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The occlusion effect on the craniofacial development is a controversial topic that has attracted the interest of many researchers but that remains unclear, mainly due to the difficulties on measure its mechanical response experimentally. This mechano-morphological relationship of the craniofacial growth is often explained by the periosteal and capsular matrices of the functional matrix hypothesis (FMH); however, its outcomes have not been analytically demonstrated yet. This computational study aims, therefore, to analytically demonstrate the mechano-morphological relationship in the craniofacial development of children with unilateral crossbite (UXB) using the finite element (FE) method.The craniofacial complex asymmetry of ten children, five of whom exhibit UXB, was 3D-analysed and compared with the biomechanical response computed from a FE analysis of each patient's occlusion. Due to the complexity of the geometry and the multitude of contacts involved, the inherent limitations of the model were evaluated by comparing computed occlusal patterns with those recorded by an occlusal analysis on 3D printed copies.Comparison's outcomes proved the reliability of our models with just a deviation error below 6% between both approaches. Out of validation process, computational results showed that the significant elongation of mandibular branch in the contralateral side could be related to the mandibular shift and increase of thickness on the crossed side, and particularly of the posterior region. These morphological changes could be associated with periodontal overpressure (4.7 kPa) and mandibular over deformation (0.002 ε) in that side, in agreement with the periosteal matrix's principles. Furthermore, the maxilla's transversal narrowing and the elevation of the maxillary and zygomatic regions on the crossed side were statistically demonstrated and seem to be related with their respective micro displacements at occlusion, as accounted by their specific capsule matrices. Our results were consistent with those reported clinically and demonstrated analytically the mechano-morphological relationship of children's craniofacial development based on the FMH's functional matrices.This study is a first step in the understanding of the occlusion's effect on the craniofacial development by computational methods. Our approach could help future engineers, researchers and clinicians to understand better the aetiology of some dental malocclusions and functional disorders improve the diagnosis or even predict the craniofacial development.

Synopsis Previous studies have focused on documenting shape variation in the caudal vertebrae in chameleons underlying prehensile tail function. The goal of this study was to test the impact of this variation on tail function using multibody dynamic analysis (MDA). First, observations from dissections and 3D reconstructions generated from contrast-enhanced µCT scans were used to document regional variation in arrangement of the caudal muscles along the antero-posterior axis. Using MDA, we then tested the effect of vertebral shape geometry on biomechanical function. To address this question, four different MDA models were built: those with a distal vertebral shape and with either a distal or proximal musculature, and reciprocally the proximal vertebral shape with either the proximal or distal musculature. For each muscle configuration, we calculated the force required in each muscle group for the muscle force to balance an arbitrary external force applied to the model. The results showed that the models with a distal-type of musculature are the most efficient, regardless of vertebral shape. Our models also showed that the m. ilio-caudalis pars dorsalis is least efficient when combining the proximal vertebral shape and distal musculature, highlighting the importance of the length of the transverse process in combination with the lever-moment arm onto which muscle force is exerted. This initial model inevitably has a number of simplifications and assumptions, however its purpose is not to predict in vivo forces, but instead reveals the importance of vertebral shape and muscular arrangement on the total force the tail can generate, thus providing a better understanding of the biomechanical significance of the regional variations on tail grasping performance in chameleons.

Measures of attachment or accommodation area on the skeleton are a popular means of rapidly generating estimates of muscle proportions and functional performance for use in large-scale macroevolutionary studies. Herein, we provide the first evaluation of the accuracy of these muscle area assessment (MAA) techniques for estimating muscle proportions, force outputs and bone loading in a comparative macroevolutionary context using the rodent masticatory system as a case study. We find that MAA approaches perform poorly, yielding large absolute errors in muscle properties, bite force and particularly bone stress. Perhaps more fundamentally, these methods regularly fail to correctly capture many qualitative differences between rodent morphotypes, particularly in stress patterns in finite-element models. Our findings cast doubts on the validity of these approaches as means to provide input data for biomechanical models applied to understand functional transitions in the fossil record, and perhaps even in taxon-rich statistical models that examine broad-scale macroevolutionary patterns. We suggest that future work should go back to the bones to test if correlations between attachment area and muscle size within homologous muscles across a large number of species yield strong predictive relationships that could be used to deliver more accurate predictions for macroevolutionary and functional studies.

Phenotypic traits have been shown to evolve in response to variation in the environment. However, the evolutionary processes underlying the emergence of phenotypic diversity can typically only be understood at the population level. Consequently, how subtle phenotypic differences at the intraspecific level can give rise to larger-scale changes in performance and ecology remains poorly understood. We here tested for the covariation between ecology, bite force, jaw muscle architecture, and the three- dimensional shape of the cranium and mandible in 16 insular populations of the lizards Podarcis melisellensis and P. sicula. We then compared the patterns observed at the among-population level with those observed at the interspecific level. We found that three-dimensional head shape as well as jaw musculature evolve similarly under similar ecological circumstances. Depending on the type of food consumed or on the level of sexual competition, different muscle groups were more developed and appeared to underlie changes in cranium and mandible shape. Our findings show that the local selective regimes are primary drivers of phenotypic variation resulting in predictable patterns of form and function. Moreover, intraspecific patterns of variation were generally consistent with those at the interspecific level, suggesting that microevolutionary variation may translate into macroevolutionary patterns of ecomorphological diversity.

