A new kinematic model of pro- and supination of the human forearm

We introduce a new kinematic model describing the motion of the human forearm bones, ulna and radius, during forearm rotation. During this motion between the two forearm extrem-positions, referred to as supination (palm up) and pronation (palm down), effects occur, that cannot be explained by the the established kinematic model of R. Fick from 1904. Especially, the motion of the ulna is not properly reproduced by Fick's model. During forearm rotation an evasive motion of the ulna is observed by various authors, using magnetic resonance imaging MRI) technology. Our new kinematic model also simulates this evasive motion. Furthermore, the model is enlarged to include angulations of the forearm bones. Using these results the influence of forearm fractures on the range of forearm motion can be predicted. This knowledge can be used by surgeons to choose the optimal therapy in re-establishing free forearm mobility.     

The Neanderthal lower arm

Neanderthal forearms have been described as being very powerful. Different individual features in the lower arm bones have been described to distinguish Neanderthals from modern humans. In this study, the overall morphology of the radius and ulna is considered, and morphological differences among Neanderthals, Upper Paleolithic Homo sapiens and recent H. sapiens are described.Comparisons among populations were made using a combination of 3D geometric morphometrics and standard multivariate methods. Comparative material included all available complete radii and ulnae from Neanderthals, early H. sapiens and archaeological and recent human populations, representing a wide geographical and lifestyle range.There are few differences among the populations when features are considered individually. Neanderthals and early H. sapiens fell within the range of modern human variation. When the suite of measurements and shapes were analyzed, differences and similarities became apparent. The Neanderthal radius is more laterally curved, has a more medially placed radial tuberosity, a longer radial neck, a more antero-posteriorly ovoid head and a well-developed proximal interosseous crest. The Neanderthal ulna has a more anterior facing trochlear notch, a lower M. brachialis insertion, larger relative mid-shaft size and a more medio-lateral and antero-posterior sinusoidal shaft. The Neanderthal lower arm morphology reflects a strong cold-adapted short forearm. The forearms of H. sapiens are less powerful in pronation and supination. Many differences between Neanderthals and H. sapiens can be explained as a secondary consequence of the hyper-polar body proportions of the Neanderthals, but also as retentions of the primitive condition of other hominoids.     

Features of the structure of the metacarpal bones of athletes in different specialties

Metacarpal bones have been examined in hand X-ray photos of 125 sportsmen at the age of 17-18 years who go in for swimming (dynamic loading on the hand) and competitive gymnastics (static loading on the hand). Under the effect of systematic trainings, which are connected with an increased loading on the hand, a number of morphological changes take place in the metacarpal bones. A prolonged loading of the dynamic character delays the synostosis process in the distal parts of the forearm bones and contributes to lengthening the I, III and IV and to widening the I-V metacarpal bones. As demonstrate decreasing indices of compactness in the swimmers, the widening diaphisis of the metacarpal bones occurs at the expense of dilatation of the medullary cavity. The static loadings result in a greater delay of the synostosis processes in the upper extremity parts mentioned, in a greater width of the I-III, V metacarpal bones in boy-gymnasts. The increased index of compactness demonstrates that the widening diaphysis of the metacarpal bones takes place at the expense of thickening of the compact substance and narrowing of the medullary cavity.     

Morphologic features of the structure of the hand bones of young volley ball players

By means of roentgenography method with subsequent roentgenogramometry and roentgenodensitometry, morphological peculiarities of structure and mineralization of the hand bones in sportsmen-volley-ball players and in schoolchildren who do not go in for sports, at the age of 14-19 years have been studied. Systematic training in volley-ball produces certain increase in dimentions of the hand bones, prolongation of their synostosis time, intensification in development of the sesamoid bones and increasing amount of mineral salts in their bones.     

Morphofunctional changes in the long tubular bones of animals which have developed while readapting after physical loads

The investigation has been performed on 120 white male rats of Wistar line. By means of the morphometry, electron microscopy and chemical methods dynamics of readaptive changes have been studied in long tubular bones during the period, when the effect of physical loadings both of dynamic and static character and of various intensity has been stopped, up to the old periods of the animals' life. Readaptation after moderate dynamic and static loadings is occurring for a long time and steadily. The changes caused by static loadings are nearly completely restored in a year. Morphofunctional rearrangements of the long tubular bones in the readaptation process after moderate dynamic loadings is characterized by residual manifestations. Prolonged readaptation after intensive physical loadings does not result in a complete restoration of all the parameters studied concerning growth and skeletal development. An intensive dynamic loading produces more stable changes, that are not subjected to a complete correction even after a passive readaptation for a year. Readaptation morphofunctional rearrangements of the long tubular skeletal bones depend on conditions of the previous regimen of the motor activity.     

