RADIOLOGICAL APPLICATIONS IN FORENSIC ANTHROPOLOGY. FRACTURE HEALING AND DATING

The accurate dating of bone fractures constitutes a critical component of trauma analysis in forensic anthropology and the research in this field represents to date a challenging opportunity to apply scientific knowledge and methods to real problems of society, including also global humanitarian and human rights issues. However, the literature review performed in order to describe the state of the art in fracture healing and dating showed that forensic studies are scarce and that the assessment of fractures lacks consensus about both the definition of fracture healing and the duration of the fracture healing process. Thus, the aim of the present PhD project, including two research lines, was to acquire a better knowledge of the process of bone remodeling both in the living and the dead with regard to the timing of injury as well as to evaluate the applicability of high-resolution radiological techniques for objective dating of the healing phase of the fracture. The 1 st retrospective study, dedicated to the living, was based on digital radiographs from the largest adult living population ever analyzed and was aimed not only at examining time frames for healing of bone fractures but also at investigating the effect of variables, including age, sex, bone type and number of fracures on the timing of healing stages of traumatic skeletal lesions. For these purposes a multivariable model was built, which showed a significant association between the healing stages and the variables analyzed, so that a dynamic nomogram was preliminary proposed to predict a time interval since fracture from digital radiographs. The 2 nd experimental study, dedicated to the dead, was based on dry human bones presenting calluses of different known age in order to preliminary assess the potential of an advanced and non-destructive imaging technology, like microcomputed tomography (micro-CT), in order to obtain a future objective dating of the healing phase of the fracture on post-cranial human bone calluses of known age. The results not only demonstrated the potential utility of micro-CT to obtain a wealth of qualitative details about the microstructure of the callus but also to reach an objective fracture dating, laying promising foundations for further studies on this topic in light of the highlighted existence of a certain trend of some parameters of trabecular microstructure relative to the age of the callus, including the degree of anisotropy, the connectivity and the trabecular spacing

Advantages and Disadvantages of Various Uncertainty Assessment Methods in Material and Technological Predictive Models

This article reviews known approaches to determining the uncertainty of predictive models: probabilistic analytical, probabilistic simulation and fuzzy. The main elements determining the specificity of a given approach are shown. The advantages and disadvantages are compared. Finally, the application guidelines are listed

An artificial-vision- and statistical-learning-based method for studying the biodegradation of type I collagen scaffolds in bone regeneration systems

[Abstract] This work proposes a method based on image analysis and machine and statistical learning to model and estimate osteocyte growth (in type I collagen scaffolds for bone regeneration systems) and the collagen degradation degree due to cellular growth. To achieve these aims, the mass of collagen -subjected to the action of osteocyte growth and differentiation from stem cells- was measured on 3 days during each of 2 months, under conditions simulating a tissue in the human body. In addition, optical microscopy was applied to obtain information about cellular growth, cellular differentiation, and collagen degradation. Our first contribution consists of the application of a supervised classification random forest algorithm to image texture features (the structure tensor and entropy) for estimating the different regions of interest in an image obtained by optical microscopy: the extracellular matrix, collagen, and image background, and nuclei. Then, extracellular-matrix and collagen regions of interest were determined by the extraction of features related to the progression of the cellular growth and collagen degradation (e.g., mean area of objects and the mode of an intensity histogram). Finally, these critical features were statistically modeled depending on time via nonparametric and parametric linear and nonlinear models such as those based on logistic functions. Namely, the parametric logistic mixture models provided a way to identify and model the degradation due to biological activity by estimating the corresponding proportion of mass loss. The relation between osteocyte growth and differentiation from stem cells, on the one hand, and collagen degradation, on the other hand, was determined too and modeled through analysis of image objects’ circularity and area, in addition to collagen mass loss. This set of imaging techniques, machine learning procedures, and statistical tools allowed us to characterize and parameterize type I collagen biodegradation when collagen acts as a scaffold in bone regeneration tasks. Namely, the parametric logistic mixture models provided a way to identify and model the degradation due to biological activity and thus to estimate the corresponding proportion of mass loss. Moreover, the proposed methodology can help to estimate the degradation degree of scaffolds from the information obtained by optical microscopy.Ministerio de Asuntos Económicos y Transformación Digital; MTM2014-52876-RMinisterio de Asuntos Económicos y Transformación Digital; MTM2017-82724-RXunta de Galicia; ED431C-2016-015Xunta de Galicia; ED431G/0