Although a functional relationship between bone structure and mastication has been shown in some regions of the rabbit skull, the biomechanics of the whole cranium during mastication have yet to be fully explored. In terms of cranial biomechanics, the rabbit is a particularly interesting species due to its uniquely fenestrated rostrum, the mechanical function of which is debated. In addition, the rabbit processes food through incisor and molar biting within a single bite cycle, and the potential influence of these bite modes on skull biomechanics remains unknown. This study combined the in silico methods of multi-body dynamics and finite element analysis to compute musculoskeletal forces associated with a range of incisor and molar biting, and to predict the associated strains. The results show that the majority of the cranium, including the fenestrated rostrum, transmits masticatory strains. The peak strains generated over all bites were found to be attributed to both incisor and molar biting. This could be a consequence of a skull shape adapted to promote an even strain distribution for a combination of infrequent incisor bites and cyclic molar bites. However, some regions, such as the supraorbital process, experienced low peak strain for all masticatory loads considered, suggesting such regions are not designed to resist masticatory forces.

Biomechanical modelling is a powerful tool for quantifying the evolution of functional performance in extinct animals to understand key anatomical innovations and selective pressures driving major evolutionary radiations. However, the fossil record is composed predominantly of hard parts, forcing palaeontologists to reconstruct soft tissue properties in such models. Rarely are these reconstruction approaches validated on extant animals, despite soft tissue properties being highly determinant of functional performance. The extent to which soft tissue reconstructions and biomechanical models accurately predict quantitative or even qualitative patterns in macroevolutionary studies is therefore unknown. Here, we modelled the masticatory system in extant rodents to objectively test the ability of current muscle reconstruction methods to correctly identify quantitative and qualitative differences between macroevolutionary morphotypes. Baseline models generated using measured soft tissue properties yielded differences in muscle proportions, bite force, and bone stress expected between extant sciuromorph, myomorph, and hystricomorph rodents. However, predictions from models generated using reconstruction methods typically used in fossil studies varied widely from high levels of quantitative accuracy to a failure to correctly capture even relative differences between macroevolutionary morphotypes. Our novel experiment emphasizes that correctly reconstructing even qualitative differences between taxa in a macroevolutionary radiation is challenging using current methods. Future studies of fossil taxa should incorporate systematic assessments of reconstruction error into their hypothesis testing and, moreover, seek to expand primary datasets on muscle properties in extant taxa to better inform soft tissue reconstructions in macroevolutionary studies.

RANKL can promote the differentiation of osteoclast precursors into mature osteoclasts by binding to RANK expressed on the surfaces of osteoclast progenitor cells during bone remodelling. The NF-κB signalling pathway is downstream of RANKL and transmits the RANKL signal to nuclear promoter-bound protein complexes from cell surface receptors, which then regulates target gene expression to facilitate osteoclastogenesis. However, this important role of the NF-κB signalling pathway is usually ignored in published mathematical models of bone remodelling. This paper describes the construction of a mathematical model of bone remodelling in a normal bone microenvironment with inclusion of the NF-κB signalling pathway. The model consisted of a set of ordinary differential equations and reconstructed variations in the bone cells, resultant bone volume, and biochemical factors involved in the NF-κB signalling pathway over time. The model was used to investigate how the NF-κB pathway is activated in osteoclast precursors to promote osteoclastogenesis during bone remodelling. Model simulations agreed well with published experimental data. It is hoped that this model can improve our understanding of bone remodelling. It has the obvious potential to examine the influence of NF-κB dysregulation on bone remodelling, and even propose potential therapeutic strategies to combat related bone diseases in future research.

