Anatomical variations of the tibialis anterior tendon.

INTRODUCTION: The tibialis anterior muscle originates from the medial part of the anterior compartment, from the upper two-thirds of the lateral surface of the tibia and the adjacent part of the interosseous membrane, and typically inserts to the medial cuneiform and first metatarsal bone. The goal of the study was to examine the insertion of the tibialis anterior tendon and create a classification in human fetuses. MATERIALS AND METHODS: Fifty spontaneously-aborted human fetuses (26 male, 24 female, 100 lower limbs), aged 18-38 weeks of gestation at death were examined. RESULTS: The classification comprised five types of tibialis anterior tendon insertion. The most common was Type V (60%), which was characterized by a single tendon inserting onto the medial cuneiform bone. The second most frequent was Type I (19%), which was characterized by a tendon which split into two equal-sized parts that insert to the medial cuneiform bone and the base of the first metatarsal. The third was Type II (12%), which was characterized by a tendon splitting into two different-sized parts that inserted onto the medial cuneiform bone (larger component) and the base of the first metatarsal (smaller component). The fourth type was Type III (5%), which was also characterized by a tendon splitting into two different-sized parts that inserted onto the medial cuneiform bone (smaller component) and the base of the first metatarsal (larger component). Finally, Type VI (4%), the least frequent type, was characterized by a tendon splitting into three different-sized parts, inserting onto the medial cuneiform bone (the smallest component) and the base of the first metatarsal (the middle and larger component). CONCLUSION: The tibialis anterior muscle is characterized by high variability in the approach of its tendon to the foot, at least in fetuses. This is classified in the present study for the first time.

Homo naledi did not have flat foot.

The collection of 1550 Homo naledi fossil remains includes six tarsal and five metatarsal bones from the right foot, forming a nearly complete humanlike flat foot arch. The missing right medial cuneiform, however, raises our interest to explore the true structure of Homo naledi's foot arch. We hypothesize that Homo naledi does not have flat foot. To verify our hypothesis, the left medial cuneiform of Homo naledi was mirrored using three-dimensional reconstruction and virtual model analysis. Then, we defined quantities of Euler, standardized the body coordinate system of foot bone and developed a new foot arch reconstruction method based on discrete bones. The reconstructed transverse foot arch corroborated our hypothesis, thus providing biomechanical evidence for interpreting the evolution of human locomotion and bringing novel ideas to the research of the biomechanical mechanism of ankle stability.

Os Conundrum: Identifying Symptomatic Sesamoids and Accessory Ossicles of the Foot.

OBJECTIVE. Sesamoids and accessory ossicles are frequently encountered normal osseous structures in the foot that may be an uncommon cause of pain. Familiarity with their imaging findings allows the radiologist to provide reassurance in normal cases and increase confidence when making the relatively uncommon diagnosis of a pathologic sesamoid or symptomatic ossicle. CONCLUSION. Image-guided injections targeted to the symptomatic ossicle can confirm the suspected diagnosis and predict therapeutic outcomes before surgical intervention.

Accessory ossicles of the foot-an imaging conundrum.

Various anatomical variations can be found in the foot and ankle, including sesamoid bones and accessory ossicles. These are usually incidental findings and remain asymptomatic; however, they may cause complications resulting in painful syndromes or degenerative changes secondary to overuse or trauma. They can also lead to fractures or simulate fractures. These complications are challenging to diagnose on radiographs. Advanced imaging with US, CT, MRI, or Tc-99m bone scan is useful for definitive diagnosis. This study aims to illustrate how imaging modalities can be used to diagnose complications of common sesamoids and accessory ossicles of the ankle and foot (hallux sesamoids, os trigonum, accessory navicular, os supranaviculare, os peroneum, os intermetatarseum, and os calcaneus secundarius) and demonstrate the imaging differences between fractures and their mimics.

Trabecular bone functional adaptation and sexual dimorphism in the human foot.

