Axial Bones Research Articles

Radiofrequency echographic multispectrometry (REMS) in rare bone conditions

In recent years there has been a growing interest in radiofrequency echographic multispectrometry (REMS), an innovative technology, free of ionized radiation, that is capable of providing important information on bone status. In particular, REMS has been shown to measure bone mineral density (BMD) at axial skeletal bones with a precision, repeatability and accuracy not inferior to those of dual-energy X-ray absorptiometry (DXA). Moreover, REMS may be useful in the assessment of impaired bone quality (e.g., in patients with type 2 diabetes mellitus) and to predict fragility fracture risk. Due to these characteristics, REMS could be usefully used in the diagnosis and follow up of rare bone diseases. In 41 adult subjects (mean age 40.5 ± 18.7 years) with osteogenesis imperfecta (OI), BMD values at all skeletal sites, obtained using both DXA and REMS, were significantly lower than in controls. BMD by REMS values were significantly lower in patients with types III and IV versus type I OI, whereas BMD by DXA did not differ significantly between the two groups. REMS has also demonstrated excellent diagnostic accuracy in some patients suffering from McCune-Albright or Ehlers-Danlos syndromes. Furthermore, with REMS it is to obtain the real BMD value in the presence of artifacts, and, being free of ionizing radiation, it could be particularly advantageous in children and in women of childbearing age or during pregnancy and breastfeeding. In conclusion, on the basis of these preliminary data, REMS can be considered a precise and reliable technique for the evaluation and monitoring of bone status in individuals with rare bone diseases. KEY WORDS: Rare bone diseases, bone mineral density (BMD), dual-energy X-ray absorptiometry (DXA), radiofrequency echographic multispectrometry (REMS), osteogenesis imperfecta.

Sexual Dimorphism in the Musculoskeletal System: Sex Hormones and Beyond.

Mounting evidence indicates that whereas some fundamental aspects of bone cell differentiation and function are similar in females and males, there is a clear contribution of sex/gender on the effects of signaling molecules on bone mass and strength and, consequently, on the effects of pharmacologic approaches to treat skeletal disorders. However, until recently, most studies were designed and performed using only 1 sex, resulting in a scarcity of published information on sexual dimorphism of the musculoskeletal system, including the mandible/masticatory muscles and the axial and appendicular bones and skeletal muscles. Further, it is now recognized that scientific rigor requires the study of both males and females. Therefore, there is an increasing need to understand the molecular and cellular basis for the differential outcomes of genetic manipulations and therapeutic agent administration depending on the sex of the experimental animals. Studies have shown higher muscle mass, cancellous bone mass, and long bone width in males compared with females as well as different traits in the pelvis and the skull, which are usually used for gender identification in forensic anthropology. Yet, most reports focus on the role of sex hormones, in particular, the consequences of estrogen deficiency with menopause in humans and in ovariectomized animal models. In addition, emerging data is starting to unveil the effects of gender-affirming hormonal therapy on the musculoskeletal system. We summarize here the current knowledge on the sex/gender-dependent phenotypic characteristics of the bone and skeletal muscles in humans and rodents, highlighting studies in which side by side comparisons were made.

Dynamic morphometric changes in the mandibular osteocytic lacunae of ovariectomized rats in response to teriparatide, as revealed by three-dimensional fluorescence analyses: Possible involvement of osteocytic perilacunar remodeling

ObjectivesTeriparatide [TPTD; human parathyroid hormone (hPTH1-34)] is an anti-osteoporotic drug with bone anabolic effects. Clinical and preclinical studies have indicated that TPTD has value in oral and maxillofacial bone therapies, including jawbone regeneration, periodontal tissue repair, and the treatment of medication-related osteonecrosis of the jaw. However, it is unclear whether the craniofacial bones respond to TPTD similarly to the axial and appendicular bones. Recent studies showed that TPTD acts on both osteocytes and osteoblasts. This study aimed to characterize distinct craniofacial bone sites, with a focus on morphometric changes in osteocytic lacunae in ovariectomized rats receiving TPTD. MethodsConventional bone histomorphometric analyses of mandibular and parietal bone sections were conducted. High-resolution confocal imaging-based three-dimensional fluorescence morphometric analyses of osteocytic lacunae in distinct mandibular and parietal bone sites were conducted. ResultsWe observed dynamic changes in the morphometric characteristics of osteocytic lacunae specifically in alveolar and other mandibular bone sites upon TPTD administration. ConclusionsThese findings suggest that osteocytes in mandibular bone (specifically, alveolar bone) have unique functional characteristics of osteocytic perilacunar remodeling.

