ImageJ. We found that the vascularized toe tips have one large sinus cavity that is divided more proximally into two chambers via a septum, and there are mucous and granular glands in the dorsal and dorsolateral integument of the digit tips. Live-animal trials revealed variable sinus-filling both within and between toes, seemingly associated with variable pressure applied to the substrate when standing, stepping, clinging, and climbing. We conclude that A. vagrans, and likely other climbing salamanders, can functionally fill, trap, and drain the blood in their vascularized toe tips to optimize attachment, detachment, and complex arboreal locomotion (e.g., landing after gliding flight). Such an adaptation could provide insights for bioinspired designs., (© 2025 The Author(s). Journal of Morphology published by Wiley Periodicals LLC.)

Adhesive toe pads have evolved numerous times over lizard evolutionary history, most notably in geckos. Despite significant variation in adult toe pad morphology across independent origins of toe pads, early developmental patterns of toe pad morphogenesis are similar among distantly related species. In these distant phylogenetic comparisons, toe pad variation is achieved during the later stages of development. We aimed to understand how toe pad variation is generated among species sharing a single evolutionary origin of toe pads (house geckos-Hemidactylus). We investigated toe pad functional variation and developmental patterns in three species of Hemidactylus, ranging from highly scansorial (H. platyurus), to less scansorial (H. turcicus), to fully terrestrial (H. imbricatus). We found that H. platyurus generated significantly greater frictional adhesive force and exhibited much larger toe pad area relative to the other two species. Furthermore, differences in the offset of toe pad extension phase during embryonic development results in the variable morphologies seen in adults. Taken together, we demonstrate how morphological variation is generated in a complex structure during development and how that variation relates in important functional outcomes., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology.)

Chatogekko amazonicus is a miniaturized gecko from northern South America and is among the smallest of toe pad bearing lizards. The toe pads of C. amazonicus are miniscule, between 18% and 27% of the plantar surface area. We aimed to investigate the relationship between adhesive toe pad morphology, body size, and adhesive capabilities. Using scanning electron microscopy, we determine that the adhesive pads of C. amazonicus exhibit branched setae similar to those of other geckos, but that are generally much smaller. When compared with other gecko taxa, we show that C. amazonicus setae occupy a similar range of seta length: snout-vent length ratio and aspect ratio as other gekkonoid species (i.e. Gekkonidae, Phyllodactylidae, and Sphaerodactylidae). We demonstrate that C. amazonicus-even with its relatively small toe pads-is capable of climbing a smooth glass surface at a nearly vertical angle. We suggest that sphaerodactylids like C. amazonicus offer an excellent system for studying toe pad morphology and function in relation to miniaturization., (© 2024 The Author(s). The Anatomical Record published by Wiley Periodicals LLC on behalf of American Association for Anatomy.)

The cross sectional, analytic and descriptive type study was conducted among 5-10 years aged Bangladeshi children at different areas of Mymensingh District (Fulbaria, Trisal, Haluaghat, Fulpur and Muktagacha), Bangladesh on 109 Bangladeshi children from January 2016 to December 2016. Nonrandom purposive sampling technique was taken for sample collection. Any kind of foot deformity resulting either from physical injury or congenital anomaly was excluded to construct standard data. The present anthropometric study was designed to construct data of 5 to 10 years aged Bangladeshi children regarding great toe length, to measure correlation of stature with great toe length and comparison of great toe length between male and female children. This study has been made out to grow interest among the researchers for future study of different country. Stature of the subject was measured with the stadiometer and great toe length was measured using slide caliper. The children were requested to stand with weight distributed equally on both feet. The legs were perpendicular to the feet. The mean great toe length of both sides of 5, 6, 7, 8, 9 and 10 years aged male were 2.90±0.51 cm, 3.00±0.38 cm, 3.18±0.42 cm, 3.41±0.26 cm, 3.34±0.32cm and 3.57±0.45 cm respectively and those of female were 2.93±0.70 cm, 2.70±0.43 cm, 3.05±0.37 cm, 3.02±0.25 cm, 3.42±0.55 cm and 3.62±0.44 cm respectively. Great toe length showed non-significant positive correlation with stature in 5 years old female, 7 years old male and female, 8 years old male, 9 and 10 years old male and female children. In 5 years old male, 6 years old male and female and 8 years old female children, great toe length showed non-significant negative correlation with stature. Comparison of great toe length between male and female children was done by Unpaired Students 't' test which was statistically non-significant.

Studying the role of the prenatal endocrine environment in humans is challenging due to the ethical and practical considerations of measuring hormone levels of the developing fetus. Because it has been difficult to ascertain whether prenatal androgens contribute to the brain and behavior in humans as it does in non-human species, retrospective markers of prenatal androgens, such as the second-to-fourth finger digit ratio (2D:4D), are of interest to the studying of human behavioral endocrinology. To assess the validity of such markers, laboratory animals have been studied. Some strains of mice have been reported to show a sex difference in 2D:4D, and pharmacological and genetic manipulation of the androgen and estrogen receptors (AR and ER) has implicated a role for prenatal androgens in mediating this sex difference, although there have been conflicting reports. Here, we compared mice with global AR overexpression to mice with wildtype (WT) littermates and mice with neural-specific AR overexpression. We found a sex difference in the right hind paw, such that males had larger digit ratios than females. Regardless of sex, mice with global AR overexpression showed an increase in the right hind 2D:4D ratio compared with both WT and neural-specific AR overexpression mice. These results support a role for non-neural AR in the development of 2D:4D and suggest that increased sensitivity to androgens via increased AR is sufficient to increase the masculinization of digit ratios. Future directions for confirming the validity of 2D:4D as a marker for prenatal androgen exposure are discussed., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Purpose: Using 320-detector row computed tomography angiography (320-CTA) to investigate the arterial supply for the toe flaps, namely the anatomical characteristics of the dorsalis pedis artery (DPA), the first dorsal metatarsal artery (FDMA), and the arteries of the first toe web space (AsFTWS)., Methods: This was a prospective study on CTA of 72 intact feet of 36 Vietnamese adults who had sequelae of thumb or metacarpal hand amputation, from June 2017 to December 2019, then preoperative CTA images were compared with surgical findings on 31 feet of 29 patients., Results: 320-CTA was able to investigate the DPA, FDMA, and AsFTWS in 100% of cases. DPA was absent in 6.9% of cases. The average diameters at its origin and termination were 3.22 and 2.56 mm, respectively. For FDMA, the rates of Gilbert type I, II, and III were 52.8%, 18.1%, and 29.2%; the average diameters at its origin and termination were 1.98 and 1.67 mm, respectively. At the first toe web space, FDMA was dominant in 54.2% of cases; the first plantar metatarsal artery (FPMA) was dominant in 29.2% of cases; both arteries were equally dominant in 16.6%. The average diameter at the origin of the lateral plantar digital artery of the great toe was 1.48 mm, of the medial plantar digital artery of the second toe was 1.21 mm. Preoperative CTA images resembled the surgical findings in all cases. The survival rate of toe flaps was 100%., Conclusion: The 320-CTA provided proper preoperative images in two and three dimensions, and helped surgeons to establish a preoperative surgical plan, thus increasing the success rate of toe transfer surgery., (© 2021. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Purpose: Selective percutaneous tenotomy of the flexor digitorum longus (FDL) is a treatment for claw toes that gives astonishingly good functional results despite tendon sacrifice. However, the involution of the FDL tendon stump after tenotomy is unknown. The aim of our study was to assess the involution of the tendon stump after selective percutaneous tenotomy of the FDL., Methods: The study included two parts. In the clinical part, an ultrasound analysis of 15 FDL tenotomies in 7 patients was carried out 3 months post-surgery. In the anatomic part, the feet of 10 bodies donated to science were dissected and examined anatomically., Results: The proximal stump of the FDL was located near the base of the proximal phalanx and moved synchronously with the flexor digitorum brevis (FDB).Separating the FDB and FDL revealed a large tissue connection between the plantar surface of the tendinous chiasm of the FDB and the dorsal part of the FDL. These connections had significant resistance ranging from 2 to 9 Newtons depending on the toe. Tenotomy of the FDL followed by proximal traction of it led to retraction of the stump up to the base of the proximal phalanx and transfer of its action to the FDB by tensioning the intertendinous structure. Histologically, these structures were mostly comprised of tendon connective tissue. Their vascular component was small., Conclusion: The presence of this intertendinous connection leads, in the case of isolated tenotomy of the FDL, to equivalent transfer of the latter to the FDB., (© 2021. The Author(s), under exclusive licence to Springer-Verlag France SAS part of Springer Nature.)