OBJECTIVES: Trabecular bone adapts to the strains placed upon the skeleton during life. Anthropological research has largely focused on linking variation in primate trabecular bone to locomotor mode, to provide a context for interpreting fossil morphology. However, intraspecific variation and its underlying mechanisms are still poorly understood. Trabecular bone is influenced by a variety of factors including body mass, age, diet, temperature, genetics, sex, and behavior. Before trabecular structure can be used to infer habitual behavior in the past, the effects of these factors need to be understood. In this article, we examine variation in trabecular structure in the human foot in four archaeological groups in relation to inferred levels of terrestrial mobility and sex. MATERIALS AND METHODS: We use high-resolution µCT scanning to examine variation in trabecular structure in the human calcaneus, talus, and first metatarsal in two relatively mobile and two relatively sedentary archaeological groups. RESULTS: The four population samples show similar patterns of trabecular variation throughout the foot, influenced by mechanical loading. Greater inferred terrestrial mobility is associated with greater bone volume fraction and thicker, more widely spaced, and less interconnected trabeculae. However, contrary to diaphyseal rigidity, only limited sexual dimorphism was found in trabecular structure. DISCUSSION: This work demonstrates that trabecular bone may serve as a useful proxy of habitual behavior in the fossil and archaeological record when other factors are carefully considered. However, the mechanisms underlying sexual dimorphism are not well understood. As such, inferring sex differences in habitual behavior is currently challenging.

One small step: A review of Plio-Pleistocene hominin foot evolution.

Bipedalism is a hallmark of being human and the human foot is modified to reflect this unique form of locomotion. Leonardo da Vinci is credited with calling the human foot "a masterpiece of engineering and a work of art." However, a scientific approach to human origins has revealed that our feet are products of a long, evolutionary history in which a mobile, grasping organ has been converted into a propulsive structure adapted for the rigors of bipedal locomotion. Reconstructing the evolutionary history of foot anatomy benefits from a fossil record; yet, prior to 1960, the only hominin foot bones recovered were from Neandertals. Even into the 1990s, the human foot fossil record consisted mostly of fragmentary remains. However, in the last two decades, the human foot fossil record has quadrupled, and these new discoveries have fostered fresh new perspectives on how our feet evolved. In this review, we document anatomical differences between extant ape and human foot bones, and comprehensively examine the hominin foot fossil record. Additionally, we take a novel approach and conduct a cladistics analysis on foot fossils (n = 19 taxa; n = 80 characters), and find strong evidence for mosaic evolution of the foot, and a variety of anatomically and functionally distinct foot forms as bipedal locomotion evolved.

Anatomía imagenológica de los huesos accesorios y sesamoideos inconstantes del miembro inferior: ensayo iconográfico / Imaging anatomy of the accessory and inconstant sesamoid bones of the lower limb: an iconographic essay

Se realiza un estudio sobre la anatomía e imagenología de los huesos sesamoideos inconstantes y de los huesos accesorios del miembro inferior. Para ello, se presenta una selección de estudios imagenológicos de pacientes que presentan este tipo de huesos, recolectados durante los últimos tres años.

Influence of the windlass mechanism on arch-spring mechanics during dynamic foot arch deformation.

The function of the human foot is described dichotomously as a compliant structure during mid-stance and a stiff lever during push-off. The arch-spring and the windlass mechanisms, respectively, describe each of these behaviours; however, their interaction has not been quantified to date. We hypothesized that by engaging the windlass mechanism with metatarsophalangeal joint (MTPJ) dorsiflexion, we would observe stiffening of the arch and reduced energy absorption and dissipation during dynamic compressions of the foot. Using a custom apparatus, the MTPJ angle was fixed at 30 degrees of plantarflexion, neutral or 30 degrees of dorsiflexion for nine participants, with the shank positioned similarly to the end of mid-stance. The arch was compressed at two speeds, with the faster speed comparable to walking around 1.5 m s-1 Six cameras captured the compression and elongation of the arch, along with other kinematic variables, synchronously with the ground reaction force. Combining these measures, we computed the energy absorbed, returned and dissipated in the arch. Contrary to our hypothesis, when the windlass mechanism was engaged, the arch elongated more, and absorbed and dissipated more energy than when it was not engaged. This engagement of the windlass altered the rotational axis of the mid-foot, which probably oriented the arch-spanning structures closer to their resting length, increasing their compliance. This study provides novel evidence for an interplay between the windlass and arch-spring mechanisms that aids in regulation of energy storage within the foot.