Osteofluorosis in free ranging California sea lions (Zalophus californianus)

We report the first case series of osteofluorosis in free ranging marine mammals and documentation of baseline bone fluoride concentrations in this population; however, the exact source is not known. A stranded subadult male California sea lion, one subadult male carcass, and one partial carcass, presumably adult male, demonstrated osseous (bony) proliferations on various appendicular and axial bones. The most severe lesions were from the index case with symmetrical segmental circumferential periosteal new bone proliferation on the diaphysis of both femurs and humeri. This case, and the second case, also had significant segmental periosteal new bone proliferation on the mandibles as well as increased tooth wear with dull enamel. Total fluoride concentrations in various bones of the cases ranged from 3,700 to 9,700 ppm dw, with a mean of 5,431 ppm dw, approximately twice the concentration in adult cattle with osteofluorosis. Ribs from four control California sea lions of various ages and both sexes had an average total fluoride of 1,575 ppm dw, which is three times as high as the bone fluoride concentration of normal adult cattle, but four times lower than the mean rib fluoride concentrations in the cases. This is the first report of osteofluorosis in free ranging marine mammals and documentation of baseline bone fluoride concentrations in this population. The exact source of the excessive fluoride levels is not known as male California sea lions have a large range and varied diet.

Is total-body MRI useful as a screening tool to rule out malignant progression in patients with multiple osteochondromas? Results in a single-center cohort of 319 adult patients.

To evaluate the results of total-body (TB) MRI used as a screening tool for assessment or exclusion of malignant transformation in patients with hereditary multiple osteochondromas (HMO). In a single-institute cohort of MO patients, 366 TB-MRI examinations, including T1-weighted and STIR images, were performed for screening and follow-up purposes to rule out the malignant transformation, and retrospectively analyzed. In each patient, the presence and location of osteochondromas in the axial and appendicular bones were recorded. Forty-seven patients underwent a second TB surveillance in this period. STIR sequences were used to identify sites of increased signal intensity that could represent suspicious thickened cartilage caps or indeterminate reactive changes related to osteochondromas. In 82% of patients, one or more OC locations were determined in one or more flat bones. In 366 exams, nine OC (2,5 %) with suspicious imaging features were identified. These proved to be peripheral chondrosarcomas after targeted MRI and resection were performed. All nine malignant lesions were in flat bones (pelvis 5, ribs 3, scapula 1). Three of these patients were 19 years of age. In 12 patients who had peripheral or intraosseous low-grade chondrosarcoma in their history, before their first TB-MRI, no new lesions were identified. Twenty-three additional TB-MRI exams, demonstrating focal high T2 signal intensity, also gave rise to performing additional targeted MRI. One OC of the distal femur was excised and appeared benign. No suspicious cartilage caps were depicted on the remaining 22 targeted MRI exams but instead increased T2 signal was clarified by reactive changes (frictional bursitis, soft tissue edema) in close relation with benign osteochondromas. No malignant lesions were found in 47 patients who had a second TB surveillance (mean interval between exams 3.2 years, range 2-5 years). TB-MRI can identify malignant transformation of osteochondromas in HMO patients. All peripheral chondrosarcomas occurred in flat bones (ribs, scapula, pelvis) in our study. TB-MRI might assist in triage between higher risk patients with a high burden of OC, including the location of OC in main flat bones vs lower risk patients without OC of the flat bones.

Polystyrene microplastics arrest skeletal growth in puberty through accelerating osteoblast senescence

Polystyrene microplastics (PS-MPs) have attracted worldwide attention to their massive accumulation in terrestrial and aquatic ecosystems. It has been demonstrated that MPs are easily to accumulate in organs and exert toxic effects. However, their exposure risk to the skeleton remains unknown. In this study, we observed PS-MPs accumulation in both the long bones and axial bones, leading to reduced body length, as well as femur and tibia length. PS-MPs treated mice exhibited redundant skeletal growth and impaired trabecular bone micro-architecture, which is due to the suppressed osteogenic ability as the number of osteoblasts decreased significantly in PS-MPs treated mice. In histological analysis, we observed the accumulation of senescent osteoblasts in the bone trabecula of PS-MPs treated mice, as well as the impaired autophagy with decreased autophagosome and reduced autophagy-related proteins in the senescent osteoblasts. Re-establishing autophagy effectively reversed the senescent phenotype in osteoblasts and ameliorated PS-MPs induced skeletal growth arrest. Hence, our study reveals the detrimental role of PS-MPs in skeletal growth in puberty through accelerating osteoblast senescence, which may be alleviated by reactivating the autophagy. This study provides new evidence of the PS-MPs on health threats and the potential therapeutic targets to reverse it.

