Development of a test bench for biomechanical simulation-a preliminary study of mandibular forces.

The aim of this study is to develop a test bench, which integrates different complexity levels and enables in that way a flexible and dynamic testing for mid and long term intervals as well as testing of maximum loads till implant failure of different osteosynthesis systems on the mandible. For this purpose, an analysis of the state of the art regarding existing test benches was combined with interviews of clinical experts to acquire a list of requirements. Based on these requirements a design for a modular test bench was developed.

Determination of muscle strength and function in plesiosaur limbs: finite element structural analyses of humerus and femur.

Background: The Plesiosauria (Sauropterygia) are secondary marine diapsids. They are the only tetrapods to have evolved hydrofoil fore- and hindflippers. Once this specialization of locomotion had evolved, it remained essentially unchanged for 135 Ma.

Foreflipper and hindflipper muscle reconstructions of in comparison to functional analogues: introduction of a myological mechanism for flipper twisting.

Background: Plesiosaurs, diapsid crown-group Sauropterygia, inhabited the oceans from the Late Triassic to the Late Cretaceous. Their most exceptional characteristic are four hydrofoil-like flippers. The question whether plesiosaurs employed their four flippers in underwater flight, rowing flight, or rowing has not been settled yet.

Three-dimensional finite element analysis of the dural folds and the human skull under head acceleration.

Bone and collagen fiber architecture adapt to external mechanical loads. In humans, due to the low insertion of the temporal muscle, mastication does not lead to a physiological loading of the calvaria. Forces applied to the skull by the dural folds can lead to compressive stresses in the calvaria.

Humerus osteology, myology, and finite element structure analysis of Cheloniidae.

Adaptation of osteology and myology lead to the formation of hydrofoil foreflippers in Cheloniidae (all recent sea turtles except Dermochelys coriacea) which are used mainly for underwater flight. Recent research shows the biomechanical advantages of a complex system of agonistic and antagonistic tension chords that reduce bending stress in bones. Finite element structure analysis (FESA) of a cheloniid humerus is used to provide a better understanding of morphology and microanatomy and to link these with the main flipper function, underwater flight.

Biomechanical Study of the Development of Long Bones: Finite Element Structure Synthesis of the Human Second Proximal Phalanx Under Growth Conditions.

Torsional loads are a possible mechanical explanation for the architecture of long bone. Finite element structure synthesis (FESS) has previously successfully been used as a deductive technique using Wolff's Law by applying expected loads to an unspecific homogeneous solid and eliminating stress free parts to verify muscle forces. The extended approach presented in this article includes further mechanobiological rules to model the development from a cartilage model to a finger bone.

Finite-Element Syntheses of Callus and Bone Remodeling: Biomechanical Study of Fracture Healing in Long Bones.

Computational simulations of fracture healing are a valuable tool to improve fracture treatment and implants. Several finite-element models have been established to predict callus formation due to mechanobiological rules. This work provides a comprehensive simulation for virtual implantation through the combination of callus simulation and finite-element structural synthesis (FESS) of (re-)modeling during and after healing based on Pauwel's theory of histogenesis and Wolff's law.

Inclusion of periodontal ligament fibres in mandibular finite element models leads to an increase in alveolar bone strains.

Alveolar bone remodelling is vital for the success of dental implants and orthodontic treatments. However, the underlying biomechanical mechanisms, in particular the function of the periodontal ligament (PDL) in bone loading and remodelling, are not well understood. The PDL is a soft fibrous connective tissue that joins the tooth root to the alveolar bone and plays a critical role in the transmission of loads from the tooth to the surrounding bone.

Biomechanical properties of predator-induced body armour in the freshwater crustacean Daphnia.

The freshwater crustacean Daphnia is known for its ability to develop inducible morphological defences that thwart predators. These defences are developed only in the presence of predators and are realized as morphological shape alterations e.g.

Skeletal immaturity, rostral sparing, and disparate hip morphologies as biomechanical causes for Legg-Calvé-Perthes' disease.