Cranial morphology in lepidosaurs is highly disparate and characterised by the frequent loss or reduction of bony elements. In varanids and geckos, the loss of the postorbital bar is associated with changes in skull shape, but the mechanical principles underlying this variation remain poorly understood. Here, we sought to determine how the overall cranial architecture and the presence of the postorbital bar relate to the loading and deformation of the cranial bones during biting in lepidosaurs. Using computer-based simulation techniques, we compared cranial biomechanics in the varanid Varanus niloticus and the teiid Salvator merianae, two large, active foragers. The overall strain magnitude and distribution across the cranium were similar in the two species, despite lower strain gradients in V. niloticus. In S. merianae, the postorbital bar is important for resistance of the cranium to feeding loads. The postorbital ligament, which in varanids partially replaces the postorbital bar, does not affect bone strain. Our results suggest that the reduction of the postorbital bar impaired neither biting performance nor the structural resistance of the cranium to feeding loads in V. niloticus. Differences in bone strain between the two species might reflect demands imposed by feeding and non-feeding functions on cranial shape. Beyond variation in cranial bone strain related to species-specific morphological differences, our results reveal that similar mechanical behaviour is shared by lizards with distinct cranial shapes. Contrary to the situation in mammals, the morphology of the circumorbital region, calvaria and palate appears to be important for withstanding high feeding loads in these lizards., Summary: In vivo measurements and computer-based simulations of the cranial mechanics of two large lizards indicate that similar mechanical behaviour is shared by lizards with distinct cranial architecture, and show the importance of the postorbital bar in resisting the feeding loads.

As a common feature, bilateral symmetry of biological forms is ubiquitous, but in fact rarely exact. In a setting of analytic geometry, bilateral symmetry is defined with respect to a point, line or plane, and the well-known notions of fluctuating asymmetry, directional asymmetry and antisymmetry are recast. A meticulous scheme for asymmetry assessments is proposed and explicit solutions to them are derived. An investigation into observational errors of points representing the geometric structure of an object offers a baseline reference for asymmetry assessment of the object. The proposed assessments are applicable to individual, part or all point pairs at both individual and collective levels. The exact relationship between the developed treatments and the widely used Procrustes method in asymmetry assessment is examined. An application of the proposed assessments to a large collection of human skull data in the form of 3D landmark coordinates finds: (a) asymmetry of most skulls is not fluctuating, but directional if measured about a plane fitted to shared landmarks or side landmarks for balancing; (b) asymmetry becomes completely fluctuating if one side of a skull could be slightly rotated and translated with respect to the other side; (c) female skulls are more asymmetric than male skulls. The methodology developed in this study is rigorous and transparent, and lays an analytical base for investigation of structural symmetries and asymmetries in a wide range of biological and medical applications.

Remodelling and adaptation of bone within the pelvis is believed to be influenced by the mechanical strains generated during locomotion. Variation in the cortical bone thickness observed in the prenatal ilium has been linked to the musculoskeletal loading associated with in utero movements; for example the development of a thicker gluteal cortex is a possible response to contractions of the gluteal muscles. This study examines if the strains generated in the prenatal iliac cortex due to musculoskeletal loading in utero are capable of initiating bone remodelling to either maintain homeostasis or form new bone. Computational modelling techniques were used firstly to predict the muscle forces and resultant joint reaction force acting on the pelvis during a range of in utero movements. Finite element analyses were subsequently performed to calculate the von Mises strains induced in the prenatal ilium. The results demonstrated that strains generated in the iliac cortex were above the thresholds suggested to regulate bone remodelling to either maintain homeostasis or form new bone. Further simulations are required to investigate the extent to which the heterogeneous cortex forms in response to these strains (i.e., remodelling) or if developmental bone modelling plays a more pivotal role.

Background and objective: Craniofacial asymmetry is a common growth disorder often caused by unilateral chewing. Although an early orthodontic treatment would avoid surgical procedures later in life, the uncertainty of defining the accurate sagittal midplane potentially leads to misdiagnosis and therefore inaccurate orthodontic treatment plans. This novel study aims to 3D-diagnose craniofacial complex malformations in children with unilateral crossbite (UXB) considering a midplane which compensates the asymmetric morphology. Methods: The sagittal midplane of 20 children, fifteen of whom exhibited UXB, was computed by a PCA-based method which compensates the asymmetry mirroring the 3D models obtained from cone-beam computed tomography data. Once determined, one side of the data was mirrored using the computed midplane to visualize the malformations on the hard and soft tissues by 3D-computing the distances between both halves. Additionally, 31 skull's landmarks were manually placed in each model to study the principal variation modes and the significant differences in the group of subjects with and without UXB through PCA and Mann-Whitney U test analyses respectively. Results: Morphological 3D-analysis showed pronounced deformities and aesthetic implications for patients with severe asymmetry (jaw deviation > 0.8¿mm) in whole craniofacial system, while initial signs of asymmetry were found indistinctly in the mandible or maxilla. We detected significant (p < 0.05) malformations for example in mandibular ramus length (0.0086), maxillary palate width (0.0481) and condylar head width (0.0408). Craniofacial malformations increased the landmarks’ variability in the group of patients with UXB over the control group requiring 8 variation modes more to define 99% of the sample’ variability. Conclusions: Our findings demonstrated the viability of early diagnosis of craniofacial asymmetry through computing the accurate sagittal midplane which compensates the individual's asymmetrical morphology. Furthermore, this study provides important computational insights into the determination of craniofacial deformities which are caused by UXB, following some empirical findings of previous clinical studies. Hence, this computational approach can be useful for the development of new software in craniofacial surgery or for its use in biomedical research and clinical practice.