Conventional Synthetic Disease-Modifying Anti-Rheumatic Drugs and the Risk of Vascular Dementia in Patients with Spondyloarthritis: A Database Cohort Study.

Axial spondyloarthritis (axSpA) is a chronic inflammatory rheumatic disease that mainly affects the axial bones, and dementia is characterized by a decline in cognitive function, leading to dependence in everyday activity. Although the association between dementia and ankylosing spondylitis has been investigated, the influence of axSpA medication on dementia risk is unclear. The aim of this study was to investigate the risk of dementia among axSpA patients and if the conventional synthetic disease-modifying anti-rheumatic drugs (csDMARDs) can reduce the risk of dementia. Patients with axSpA whose data were recorded during 2004-2008 and who were followed up until the end of 2010 were recruited. A control cohort was matched by age and sex. A Cox multivariate proportional hazards model was applied to analyze the risk factors for dementia. The hazard ratio (HR) and adjusted HR (aHR) were estimated between the study and control cohorts. The effects of csDMARDs and steroid use on the risk of different types of dementia were also analyzed. In total, 2341 and 11,705 patients constituted the axSpA and control cohort, respectively. The axSpA cohort had a greater risk of vascular dementia (aHR = 2.09 (1.36-3.20). The risk of dementia (aHR = 1.01 (0.55-1.85) did not significantly differ between patients with axSpA who received csDMARDs. In conclusion, patients with axSpA are at a risk of vascular dementia, which could be reduced by csDMARDs.

Anatomy of the axial and pelvic limb bones of the West African Black-crowned crane (Balearica pavonina pavonina)

Anatomy of the axial and pelvic limb bones of the West African Black-crowned crane (Balearica pavonina pavonina)

Morphological and morphometric studies on the axial skeleton of the sitatunga (Tragelaphus spekii gratus)

BackgroundAnatomical features of the skeleton of wild animals contribute largely to their adaptation. A dearth of information on the skeletal anatomy of the sitatunga (Tragelaphus spekii gratus) necessitated this study. Two adult sitatunga carcasses weighing 54 kg and 57 kg were obtained after post-mortem examination. Bone preparation was achieved through cold water maceration protocol.ResultThe tympanic bulla was elongated and massive, resulting in the rudimentary appearance of the styloid and muscular processes of the temporal bone. The lacrimal bone had a somewhat triangular presentation with the lacrimal foramen on the caudal border of the facial surface while its dorsal border formed the lateral margin of the frontal sinus. There was no observable lacrimal fossa on this facial surface of the lacrimal bone. The facial tubercle was absent. The vertebral column formula was C7 T13 L6 S4 C10-14, and the atlas dorsal median tubercle was smooth, devoid of ridges. The spinous process of the axis extended the entire arch length to hang little above the odontoid process. The thoracic spinous processes were oriented dorso-caudally from T1 to T11; spinous process of T12 was vertical, while that of T13 was oriented dorso-cranially. The length of the transverse process of L1 and L6 were the same, and smaller than the length of those of L2-L5. There was incomplete fusion of sacral spinous processes. Three dorsal and ventral sacral foramina were identified laterally on each side of the vertebrae. The ribs were 26 in number (13 pairs). The sternum was comprised of 5 sternabrae separated by intersternal cartilage. The average number of bones of the axial skeleton was 75. Morphometric in formation included the length of skull, mandible and ribs; body length of vertebrae and spinous process length and height of the vertebrae.ConclusionThis study recorded anatomical features and biometric information on axial skeletal bones of the Sitatunga (Tragelaphus spekii gratus) thereby providing baseline data for future biomedical, archaeological and comparative skeletal anatomical studies.

Chondroblastoma of Thoracic Vertebrae: a Case Report and Review of the Literature.