Comparison of pathological lesions in navicular bone (os sesamoideum distale) and analysis of remodelling capacity in warmblood and coldblood horses.

The problem of navicular bone lesions is better understood in warmblood horses. The aim of our research was to compare pathologic lesions of navicular bone of different types of horses divided into age groups. An extra goal was to compare radiographs with anatomical status of navicular bone dissected from the hoof capsule. The study group included 161 horses, out of which 100 individuals were warmbloods, and 61 - coldbloods. In total 280 navicular bones were analysed. The flexor surface, distal border fragments, enthesophytes and the process of obliteration of nutrient foramina were analysed. Some navicular bones were also subject to histology test. A greater tendency for the obliteration of nutrient foramina was observed in coldblood horses than in warmbloods. This fact can be explained as increased remodelling, covering the phenomenon of closure of synovial invaginations and canaliculi within the navicular bone. As a result, the synovial groove disappears and blood vessels cannot enter the distal border. New bone formation on the distal border is more frequently observed in coldblood horses. The development of enthesophytes both on the distal and proximal borders depends to a large extent on the age of horses of both types. Warmbloods, however, are more prone to have the lesions located on the flexor surface, leading as a consequence to deep erosions. They might be found even in very young horses in the form of grooves crossing the sagittal ridge. The frequency of lesions varies depending on the type of the horse. Post-mortem analysis of navicular bones helped interpret radiographs in a more precise manner.

Association between Forefoot Bone Length and Performance in Male Endurance Runners.

Recently, we reported that the forefoot bones were longer in sprinters than in non-sprinters, and that longer forefoot bones correlated with higher sprint performance in sprinters. To further understand the superiority of long forefoot bones in athletic performance, we examined whether forefoot bone length was associated with running performance in endurance runners. The length of the forefoot bones of the big and second toes were measured using magnetic resonance imaging in 45 male well-trained endurance runners and 45 male untrained subjects. After normalization with the foot length, it was found that the forefoot bones of the big and second toes were significantly longer in endurance runners than in untrained subjects (P<0.05 for both). Furthermore, longer forefoot bones of the big toe, but not of the second toe, correlated significantly with better personal best 5000-m race time in endurance runners (r=-0.322, P=0.031). The present findings demonstrated that forefoot bones were longer in endurance runners than in untrained subjects. These findings were similar to our findings for sprinters. In addition, we found that longer forefoot bones may be advantageous for achieving higher running performance in endurance runners.

Macro-anatomical and morphometric studies of the hindlimb of grasscutter (Thryonomys swinderianus, Temminck-1827).

The hindlimb of the grasscutter (Thryonomys swinderianus, Temminck-1827) was studied using 12 adult (≥6 months) rats of either sex with the mean weights of 1.42 ± 0.20 kg and 0.82 ± 0.13 kg for buck (n = 6) and doe (n = 6), respectively (p < .05). Characteristics of the bones were studied by gross observation after their preparation. Measurements of different segments of the hindlimb were also taken, giving a total average length of 31.80 cm. Correlation coefficients between length of bone and weight of rats were positive (p < .05) in bucks for all bone segments, except the pes (p > .05), whereas those in does were all non-significant (p > .05), with significant sexual dimorphism in the relationships. The average total number of bones in the hindlimb was 92, with no apparent sexual dimorphism. The bones of the hindlimb revealed important differences and similarities in morphology with those of other rodents. The Os coxae presented a relatively large obturator foramen, formed by the ramus of the ischium and shaft of the pubis. The femur had a body and two extremities with a prominent head, well-defined neck and trochanter. The fibula, a slender bone with triangular-shaped proximal extremity, ran down the length of tibia with proximal attachment (via cartilage) and distal fusion, leaving an extensive interosseus space. The pes revealed eight tarsals and four metatarsals; each of the metatarsals showed three phalanges.

