Biomechanical model of the human foot: kinematics and kinetics during the stance phase of walking

A model of the human foot is proposed in which the foot is represented as eight rigid segments and eight monocentric, single-degree-of-freedom joints. The soft tissue under the foot is divided into seven independent sites of contact, or loading, and each of these is modelled as a nonlinear spring and a nonlinear damper in-parallel. The model was used to estimate the kinematics and kinetics of the foot during the stance phase of walking. The force sustained at each loading site was calculated from walking trials in which only portions of the foot landed on a small force platform. The position of the calcaneus was defined by surface markers, whereas the position of the distal segments were based upon chalk footprints and an estimate of the compression of the plantar soft tissue. The results suggest that the joints that constitute the longitudinal arch extend slightly when the forefoot is loaded. During push-off, these joints flex as the metatarsophalangeal joints extend. Similar kinematic results were estimated when the distal segments of the foot were defined by surface markers. The magnitude of the joint moments of force depended largely on the distribution of the load under the foot which varied considerably between subjects. The stable, yet resilient properties of the foot, as highlighted by this model, should be considered in three-dimensional dynamic models used to study human locomotion. The model provides an objective tool to quantify foot motion and loading, which may prove useful for describing foot function in normal and pathological conditions.

The hallux sesamoids revisited

The hallux sesamoids are vulnerable to significant injury and weight-bearing stress in both the athlete and the nonathlete. Unfortunately, they are often dismissed as inconsequential accessory bones. The historical significance, embryology, anatomy, and physiology of the sesamoids and the salient features of both traumatic and nontraumatic pathologic conditions affecting these structures are presented. Because the sesamoids can be responsible for prolonged disabling foot pain and discomfort, it is important for both clinician and radiologist to pay attention to these bones and recognize the early signs of abnormality.

Hallux fractures: diagnosis and treatment

The authors present a review of the literature, mechanisms of injury, and radiographic presentations of hallux fractures. Sixty cases (64 injuries) were reviewed. Recommendations for treating each type of injury are also presented.

The arterial supply of the sesamoid bones of the hallux: the course and source of the nutrient arteries as an anatomical basis for surgical approaches to the great toe

The arterial supply of the hallux sesamoids was studied in 29 human feet by anatomical dissection. Eight of them underwent radiographic analysis prior to dissection. The sesamoid arteries branch off from the digital plantar arteries of the hallux, which, in turn, are derived from the medial plantar artery and the plantar arch (type A), the plantar arch (type B), or the medial plantar artery (type C). The respective frequencies of types A, B, and C were 52%, 24%, and 24%. The number of sesamoid arteries varied from one (55%) to three (10%) and the number increased with the size of the sesamoid bones. Anatomical knowledge of the course and distribution of these vessels may be of great help to the orthopedist in the understanding of the pathogenesis of avascular necrosis and may provide insight into several technical aspects regarding surgery of the hallux.

Hallucal tarsometatarsal joint in Australopithecus afarensis

Hallucal tarsometatarsal joints from African pongids, modern humans, and Australopithecus afarensis are compared to investigate the anatomical and mechanical changes that accompanied the transition to terrestrial bipedality. Features analyzed include the articular orientation of the medial cuneiform, curvature of the distal articular surface of the medial cuneiform, and the articular configuration of the hallucal metatarsal proximal joint surface. Morphological characteristics of the hallucal tarsometatarsal joint unequivocally segregate quadrupedal pongids and bipedal hominids.

Normal and pathologic anatomy of hallux valgus

The author reviews the pathologic entity of hallux valgus, using anatomic illustrations. Although this description is not considered to represent new information, foot surgeons must continue to appreciate the delicate biomechanical imbalances leading to this anomaly.

Hallux interphalangeal joint sesamoidectomy using minimal incision technique

There has been little emphasis placed on the excision of accessory bones of the foot. The authors present a review of the literature and a description of a surgical procedure for excision of the hallux interphalangeal joint sesamoid using minimal incision technique. A detailed analysis of the anatomy involved is also presented. A variety of other procedures for excision of this accessory bone are reviewed.

The role of the akin osteotomy in the surgical management of hallux abducto valgus

The Akin osteotomy has gained widespread popularity in foot surgery. This article reviews the proper indications, technique, modifications, and complications of the procedure. It also identifies the true role in the surgical management of the hallux abducto valgus deformity.

An irreducible dislocation of the great toe. Report of two cases and review of the literature

Irreducible dislocation of an interphalangeal (IP) joint of the great toe is a rare condition. Twenty-two cases including the present two cases are reported in available literature. Two different types are identifiable. In one type, where the ruptured volar plate is displaced into the joint space between two phalanges, the toe is slightly elongated, but the deformity of the toe is not so marked. In the other type, where the volar plate is completely displaced over the proximal phalangeal neck, the deformity of the toe is extreme as the IP joint is locked in hyperextension. In the former type, the dislocation is often misinterpreted to have been repositioned manually because of relatively slight deformity. In either type of dislocation, the volar plate is detached from both the distal and proximal phalanges, and so displaced into the joint, as to form a barrier to manual repositioning. Open reduction is mandatory.

The proximal phalangeal osteotomy. A technically advanced approach

A historical review of osteotomies of the proximal phalanx has been presented. The techniques have remained relatively unchanged since their introduction by O. F. Akin in 1925. This article describes a minimal incision osteotomy technique using a medial approach to the hallux and wedge-shaped burs. The results suggest that the procedure produces good clinical results and is highly accepted by the patient. The procedure is compatible with a hospital or outpatient surgical facility. The procedure is recommended to those surgeons who are well-trained in ambulatory foot surgery. A statistical survey of the end-results is not available at the present time.