The addition of muscle to the lateral arm and radial forearm flaps for wound coverage.

There is good evidence of the benefit of transferring vascularized muscle into wounds that are contaminated or have been infected previously. This benefit particularly applies in cavities around bones and joints. We present two patients in whom the inclusion of a portion of muscle in the lateral arm and radial forearm flaps allowed the effective combination of good-quality skin cover with the properties of vascularized muscle.     

Ultrastructure of the ascus apical apparatus of Encoelia furfuracea (Helotiales)

The ultrastructural characteristics of the ascus apical apparatus of Encoelia furfuracea are described by means of transmission electron microscopy. The structure of its ascus apex is considerably different from that of E. tiliacea and E. fimbriata, and from other members of Helotiales in which these structures have been studied. Remarkable interspecific differences in the ascus apical apparatus provide additional data indicating heterogeneity of the genus.     

Quantitative genetic variation in the skeleton of the mouse: II. Description of variation within and between inbred strains

Variation in the skeletons of over 400 male and female mice from 12 genotypes was investigated by using multivariate statistical methods. A series of discriminant functions explains the differences in the shape of six bones: mandible, os coxae, femur, tibia-fibula, scapula, and humerus. The anatomical features of bone shape described by these functions are summarized together with illustrations of the typical shapes of each bone from the 12 genotypes. Variability within genotypes was investigated by using the Mahalanobis D2 distance--a measure of the difference between two points representing multivariate data--from the group mean. A series of variants were detected ranging from grossly abnormal bones to bones showing subtle differences localized to specific regions. Examples of the variants found are illustrated.     

Curvature of the forelimb bones of anthropoid primates: Overall allometric patterns and specializations in suspensory species

It has previously been reported that brachiating primates, particularly gibbons, are characterized by distinctively straight forelimb long bones, yet no hypotheses have been proposed to explain why straight limb bones may be adaptive to suspensory locomotion. This study explores quantitatively the curvature of the long bones in 13 species of anthropoid primates and analyzes the functional consequences of curvature in biomechanical terms. These analyses demonstrate that, whereas the humeri of gibbons and spider monkeys are functionally less curved than those of other taxa, the ulnae of brachiators are neither more nor less curved than those of other anthropoids, and the gibbon radius is far more curved than would be predicted from body size alone. The humerus is likely significantly less curved in brachiators because of its torsion-dominated loading regime and the greatly increased stress magnitude developed in torsionally loaded curved beams. The large curvature of the radius is localized in the region of attachment of the supinator muscle. Analysis presented here of muscle mass allometry in catarrhines demonstrates that gibbons are characterized by an extremely massive supinator, and the large radial curvature is therefore most likely due to forearm muscle mechanics. This study also demonstrates that the overall pattern of limb bone curvature for anthropoids is distinct from the pattern reported for mammals as a whole. This distinctive scaling relationship may be related to the increased length of the limb bones of primates in comparison to other mammals.     

Development of the Osteocranium in Natrix natrix (Serpentes,Colubridae) Embryogenesis II: Development of the jaws,palatal complex and associated bones

Snakes differ from the other vertebrates with their hyperkinetic skull. To establish the developmental features of the skull bones, involved in prey capture and ingestion, the Grass snake Natrix natrix (Serpentes, Colubridae) embryos are studied at all the successive stages of embryogenesis. Thirty-five N. natrix embryos are examined. Twenty embryos are studied with histological methods; fifteen embryos are cleared and double-stained with alizarin red and alcian blue. The sequence of appearance and formation of the upper and lower jaw bones, palatal complex and associated bones is described in accordance with the table of developmental stages. New features in the ossification mode of some bones are revealed: each bone, namely, the vomer, septomaxilla and maxilla, is formed from three separate ossification centres. Three ossification centres in the maxilla, two ossification centres in the bodies of the septomaxilla and vomer, as well as the unknown additional ossification centre in the vomer had not been previously described in snake embryos. The new data can be used in further comparative research on the reptile skull development and vertebrate phylogeny.     

