Inferences regarding the diet of extinct hominins: structural and functional trends in dental and mandibular morphology within the hominin clade

This contribution investigates the evolution of diet in the Pan – Homo and hominin clades. It does this by focusing on 12 variables (nine dental and three mandibular) for which data are available about extant chimpanzees, modern humans and most extinct hominins. Previous analyses of this type have approached the interpretation of dental and gnathic function by focusing on the identification of the food consumed (i.e. fruits, leaves, etc.) rather than on the physical properties (i.e. hardness, toughness, etc.) of those foods, and they have not specifically addressed the role that the physical properties of foods play in determining dental adaptations. We take the available evidence for the 12 variables, and set out what the expression of each of those variables is in extant chimpanzees, the earliest hominins, archaic hominins, megadont archaic hominins, and an inclusive grouping made up of transitional hominins and pre-modern Homo . We then present hypotheses about what the states of these variables would be in the last common ancestor of the Pan – Homo clade and in the stem hominin. We review the physical properties of food and suggest how these physical properties can be used to investigate the functional morphology of the dentition. We show what aspects of anterior tooth morphology are critical for food preparation (e.g. peeling fruit) prior to its ingestion, which features of the postcanine dentition (e.g. overall and relative size of the crowns) are related to the reduction in the particle size of food, and how information about the macrostructure (e.g. enamel thickness) and microstructure (e.g. extent and location of enamel prism decussation) of the enamel cap might be used to make predictions about the types of foods consumed by extinct hominins. Specifically, we show how thick enamel can protect against the generation and propagation of cracks in the enamel that begin at the enamel– dentine junction and move towards the outer enamel surface.

Ligament balancing in TKA: Evaluation of a force-sensing device and the influence of patellar eversion and ligament release

Ligament balancing in total knee arthroplasty may have an important influence on joint stability and prosthesis lifetime. In order to provide quantitative information and assistance during ligament balancing, a device that intraoperatively measures knee joint forces and moments was developed. Its performance and surgical advantages were evaluated on six cadaver specimens mounted on a knee joint loading apparatus allowing unconstrained knee motion as well as compression and varus-valgus loading. Four different experiments were performed on each specimen. (1) Knee joints were axially loaded. Comparison between applied and measured compressive forces demonstrated the accuracy and reliability of in situ measurements (1.8N). (2) Assessment of knee stability based on condyle contact forces or varus-valgus moments were compared to the current surgical method (difference of varus-valgus loads causing condyle lift-off). The force-based approach was equivalent to the surgical method while the moment-based, which is considered optimal, showed a tendency of lateral imbalance. (3) To estimate the importance of keeping the patella in its anatomical position during imbalance assessment, the effect of patellar eversion on the mediolateral distribution of tibiofemoral contact forces was measured. One fourth of the contact force induced by the patellar load was shifted to the lateral compartment. (4) The effect of minor and major medial collateral ligament releases was biomechanically quantified. On average, the medial contact force was reduced by 20% and 46%, respectively. Large variation among specimens reflected the difficulty of ligament release and the need for intraoperative force monitoring. This series of experiments thus demonstrated the device's potential to improve ligament balancing and survivorship of total knee arthroplasty.

Effects of anatomic conformation on three-dimensional motion of the caudal lumbar and lumbosacral portions of the vertebral column of dogs

OBJECTIVE: To determine the association between the 3-dimensional (3-D) motion pattern of the caudal lumbar and lumbosacral portions of the canine vertebral column and the morphology of vertebrae, facet joints, and intervertebral disks. SAMPLE POPULATION: Vertebral columns of 9 German Shepherd Dogs and 16 dogs of other breeds with similar body weights and body conditions. PROCEDURE: Different morphometric parameters of the vertebral column were assessed by computed tomography (CT) and magnetic resonance imaging. Anatomic conformation and the 3-D motion pattern were compared, and correlation coefficients were calculated. RESULTS: Total range of motion for flexion and extension was mainly associated with the facet joint angle, the facet joint angle difference between levels of the vertebral column in the transverse plane on CT images, disk height, and lever arm length. CONCLUSIONS AND CLINICAL RELEVANCE: Motion is a complex process that is influenced by the entire 3-D conformation of the lumbar portion of the vertebral column. In vivo dynamic measurements of the 3-D motion pattern of the lumbar and lumbosacral portions of the vertebral column will be necessary to further assess biomechanics that could lead to disk degeneration in dogs.