The functional morphology of squamate fibrillar adhesive systems has been extensively investigated and has indirectly and directly influenced the design of synthetic counterparts. Not surprisingly, the structure and geometry of exemplar fibrils (setae) have been the subject of the bulk of the attention in such research, although variation in setal morphology along the length of subdigital adhesive pads has been implicated to be important in the effective functioning of these systems. Adhesive setal field configuration has been described for several geckos, but that of the convergent Anolis lizards, comprised of morphologically simpler fibrils, remains largely unexplored. Here, we examine setal morphology along the proximodistal axis of the digits of Anolis equestris and compare our findings to those for a model gecko, Gekko gecko. Consistent with previous work, we found that the setae of A. equestris are generally thinner, shorter, and present at higher densities than those of G. gecko and terminate in a single spatulate tip. Contrastingly, the setae of G. gecko are hierarchically branched in structure and carry hundreds of spatulate tips. Although the splitting of contacts into multiple smaller tips is predicted to increase the adhesive performance of a fiber compared to an unbranched one, we posited that the adhesive performance of G. gecko and A. equestris would be relatively similar when the configuration of the setal fields of each was accounted for. We found that, as in geckos, setal morphology of A. equestris follows a predictable pattern along the proximodistal axis of the pad, although there are several critical differences in the configuration of the setal fields of these two groups. Most notably, the pattern of variation in setal length of A. equestris is effectively opposite to that exhibited by G. gecko. This difference in clinal variation mirrors the difference in the direction in which the setal fields of anoles and geckos are peeled from the substrate, consistent with the hypothesis that biomechanical factors are the chief determinants of these patterns of variation. Future empirical work, however, is needed to validate this. Our findings set the stage for future comparative studies investigating the functional morphology of these convergent adhesive apparatuses. Such investigations will lead to an enhanced understanding of the interactions between form, function, and environment of fibril-based biological adhesive systems., (© 2020 Anatomical Society.)

The skin of the foot provides the interface between the bird and the substrate. The foot morphology involves the bone shape and the integument that is in contact with the substrate. The podotheca is a layer of keratinized epidermis forming scales that extends from the tarsometatarsus to the toe extremities. It varies in size, shape, amount of overlap and interacts with the degree of fusion of the toes (syndactyly). A study of toe shape and the podotheca provides insights on the adaptations of perching birds. Our analysis is based on micro-CT scans and scanning electron microscopy images of 21 species from 17 families, and includes examples with different orientations of the toes: zygodactyl (toes II and III forward), anisodactyl (toes II, III, and IV forward), and heterodactyl (toes III and IV forward). We show that in these three groups, the skin forms part of a perching adaptation that involves syndactyly to different degrees. However, syndactyly does not occur in Psittacidae that use their toes also for food manipulation. The syndactyly increases the sole surface and may reinforce adherence with the substrate. Scale shape and toe orientation are involved in functional adaptations to perch. Thus, both bone and skin features combine to form a pincer-like foot., (© 2020 Wiley Periodicals LLC.)

The objective of the present study was to model in 3D the detailed morphometric features of the thoracic and pelvic limb bones of the gazelle (Gazella subgutturosa), whose natural habitat is only in the Sanliurfa province, by using multidetector computerized tomography (MDCT) images. Materials from 14 (7 male and 7 female) dead gazelles were collected from the Harran University Veterinary Medicine Faculty clinics during or after treatment. MDCT images of the gazelles were taken and saved as DICOM (Digital Imaging and Communications in Medicine) files. MIMICS 20.1 software was used to generate a 3D reconstruction of the data, and morphological and morphometrical evaluation was performed. In respect of morphological features, the combined metacarpus (Mc) III and metacarpus Mc IV were the main weight-bearing metacarpal bone, while Mc II and Mc V were rudimentary. On the femur, the lateral condyle was bigger than the medial condyle at the caudodistal end and the medial wing of the trochlea femoris was larger than the lateral. As with the thoracic limb, the combined metatarsus (Mt) III and metatarsus Mt IV were the main weight-bearing metacarpal bone and they displayed a synostosis structure. There was no secondary metatarsus in the gazelles' pelvic limb. Based on digital measurements, the tibia was the longest bone of the gazelles' skeletal system, and there was a statistically significant sexual dimorphism throughout the skeleton at the levels of p < .05, p < .01 and p < .001. As a result, the present study's findings are useful as reference data for further studies on anatomy, surgery and archaezoology, while also being useful for classifying species and for forensic sciences., (© 2020 Wiley-VCH GmbH.)

Negative interactions between species can generate divergent selection that causes character displacement. However, other processes cause similar divergence. We use spatial and temporal replication across island populations of Anolis lizards to assess the importance of negative interactions in driving trait shifts. Previous work showed that the establishment of Anolis sagrei on islands drove resident Anolis carolinensis to perch higher and evolve larger toepads. To further test the interaction's causality and predictability, we resurveyed a subset of islands nine years later. Anolis sagrei had established on one island between surveys. We found that A. carolinensis on this island now perch higher and have larger toepads. However, toepad morphology change on this island was not distinct from shifts on six other islands whose Anolis community composition had not changed. Thus, the presence of A. sagrei only partly explains A. carolinensis trait variation across space and time. We also found that A. carolinensis on islands with previously established A. sagrei now perch higher than a decade ago, and that current A. carolinensis perch height is correlated with A. sagrei density. Our results suggest that character displacement likely interacts with other evolutionary processes in this system, and that temporal data are key to detecting such interactions., (© 2020 The Authors. Evolution © 2020 The Society for the Study of Evolution.)

Digit tip regeneration is one of the few examples of true multi-tissue regeneration in an adult mammal. The key step in this process is the formation of the blastema, a transient proliferating cell mass that generates the different cell types of the digit to replicate the original structure. Failure to form the blastema results in a lack of regeneration and has been postulated to be the reason why mammalian limbs cannot regrow following amputation. Understanding how the blastema forms and functions will help us to determine what is required for mammalian regeneration to occur and will provide insights into potential therapies for mammalian tissue regeneration and repair. This review summarizes the cellular and molecular mechanisms that influence murine blastema formation and govern digit tip regeneration.