Estudo anatômico, ultrassonográfico e tomográfico do aparato podotroclear de equinos adultos / Anatomic, tomographic and sonographic study of podotrochlear apparatus of adult horses

A síndrome do navicular é uma condição que envolve o aparato podotroclear e representa uma das causas mais comuns de claudicação dos membros torácicos de equinos. Portanto, o estudo complementar da região reveste-se de grande interesse quando se refere ao diagnóstico e tratamento das claudicações dos equinos. O objetivo deste estudo foi demonstrar as diferenças dos achados imagenológicos entre a ultrassonografia e a tomografia computadorizada na avaliação das estruturas palmares do aparato podotroclear de equinos adultos e hígidos, bem como a descrição das estruturas observadas nas imagens obtidas com essas técnicas. Para isso, foram realizadas imagens de quatro peças anatômicas, as quais foram posteriormente seccionadas e utilizadas para a descrição anatômica. A utilização de peças anatômicas auxilia no conhecimento da anatomia normal, o que leva à melhor interpretação das imagens e aumenta a especificidade diagnóstica na detecção das alterações que as doenças acarretam. A ultrassonografia fornece informações relevantes quanto às estruturas estudadas, e sua associação com a tomografia computadorizada aumentou a acurácia da investigação. Apesar de o uso da tomografia computadorizada ser mais indicada para tecido ósseo, ela fornece informações importantes, podendo ser usada como uma ferramenta útil quando não se tem disponível a ressonância magnética em razão do custo ou da disponibilidade.(AU)

The navicular syndrome is a condition involving the podotrochlear apparatus and represents one of the most common causes of forelimb lameness in horses. Therefore, further study of this region is of interest when it comes to diagnosis and treatment of lameness in horses. The aim of this study was to demonstrate the differences between the imaging findings of ultrasonography and computed tomography in the evaluation of the palmar structures of the podotrochlear apparatus of healthy adult horses and description of the structures observed in images obtained with these techniques. For this, four images of four anatomical parts were performed, and subsequently sectioned and used for the anatomical description. The use of anatomical parts helps in the understanding of normal anatomy leading to a better interpretation of the images and increasing the specificity of the diagnostic for detecting changes that cause diseases. Ultrasonography provides relevant information about these structures to be studied and the association with computed tomography (CT) increased the accuracy of the investigation. Despite the use of CT being more suitable for bone tissue it provides important information and can be used as a useful tool when there is no available MRI.(AU)

Prevalence and distribution of sesamoid bones and accessory ossicles of the foot as determined by digital tomosynthesis.

We previously reported that digital tomosynthesis (DTS) is a reliable tool for evaluating bony structures of the hand. The current study aimed to identify the prevalence and distribution of sesamoid bones and accessory ossicles of the foot using DTS and to compare the results to those of conventional radiography (CR). Foot images (DTS, 213; CR, 44) of 213 patients taken at a tertiary hospital were retrospectively reviewed. Sesamoid bones were identified in the metatarsaophalangeal (MTP), distal interphalangeal (DIP) and interphalangeal (IP) joints of the great (I), second (II), third (III), fourth (IV), and fifth (V) toes. Accessory ossicles were observed in the midfoot and hindfoot. The mean number of sesamoid bones and accessory ossicles was 3.9 ± 1.3 for the left foot and 3.7 ± 1.0 for the right foot on CR; and 3.9 ± 1.4 for the left foot and 3.9 ± 1.3 for the right foot on DTS. Sesamoid bones were observed in MTP I (100%), MTP II (5%), MTP III (2%), MTP IV (2%), MTP V (14%), and IP (68%) on CR. Sesamoid bones were observed in MTP I (100%), MTP II (8%), MTP III (1%), MTP IV (2%), MTP V (25%), and IP I(65%) on DTS. Among accessory ossicles, the most common bone identified was os tibiale externum (23% on CR and 33% on DTS) andos peroneum (14% on CR and 21% on DTS), and os trigonum (32% on CR and 0.5% on DTS). DTS was useful for finding sesamoid bones and accessory ossicles, although there were some limitations in observing the hindfoot. Clin. Anat. 30:1072-1076, 2017. © 2017 Wiley Periodicals, Inc.

Radiographic Measurements of the Affected and Unaffected Feet in Patients with Unilateral Hallux Limitus A Case-Control Pilot Study.