VIRTOPSY - the Swiss virtual autopsy approach

The aim of the VIRTOPSY project () is utilizing radiological scanning to push low-tech documentation and autopsy procedures in a world of high-tech medicine in order to improve scientific value, to increase significance and quality in the forensic field. The term VIRTOPSY was created from the terms virtual and autopsy: Virtual is derived from the Latin word 'virtus', which means 'useful, efficient and good'. Autopsy is a combination of the old Greek terms 'autos' (=self) and 'opsomei' (=I will see). Thus autopsy means 'to see with ones own eyes'. Because our goal was to eliminate the subjectivity of "autos", we merged the two terms virtual and autopsy - deleting "autos" - to create VIRTOPSY. Today the project VIRTOPSY combining the research topics under one scientific umbrella, is characterized by a trans-disciplinary research approach that combines Forensic Medicine, Pathology, Radiology, Image Processing, Physics, and Biomechanics to an international scientific network. The paper will give an overview of the Virtopsy change process in forensic medicine.

A patient-specific finite element methodology to predict damage accumulation in vertebral bodies under axial compression, sagittal flexion and combined loads

Due to the inherent limitations of DXA, assessment of the biomechanical properties of vertebral bodies relies increasingly on CT-based finite element (FE) models, but these often use simplistic material behaviour and/or single loading cases. In this study, we applied a novel constitutive law for bone elasticity, plasticity and damage to FE models created from coarsened pQCT images of human vertebrae, and compared vertebral stiffness, strength and damage accumulation for axial compression, anterior flexion and a combination of these two cases. FE axial stiffness and strength correlated with experiments and were linearly related to flexion properties. In all loading modes, damage localised preferentially in the trabecular compartment. Damage for the combined loading was higher than cumulated damage produced by individual compression and flexion. In conclusion, this FE method predicts stiffness and strength of vertebral bodies from CT images with clinical resolution and provides insight into damage accumulation in various loading modes.

Cement distribution, volume, and compliance in vertebroplasty: some answers from an anatomy-based nonlinear finite element study

STUDY DESIGN: The biomechanics of vertebral bodies augmented with real distributions of cement were investigated using nonlinear finite element (FE) analysis. OBJECTIVES: To compare stiffness, strength, and stress transfer of augmented versus nonaugmented osteoporotic vertebral bodies under compressive loading. Specifically, to examine how cement distribution, volume, and compliance affect these biomechanical variables. SUMMARY OF BACKGROUND DATA: Previous FE studies suggested that vertebroplasty might alter vertebral stress transfer, leading to adjacent vertebral failure. However, no FE study so far accounted for real cement distributions and bone damage accumulation. METHODS: Twelve vertebral bodies scanned with high-resolution pQCT and tested in compression were augmented with various volumes of cements and scanned again. Nonaugmented and augmented pQCT datasets were converted to FE models, with bone properties modeled with an elastic, plastic and damage constitutive law that was previously calibrated for the nonaugmented models. The cement-bone composite was modeled with a rule of mixture. The nonaugmented and augmented FE models were subjected to compression and their stiffness, strength, and stress map calculated for different cement compliances. RESULTS: Cement distribution dominated the stiffening and strengthening effects of augmentation. Models with cement connecting either the superior or inferior endplate (S/I fillings) were only up to 2 times stiffer than the nonaugmented models with minimal strengthening, whereas those with cement connecting both endplates (S + I fillings) were 1 to 8 times stiffer and 1 to 12 times stronger. Stress increases above and below the cement, which was higher for the S + I cases and was significantly reduced by increasing cement compliance. CONCLUSION: The developed FE approach, which accounts for real cement distributions and bone damage accumulation, provides a refined insight into the mechanics of augmented vertebral bodies. In particular, augmentation with compliant cement bridging both endplates would reduce stress transfer while providing sufficient strengthening.