Background: The flexor hallucis longus (FHL) muscle often has a tendinous slip with a variable number of branches. We aimed at developing the FHL branch test to determine the number of FHL branches., Methods: In anatomical validation study, 6 intact cadavers were used. The toe flexion angles were measured while the FHL and flexor digitorum longus (FDL) were manually pulled individually. For electrophysiological studies, 4 healthy men participated. The FHL was electrically stimulated, and electromyography (EMG) of the FHL and FDL were recorded during the FHL branch test., Results: The toe flexion angles' changes in the FHL pulling condition were equivalent with pulling FDL in toes with FHL branching. The electrical stimulation of the FHL produced similar flexion as the FHL branch test. EMG of the FHL was higher than FDL during the FHL branch test (p=0.036)., Conclusions: The FHL branch test could be used to evaluate the number of FHL branches., (Copyright © 2019 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.)

Background: Ingrowing toenails are a common and painful condition often requiring surgical management. Practitioners who perform surgery on ingrowing toenails include orthopaedic surgeons, general practitioners, podiatrists and podiatric surgeons. There has been limited investigation into the specific surgical approaches used by Australian podiatric surgeons for ingrowing toenails, or the associated infection rates for these procedures. The aim of this study was to assess the frequency and type of ingrowing toenail surgery performed by podiatric surgeons, and identify risk factors for post-operative infection., Methods: Data was entered into the Australian College Podiatric Surgeons (ACPS) National Audit Tool for all patients who underwent foot and ankle surgery performed by podiatric surgeons in Australia between January 2014 and December 2017. Infection within the first 30 days following surgery was recorded according to the ACPS national audit descriptors. Infection rates, risk ratios (RR) and 95% Confidence Intervals (CI) were calculated to determine postoperative infection risk., Results: Of 7682 records, 1831 reported 2712 diagnoses of ingrowing nails. Patients with a diagnosis of ingrowing toenails were younger, less likely to have systemic disease, and a lower proportion were female compared to those without ingrowing toenails. Furthermore, they were more likely to be diagnosed with a post-operative infection than those without ingrowing toenails (RR = 2.72; CI = 2.00-3.69; P < 0.01). Univariate risk factors for post-operative infection following ingrowing toenail surgery include age greater than 60 years (RR = 3.16; CI = 1.53-6.51; P < 0.01), surgery performed in an office setting (RR = 1.77; CI = 1.05-2.98; P = 0.04), and radical excision of toenail bed procedure (RR = 2.35; CI = 1.08-5.01; P = 0.04). Patients that underwent radical excision or office based procedures were on average older, and more likely to have systemic disease. Further, radical excision procedures were more likely to be performed in office base settings., Conclusions: Ingrowing toenail surgery carries a greater risk of postoperative infection than other procedures performed by podiatric surgeons. Radical excision of toenail bed was associated with higher postoperative infection rates compared to other ingrowing toenail procedures. Procedures performed in an office setting carry a higher risk of infection. Further research into these associations is recommended.

As the main actuator of high-speed running, the ostrich feet are highly capable of cushioning and shock absorption. In this study, based on the elastic modulus scales and assembly order of the 3rd toe soft tissues and the functions of the metatarsophalangeal (MTP) joint, we designed fourteen bio-inspired feet. The impact process on loose sand was simulated on the finite element software Abaqus. Also the stress distributions and deformations of each component of the bio-inspired feet were clarified. With the peak acceleration as the index, the cushioning performances of the bio-inspired feet were compared on both loose sand and solid ground through height-variable impact tests. The 15-15-15 HA (hardness unit) bio-inspired foot showed lower peak acceleration and thereby better cushioning performance, but larger deformation, less-uniform stress distribution and thereby lower stability than the 15-35-55 HA bio-inspired foot. In fact, the silicon rubbers with different hardness degrees (which simulate the elasticity modulus scales of the digital cushions, fascia and skin) and the spring mechanism (which simulates the functions of the MTP joint) work as an "integrated system" of cushioning and shock absorption., Competing Interests: The authors have declared that no competing interests exist.

This study considered possible sexual dimorphism in the relative lengths of the second, third and fourth digits (digit ratio), in calves. Furthermore, a different length of the bone structures of the third (3D) and of the fourth (4D) digits has been examined as an evolutionary adaptation to locomotion on soft ground. The length of the digital bones of the right fore-limb of 33 females and 15 male calves was measured in vivo using a portable X-ray machine. The vestigial structure of the second digit (2D), and 3D and 4D, from metacarpus to the third phalanx were considered in a mixed model, as well as some ratios between 2D and different parts of 3D or 4D (2D:3D and 2D:4D). A covariate for the mean finger length was considered for digit ratios to control for possible biases due to shape allometry. Shorter first phalanx and trotter were found in 3D than in 4D, and the reverse for the third phalanx. The 2D was significantly shorter in females, as well as the second phalanges of 3D and 4D. Significant sex differences in 2D:3D and 2D:4D were found for some digit parts of 3D and 4D and for the first phalanges of 3D:4D. These ratios were always shorter in females, in contrast to that found in most mammals. The asymmetry between 3D and 4D could mean a functional adaptation for locomotion. Sex differences in 2D:4D and 3D:4D were found, but with a reverse pattern than in most mammal species (males > females rather than males < females). In this regard digit ratio in calves was similar to that of Old World monkeys. This study is the first investigation of digit ratio in Ungulates, whose limbs differ from the limbs of most mammals, maintaining five digits. The reverse pattern of sex differences (digit ratios: males> females) could be due to the peculiar nature of the vestigial dewclaw of 2D and to the hormone patterns acting on this digit during development, but further research is required around this topic., Competing Interests: Declaration of Competing Interest The authors have declared that no competing interests exist., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

Extreme climate events such as droughts, cold snaps, and hurricanes can be powerful agents of natural selection, producing acute selective pressures very different from the everyday pressures acting on organisms. However, it remains unknown whether these infrequent but severe disruptions are quickly erased by quotidian selective forces, or whether they have the potential to durably shape biodiversity patterns across regions and clades. Here, we show that hurricanes have enduring evolutionary impacts on the morphology of anoles, a diverse Neotropical lizard clade. We first demonstrate a transgenerational effect of extreme selection on toepad area for two populations struck by hurricanes in 2017. Given this short-term effect of hurricanes, we then asked whether populations and species that more frequently experienced hurricanes have larger toepads. Using 70 y of historical hurricane data, we demonstrate that, indeed, toepad area positively correlates with hurricane activity for both 12 island populations of Anolis sagrei and 188 Anolis species throughout the Neotropics. Extreme climate events are intensifying due to climate change and may represent overlooked drivers of biogeographic and large-scale biodiversity patterns., Competing Interests: The authors declare no competing interest.