The evolution of the mammalian jaw is one of the most important innovations in vertebrate history, and underpins the exceptional radiation and diversification of mammals over the last 220 million years1,2. In particular, the transformation of the mandible into a single tooth-bearing bone and the emergence of a novel jaw joint—while incorporating some of the ancestral jaw bones into the mammalian middle ear—is often cited as a classic example of the repurposing of morphological structures3,4. Although it is remarkably well-documented in the fossil record, the evolution of the mammalian jaw still poses the paradox of how the bones of the ancestral jaw joint could function both as a joint hinge for powerful load-bearing mastication and as a mandibular middle ear that was delicate enough for hearing. Here we use digital reconstructions, computational modelling and biomechanical analyses to demonstrate that the miniaturization of the early mammalian jaw was the primary driver for the transformation of the jaw joint. We show that there is no evidence for a concurrent reduction in jaw-joint stress and increase in bite force in key non-mammaliaform taxa in the cynodont–mammaliaform transition, as previously thought5–8. Although a shift in the recruitment of the jaw musculature occurred during the evolution of modern mammals, the optimization of mandibular function to increase bite force while reducing joint loads did not occur until after the emergence of the neomorphic mammalian jaw joint. This suggests that miniaturization provided a selective regime for the evolution of the mammalian jaw joint, followed by the integration of the postdentary bones into the mammalian middle ear.

Alveolar bone, together with the underlying trabecular bone, fulfils an important role in providing structural support against masticatory forces. Diseases such as osteoporosis or periodontitis cause alveolar bone resorption which weakens this structural support and is a major cause of tooth loss. However, the functional relationship between alveolar bone remodelling within the molar region and masticatory forces is not well understood. This study investigated this relationship by comparing mammalian species with different diets and functional loading (Felis catus, Cercocebus atys, Homo sapiens, Sus scrofa, Oryctolagus cuniculus, Ovis aries). We performed histomorphometric analyses of trabecular bone morphology (bone volume fraction, trabecular thickness and trabecular spacing) and quantified the variation of bone and tooth root volumes along the tooth row. A principal component analysis and non-parametric MANOVA showed statistically significant differences in trabecular bone morphology between species with contrasting functional loading, but these differences were not seen in sub-adult specimens. Our results support a strong, but complex link between masticatory function and trabecular bone morphology. Further understanding of a potential functional relationship could aid the diagnosis and treatment of mandibular diseases causing alveolar bone resorption, and guide the design and evaluation of dental implants.

Objectives Legg–Calvé–Perthes’ disease (LCP) is an idiopathic osteonecrosis of the femoral head that is most common in children between four and eight years old. The factors that lead to the onset of LCP are still unclear; however, it is believed that interruption of the blood supply to the developing epiphysis is an important factor in the development of the condition. Methods Finite element analysis modelling of the blood supply to the juvenile epiphysis was investigated to understand under which circumstances the blood vessels supplying the femoral epiphysis could become obstructed. The identification of these conditions is likely to be important in understanding the biomechanics of LCP. Results The results support the hypothesis that vascular obstruction to the epiphysis may arise when there is delayed ossification and when articular cartilage has reduced stiffness under compression. Conclusion The findings support the theory of vascular occlusion as being important in the pathophysiology of Perthes disease. Cite this article: M. Pinheiro, C. A. Dobson, D. Perry, M. J. Fagan. New insights into the biomechanics of Legg-Calvé-Perthes’ disease: The Role of Epiphyseal Skeletal Immaturity in Vascular Obstruction. Bone Joint Res 2018;7:148–156. DOI: 10.1302/2046-3758.72.BJR-2017-0191.R1.

The evolution of the mammalian jaw during the transition from non-mammalian synapsids to crown mammals is a key event in vertebrate history and characterised by the gradual reduction of its individual bones into a single element and the concomitant transformation of the jaw joint and its incorporation into the middle ear complex. This osteological transformation is accompanied by a rearrangement and modification of the jaw adductor musculature, which is thought to have allowed the evolution of a more-efficient masticatory system in comparison to the plesiomorphic synapsid condition. While osteological characters relating to this transition are well documented in the fossil record, the exact arrangement and modifications of the individual adductor muscles during the cynodont–mammaliaform transition have been debated for nearly a century. We review the existing knowledge about the musculoskeletal evolution of the mammalian jaw adductor complex and evaluate previous hypotheses in the light of recently documented fossils that represent new specimens of existing species, which are of central importance to the mammalian origins debate. By employing computed tomography (CT) and digital reconstruction techniques to create three-dimensional models of the jaw adductor musculature in a number of representative non-mammalian cynodonts and mammaliaforms, we provide an updated perspective on mammalian jaw muscle evolution. As an emerging consensus, current evidence suggests that the mammal-like division of the jaw adductor musculature (into deep and superficial components of the m. masseter, the m. temporalis and the m. pterygoideus) was completed in Eucynodontia. The arrangement of the jaw adductor musculature in a mammalian fashion, with the m. pterygoideus group inserting on the dentary was completed in basal Mammaliaformes as suggested by the muscle reconstruction of Morganucodon oehleri. Consequently, transformation of the jaw adductor musculature from the ancestral (‘reptilian’) to the mammalian condition must have preceded the emergence of Mammalia and the full formation of the mammalian jaw joint. This suggests that the modification of the jaw adductor system played a pivotal role in the functional morphology and biomechanical stability of the jaw joint.