Legg-Calvé-Perthes' (Perthes') disease is a developmental disease of the hip joint that may result in numerous short and long term problems. The etiology of the disease remains largely unknown, but the mechanism is believed to be vascular and/or biomechanical in nature. There are several anatomical characteristics that tend to be prevalent in children with Perthes' disease, namely: skeletal immaturity, reduced height, and rostral sparing.

Structure and function of the septum nasi and the underlying tension chord in crocodylians.

A long rostrum has distinct advantages for prey capture in an aquatic or semi-aquatic environment but at the same time poses severe problems concerning stability during biting. We here investigate the role of the septum nasi of brevirostrine crocodilians for load-absorption during mastication. Histologically, both the septum nasi and the septum interorbitale consist of hyaline cartilage and therefore mainly resist compression.

The biomechanical function of periodontal ligament fibres in orthodontic tooth movement.

Orthodontic tooth movement occurs as a result of resorption and formation of the alveolar bone due to an applied load, but the stimulus responsible for triggering orthodontic tooth movement remains the subject of debate. It has been suggested that the periodontal ligament (PDL) plays a key role. However, the mechanical function of the PDL in orthodontic tooth movement is not well understood as most mechanical models of the PDL to date have ignored the fibrous structure of the PDL.

Development and three-dimensional morphology of the zygomaticotemporal suture in primate skulls.

Cranial sutures are an essential part of the growing skull, allowing bones to increase in size during growth, with their morphology widely believed to be dictated by the forces and displacements that they experience. The zygomaticotemporal suture in primates is located in the relatively weak zygomatic arch, and externally it appears a very simple connection. However, large forces are almost certainly transmitted across this suture, suggesting that it requires some level of stability while also allowing controlled movements under high loading.

Quantitative interpretation of tracks for determination of body mass.

To better understand the biology of extinct animals, experimentation with extant animals and innovative numerical approaches have grown in recent years. This research project uses principles of soil mechanics and a neoichnological field experiment with an African elephant to derive a novel concept for calculating the mass (i.e.

Boundary conditions for heat transfer and evaporative cooling in the trachea and air sac system of the domestic fowl: a two-dimensional CFD analysis.

Various parts of the respiratory system play an important role in temperature control in birds. We create a simplified computational fluid dynamics (CFD) model of heat exchange in the trachea and air sacs of the domestic fowl (Gallus domesticus) in order to investigate the boundary conditions for the convective and evaporative cooling in these parts of the respiratory system. The model is based upon published values for respiratory times, pressures and volumes and upon anatomical data for this species, and the calculated heat exchange is compared with experimentally determined values for the domestic fowl and a closely related, wild species.

The mechanical significance of the temporal fasciae in Macaca fascicularis: an investigation using finite element analysis.

Computational finite element analyses (FEAs) of the skull predict structural deformations under user specified loads and constraints, with results normally presented as stress and strain distributions over the skull's surface. The applied loads are generally a representation of the major adductor musculature, with the skull constrained at bite positions and at the articulating joints. However, virtually all analyses ignore potentially important anatomical structures, such as the fasciae that cover the temporalis muscle and attach onto the zygomatic arch.

Biology of the sauropod dinosaurs: the evolution of gigantism.

The herbivorous sauropod dinosaurs of the Jurassic and Cretaceous periods were the largest terrestrial animals ever, surpassing the largest herbivorous mammals by an order of magnitude in body mass. Several evolutionary lineages among Sauropoda produced giants with body masses in excess of 50 metric tonnes by conservative estimates. With body mass increase driven by the selective advantages of large body size, animal lineages will increase in body size until they reach the limit determined by the interplay of bauplan, biology, and resource availability.

Functional Analysis of the Primate Shoulder.

Studies of the shoulder girdle are in most cases restricted to morphological comparisons and rarely aim at elucidating function in a strictly biomechanical sense. To fill this gap, we investigated the basic functional conditions that occur in the shoulder joint and shoulder girdle of primates by means of mechanics. Because most of nonhuman primate locomotion is essentially quadrupedal walking-although on very variable substrates-our analysis started with quadrupedal postures.