Toe joint articulation has been shown to affect gait mechanics, as evidenced by walking simulations, biped robots, and foot prostheses. However, it is not known how parameters such as toe length, foot arch length (i.e., heel-to-toe-joint length) or toe joint axis angle affect human walking. We utilized a previously developed adjustable ankle-toe prosthesis to systematically examine these three foot parameters. We tested ten able-bodied persons walking on a force instrumented-treadmill while wearing a pair of adjustable prostheses attached bilaterally below simulator boots (which fixated their biological ankles). We collected motion and ground reaction force data to compute lower-limb kinematics and kinetics as well as COM power and work. We observed that increasing the foot arch length by 60 mm (35%) increased COM Push-off work by ~5 J, due to increased energy storage and return by the ankle spring. Increasing the toe length by 40 mm (80%) and changing the toe joint axis by ±9° from a neutral angle resulted in negligible effects on COM mechanics and lower limb kinetics. This study provides further insights regarding toe joint function; knowledge which may benefit the design/integration of toe joints into prostheses, exoskeletons and legged robots., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The differences in the anatomy of the foot and the hand may affect the dorsal flap design for web space reconstruction. In this study, the authors aimed to identify the differences in web space anatomy of the foot and the hand and provide a guideline of flap design for web space reconstruction in the foot and the hand. The right hands and right feet of adult volunteers were measured, including surgical landmarks (i.e., the dorsal prominence of proximal interphalangeal and metacarpophalangeal joints [or metatarsophalangeal joints]), proximal phalangeal length, tip of the web space, and width of web space. The web spaces and other parameters were analyzed and compared between the foot and the hand by using a paired t test with p < .05 to indicate statistical significance. A total of 108 web spaces of the foot and hand from 18 adult volunteers were analyzed. The parameters that were significantly different between the foot and the hand included (1) proximal phalangeal length (34.63 vs 60.16 mm), (2) average web height ratio (0.72 vs 0.51), (3) average web width ratio (0.69 vs 0.81), (4) mean slope angle (4.89° vs 19.26°), and (5) average abduction angle (25.33° vs 31.07°). In conclusion, the foot web space had a higher slope angle, less abduction angle, and shorter proximal phalangeal length. Therefore, the flap design for foot web space reconstruction requires a longer and narrower flap than the design for the hand. The recommended flap design length should be at least 72% of proximal phalangeal length for the foot versus 51% for the hand, and the width should be at least 69% of the distance between the tips of adjacent metatarsophalangeal joints for the foot versus 81% for the hand., (Copyright © 2019 the American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.)

Various conditions may result in forefoot pain. Magnetic resonance (MR) imaging allows accurate assessment of many of these conditions. We provide an overview of forefoot disorders divided into bones, capsule and plantar plate, musculotendinous structures, neurovascular structures, and subcutaneous tissue. We review normal anatomical features as well as MR imaging findings of common disorders., (Copyright © 2019 Canadian Association of Radiologists. Published by Elsevier Inc. All rights reserved.)

The ventral structures of the avian digits are the critical interface between a bird and the item within its grasp (e.g., prey, landing substrate, or object), and as such are vital for ensuring the hunting success and survival of predatory birds. Here, we present the first descriptive analysis of the ventral structures of the toes, toepad morphology, and toepad surface area of several diurnal (Accipitriformes and Falconiformes) and nocturnal species (Strigiformes) of Australian raptors. We compare these with nonpredatory taxa (passeriform and psittaciform) to elucidate possible functional explanations for these differences. Although all groups shared the structural characters of joint, phalanx, ungual, and central (tarsal) pad features, the positioning of these structures in relation to the underlying skeletal framework and subsequent gross morphology differed markedly. Toepads overlying the phalangeal joints were much more developed in raptorial species with protrusional toepads only found on goshawks (Accipiter sp.), falcons, and owls. In contrast, the ventral surface of representative passeriform and parrot species showed overall uniformity in contact surface area, with much flatter toepads. There was only a very low phylogenetic signal in the data indicating that phylogenetic relationships did not have a significant effect on toepad surface area. Linear discriminant analysis indicated that functional prey sizes correlated positively with toepad surface areas. Generalized linear modelling showed that there was a positive, significant relationship between body mass and toepad surface area, and prey category significantly affected the toepad surface areas for Digit I and Digit IV. Overall, the ventral surface of the raptorial foot is subject to considerable variation, with active hunters showing the greatest differences in structures, specifically markedly developed toepads to protrusional toepads, potentially as a means to enable more efficient predatory behaviors and facilitate diet preferences for more difficult to catch prey items., (© 2019 Wiley Periodicals, Inc.)

Horses are a classic example of macroevolution in three major traits-large body size, tall-crowned teeth (hypsodonty), and a single toe (monodactyly)-but how and why monodactyly evolved is still poorly understood. Existing hypotheses usually connect digit reduction in horses to the spread and eventual dominance of open-habitat grasslands, which took over from forests during the Cenozoic; digit reduction has been argued to be an adaptation for speed, locomotor economy, stability, and/or increased body size. In this review, we assess the evidence for these (not necessarily mutually exclusive) hypotheses from a variety of related fields, including paleoecology, phylogenetic comparative methods, and biomechanics. Convergent evolution of digit reduction, including in litopterns and artiodactyls, is also considered. We find it unlikely that a single evolutionary driver was responsible for the evolution of monodactyly, because changes in body size, foot posture, habitat, and substrate are frequently found to influence one another (and to connect to broader potential drivers, such as changing climate). We conclude with suggestions for future research to help untangle the complex dynamics of this remarkable morphological change in extinct horses. A path forward should combine regional paleoecology studies, quantitative biomechanical work, and make use of convergence and modern analogs to estimate the relative contributions of potential evolutionary drivers for digit reduction., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.)

In this study we developed an analytical relationship between adhesive digit orientation and adhesive force capacity to describe the tendencies of climbing organisms that use adhesion for climbing to align their toes in the direction of loading, maximizing adhesive force capacity. We fabricated a multi-component adhesive device with multiple contact surfaces, or digits, to act as a model system mimicking the angular motion of a foot and found the synthetic experiments agree with the developed analytical relationship. In turn, we find that observations of gekkonid lizards climbing on vertical substrates correlate well with our analytical relationship; a reduction in toe spacing is seen on the forelimbs when the animals are facing up. Interestingly, the toes on the hindlimbs tend to have an increase in spacing, possibly a mechanism for stabilization rather than load-bearing., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.)

Recently-developed, molecularly-based phylogenies of geckos have provided the basis for reassessing the number of times adhesive toe-pads have arisen within the Gekkota. At present both a single origin and multiple origin hypotheses prevail, each of which has consequences that relate to explanations about digit form and evolutionary transitions underlying the enormous variation in adhesive toe pad structure among extant, limbed geckos (pygopods lack pertinent features). These competing hypotheses result from mapping the distribution of toe pads onto a phylogenetic framework employing the simple binary expedient of whether such toe pads are present or absent. It is evident, however, that adhesive toe pads are functional complexes that consist of a suite of integrated structural components that interact to bring about adhesive contact with the substratum and release from it. We evaluated the competing hypotheses about toe pad origins using 34 features associated with digit structure (drawn from the overall form of the digits; the presence and form of adhesive scansors; the proportions and structure of the phalanges; aspects of digital muscular and tendon morphology; presence and form of paraphalangeal elements; and the presence and form of substrate compliance-enhancing structures). We mapped these onto a well-supported phylogeny to reconstruct their evolution. Nineteen of these characters proved to be informative for all extant, limbed geckos, allowing us to assess which of them exhibit co-occurrence and/or clade-specificity. We found the absence of adhesive toe pads to be the ancestral state for the extant Gekkota as a whole, and our data to be consistent with independent origins of adhesive toe pads in the Diplodactylidae, Sphaerodactylidae, Phyllodactylidae, and Gekkonidae, with a strong likelihood of multiple origins in the latter three families. These findings are consistent with recently-published evidence of the presence of adhesively-competent digits in geckos generally regarded as lacking toe pads. Based upon morphology we identify other taxa at various locations within the gekkotan tree that are promising candidates for the expression of the early phases of adhesively-assisted locomotion. Investigation of functionally transitional forms will be valuable for enhancing our understanding of what is necessary and sufficient for the transition to adhesively-assisted locomotion, and for those whose objectives are to develop simulacra of the gekkotan adhesive system for biotechnological applications., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.)