A statistical study of the relationship between the neuro-occlusal stimulus produced in paediatric patients with unilateral bitting and the abnormal stomatognathic system growth is proposed to improve early treatments and avoid surgical treatments later in life. Therefore, 3D morphological and finite element analyses were performed to study malformations and function imbalances, respectively.

Background Cephalometric analysis is used to evaluate facial growth, to study the anatomical relationships within the face. Cephalometric assessment is based on 2D radiographic images, either the sagittal or coronal planes and is an inherently inaccurate methodology. The wide availability of 3D imaging techniques, such as computed tomography and magnetic resonance imaging make routine 3D analysis of facial morphology feasible. 3D cephalometry may not only provide a more accurate quantification of the craniofacial morphology and longitudinal growth, but also the differentiation of subtle changes in occlusion. However, a reliable protocol for the computation of craniofacial symmetry and quantification of craniofacial morphology is still a topic of extensive research. Here, a protocol for 3D cephalometric analysis for both the identification of the natural head position (NHP) and the accurate quantification of facial growth and facial asymmetry is proposed and evaluated. A phantom study was conducted to assess the performance of the protocol and to quantify the ability to repeatedly and reliably align skulls with the NHP and quantify the degree of accuracy with which facial growth and facial asymmetry can be measured. Results The results obtained show that the protocol allows consistent alignment with the NHP, with an overall average error (and standard deviation) of just 0.17 (9.10e-6) mm, with variations of 0.21 (2.77e-17) mm in the frontonasal suture and 0.30 (5.55e-17) mm in the most prominent point in the chin. The average errors associated with simulated facial growth ranged from 1.83 to 3.75% for 2 years’ growth and from − 9.57 to 14.69% for 4 years, while the error in the quantification of facial asymmetry ranged from − 11.38 to 9.31%. Conclusions The protocol for 3D skull alignment produces accurate and landmark free estimation of the true symmetry of the head. It allows a reliable alignment of the skull in the NHP independently of user-defined landmarks, as well as an accurate quantification of facial growth and asymmetry.

The newborn mammalian cranial vault consists of five flat bones that are joined together along their edges by soft fibrous tissues called sutures. Early fusion of these sutures leads to a medical condition known as craniosynostosis. The mechanobiology of normal and craniosynostotic skull growth is not well understood. In a series of previous studies, we characterized and modeled radial expansion of normal and craniosynostotic (Crouzon) mice. Here, we describe a new modeling algorithm to simulate bone formation at the sutures in normal and craniosynostotic mice. Our results demonstrate that our modeling approach is capable of predicting the observed ex vivo pattern of bone formation at the sutures in the aforementioned mice. The same approach can be used to model different calvarial reconstruction in children with craniosynostosis to assist in the management of this complex condition.

The neurocranium of sarcopterygian fishes was originally divided into an anterior (ethmosphenoid) and posterior (otoccipital) portion by an intracranial joint, and underwent major changes in its overall geometry before fusing into a single unit in lungfishes and early tetrapods1. Although the pattern of these changes is well-documented, the developmental mechanisms that underpin variation in the form of the neurocranium and its associated soft tissues during the evolution of sarcopterygian fishes remain poorly understood. The coelacanth Latimeria is the only known living vertebrate that retains an intracranial joint2,3. Despite its importance for understanding neurocranial evolution, the development of the neurocranium of this ovoviviparous fish remains unknown. Here we investigate the ontogeny of the neurocranium and brain in Latimeria chalumnae using conventional and synchrotron X-ray micro-computed tomography as well as magnetic resonance imaging, performed on an extensive growth series for this species. We describe the neurocranium at the earliest developmental stage known for Latimeria, as well as the major changes that the neurocranium undergoes during ontogeny. Changes in the neurocranium are associated with an extreme reduction in the relative size of the brain along with an enlargement of the notochord. The development of the notochord appears to have a major effect on the surrounding cranial components, and might underpin the formation of the intracranial joint. Our results shed light on the interplay between the neurocranium and its adjacent soft tissues during development in Latimeria, and provide insights into the developmental mechanisms that are likely to have underpinned the evolution of neurocranial diversity in sarcopterygian fishes.