Three Dimensional Nonlinear Statistical Modeling Framework for Morphological Analysis

This dissertation describes a novel three-dimensional (3D) morphometric analysis framework for building statistical shape models and identifying shape differences between populations. This research generalizes the use of anatomical atlases on more complex anatomy as in case of irregular, flat bones, and bones with deformity and irregular bone growth. The foundations for this framework are: 1) Anatomical atlases which allow the creation of homologues anatomical models across populations; 2) Statistical representation for output models in a compact form to capture both local and global shape variation across populations; 3) Shape Analysis using automated 3D landmarking and surface matching. The proposed framework has various applications in clinical, forensic and physical anthropology fields. Extensive research has been published in peer-reviewed image processing, forensic anthropology, physical anthropology, biomedical engineering, and clinical orthopedics conferences and journals. The forthcoming discussion of existing methods for morphometric analysis, including manual and semi-automatic methods, addresses the need for automation of morphometric analysis and statistical atlases. Explanations of these existing methods for the construction of statistical shape models, including benefits and limitations of each method, provide evidence of the necessity for such a novel algorithm. A novel approach was taken to achieve accurate point correspondence in case of irregular and deformed anatomy. This was achieved using a scale space approach to detect prominent scale invariant features. These features were then matched and registered using a novel multi-scale method, utilizing both coordinate data as well as shape descriptors, followed by an overall surface deformation using a new constrained free-form deformation. Applications of output statistical atlases are discussed, including forensic applications for the skull sexing, as well as physical anthropology applications, such as asymmetry in clavicles. Clinical applications in pelvis reconstruction and studying of lumbar kinematics and studying thickness of bone and soft tissue are also discussed

Mechanisms of Urodele Limb Regeneration

This review explores the historical and current state of our knowledge about urodele limb regeneration. Topics discussed are (1) blastema formation by the proteolytic histolysis of limb tissues to release resident stem cells and mononucleate cells that undergo dedifferentiation, cell cycle entry and accumulation under the apical epidermal cap. (2) The origin, phenotypic memory, and positional memory of blastema cells. (3) The role played by macrophages in the early events of regeneration. (4) The role of neural and AEC factors and interaction between blastema cells in mitosis and distalization. (5) Models of pattern formation based on the results of axial reversal experiments, experiments on the regeneration of half and double half limbs, and experiments using retinoic acid to alter positional identity of blastema cells. (6) Possible mechanisms of distalization during normal and intercalary regeneration. (7) Is pattern formation is a self-organizing property of the blastema or dictated by chemical signals from adjacent tissues? (8) What is the future for regenerating a human limb

Program and Abstracts from the Celebration of Student Scholarship, 2019

Program and Abstracts from the Celebration of Student Scholarship on April 24, 2019

Application Of Morphometric Analysis And Tissue Engineering To Bioengineering Personalised Autologous Bone Tissues For The Reconstruction Of Congenital Midface Deformities