Background: We sought to show the biomechanical and morphometric properties of flexor hallucis longus (FHL) and flexor digitorum longus (FDL) tendon grafts harvested by specific surgical approaches and to assess the contribution of FHL slips to the long flexor tendons of the toes., Methods: Thirteen fresh-frozen amputated feet (average age, 79 years) were dissected. The connections between the FHL and FDL tendons and the contribution of FHL slips to the long flexor tendons were classified. The biomechanical properties of the tendons and slips were measured using a tensile device., Results: The connections between the FHL and FDL tendons were reviewed in two groups. Group 1 had FHL slips (11 cases) and group 2 had cross-slips (two cases). The FHL slips joined the second and third toe long flexor tendon structures. Tendon length decreased significantly from the second to the fifth toe ( P < .001). Apart from the second toe tendon being thicker than that of the fourth toe ( P = .02) and Young's modulus being relatively smaller in the third versus the fourth toe tendon ( P = .01), biomechanical and morphometric properties of second to fourth tendons were similar. Mechanical properties of those tendons were significantly different from fifth toe tendons and FHL slips. Morphometric and biomechanical properties of FHL slips were similar to those of the fifth toe tendon., Conclusions: Herein, FHL slips were shown to have biomechanical properties that might contribute to flexor functions of the toes. During the harvesting of tendon grafts from the FHL by minimally invasive incision techniques from the distal plane of the master knot of Henry, cutting slips between FHL and FDL tendons could be considered a cause of postoperative function loss in toes.

The first toe-to-hand transplantation was done in 1898 by Nicoladoni. It was a staged procedure and the toe flap was based on a pedicle. With advancement of optical instruments and microsurgeons' skills in 1964 the first microvascular toe-to-hand transplantation on a rhesus monkey was done. The technique's development has not stopped, many authors have modified it to achieve better outcomes for both traumatic and congenital hand defects. The most commonly used toes for transplantation are first, second, and second to third toe block. Well described plantar and dorsal vascular systems for first web space vessels as well as possibility to perform successful perforator anastomosis allows us to improve toe-to-hand transplantation further. There is a paucity of studies on single fourth toe-to-hand transplantation. We performed fourth-toe transplantation for three pediatric patients (mean age, 73 mo) with congenital (n=2) and traumatic (n=1) hand defects. Common plantar digital arteries were used for blood supply to the transplanted toes. No vascular problems occurred, and all transplanted toes survived. Patients and parents are satisfied with functional and esthetic outcomes. Early podometry results show insignificant changes which should not harm the foot in the long-term. We believe the fourth-toe transplantation is a promising method to use to reconstruct congenital or traumatic absence of digits for pediatric population.

Mice are intrinsically capable of regenerating the tips of their digits after amputation. Mouse digit tip regeneration is reported to be a peripheral nerve-dependent event. However, it is presently unknown what types of nerves and Schwann cells innervate the digit tip, and to what extent these cells regenerate in association with the regenerative response. Given the necessity of peripheral nerves for mammalian regeneration, we investigated the neuroanatomy of the unamputated, regenerating, and regenerated mouse digit tip. Using immunohistochemistry for β-III-tubulin (β3T) or neurofilament H (NFH), substance P (SP), tyrosine hydroxylase (TH), myelin protein zero (P0), and glial fibrillary acidic protein (GFAP), we identified peripheral nerve axons (sensory and sympathetic), and myelinating- and non-myelinating-Schwann cells. Our findings show that the digit tip is innervated by two digital nerves that each bifurcate into a bone marrow (BM) and connective tissue (CT) branch. The BM branches are composed of sympathetic axons that are ensheathed by non-myelinating-Schwann cells whereas the CT branches are composed of sensory and sympathetic axons and are ensheathed by myelinating- and non-myelinating-Schwann cells. The regenerated digit neuroanatomy differs from unamputated digit in several key ways. First, there is 7.5 fold decrease in CT branch axons in the regenerated digit compared to the unampuated digit. Second, there is a 5.6 fold decrease in myelinating-Schwann cells in the regenerated digit compared to the unamputated digit that is consistent with the decrease in CT branch axons. Importantly, we also find that the central portion of the regenerating digit blastema is aneural, with axons and Schwann cells restricted to peripheral and distal blastema regions. Finally, we show that even with impaired innervation, digits maintain the ability to regenerate after re-amputation. Taken together, these data indicate that nerve regeneration is impaired in the context of mouse digit tip regeneration., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Semiaquatic walking has resulted in the evolution of functional and morphological changes in various hoofed mammals, such as hippopotamus and Brazilian tapir. The biomechanics of skilful walking in wetlands or at the bottom of a waterbody involve the medio-lateral opening and closing of the feet to effectively support and stabilize the body on soft ground and to reduce the water resistance during recovery stroke, respectively. We demonstrate that the opening and closing of the feet in hippopotamus and Brazilian tapir are mediated by the adduction and abduction of the most medial and lateral phalanges from the CT examination. The axial toes, metacarpals and metatarsals do not contribute to changes in the width and shape of the feet, unlike the medial and lateral toes. We suggest that this semiaquatic walking motion is derived from the original terrestrial mode of locomotion, in contrast to the highly functional swimming motion using webs or fins in morphologically modified feet and tail. From the present data we demonstrate that semiaquatic locomotion evolved due to the acquisition of adductor-abductor mobility in the phalanges of the most medial and lateral digits, as shown in hippopotamus and Brazilian tapir., (© 2018 Blackwell Verlag GmbH.)

Objectives:  The aim of our study was to describe the effect of prenatal testosterone exposure on 2D:4D in both sexes, and to determine whether this effect is mediated via the androgen receptor. In addition, the sex differences in lengths of 2D, 4D, and 2D:4D ratio were analyzed., Background:  Clinical studies suggest a negative correlation between prenatal testosterone exposure and ratio of the lengths of the second and fourth digits (2D:4D). However, less is known about the underlying molecular mechanisms., Methods:  Pregnant rats were treated with olive oil, testosterone, flutamide or testosterone with flutamide daily from the fourteenth day of pregnancy until delivery. The finger lengths of adult offspring were measured using both, digital scanning of the paws and μCT analysis of the phalanges., Results:  None of the aforementioned methods revealed any effect of testosterone on 2D:4D. μCT measurements showed that prenatal hyperandrogenism in both sexes leads to shorter 2D compared to controls. Moreover, the testosterone treatment in males resulted in the shortening of 4D when compared to controls., Conclusion:  Prenatal hyperandrogenism leads to shorter lengths of 2D and 4D; however, it does not affect 2D:4D ratio. Whether other steroid hormones and/or testosterone metabolites affect the 2D:4D ratio requires further investigation (Tab. 5, Fig. 3, Ref. 32).