Legg-Calve-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. We present an overview of the literature, summarizing the current understanding of the pathogenesis, particularly related to how the formation of the vasculature to the femoral epiphysis places children aged 5-8 at a higher risk for Perthes' disease, how skeletal immaturity and rostral sparing could increase the probability of developing Perthes' disease, and how animal models have aided our understanding of the disease. In doing so, we also explore why Perthes' disease is correlated to latitude, with populations at higher latitudes having higher incidence rates than populations closer to the Equator. Finally, we present five hypotheses detailing how Perthes' disease could have a biomechanical cause. Clin. Anat. 29:759-772, 2016. © 2016 Wiley Periodicals, Inc.

During early stages of postnatal development, pressure from the growing brain as well as cerebrospinal fluid, i.e. intracranial pressure (ICP), load the calvarial bones. It is likely that such loading contributes to the peripheral bone formation at the sutural edges of calvarial bones, especially shortly after birth when the brain is growing rapidly. The aim of this study was to quantify ICP during mouse development. A custom pressure monitoring system was developed and calibrated. It was then used to measure ICP in a total of seventy three wild type mice at postnatal (P) day 3, 10, 20, 31 and 70. Retrospectively, the sample in each age group with the closest ICP to the average value was scanned using micro-computed tomography to estimate cranial growth. ICP increased from 1.33±0.87mmHg at P3 to 1.92±0.78mmHg at P10 and 3.60±1.08mmHg at P20. In older animals, ICP plateaued at about 4mmHg. There were statistically significant differences between the ICP at the P3 vs. P20, and P10 vs. P20. In the samples that were scanned, intracranial volume and skull length followed a similar pattern of increase up to P20 and then plateaued at older ages. These data are consistent with the possibility of ICP being a contributing factor to bone formation at the sutures during early stages of development. The data can be further used for development and validation of computational models of skull growth.

The evolution of the mammalian jaw is one of the most important innovations in vertebrate history, and underpins the exceptional radiation and diversification of mammals over the last 220 million years

In vivo bone strain data provide direct evidence of strain patterns in the cranium during biting. Compared with those in mammals, in vivo bone strains in lizard skulls are poorly documented. This paper presents strain data from the skulls of Anolis equestris, Gekko gecko, Iguana iguana and Salvator merianae during transducer biting. Analysis of variance was used to investigate effects of bite force, bite point, diet, cranial morphology and cranial kinesis on strain magnitude. Within individuals, the most consistent determinants of variance in bone strain magnitude were gauge location and bite point, with the importance of bite force varying between individuals. Inter-site variance in strain magnitude - strain gradient - was present in all individuals and varied with bite point. Between individuals within species, variance in strain magnitude was driven primarily by variation in bite force, not gauge location or bite point, suggesting that inter-individual variation in patterns of strain magnitude is minimal. Between species, variation in strain magnitude was significantly impacted by bite force and species membership, as well as by interactions between gauge location, species and bite point. Independent of bite force, species differences in cranial strain magnitude may reflect selection for different cranial morphology in relation to feeding function, but what these performance criteria are is not clear. The relatively low strain magnitudes in Iguana and Uromastyx compared with those in other lizards may be related to their herbivorous diet. Cranial kinesis and the presence or absence of postorbital and supratemporal bars are not important determinants of inter-specific variation in strain magnitude.

Legg-Calve-Perthes disease (LCP) is one of the most poorly understood diseases in paediatric orthopaedics. One common trait of LCP is the marked morphological difference between healthy and pathological hips, early deviations of which (i.e. prior to disease onset) have been suggested to lead to the overload and collapse of the epiphysis. Here, the impact of common variations in geometry is investigated with a finite element model of a juvenile femur under single leg standing and landing. Here, the impact of typical variations in geometry is investigated with a finite element model of a juvenile femur under single leg standing and landing. The variations appear to have only a limited effect on the stress distribution in the femoral epiphysis even during high impact activities. This suggests that, for this individual at least, they would be unlikely to cause epiphyseal overload and collapse, even in the presence of a skeletally immature epiphysis.

During postnatal calvarial growth the brain grows gradually and the overlying bones and sutures accommodate that growth until the later juvenile stages. The whole process is coordinated through a complex series of biological, chemical and perhaps mechanical signals between various elements of the craniofacial system. The aim of this study was to investigate to what extent a computational model can accurately predict the calvarial growth in wild‐type (WT) and mutant type (MT) Fgfr2 (C342Y/+) mice displaying bicoronal suture fusion. A series of morphological studies were carried out to quantify the calvarial growth at P3, P10 and P20 in both mouse types. MicroCT images of a P3 specimen were used to develop a finite element model of skull growth to predict the calvarial shape of WT and MT mice at P10. Sensitivity tests were performed and the results compared with ex vivo P10 data. Although the models were sensitive to the choice of input parameters, they predicted the overall skull growth in the WT and MT mice. The models also captured the difference between the ex vivo WT and MT mice. This modelling approach has the potential to be translated to human skull growth and to enhance our understanding of the different reconstruction methods used to manage clinically the different forms of craniosynostosis, and in the long term possibly reduce the number of re‐operations in children displaying this condition and thereby enhance their quality of life.