BACKGROUND: Controversy exists regarding the structural and functional causes of hallux limitus, including metatarsus primus elevatus, a long first metatarsal, first-ray hypermobility, the shape of the first metatarsal head, and the presence of hallux interphalangeus. Some articles have reported on the radiographic evaluation of these measurements in feet affected by hallux limitus, but no study has directly compared the affected and unaffected feet in patients with unilateral hallux limitus. This case-control pilot study aimed to establish whether any such differences exist. METHODS: Dorsoplantar and lateral weightbearing radiographs of both feet in 30 patients with unilateral hallux limitus were assessed for grade of disease, lateral intermetatarsal angle, metatarsal protrusion distance, plantar gapping at the first metatarsocuneiform joint, metatarsal head shape, and hallux abductus interphalangeus angle. Data analysis was performed using a statistical software program. RESULTS: Mean radiographic measurements for affected and unaffected feet demonstrated that metatarsus primus elevatus, a short first metatarsal, first-ray hypermobility, a flat metatarsal head shape, and hallux interphalangeus were prevalent in both feet. There was no statistically significant difference between feet for any of the radiographic parameters measured (Mann-Whitney U tests, independent-samples t tests, and Pearson χ(2) tests: P > .05). CONCLUSIONS: No significant differences exist in the presence of the structural risk factors examined between affected and unaffected feet in patients with unilateral hallux limitus. The influence of other intrinsic factors, including footedness and family history, should be investigated further.

The evolutionary origin and population history of the grauer gorilla.

Gorillas living in western central Africa (Gorilla gorilla) are morphologically and genetically distinguishable from those living in eastern central Africa (Gorilla beringei). Genomic analyses show eastern gorillas experienced a significant reduction in population size during the Pleistocene subsequent to geographical isolation from their western counterparts. However, how these results relate more specifically to the recent biogeographical and evolutionary history of eastern gorillas remains poorly understood. Here we show that two rare morphological traits are present in the hands and feet of both eastern gorilla subspecies at strikingly high frequencies (>60% in G. b. graueri; ∼28% in G. b. beringei) in comparison with western gorillas (<1%). The intrageneric distribution of these rare traits suggests that they became common among eastern gorillas after diverging from their western relatives during the early to middle Pleistocene. The extremely high frequencies observed among grauer gorillas-which currently occupy a geographic range more than ten times the size of that of mountain gorillas-imply that grauers originated relatively recently from a small founding population of eastern gorillas. Current paleoenvironmental, geological, and biogeographical evidence supports the hypothesis that a small group of eastern gorillas likely dispersed westward from the Virungas into present-day grauer range in the highlands just north of Lake Kivu, either immediately before or directly after the Younger Dryas interval. We propose that as the lowland forests of central Africa expanded rapidly during the early Holocene, they became connected with the expanding highland forests along the Albertine Rift and enabled the descendants of this small group to widely disperse. The descendant populations significantly expanded their geographic range and population numbers relative to the gorillas of the Virunga Mountains and the Bwindi-Impenetrable Forest, ultimately resulting in the grauer gorilla subspecies recognized today. This founder-effect hypothesis offers some optimism for modern conservation efforts to save critically endangered eastern gorillas from extinction.

Radiographic Indicators of Surgery and Functional Outcome in Ponseti-Treated Clubfeet.

BACKGROUND: Evaluation of the results of treatment for clubfoot by the Ponseti technique is based on clinical and functional parameters. There is a need to establish universally recognized quantitative measurements to compare, better understand, and more precisely evaluate therapeutic outcome. METHODS: Nine angles were measured on standard radiographs of 145 children with idiopathic clubfeet treated between 2000 and 2010 with the Ponseti method. The average follow-up was 6.3 years. The need for additional surgery and the functional outcome was correlated to the radiologic measurements. RESULTS: Three radiologic parameters were identified as having significant (P ≤ .001) predictive value. The lateral tibiocalcaneal angle with the ankle at maximal dorsiflexion measuring fixed equinus was larger in the preoperated group (77 ± 12 degrees) compared to the nonoperated group (67 ± 14 degrees). Functional outcome was better with smaller angles. The lateral talocalcaneal angle with the ankle at maximal dorsiflexion measuring hindfoot rigidity was smaller (29 ± 8 degrees) in the preoperated group compared to the nonoperated group (35 ± 9 degrees). Functional outcome was better with larger angles. The lateral talo-first metatarsal angle with the ankle at maximal plantarflexion measuring foot cavus was larger in the preoperated group (31 ± 10 degrees) compared to the nonoperated group (22 ± 11 degrees), whereas functional outcome did not correlate with this angle. CONCLUSIONS: The lateral view with the foot in maximal dorsiflexion was found to be the most significant and useful view to detect abnormality in Ponseti-treated clubfeet. In our practice now, we are using only this view in order to reduce the radiation exposure to the child. LEVEL OF EVIDENCE: Level III, retrospective case series.