Purpose: Biphalangealism of the toes is an exclusively human phenomenon. The aim of this study was to evaluate the development of the lateral toes in childhood by following the ossification pattern of the phalanges., Methods: Foot radiographs of 913 adults have been evaluated for biphalangealism of 3rd to 5th toe. The pediatric group, aged 6-15 years of age, was assessed for the number of ossification centers in the foot., Results: In adults, the mean prevalence of biphalangealism in the 5th toe was 41.39%, in the 4th toe was 2.15%, and in the 3rd toe was 0.48%. In children, 45% feet had four ossification centers in the 5th toe. The epiphysis center of the middle and distal phalanx was missing. In the 4th toe, four centers were present in of 2.47% of cases. Those values are similar to the prevalence of the biphalangeal toes in adult population. The remaining toes had 5 or 6 ossification centers. In the 5-center toe, the epiphysis of the middle phalanx was missing., Conclusion: A missing distal phalanx epiphyseal ossification center is considered indicative of a biphalangeal toe, and the toes with 5 or 6 ossification centers are indicative of triphalangeal toes. The reason for such evolution of the lateral toes is still debated, but the differences in anatomy most likely have no impact on foot function.

Despite the fact that there are numerous reports on muscular variations in the sole of the foot, routine dissection in a formaldehyde-fixed cadaver revealed an accessory flexor digiti quinti muscle, which to the best of our knowledge is a very unusual variant. This was in the form of a slender, 38 mm long muscular slip, with a proximal and distal tendon extending from the common flexor digitorum longus tendinous plate out to the distal phalanx of the fifth toe. An associated finding was the absence of the musculotendinous portion of the flexor digitorum brevis to the same toe. A developmental explanation for this variation is presented. Clinical implications with regard to this anatomical condition may result in clawing of the fifth toe.

Flexor tendons function as energy storage and shock absorption structures in the tarsometatarso-phalangeal joint (TMTPJ) of ostrich feet during high-speed and heavy-load locomotion. In this study, mechanisms underlying the energy storage and shock absorption of three flexor tendons of the third toe were studied using histology and scanning electron microscopy (SEM). Macroscopic and microscopic structures of the flexor tendons in different positions of TMTPJ were analyzed. Histological slices showed collagen fiber bundles of all flexor tendons in the middle TMTPJ were arranged in a linear-type, but in the proximal and distal TMTPJ, a wavy-type arrangement was found in the tendon of the M. flexor digitorum longus and tendon of the M. flexor perforans et perforatus digiti III, while no regular-type was found in the tendon of the M. flexor perforatus digiti III. SEM showed that the collagen fiber bundles of flexor tendons were arranged in a hierarchically staggered way (horizontally linear-type and vertically linear-type). Linear-type and wavy-type both existed in the proximal TMTPJ for the collagen fiber bundles of the tendon of the M. flexor perforatus digiti III, but only the linear-type was found in the distal TMTPJ. A number of fibrils were distributed among the collagen fiber bundles, which were likely effective in connection, force transmission and other functions. The morphology and arrangement of collagen fiber bundles were closely related to the tendon functions. We present interpretations of the biological functions in different positions and types of the tendons in the TMTPJ of the ostrich feet., (© 2017 Wiley Periodicals, Inc.)

Four heteropod lizard trackways discovered in the Hasandong Formation (Aptian-early Albian), South Korea assigned to Sauripes hadongensis, n. ichnogen., n. ichnosp., which represents the oldest lizard tracks in the world. Most tracks are pes tracks (N = 25) that are very small, average 22.29 mm long and 12.46 mm wide. The pes tracks show "typical" lizard morphology as having curved digit imprints that progressively increase in length from digits I to IV, a smaller digit V that is separated from the other digits by a large interdigital angle. The manus track is 19.18 mm long and 19.23 mm wide, and shows a different morphology from the pes. The predominant pes tracks, the long stride length of pes, narrow trackway width, digitigrade manus and pes prints, and anteriorly oriented long axis of the fourth pedal digit indicate that these trackways were made by lizards running bipedally, suggesting that bipedality was possible early in lizard evolution.

Background: Postaxial polydactyly, type B is the most common type of polydactyly. The vestigial sixth finger is attached by a narrow neurovascular pedicle to the lateral aspect of the hand or foot at the level of the metacarpal-phalangeal joint or the metatarsal-phalangeal joint. The occurrence of this type of polydactyly varies among racial groups, by sex and sidedness. Postaxial polydactyly, type A is a fully developed extra digit on the lateral aspect of the hand or foot with a bifid fifth or sixth metacarpal/metatarsal and is much less common., Methods: In a malformations surveillance program, the frequency in racial groups, sex ratio and the frequency of other anomalies can be established., Results: Five hundred forty-five affected infants were identified from 1972 to 2012 in the surveillance of 289,365 liveborn and stillborn infants and elective terminations because of fetal anomalies detected prenatally. Postaxial polydactyly, type B was an isolated anomaly in 95% of the affected newborns. There were more affected males than females. Black infants were affected more often than White infants: 0.91/100 vs. 0.035/100 infants. The dangling extra digit was much more common in the hands than in the feet., Conclusions: Postaxial polydactyly, type B is almost always an isolated, mild malformation with no medical significance. Postaxial polydactyly, types B and A occurred in several infants, suggesting that either the underlying mutation(s) can cause both types of postaxial polydactyly or that some affected infants have more than one mutation. Autosomal dominant inheritance with variable expressivity is postulated., (© 2018 Wiley Periodicals, Inc.)

Although recent studies have reported that the forefoot bones are longer in sprinters than in non-sprinters, these reports included a relatively small number of subjects. Moreover, while computer simulation suggested that longer forefoot bones may contribute to higher sprint performance by enhancing plantar flexor moment during sprinting, the correlation between forefoot bone length and sprint performance in humans has not been confirmed in observational studies. Thus, using a relatively large sample, we compared the length of the forefoot bones between sprinters and non-sprinters. We also examined the relationship between forefoot bone length and performance in sprinters. The length of forefoot bones of the big and second toes in 36 well-trained male sprinters and 36 male non-sprinters was measured using magnetic resonance imaging. The length of forefoot bones in the big and second toes was significantly longer in sprinters than in non-sprinters. After dividing the sprinters into faster and slower groups according to their personal best time in the 100-m sprint, it was found that the forefoot bone length of the second toe, but not that of the big toe, was significantly longer in faster group than in slower group. Furthermore, the forefoot bone length of the second toe correlated significantly with the personal best time in the 100-m sprint. This study supported evidence that the forefoot bones are longer in sprinters than in non-sprinters. In addition, this is the first study to show that longer forefoot bones may be advantageous for achieving superior sprint performance in humans., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Understanding macroevolutionary dynamics of trait evolution is an important endeavor in evolutionary biology. Ecological opportunity can liberate a trait as it diversifies through trait space, while genetic and selective constraints can limit diversification. While many studies have examined the dynamics of morphological traits, diverse morphological traits may yield the same or similar performance and as performance is often more proximately the target of selection, examining only morphology may give an incomplete understanding of evolutionary dynamics. Here, we ask whether convergent evolution of pad-bearing lizards has followed similar evolutionary dynamics, or whether independent origins are accompanied by unique constraints and selective pressures over macroevolutionary time. We hypothesized that geckos and anoles each have unique evolutionary tempos and modes. Using performance data from 59 species, we modified Brownian motion (BM) and Ornstein-Uhlenbeck (OU) models to account for repeated origins estimated using Bayesian ancestral state reconstructions. We discovered that adhesive performance in geckos evolved in a fashion consistent with Brownian motion with a trend, whereas anoles evolved in bounded performance space consistent with more constrained evolution (an Ornstein-Uhlenbeck model). Our results suggest that convergent phenotypes can have quite distinctive evolutionary patterns, likely as a result of idiosyncratic constraints or ecological opportunities., (© 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.)