The role of soft tissues in skull biomechanics remains poorly understood. Not least, the chondrocranium, the portion of the braincase which persists as cartilage with varying degrees of mineralization. It also remains commonplace to overlook the biomechanical role of sutures despite evidence that they alter strain distribution. Here, we examine the role of both the sutures and the chondrocranium in the South American tegu lizard Salvator merianae. We use multi-body dynamics analysis (MDA) to provide realistic loading conditions for anterior and posterior unilateral biting and a detailed finite element model to examine strain magnitude and distribution. We find that strains within the chondrocranium are greatest during anterior biting and are primarily tensile; also that strain within the cranium is not greatly reduced by the presence of the chondrocranium unless it is given the same material properties as bone. This result contradicts previous suggestions that the anterior portion (the nasal septum) acts as a supporting structure. Inclusion of sutures to the cranium model not only increases overall strain magnitudes but also leads to a more complex distribution of tension and compression rather than that of a beam under sagittal bending.

Insect head shapes are remarkably variable but the influences of these changes on biomechanical performance are unclear. Among “basal” winged insects, such as dragonflies, mayflies, earwigs, and stoneflies, some of the most prominent anatomical changes are the general mouthpart orientation, eye size and the connection of the endoskeleton to the head. Here, we assess these variations for the first time using modern engineering methods including multibody dynamics modelling and finite element analysis in order to quantify and compare their influence on overall head performance. We show that a range of peculiar structures such as the genal/subgenal, epistomal, and circumoccular areas are consistently highly loaded in all species, despite drastically differing morphologies in species with forward projecting (prognathous) and downwards projecting (orthognathous) mouthparts. Sensitivity analyses show that the presence of eyes has a negligible influence on head capsule strain if a circumoccular ridge is present. In contrast, the connection of the dorsal endoskeletal arms to the head capsule especially affects overall head loading in species with downward projecting mouthparts. Analysis of the relative strains between species for each head region reveals that most head regions map onto a similar biomechanical performance space thus showing a many to one mapping of differing forms to the same functional space. Concerted changes in head substructures such as the subgenal area, the endoskeleton and the epistomal area lead to a consistent relative loading pattern in prognathous and orthognathous insects. It appears that biting-chewing loads are managed by a system of strengthening ridges on the head capsule irrespective of the general mouthpart and head orientation. Concerted changes in ridge and endoskeleton configuration allow more radical anatomical changes such as general mouthpart orientation which could be an explanation for the variability of this trait among insects. In an evolutionary context, many to one mapping of diverse forms to similar functions indeed could have fostered the dynamic diversification processes seen in insects.

Proceedings of the Royal Society of London / B 284(1848), 20162412 -(2017). doi:10.1098/rspb.2016.2412, Despite large-scale molecular attempts, the relationships of the basal winged insect lineages dragonflies, mayflies and neopterans, are still unresolved. Other data sources, such as morphology, suffer from unclear functional dependencies of the structures considered, which might mislead phylogenetic inference. Here, we assess this problem by combining for the first time biomechanics with phylogenetics using two advanced engineering techniques, multibody dynamics analysis and finite-element analysis, to objectively identify functional linkages in insect head structures which have been used traditionally to argue basal winged insect relationships. With a biomechanical model of unprecedented detail, we are able to investigate the mechanics of morphological characters under biologically realistic load, i.e. biting. We show that a range of head characters, mainly ridges, endoskeletal elements and joints, are indeed mechanically linked to each other. An analysis of character state correlation in a morphological data matrix focused on head characters shows highly significant correlation of these mechanically linked structures. Phylogenetic tree reconstruction under different data exclusion schemes based on the correlation analysis unambiguously supports a sistergroup relationship of dragonflies and mayflies. The combination of biomechanics and phylogenetics as it is proposed here could be a promising approach to assess functional dependencies in many organisms to increase our understanding of phenotypic evolution., Published by The Royal Society, London

Neck muscle fatigue has been shown to alter an individual’s balance in a similar way to that reported in subjects suffering from neck pain or subjects that have suffered a neck injury. The main purpose of the present study was to quantify the effects of neck fatigue on neck muscle electromyography (EMG) activity, balance, perceived fatigue and perceived stability. Forty four elite amateur rugby league players resisted with their neck muscles approximately 35% maximum voluntary isometric contraction (MVIC) force for 15 minutes in eight different directions. Sway velocity and surface electromyography were measured. Questionnaires were used to record perceived effort and stability. Repeated measures ANOVA showed that after 15 minutes isometric contraction, significant changes were seen in sway velocity, perceived sway and EMG median frequency. There were no differences in perceived efforts. The changes in sway velocity and median frequency were more pronounced after extension and right and left posterior oblique contractions but there was no significant difference in sway velocity after contraction in the right lateral flexion, right anterior oblique and left anterior oblique direction of contraction. All the subjects showed oriented whole-body leaning in the plane of the contraction. The experiment produced significantly altered and perceived altered balance in this group of physically fit individuals. The results may contribute to our understanding of normal functional capacities of athletes and will provide a basis for further investigation in healthy non-athletes and participants that have suffered neck injuries. This may ultimately help develop accurate and valid rehabilitation outcome measures.