Chondroblastoma is a rare benign cartilaginous bone tumor typically seen at the epiphysis of long axial bones. In this regard, there are rare findings about spinal chondroblastomas. We report a 29-year-old man with T1 vertebral chondroblastoma misdiagnosed with a traumatic fracture following an accident. The patient was admitted to our clinic with a chief complaint of axial back pain and kyphosis following posterior spinal fixation. We report his clinical and imaging data before his past operation and at this admission. Our patient underwent a two-stage operation. In the first stage, posterior spinal reconstruction and kyphosis correction was performed. In the second stage, mass resection was performed anteriorly in the T1 vertebral body as much as possible. The results confirmed the chondroblastoma diagnosis histologically. Our patient remained symptom-free with no growth in tumor remnant during 6months follow-up. Although vertebral chondroblastoma is a sporadic tumor, it should be considered in the differential diagnosis when facing a vertebral infiltrative osteolytic mass, even when mimicking a traumatic fracture after the accident. In addition, histological confirmation is necessary under such conditions. We also reviewed the literature's clinical presentations, imaging findings, and treatments of 34 case reports with vertebral chondroblastoma.

Light-Chain Multiple Myeloma Presenting as a Bone Tumor in the Right Knee Joint – a Case Report

Myeloma is the neoplastic proliferation of plasma cells. The peak age of onset of this disease is the seventh decade, and it is rare in young patients. Myeloma usually presents as lytic lesions in axial bones and rarely present as a joint disease. Usually, the tumor cells secrete monoclonal immunoglobulins. Non-secretory myeloma is a rare clinical entity. The incidence of light-chain myeloma is 16 – 20 % among all multiple myelomas, and the more common subtype is the lambda chain type. We present a case of kappa light chain-type myeloma in a 29-year-old male with the presenting lesion in the right knee joint. The case is presented for its rarity due to the age of patient, presentation, and type of myeloma.

Palaeobiological inferences for the South American dicraeosaurid Brachytrachelopan mesai (Dinosauria; Sauropoda) based on bone histology of the holotype

ABSTRACT Brachytrachelopan is a dicraeosaurid sauropod that comes from the Jurassic of Argentine Patagonia. With the purpose to infer different palaeobiological traits (e.g., ontogenetic stage, growth dynamics, temporal correlation between morphological and anatomical parameters of maturation), we perform an osteohistological study on different postcranial elements from the holotype individual, including axial (i.e., cervical hemispinous process, dorsal ribs) and appendicular (i.e., femur) bones. The absence of a distinct external fundamental system indicates that the individual died before full body size achievement (i.e., somatic maturity). Furthermore, although not conclusive, the histological data suggest that despite its body size, which is comparable with fully grown individuals of other dicraeosaurid taxa, the individual also corresponds to a sexually immature specimen. Predominance of highly vascularised fibrolamelar with only a cyclical growth mark (CGM) in the outer cortex of the femur reveals a sustained, accelerated growth, typical feature of neosauropod dinosaurs. The external anatomy (i.e., neurocentral sutures are visible in presacral vertebrae) is consistent with histological data, since both indicate some degree of immaturity. Dorsal ribs are best elements to estimate age. The new evidence reinforces the hypothesis that mechanical forces were higher in the anterior edge of cervical hemispinous processes, although, these findings do not support the presence of horn cores or interspinous ligament system in the neck of Brachytrachelopan.

Case report: Thoracic and lumbar plasma cell myeloma mimicking hemangiomas on MRI and 18F-FDG PET/CT

Plasma cell myeloma (PCM) is a malignant clonal disease of abnormal proliferation of plasma cells, which is the second most common hematological malignancy after leukemia. PCM often diffuses and involves the bones of the whole body, especially the spinal column, ribs, skull, pelvis, and other axial bones and flat bones. Herein, we present a 55-year-old man who came to the hospital seeking medical help for low-back pain and numbness in his lower limbs. Computed tomography (CT) was performed because the clinician suspected that the patient had a herniated disc, and the results showed that the 7th thoracic vertebrae and the 3rd lumbar vertebrae showed a low density of bone destruction with “honeycombing” changes. Magnetic resonance imaging (MRI) showed that the corresponding lesions presented long T1 and long T2 signals, and the lesions were significantly enhanced in contrast-enhanced T1WI sequences, and fluoro18-labeled deoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) showed mild radioactive uptake in the lesions. Based on these imaging findings, the patient was considered for a diagnosis of hemangiomas, and surgery was performed because the affected vertebra was pressing on the spinal cord. However, intraoperative frozen section examination showed that the patient had plasma cell myeloma. Our case study suggests that PCM involving a single thoracic and lumbar spine is rare and should be considered as one of the imaging differential diagnoses of hemangiomas. Moreover, the diagnosis of PCM is difficult when the number of lesions is small, especially when the plasma cell ratio is within the normal reference range in laboratory tests.