Biomechanics of the skull and the beak in Rampnastos (Ramphastidae, Aves) I. Description of anatomical elements

The different cranial kinetic systems described in Birds are limited in Ramphastos by the dorsal and backward position of the nostrils, the shape of the fronto-nasal suture, the lateral fit-in between nasal, lacrymal and frontal bones, and the divergent directions of the 2 otic processes of the quadrate, 5 ligaments joint the posterior skull elements to the quadrate and the mandible. Small sesamoid bones strengthen the external jugo-mandibular ligament in its retro-articular portion. The nomenclature of the aponeuroses is not useful by itself to compare the organizations and homology of the diverses muscular layers in the different birds groups. The differences observed in the relative position of the muscular bundles have to be related to the shape and particular relationships between skeletal structures. We have to consider the osteo-muscular systems as a whole and analyse them from a functional viewpoint.     

Ossification of the cartilage skeleton of the extremities of human embryos

Certain sequence in appearance of ossification points has been stated in the cartilage models of the superior and inferior extremities of the human embryos at the end of the embryonal and the beginning of the fetal periods of development. The change in the size (length) of the ossification points in anlages of the long tubular bones during the successive stages of embryogenesis is of linear character and can be described by means of the equation y = ax + b, where y--age of the embryo (days), x--length of the osseous points. Coefficients a and b are calculated for estimation the age of the embryos according to the length of the osseous points in the anlages of the brachial, femoral and radial bones.     

The thickness of the walls of tubular bones

Some bones have slender marrow cavities and relatively thick walls. Others have wide cavities and thinner walls. Such differences are described by a quantity K , the ratio of the internal to the external diameter. A theoretical analysis shows that the optimum value of K , which allows the mass of a bone to be minimized, depends on whether the bone is selected principally for yield or fatigue strength, for ultimate strength, for impact strength or for stiffness. It also depends on whether the cavity is filled with marrow or with gas. The values of K found in the limb bones of mammals, birds and a few reptiles are surveyed, and compared to the theoretical optima.     

Fasciocutaneous vessels in the upper arm: application to the design of new fasciocutaneous flaps

The principles of the blood supply to the upper arm are described. Despite the large, fleshy nature of the biceps and the triceps, the blood supply to upper arm skin is not from the underlying muscles, but is by fasciocutaneous perforators emerging along the medial and lateral intermuscular septa. Fifty dissections of preserved cadavers have shown that on the lateral side the fasciocutaneous perforators consistently arise from the middle collateral artery. The available length of this vessel and its diameter have been measured and are reported. The design of a flap based on this vessel, in a manner analogous to the Chinese forearm flap on the radial artery, is described.     

Axial and appendicular skeleton of Homo antecessor.

The human trunk and limb bones recovered from the Gran Dolina site, in the Sierra de Atapuerca (Burgos, Spain) are studied. All these fossils were excavated at the level called TD6 between 1994 and 1995 and have been dated in excess of 780,000 years ago. These remains have been recently attributed to a new Homo species named Homo antecessor. Axial (vertebrae and ribs) and part of the appendicular (clavicles, radii, femur and patellae) skeleton are studied here. Hand and foot bones have been studied elsewhere (Lorenzo et al., 1999). Four is the minimum number of individuals represented by the postcranial remains recovered up to now. All elements are briefly described anatomically, measured and compared with other fossil hominids and modern humans in order to establish, as far as possible, what postcranial morphology characterized this new species of our genus.The H. antecessor postcrania, generally, display a set of morphological traits that are more similar to modern humans than to the Middle and Upper Pleistocene European hominids. Our results do not contradict the previous phylogenetic analysis, i.e., that H. antecessor represents the last common ancestor for H. sapiens (modern humans) and H. neanderthalensis (Neandertals).     