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. Here we examine the 2- and 3-dimensional (3D) morphology of the zygomaticotemporal suture in an ontogenetic series of Macaca fascicularis skulls. High resolution microcomputed tomography data sets were examined, and virtual and physical 3D replicas were created to assess both structure and general stability. The zygomaticotemporal suture is much more complex than its external appearance suggests, with interlocking facets between the adjacent zygomatic and temporal bones. It appears as if some movement is permitted across the suture in younger animals, but as they approach adulthood the complexity of the suture's interlocking bone facets reaches a level where these movements become minimal.

The falx cerebri and the tentorium cerebelli are two projections of the dura mater in the cranial cavity which ossify to varying degrees in some mammalian species. The idea that the ossification of these structures may be necessary to support the loads arising during feeding has been proposed and dismissed in the past, but never tested quantitatively. To address this, a biomechanical model of a domestic cat ( Felis silvestris catus ) skull was created and the material properties of the falx and tentorium were varied for a series of loading regimes incorporating the main masticatory and neck muscles during biting. Under these loading conditions, ossification of the falx cerebri does not have a significant impact on the stress in the cranial bones. In the case of the tentorium, however, a localized increase in stress was observed in the parietal and temporal bones, including the tympanic bulla, when a non-ossified tentorium was modelled. These effects were consistent across the different analyses, irrespective of loading regime. The results suggest that ossification of the tentorium cerebelli may play a minor role during feeding activities by decreasing the stress in the back of the skull.

This paper reports on word recognition experiments using a silent speech interface based on magnetic sensing of articulator movements. A magnetic field was generated by permanent magnet pellets fixed to relevant speech articulators. Magnetic field sensors mounted on a wearable frame measured the fluctuations of the magnetic field during speech articulation. These sensor data were used in place of conventional acoustic features for the training of hidden Markov models. Both small vocabulary isolated word recognition and connected digit recognition experiments are presented. Their results demonstrate the ability of the system to capture phonetic detail at a level that is surprising for a device without any direct access to voicing information.

An accurate, dynamic, functional model of the skull that can be used to predict muscle forces, bite forces, and joint reaction forces would have many uses across a broad range of disciplines. One major issue however with musculoskeletal analyses is that of muscle activation pattern indeterminacy. A very large number of possible muscle force combinations will satisfy a particular functional task. This makes predicting physiological muscle recruitment patterns difficult. Here we describe in detail the process of development of a complex multibody computer model of a primate skull (Macaca fascicularis), that aims to predict muscle recruitment patterns during biting. Using optimisation criteria based on minimisation of muscle stress we predict working to balancing side muscle force ratios, peak bite forces, and joint reaction forces during unilateral biting. Validation of such models is problematic; however we have shown comparable working to balancing muscle activity and TMJ reaction ratios during biting to those observed in vivo and that peak predicted bite forces compare well to published experimental data. To our knowledge the complexity of the musculoskeletal model is greater than any previously reported for a primate. This complexity, when compared to more simple representations provides more nuanced insights into the functioning of masticatory muscles. Thus, we have shown muscle activity to vary throughout individual muscle groups, which enables them to function optimally during specific masticatory tasks. This model will be utilised in future studies into the functioning of the masticatory apparatus.

The techniques used to validate finite element (FE) models against experimental results have changed little during the last decades, even though the traditional approach of using single point measurements from strain gauges has major limitations: the strain distribution across the surface is not captured and the accurate determination of strain gauge positions on the model surface is difficult if the 3D surface topography of the bone surface is not measured. The full-field strain measurement technique of digital speckle pattern interferometry (DSPI) can overcome these problems, but the potential of this technique has not yet been fully exploited in validation studies. Here we explore new ways of quantifying and visualising the variation in strain magnitudes and orientations within and between repeated DSPI measurements as well as between the DSPI measurements and FEA results. We show that our approach provides a much more comprehensive and accurate validation than traditional methods. The measurement repeatability and the correspondence between measured and predicted strains vary to a great degree within and between measurement areas. The two models used in this study predict the measured strain directions and magnitudes surprisingly well considering that homogeneous and isotropic mechanical properties were assigned to the models. However, the full-field comparisons also reveal some discrepancies between measured and predicted strains that are most probably caused by inaccuracies in the models' geometries and the degree of simplification of the modelled material properties.