Walter Georg Kühne (1911-1991) and the discovery of the first semi-articulated titanosaurian sauropod from Europe

ABSTRACT In 1954 Walter Georg Kühne (1911–1991), the renowned discoverer of Mesozoic mammals, explored the south-Pyrenean basins of Catalonia with the aim of finding Cretaceous mammal-bearing sites. As a result, the German palaeontologist discovered one of the most important dinosaur fossils in the history of dinosaur research in Spain. In the Tremp Basin, near Orcau village, he found the remains of a large sauropod dinosaur, but a series of incomprehensible vicissitudes made the find forgotten and its extraction incomplete for over 60 years. Unprecedented research into the history of this discovery, including unpublished documents, images, and field notes, has revealed details on the costs of the campaigns, the daily logistics, the field techniques, and the fossils unearthed in the 1954 and 1955 excavations. More importantly, this new research ascertains that Kühne had already determined that the dinosaur skeleton was articulated from the pelvic girdle onwards. Even without being published, that was a historically significant achievement as, back then, the new specimen became the first and semi-articulated titanosaurian sauropod found in Europe. Currently, the sauropod fossils found by Kühne in Orcau, together with additional appendicular and axial bones, are the holotype of Abditosaurus kuehnei.

Characterizing the Mechanical Behavior of Bone and Bone Surrogates in Compression Using pQCT.

Many axial and appendicular skeleton bones are subjected to repetitive loading during daily activities. Until recently, the structural analysis of fractures has been limited to 2D sections, and the dynamic assessment of fracture progression has not been possible. The structural failure was analyzed using step-wise micro-compression combined with time-lapsed micro-computed tomographic imaging. The structural failure was investigated in four different sample materials (two different bone surrogates, lumbar vertebral bodies from bovine and red deer). The samples were loaded in different force steps based on uniaxial compression tests. The micro-tomography images were used to create three-dimensional models from which various parameters were calculated that provide information about the structure and density of the samples. By superimposing two 3D images and calculating the different surfaces, it was possible to precisely analyze which trabeculae failed in which area and under which load. According to the current state of the art, bone mineral density is usually used as a value for bone quality, but the question can be raised as to whether other values such as trabecular structure, damage accumulation, and bone mineralization can predict structural competence better than bone mineral density alone.

Protective Effect on Bone of Nacre Supplementation in Ovariectomized Rats

ABSTRACTNacre has emerged as a beneficial natural product for bone cells and tissues, but its effect was only studied by gavage in the ovariectomized mouse model. We sought to assess the antiosteoporotic effect of nacre through a nutritional supplementation in the ovariectomized rat model. Sixteen‐week‐old female Wistar rats were either Sham‐operated or bilateral ovariectomized (OVX) and then fed with standard diet (Sham and OVX groups) or standard diet supplemented with either 0.25% CaCO3 or nacre (OVX CaCO3 and OVX Nacre group, respectively) for 28 days (n = 10/group). The bone microarchitecture was assessed at appendicular and axial bones by micro‐computed tomography (μCT). Histomorphometric analysis was performed to determine cellular and dynamic bone parameters. Bone metabolism was also evaluated by biochemical markers and gene expression levels. Nacre‐based diet prevented the OVX‐induced bone loss better than that of the CaCO3 supplement, given the significant changes in trabecular bone volume fraction (BV/TV) both at the femoral distal metaphysis (difference, 35%; p = 0.004) and at the second lumbar spine (difference, 11%; p = 0.01). Trabecular osteoclast surfaces (Oc.S/BS) were also 1.5‐fold lower at the tibial proximal metaphysis in OVX Nacre group compared with OVX CaCO3 group (p = 0.02). By principal component analysis (PCA), OVX Nacre group formed a cluster away from OVX group and with a trend closest to Sham group. These data were consistent with biological measurements demonstrating a positive profile related to nacre supplementation, which blunted an increase in serum CTX level and enhanced serum P1NP secretion 14 days post‐OVX compared with CaCO3 supplementation. Bmp2 mRNA expression in OVX Nacre group was +1.76‐fold (p = 0.004) and +1.30‐fold (p = 0.20) compared with OVX and OVX CaCO3 groups, respectively. We conclude that supplementation with nacre could effectively limit bone loss induced by estrogen deficiency just after OVX in rats by modulating the negative imbalance of bone turnover. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Paleohistology of the crocodyliform Mariliasuchus amarali Carvalho & Bertini, 1999 (Mesoeucrocodylia, Notosuchia) based on a new specimen from the Upper Cretaceous of Brazil

Mariliasuchus amarali Carvalho & Bertini, 1999 was a terrestrial quadruped crocodyliform from the Late Cretaceous of the Bauru Group, Brazil. In this paper we present the first study of the bone histology of this species. Moderate growth rate, interspersed by growth marks, was observed in thin sections of a rib and appendicular bones; growth patterns observed in M. amaralis appear similar to those observed in Triassic archosauriforms. The M. amarali cross-sections indicate growth variability between both the axial and appendicular bones. Distinctive remodeling processes were found in the radius, which had extensive inner cortex remodeling composed of compacted coarse cancellous bone. Furthermore, the medullary region was infilled with spongy bone.