The foot of Homo naledi.

Modern humans are characterized by a highly specialized foot that reflects our obligate bipedalism. Our understanding of hominin foot evolution is, although, hindered by a paucity of well-associated remains. Here we describe the foot of Homo naledi from Dinaledi Chamber, South Africa, using 107 pedal elements, including one nearly-complete adult foot. The H. naledi foot is predominantly modern human-like in morphology and inferred function, with an adducted hallux, an elongated tarsus, and derived ankle and calcaneocuboid joints. In combination, these features indicate a foot well adapted for striding bipedalism. However, the H. naledi foot differs from modern humans in having more curved proximal pedal phalanges, and features suggestive of a reduced medial longitudinal arch. Within the context of primitive features found elsewhere in the skeleton, these findings suggest a unique locomotor repertoire for H. naledi, thus providing further evidence of locomotor diversity within both the hominin clade and the genus Homo.

Stress Fractures of the Foot.

Stress fractures of the foot and ankle may be more common among athletes than previously reported. A low threshold for investigation is warranted and further imaging may be appropriate if initial radiographs remain inconclusive. Most of these fractures can be treated conservatively with a period of non-weight-bearing mobilization followed by gradual return to activity. Early surgery augmented by bone graft may allow athletes to return to sports earlier. Risk of delayed union, nonunion, and recurrent fracture is high. Many of the patients may also have risk factors for injury that should be modified for a successful outcome.

Skeletal plasticity in response to embryonic muscular activity underlies the development and evolution of the perching digit of birds.

Most birds have an opposable digit 1 (hallux) allowing the foot to grasp, which evolved from the non-opposable hallux of early theropod dinosaurs. An important morphological difference with early theropods is the twisting of the long axis of its metatarsal. Here, we show how embryonic musculature and the onset of its activity are required for twisting of metatarsal 1 (Mt1) and retroversion of the hallux. Pharmacologically paralyzed embryos do not fully retrovert the hallux and have a straight Mt1 shaft, phenocopying the morphology of early tetanuran dinosaurs. Molecular markers of cartilage maturation and ossification show that differentiation of Mt1 is significantly delayed compared to Mt2-4. We hypothesize on how delayed maturation may have increased plasticity, facilitating muscular twisting. Our experimental results emphasize the importance of embryonic muscular activity in the evolutionary origin of a crucial adaptation.

The foot core system: a new paradigm for understanding intrinsic foot muscle function.

The foot is a complex structure with many articulations and multiple degrees of freedom that play an important role in static posture and dynamic activities. The evolutionary development of the arch of the foot was coincident with the greater demands placed on the foot as humans began to run. The movement and stability of the arch is controlled by intrinsic and extrinsic muscles. However, the intrinsic muscles are largely ignored by clinicians and researchers. As such, these muscles are seldom addressed in rehabilitation programmes. Interventions for foot-related problems are more often directed at externally supporting the foot rather than training these muscles to function as they are designed. In this paper, we propose a novel paradigm for understanding the function of the foot. We begin with an overview of the evolution of the human foot with a focus on the development of the arch. This is followed by a description of the foot intrinsic muscles and their relationship to the extrinsic muscles. We draw the parallels between the small muscles of the trunk region that make up the lumbopelvic core and the intrinsic foot muscles, introducing the concept of the foot core. We then integrate the concept of the foot core into the assessment and treatment of the foot. Finally, we call for an increased awareness of the importance of the foot core stability to normal foot and lower extremity function.