Anoline lamellae terminate in an epidermal free margin carrying the majority of its setae. How the free margin is extruded from the body of the scale is not well understood. Two hypotheses have been advanced to account for it, one advocating distal migration of the outer epidermal layers relative to the body of the lamella, and the other proposing regression of the dermal core. Available evidence provides partial support for both. We assembled a series of specimens of Anolis grahami representing all shedding cycle stages, and prepared histological sections of the toe pads to allow measurement of appropriate lamellar components through the shedding cycle. Through its proliferative phases the lamellae increase markedly in length, with the distance between the distal tip of the dermal core and that of the lamella accounting for most of this, indicating that epidermal extrusion is responsible for production of the new free margin. The dermal core showed no evidence of regression. Concomitant with epidermal extrusion, the lacunar cells on the inner lamellar face hypertrophy and keep pace with the increasing thickness of the outer lamellar face resulting from the lengthening of the replacement setae. The integrated changes observed are consistent with continuity of functioning and alignment of the exposed setal carpet of the outer epidermal generation while ensuring that the new setal carpet is fully aligned and functional immediately after shedding. At shedding the original proportions of the lamellae are restored. Development of the new free margin results from a combination of distal displacement of Oberhäutchen cells along with arrested maturation of the epidermis in this region. Changes in length of the lamellae during the proliferative stages may impact the overall size of the adhesive toe pad, which may have consequences for assessments of the relationship between whole animal clinging ability and adhesive pad area. J. Morphol. 278:360-368, 2017. © 2017 Wiley Periodicals, Inc., (© 2017 Wiley Periodicals, Inc.)

Phenotypic convergence between distantly related taxa often mirrors adaptation to similar selective pressures and may be driven by genetic convergence. The giant panda (Ailuropoda melanoleuca) and red panda (Ailurus fulgens) belong to different families in the order Carnivora, but both have evolved a specialized bamboo diet and adaptive pseudothumb, representing a classic model of convergent evolution. However, the genetic bases of these morphological and physiological convergences remain unknown. Through de novo sequencing the red panda genome and improving the giant panda genome assembly with added data, we identified genomic signatures of convergent evolution. Limb development genes DYNC2H1 and PCNT have undergone adaptive convergence and may be important candidate genes for pseudothumb development. As evolutionary responses to a bamboo diet, adaptive convergence has occurred in genes involved in the digestion and utilization of bamboo nutrients such as essential amino acids, fatty acids, and vitamins. Similarly, the umami taste receptor gene TAS1R1 has been pseudogenized in both pandas. These findings offer insights into genetic convergence mechanisms underlying phenotypic convergence and adaptation to a specialized bamboo diet., Competing Interests: The authors declare no conflict of interest.

White's tree frog (Litoria caerulea) has large, adhesive toe pads that are among the softest of all known biological structures. To explore the morphological basis for the physical properties of the toe pads, the internal microstructure of the toe pads in L. caerulea was examined using both light and transmission electron microscopy. Three design elements that are distinct from other areas of skin were observed. First, the keratinocytes comprising the adhesive surface of the toe pad all contained keratin filament bundles (tonofibrils) exhibiting structural anisotropy. Specifically, the curved conformation of the hierarchical (branching) tonofibrils was characterized by the formation of anastomoses consisting of tonofibrils beneath the adhesive cell surface and stem keratin filament bundles concentrated in the lower-middle part of the dorsal-side of adhesive cells. Second, the cytoplasm of keratinocytes in the most superficial cell layer contained glycoproteins (stained by periodic acid/Schiff reagent) that are considered to confer high viscoelasticity. Third, the dermis contained large lymph spaces interspersed with elastic fibers and collagen fibers, which were relatively sparsely distributed compared to the dorsal skin of the toe pads. The profiles of these structures were easily deformed by the slight application of pressure. These findings reaffirmed that the unique internal architecture of the toe pads in L. caerulea contributed to their remarkable softness and high deformability, which in turn increased the contact area and provided improved adaptability to the local topography of natural surfaces. J. Morphol. 277:1509-1516, 2016. © 2016 Wiley Periodicals, Inc., (© 2016 Wiley Periodicals, Inc.)

Background: Instability of the metatarsophalangeal (MTP) joints of the lesser toes (digiti 2-5) is increasingly being treated by repair of the plantar plate (PP). This systematic review examines the anatomy of the plantar plate of the lesser toes, and the relation between the integrity of the plantar plates of the lesser toes and lesser MTP joint stability., Methods: The databases of Embase.com, Medline (Ovid), Web of Science, Scopus, Cochrane, Pubmed not medline, Cinahl (ebsco), ProQuest, Lilacs, Scielo and Google Scholar were searched in June 2015 from inception. Studies were included if they were in English, contained primary data, and had a focus on plantar plate anatomy of the lesser toes or on the relationship between integrity of the plantar plate and MTP joint (in)stability. Study characteristics were extracted into two main tables and descriptive anatomical and histological data were summarized into one schematic 3D drawing of the plantar plate., Results: Nine studies were included in this systematic review, of which five addressed plantar plate anatomy as such and four focused directly and indirectly on plantar plate integrity related to MTP joint stability., Conclusion: This is the first systematic review regarding plantar plate anatomy related to MTP joint stability of the lesser toes. This review iterates the importance of plantar plate anatomy and integrity for MTP joint stability, and it delineates the lack of primary data regarding plantar plate anatomy of the lesser toes and MTP joint stability.

While many gecko-inspired hierarchically structured surfaces perform as well as or better than the natural adhesive system, these designs often fail to function across a variety of contexts. For example, the gecko can adhere to rough, wet and dirty surfaces; however, most synthetic mimics cannot maintain function when faced with a similar situation. The solution to this problem lies in a more thorough investigation of the natural system. Here, we review the adhesive system of the gecko toe pad, as well as the far less-well-studied anti-adhesive system that results from the chemistry and structure of the toe pad (superhydrophobicity). This paradoxical relationship serves as motivation to study functional optimization at the system level. As an example, we experimentally investigate the role of surface lipids in adhesion and anti-adhesion, and find a clear performance trade-off related to shear adhesion in air on a hydrophilic surface. This represents the first direct investigation of the role of surface lipids in gecko adhesion and anti-adhesion, and supports the argument that a system-level approach is necessary to elucidate optimization in biological systems. Without such an approach, bioinspired designs will be limited in functionality and context, especially compared to the natural systems they mimic.This article is part of the themed issue 'Bioinspired hierarchically structured surfaces for green science'., (© 2016 The Author(s).)