Hallux sesamoid bones. Anatomical observations with special reference to osteoarthritis and hallux valgus

The normal characteristics of the hallux sesamoid bones were studied in 200 toes (100 dissections and 100 radiographs from patients with hallux valgus), and pathological changes were recorded. Normally each sesamoid articulated with a separate groove on the plantar surface of the first metatarsal head. A bony ridge on the head separated these grooves. Bipartite sesamoids were found in 4% of the toes. Osteoarthritic changes manifested by deformity, irregularity, lipping, cysts in the sesamoids and in the heads of the first metatarsal, and erosions in the articular surfaces were present in 32% of the dissected toes. Fusion of the sesamoids was found in 6%. Ankylosis between the sesamoids and the head of the metatarsal was observed in 4%. In the toes affected by hallux valgus the sesamoids, together with the plantar pad and the tendon of the flexor hallucis brevis, were displaced laterally to a variable degree. In severe deformities the lateral sesamoid was dislocated lateral to the first metatarsal head and the medial sesamoid occupied the groove originally corresponding to the lateral sesamoid, while the metatarsal ridge separating the two sesamoids tended to disappear. Osteoarthritis of the metatarsophalangeal joint frequently accompanied hallux valgus.

The prevalence of hallux valgus in South African males

The prevalence of hallux valgus and its relationship to the metatarsal angles have been assessed in South African males from two Black communities and one White community. After the age of 11 years there is a small increase in the metatarsal angle of White males, but this remains within the normal range. In comparison with White females, who seem to be predisposed to the disorder of hallux valgus, neither White nor Black males show a significant increase in hallux angles after adolescence. Males of all ages and race groups seldom develop clinical hallux valgus, and this apparent resistance to the deformity is associated with a minimal increase in the metatarsal angle, and therefore in the width of the foot.

[An anatomical study of the interphalangeal sesamoid bone of the hallux]

The existence of sesamoid bone on the interphalangeal joint of the hallux has not been sufficiently recognized. The frequency of this sesamoid bone has been described to be low probability in the orthopaedic and anatomical literature. We have, however, experienced some cases of the interphalangeal joint dislocation giving difficulty to usual manipulative reduction because of the presence of the sesamoid bone. In order to ascertain the existence of sesamoid bone on the interphalangeal joint of the hallux, anatomical and radiographic study have been performed with 144 feet of 73 adult cadavers, 32 feet of 16 fetal cadavers and 958 patients. The following results were obtained: The sesamoid bone was seen in 90.9% by radiographical examination and in 95.9% by macroscopic observation for 144 feet on 73 adult cadavers. Cartilagenous sesamoid bone was found in 93.8%, 32 feet of 16 fetal cadavers using stereoscopic microscope. In the radiographical examination of 958 feet of the patients, the sesamoid bones were approved in 56.3%, but it increased to 93.0% using 1/4 sensitivity intensifying screen. The sesamoid bone of the interphalangeal joint on adult cadavers was located at the central portion in parallel with interphalangeal joint space and buried in the fibrocartilagines plantares. This sesamoid bone had two cartilagenous joint surfaces against the base of distal phalanx and the head of proximal phalanx. The sesamoid bone had the shape of longitudinal ellipse and the length, width and thickness were measured. The size of sesamoid bone on the male cadaver were larger than that of the female on the three parameters and there were no special difference between the right and the left sides.

The prevalence of hallux valgus in three South African populations

The prevalence of hallux valgus and its relationship to the metatarsal angles have been assessed in females between the ages of 2 and 20 years in three populations: an urban White community, an urban Black community and a rural Black Community. By the age of 10 years the mean hallux angle is significantly greater in the White girls than in girls in the two Black groups. The angle between the first and second metatarsals is greater in the White than in the black children and this difference increases throughout childhood and adolescence. It is suggested that young White girls may be predisposed to the abnormality of hallux valgus by having significantly greater metatarsal angles.

The etiology of hallux valgus in Japan

Until recent years, hallux valgus did not exist in Japan. Changing customs and styles of footwear during the past ten years have led to an increasing number of patients with the classic hallux valgus deformity. These are not mild deformities, but are painful and require surgical correction. The ratio of the width to the length of the foot is similar in both sexes and was measured in children up to the age of 14. Coincidentally, at about that time students may freely wear any type of fashionable shoe. We conclude, therefore, that the hallux valgus deformities we are now seeing with greater frequency are caused, at least in part, by the change in footwear.

The sesamoids of the hallux

The seemingly innocuous tiny sesamoids play an important role in the function and pathomechanics of the hallux. The recent active participation of people of all ages in jogging and long-distance running, activities introducing repetitive stressful forces on the forefoot, induces sesamoiditis. Bones normally asymptomatic, such as the sesamoids, require renewed interest in embryology, anatomy, congenital variations, infection, osteochondritis, trauma and effective treatment.

[Locomotory trends in primates expressed by the foot ratios. The adaptation to bipedalism (author's transl)]

This paper is an attempt to complete previous works on this topic, especially Schultz, by new measurements and indices. From the calculated indices, listed at the end in a table, graphics are drawn and related to four main contents: (1) relative length of the foot to the hind limb and its segments; (2) relative length of the different foot segments to the foot length and between them; (3) relative length of the first toe, or hallux, to the foot, tarsus and longest external toe lengths; (4) position of the morphological axis of the toes: here we define the notion of axony. In conclusion, we try to answer the following questions: (1) what are the mensural distinctions of the human foot? (2) are foot ratios suitable to establish a satisfactory morphological classification of the locomotory adaptations in primates?