Congenital craniofacial bone deformities frequently occur in conditions such as Craniofacial microsomia (CM) and Treacher Collins Syndrome (TCS). Affected children may suffer from functional impairment and poor self-esteem. Reconstruction aims to restore form and function but often involves multiple invasive surgeries throughout childhood. The reliance on foreign-body implants and autologous tissue-transfer is also associated with morbidity. The aim of this work was to assess whether morphometric analysis and tissue engineering using paediatric adipose derived stem cells could facilitate bioengineering personalised autologous facial bone implants to provide a more accurate and life-long solution for the treatment of midface deformities. Paediatric facial CT scans (n=70) from control, CM and TCS subjects were used to build a dense surface model of the midface to study normal and dysmorphic postnatal midface development. This enabled relating of soft and skeletal tissue growth, analysis of asymmetry and evaluation of surgical correction. This work also establishes the foundations for developing a surgical planning tool. Paediatric craniofacial bone was also analysed in order to establish a reference for tissue engineering and reverse engineer the bone microenvironment to fabricate biomaterials and culture conditions that enhance osteogenic maturation. It was possible to bioengineer bone tissue using hADSC cultured on a bone biomimetic hybrid POSS-PCL-Fibrin scaffold. Cellularised scaffolds survived subcutaneous implantation in nude mice for 4 months, underwent vascularisation and showed evidence of mature extracellular matrix formation and cellular composition similar to native bone The results of this work support a multi-faceted approach to bone tissue engineering. Increased understanding of paediatric facial bones permits recreation of the bone microenvironment to enable osteogenic maturation of hADSC. These tissues could eventually be custom-shaped using an operative planning tool based on these computer models. Future work using larger data sets, bioreactors, 3D printing and large animal defect models will seek to build on these promising results

Clinical translation of a regeneration strategy for spinal cord injury

The complex and vulnerable tissue of the spinal cord does not heal after injury, leaving patients with lifelong disability after spinal cord injury (SCI). Many milestones have been reached during the last century through specialized centers for SCI, greatly increasing life expectancy and quality of life by battling common medical problems such as urinary tract infections, pressure ulcers, spasticity, neurogenic pain, and sexual function as well as providing means of rehabilitation to a meaningful and productive life after SCI. Despite the advances in preclinical knowledge of mechanisms in SCI and several clinical trials completed, to date no pivotal treatment exists for acute spinal cord injury or for the regeneration of lost function in the chronic state. The first reports of experimental regeneration of central axons through peripheral nerve grafts are more than a century old. In the last decades, regeneration of function after SCI has been reported by several research groups in different species using peripheral nerve grafts and FGF1. The regeneration strategy was furthered refined in our group by the use of a biodegradable scaffold for exact positioning of the nerve grafts. This thesis describes the translational process to reach a clinical trial of glial scar resection and implantation of peripheral nerve grafts and FGF1 using a biodegradable guiding scaffold. In paper I, we show that both the cranial and caudal demarcation of a thoracic spinal cord injury can be defined with electromyography of intercostal muscles in chronic SCI patients. We also present an MRI protocol with acceptable image contrast despite the presence of spinal instrumentation and showed that the injury length found with electromyography correlates well with length of injury on MRI. In paper II, we use a novel conversion table between spinal cord neuronal segments and vertebral segments and combine data on human spinal cord cross-sectional diameters from different published sources to yield continuous estimates on human spinal cord size and variability. In paper III, we describe the design of a set of spinal cord injury guiding devices based on the data from paper II, covering the normal variability found in human thoracic spinal cord segments T2–T12 with an acceptable error-of-fit for the elliptical shape as well as guiding channels proposed. In paper IV, we detail the adverse events reported during the first 60 days postoperatively in the ongoing clinical trial “Safety and Efficacy of SC0806 (Fibroblast Growth Factor 1 and a Device) in Traumatic Spinal Cord Injury Subjects.” Early results from the first six complete (AIS-A) thoracic spinal cord injury subjects operated on in the ongoing trial show that with precise preoperative and intraoperative neurophysiology, surgery and implantation can be performed without negative effects on neurological level, and safety and tolerability are acceptable to merit the continuation of the trial. In paper V, we describe the construction of a cost-effective light-sheet microscope by modification of an outdated microarray-scanner. The microscope was applied to an experimental model of hypoglossal nerve avulsion injury, and proliferation of Iba1+ cells could be quantified automatically demonstrating a possible application of the microscope. In conclusion, reaching clinical trial in a translational process is a significant and collaborative undertaking requiring co-operation of multiple institutions and professions as well as rigorous external control of data quality and adverse events to ensure safety of study subjects. The papers in this thesis detail some relevant steps necessary for the clinical translation of regeneration strategies in chronic SCI