Background: This study compared the effects of barefoot policy, a policy instructing preschool children to go without shoes, on untouched-toes, which do not touch the ground while standing normally, of preschool children attending kindergartens that follow this rule, to preschooler in kindergartens where they must wear shoes, i.e., no-barefoot policy., Methods: The study used longitudinal data from measurements taken 2 years apart of the amount of times. The subjects were 59 children (34 boys and 25 girls) who went to a kindergarten that followed barefoot policy and 179 children (103 boys and 76 girls) who went to a kindergarten that did not follow barefoot policy. Images were taken of the contact surface area of the soles of the children's feet by having them stand on the measurement device with their bare feet., Results: The number of untouched-toes in children participating in the study was determined from the pictures. In boys who attended kindergartens following barefoot policy, the ratio of the children without untouched-toes significantly increased for 2 years of childhood (35.3-64.7 %). The number of untouched-toes were significantly fewer in boys from kindergartens following barefoot policy than in boys from kindergartens not following the policy, and the magnitude of the difference grew for the two study years (ES: 0.41-0.63). In girls, there were no significant differences between the two groups in the ratio of girls without untouched-toes and the number of untouched-toes., Conclusions: In conclusion, the ground contact of the toes becomes better for boys in kindergarten with a barefoot policy. The results were inconclusive with regard to girls, and other factors may need to be examined. In the future, it will be necessary to increase the number of the subjects and perform detailed examinations.

The human lateral toes are characterised by extreme reduction compared with other primates, and in particular other hominoids. Some phalangeal non-metric variants have been well identified in humans, in particular: triphalangeal/biphalangeal patterns, and the presence/absence of phalangeal secondary centres of ossification. The purpose of the present study was to describe and analyse an original non-metric variation of the middle phalanges of the lateral toes. The material consisted of 2541 foot radiographs that came from 2541 different European adult individuals. Two morphological types of the middle phalanx were defined as a simple binary trait: long type (L) and short type (S). In feet with a triphalangeal pattern in all lateral toes (1413 cases), a mediolateral increasing gradient was observed in the occurrence of type S: 8.1% in II; 30.7% in III; 68.4% in IV; and 99.1% in V. In feet with a biphalangeal pattern in one or more lateral toes (III-V; 1128 cases), type S occurred more frequently than in triphalangeal feet. Of the 30 theoretical arrangements of the L/S types in the lateral toes (II-V) in a complete foot, only 13 patterns were observed. Seven patterns represented 95.6% of the population: LLSS (20.9%), LLLS (17.1%), LSS (15.9%), SSS (14.5%), LSSS (12.7%), LLS (10.1%) and SSSS (4.4%). Type L can be interpreted as the primitive pattern (plesiomorphy), and type S as a derived pattern (apomorphy) that seems specific to the human species (i.e. autapomorphy). Within the specific evolution of the human foot in relation to the acquisition of constant erect posture and bipedalism, the short type of the middle phalanges can reasonably be considered as directly linked to the reduction of the lateral toes., (© 2016 Anatomical Society.)

Tree frogs have become an object of interest in biomimetics due to their ability to cling to wet and slippery surfaces. In this study, we have investigated the adhesion and friction behavior of toe pads of White's tree frog (Litoria caerulea) using atomic force microscopy (AFM) in an aqueous medium. Facilitating special types of AFM probes with radii of ∼400 nm and ∼13 μm, we were able to sense the frictional response without damaging the delicate nanopillar structures of the epithelial cells. While we observed no significant adhesion between both types of probes and toe pads in wet conditions, frictional forces under such conditions were very pronounced and friction coefficients amounted between 0.3 and 1.1 for the sliding friction between probes and the epithelial cell surfaces.

Because connections exist between the flexor hallucis longus (FHL) and flexor digitorum longus (FDL), the FHL is surmised to exert a flexion action on the lesser toes, but this has not been studied quantitatively. The objectives of this study have thus been to clarify the types of FHL and FDL connections and branching, and to deduce the toe flexion actions of the FHL. One hundred legs from 55 cadavers were used for the study, with FHLs and FDLs harvested from the plantar aspect of the foot, and connections and branches classified. Image-analysis software was then used to analyze cross-sectional areas (CSAs) of each tendon, and the proportion of FHL was calculated in relation to flexor tendons of each toe. Type I (single slip from FHL to FDL tendon) was seen in 86 legs (86%), Type II (crossed connection) in 3 legs (3%), and Type III (single slip from FDL to FHL tendon) or Type IV (no connection between muscles) in 0 legs (0%). In addition, Type V (double slip from FHL to FDL tendon) was seen in 11 legs (11%), representing a new type not recorded in previous classifications. In terms of the various flexor tendons, the proportion of FHL showing tendons to toes 2 and 3 was high, at approximately 50-70%. Consequently, considering the branching type and proportion of CSA, the FHL was conjectured to not only act to flex the hallux, but also play a significant role in the flexion of toes 2 and 3. These results offer useful information for future clarification of the functional roles of tendinous slips from the FHL., (Copyright © 2015 Elsevier GmbH. All rights reserved.)

Purpose: Despite some theoretical reservations, the AOFAS clinical rating system with its scales for ankle-hindfoot, midfoot, hallux and lesser toes is one of the most widely used assessment tools in foot and ankle surgery. This study was designed to generate age- and gender-related norm values for all four subscales., Methods: Despite not being used in a self-administered manner, the AOFAS score underwent cross cultural adaptation to guarantee unrestricted comparability of data. A data pool was generated using the results of personal interviews and clinical examination of 625 individuals, including staff and visitors to our hospital, and excluding people scheduled for foot surgery or in after-treatment. These data served as a basis to calculate all four parts of the AOFAS clinical rating system., Results: Mean value for the ankle-hindfoot scale was calculated as 91.6 points (±0.9 confidence interval), and 89.3 points for the midfoot scale (±1.0 CI), 88.3 for the hallux metatarsophalangeal-interphalangeal scale (± 0.9 CI) and 91.0 for the lesser metatarsophalangeal-interphalangeal scale (± 0.8 CI). Results showed a decrease with age in all four scales. Males showed better results than females. Individuals with previous surgery showed lower results in the respective score., Conclusions: While lowered scoring results prior to surgery reflect the degree of restrictions due to pain, function and alignment problems, post-operative increases in clinical scoring should indicate return to age-related norm values. Our data calculated these norm values for the first time for all four AOFAS scales, giving a basis for better interpretation of published results in foot and ankle surgery. Our data showed and quantified the decrease of norm values with age, especially for hallux and lesser toes scores, as well as lower norm values for females and for individuals that had had surgery of the foot., Level of Evidence: Level I, diagnostic study.

Second-to-fourth digit ratio is a widely investigated sexually dimorphic morphological trait in human studies and could reliably indicate the prenatal steroid environment. Conducting manipulative experiments to test this hypothesis comes up against ethical limits in humans. However, oviparous tetrapods may be excellent models to experimentally investigate the effects of prenatal steroids on offspring second-to-fourth digit ratio. In this field study, we injected collared flycatcher (Ficedula albicollis) eggs with physiological doses of testosterone. Fledglings from eggs with elevated yolk testosterone, regardless of their sex, had longer second digits on their left feet than controls, while the fourth digit did not differ between groups. Therefore, second-to-fourth digit ratio was higher in the testosterone-injected group, but only on the left foot. This is the first study which shows experimentally that early testosterone exposure can affect second-to-fourth digit ratio in a wild population of a passerine bird.