Differential immune landscapes in appendicular versus axial skeleton.

Roughly 400,000 people in the U.S. are living with bone metastases, the vast majority occurring in the spine. Metastases to the spine result in fractures, pain, paralysis, and significant health care costs. This predilection for cancer to metastasize to the bone is seen across most cancer histologies, with the greatest incidence seen in prostate, breast, and lung cancer. The molecular process involved in this predilection for axial versus appendicular skeleton is not fully understood, although it is likely that a combination of tumor and local micro-environmental factors plays a role. Immune cells are an important constituent of the bone marrow microenvironment and many of these cells have been shown to play a significant role in tumor growth and progression in soft tissue and bone disease. With this in mind, we sought to examine the differences in immune landscape between axial and appendicular bones in the normal noncancerous setting in order to obtain an understanding of these landscapes. To accomplish this, we utilized mass cytometry by time-of-flight (CyTOF) to examine differences in the immune cell landscapes between the long bone and vertebral body bone marrow from patient clinical samples and C57BL/6J mice. We demonstrate significant differences between immune populations in both murine and human marrow with a predominance of myeloid progenitor cells in the spine. Additionally, cytokine analysis revealed differences in concentrations favoring a more myeloid enriched population of cells in the vertebral body bone marrow. These differences could have clinical implications with respect to the distribution and permissive growth of bone metastases.

Thanatosdrakon amaru, gen. et sp. nov., a giant azhdarchid pterosaur from the Upper Cretaceous of Argentina

The largest pterosaur discovered in South America and one of the largest flying vertebrates in the world is described. Thanatosdrakon amaru gen. et sp. nov. is a new azhdarchid found in the upper-most levels of the Plottier Formation (upper Coniacian–lower Santonian, Neuquén Basin), Mendoza, Argentina. Two specimens were identified, the holotype (UNCUYO-LD 307) and the paratype, with an estimated wingspan of ∼7 m and ∼9 m, respectively. The cladistic analysis, based on 216 characters and 97 taxa, recovered Thanatosdrakon deeply nested within Azhdarchidae. Relationships within this clade are well resolved and the clade Quetzalcoatlinae presents two well-defined sister-groups: (Arambourgiania, Mistralazhdarcho, Aerotitan, Hatzegopteryx, Albadraco) + (Cryodrakon, Thanatosdrakon, Quetzalcoatlus ssp.). Thanatosdrakon is the oldest taxon of the clade Quetzalcoatlinae so far. It is represented by several well-preserved axial and appendicular bones in three dimensions. Some of these elements have never been described in giant azhdarchids (e.g. complete norarium, dorsosacral vertebrae and caudal vertebra) and this allows to expand the knowledge about the anatomy of this diverse group of pterosaurs. Finally, from a paleoecological point of view, Thanatosdrakon was found in floodplain deposits of ephemeral meandering systems indicating that this large flying species inhabited continental environments.

La tumeur à cellules géantes des os en 2022

Giant cell tumors of bone (GCTs) are rare mesenchymal tumors classified as intermediate in the WHO 2020 classification, i.e. neither completely benign nor definitely malignant, due to recurrence (frequent) and pulmonary metastases (rare). They involve the end of long bones as well as the axial bones of mature skeletons. They are made of mononuclear stromal tumor cells of (pre-) osteoblastic phenotype, mononuclear cells of the monocyte-macrophage lineage and osteoclast-like multinuclear giant cells responsible for tumor osteolysis. In 95% of cases, the stromal cells have a specific mutation in the H3F3A gene which encodes histone H3.3. The mutated H3.3 G34W protein (90% of cases) can be easily detected by immunohistochemistry, even on small samples. Many tumors or bone pseudotumors contain osteoclast-like giant cells, cells of the bone microenvironment, and should not be confused with GCT: mainly brown tumor of hyperparathyroidism, aneurysmal bone cyst, chondroblastoma, non-ossifying fibroma and central giant cell granuloma.