On a longirostrine crocodylomorph (Thalattosuchia) from the Middle Jurassic of Tunisia

The geographic origins and distributional patterns of Gondwanan teleosauroids during the Jurassic have been fiercely debated over many years. Unlike the rich thalattosuchian fossil record from Laurasia, teleosauroids described from Gondwanan ecosystems are relatively scarce. Most of the known occurrences consist of isolated and fragmentary bones collected in Madagascar, Morocco, Tunisia, India, and Ethiopia. Nevertheless, these specimens, although fragmentary, have provided substantial information for assessing the evolutionary scenarios of multiple teleosauroid lineages and have shown that certain teleosauroid taxa were widespread rather than endemic to Western Europe. Here, a partial skeleton of a teleosauroid crocodylomorph is described. It was found in the late Middle Jurassic (Callovian) deposits of southeastern Tunisia by a team of French and Tunisian paleontologists; however, it has not been thoroughly studied at both macro- and microscopic scale until now. The new specimen is composed of an incomplete symphyseal portion of a lower jaw in addition to isolated teeth, osteoderms (both dorsal and ventral), thoracic and caudal vertebrae, and several thoracic ribs. The specimen has several morphological characters that are reminiscent of longirostrine teleosauroids. Due to the total absence of other cranial bones, as well as the pectoral and pelvic girdles, the specimen is not diagnostic to the generic level. However, these new remains represent the youngest ascertained occurrence of a definitive non-machimosaurin teleosauroid in Africa, provide additional insights into the geographic distribution of Thalattosuchia, and raise once again the question whether the origins of this clade were Gondwanan or Laurasian.     

A control theoretic model of the forearm

In this paper, a control theoretic model of the forearm is developed and analyzed, and a computational method for predicting muscle activations necessary to generate specified motions is described. A detailed geometric model of the forearm kinematics, including the carrying angle and models of how the biceps and the supinator tendons wrap around the bones, is used. Also, including a dynamics model, the final model is a system of differential equations where the muscle activations play the role of control signals. Due to the large number of muscles, the problem of finding muscle activations is redundant, and this problem is solved by an optimization procedure. The computed muscle activations for ballistic movements clearly recaptures the triphasic ABC (Activation-Braking-Clamping) pattern. It is also transparent, from the muscle activation patterns, how the muscles cooperate and counteract in order to accomplish desired motions. A comparison with previously reported experimental data is included and the model predictions can be seen to be partially in agreement with the experimental data.     

Mammalian tooth marks on the bones of dinosaurs and other Late Cretaceous vertebrates

Abstract: We describe bones from the Late Cretaceous of Alberta – including bones of large dinosaurs, a femur from the aquatic reptile Champsosaurus, and a dentary from the marsupial Eodelphis– that bear tooth marks made by animals with opposing pairs of teeth. Of the animals known from the Late Cretaceous of North America, only mammals are capable of making such tooth marks. In particular, multituberculates, which have paired upper and lower incisors, are the most likely candidates for the makers of these traces. The traces described here represent the oldest known mammalian tooth marks. Although it is possible that some of these tooth marks represent feeding traces, the tooth marks often penetrate deep into the dense cortices of the bone. This raises the possibility that, much as extant mammals gnaw bone and antler, some Cretaceous mammals may have consumed the bones of dinosaurs and other vertebrates as a source of minerals. However, none of the tooth marks described here resemble the extensive gnaw traces produced by Cenozoic multituberculates or rodents. This suggests that specialized gnawing forms may have been rare or absent in the Late Cretaceous of North America.     

A new morphometric analysis of the hominid pelvic bone

This study is based upon a new morphometric technique providing both size and shape variables. It has been applied to 189 pelvic bones of extant humans and African apes as well as to 13 hominid pelvic bones of various taxonomic status. The main aim of this work is to include such fossil bones in the same study in order to set a synthetic comparison of their shape in the light of the yardstick given by the African ape/human pelvic bone comparison. To do so, ratio diagrams are chosen because they are simple and very expressive tools with which to present such comparisons. Shape differences are very well illustrated and quantified by this technique. The ilium appears to be the most different of the three parts of the pelvic bone. Compared to these differences, discrepancies between fossil hominid and extant human bones are of a totally different scale. This shows the architectural unity related to the acquisition of bipedalism by hominids. It is nonetheless possible to detect two levels of difference. The first separates Australopithecus from Homo and could be seen as reflecting locomotor differences between both genera. The second splits both Homo erectus and Neanderthal from modern human pelvic bones. It appears from the hominid fossil record of pelvic bones that two periods of stasis exist and are separated by a period of very rapid evolution corresponding to the emergence of the genus Homo. We are of the opinion that the same could be true for the split between African ape and hominid lineages at the end of the Miocene.