Principles of determination and verification of muscle forces in the human musculoskeletal system: Muscle forces to minimise bending stress.

While there are a growing number of increasingly complex methodologies available to model geometry and material properties of bones, these models still cannot accurately describe physical behaviour of the skeletal system unless the boundary conditions, especially muscular loading, are correct. Available in vivo measurements of muscle forces are mostly highly invasive and offer no practical way to validate the outcome of any computational model that predicts muscle forces. However, muscle forces can be verified indirectly using the fundamental property of living tissue to functional adaptation and finite element (FE) analysis.

Functional shape of the skull in vertebrates: which forces determine skull morphology in lower primates and ancestral synapsids?

In order to determine the extent to which the shape of the synapsid skull is adapted for resisting the mechanical loads to which it is subjected, block- or simple plate-shaped finite-element models were constructed and loaded with external muscle and bite forces in locations estimated to resemble points of application of these forces. These 2D or 3D finite-element models were iteratively loaded and modified by removing elements that experience only low stresses, and the resulting morphologies of the models were compared with fossil skulls of synapsids and the skulls of extant mammals. The results suggest that the stress flows in these unspecific models are very similar to the arrangement of bone material in real skulls.

Finite-element model construction for the virtual synthesis of the skulls in vertebrates: case study of Diplodocus.

The measurement of strains in real skulls is an inductive method that yields information about the stresses occurring in the a priori existing shape. In contrast, the approach taken here to determine the relationship between skull function and skull shape applies Wolff's law through a deductive technique of structure synthesis. This article describes the application of this method in the exact virtual synthesis of a sauropod skull, e.

A biomechanical approach to craniofacial shape in primates, using FESA.

The head of a land-living vertebrate is exposed to the forces of acceleration, in particular the permanent earth acceleration (= gravity) and the muscle-generated bite and chewing forces. In mammals, at least, the latter seem to play the dominant role. Bite forces are applied to the teeth and close the circle of forces by passing through the facial skeleton to the insertions of the mandibular adductors.

Posterolateral aspect and stability of the knee joint. II. Posterolateral instability and effect of isolated and combined posterolateral reconstruction on knee stability: a biomechanical study.

This study evaluated the correlation between the number of transected posterolateral structures (PLS) and the grade of posterolateral rotational instability, determined the effect of the popliteus muscle-tendon unit on the tibial rotation, and examined the effect of an isolated posterior cruciate ligament (PCL) and combined PCL-PLS reconstruction on knee stability. Sectioning the popliteofibular and lateral collateral ligaments both caused an increase in tibial external rotation. Cutting the PT resulted in a statistically highly significant excessive external rotation and externally shifted neutral position of the tibia over the full range of motion.

Posterolateral aspect and stability of the knee joint. I. Anatomy and function of the popliteus muscle-tendon unit: an anatomical and biomechanical study.

This study examined ten human adult cadaveric knees to dissect the popliteus muscle-tendon unit (PMTU), including its numerous attachments to other posterior and posterolateral structures, and to determine the effect of tensioning the PMTU on the internal and external rotation, total rotational arcs, and neutral tibial rotation in full extension and 30 degrees, 60 degrees, and 90 degrees of knee flexion. The junction between the popliteus tendon and the fibular head commonly described as the popliteofibular ligament became lax in internal and tense in external tibial rotation. The internal and external rotational arcs increased gradually between extension and 90 degrees of flexion.

Quantitative comparison of three different types of anterior cruciate ligament reconstruction methods: laxity and 3-D kinematic measurements.

In this project, we compared knee laxity and 3-D knee kinematics after ACL reconstruction on cadaver knees using (1) bone-patellar tendon-bone two-tunnel; (2) synthetic ligament two-tunnel; and (3) synthetic ligament "over-the-top" technique. We used a computer assisted system, based on the acquisition of the knee's movement with magnetic sensors (Polhemus, Vermont, USA). The use of personalised three-dimensional (3D) models of the bones enabled us to ensure a reproducible measurement of three-dimensional kinematic and laxity parameters.