Vertebral Elements Research Articles

The overlooked first intercostal ligament: Does it help to stabilize the Weberian apparatus?

The Weberian apparatus is a novel hearing adaptation that facilitates increased hearing sensitivity in otophysan fishes. The apparatus is a complex system composed of modifications to anterior vertebral elements, the inner ear, and the swim bladder. A critical piece of the system that often receives minor attention are the various ligaments that bridge these three regions. The most famous of the ligaments is the interossicular ligament, which connects the Weberian ossicle chain (scaphium-intercalarium-tripus). Several other ligaments are present, including the suspensor (tripus to parapophysis 4) and the triple ligament (tripus-os suspensorium-tunica externa). Here, by combining diffusible iodine-based contrast enhancement (DICE) and propagation phase-contrast synchrotron radiation micro-computed tomography (PPC-SRμCT) with classic histological methods, we shine new light on the first intercostal ligament (ICL1) and discuss its potential function in relation to the Weberian apparatus. ICL1 is nearly absent from the cypriniform literature, typically only mentioned in a general discussion together with other intercostal ligaments. This study examines the development and structure of ICL1 comparatively with the other definitive Weberian ligaments in the zebrafish (Danio rerio). We provide a comprehensive view of three-dimensional shape, development, and composition to generate hypotheses regarding potential functions of ICL1 within the greater Weberian apparatus. Given new detail presented herein regarding the structure of ICL1, modifications to rib 5 and parapophysis 4 for ICL1 attachment, and the alignment of ICL1 with the os suspensorium, we propose a supportive (anchoring) role of ICL1 to aid in minimizing non-optimal movement of the structures of the fourth vertebra. This addition would focus vibrations anteriorly through the ossicle chain with minimal signal loss in zebrafish and other species with similar Weberian apparatus morphologies. We conclude that ICL1 should be included in future analyses of Weberian apparatus function where ligaments are addressed.

Interplay between Two Paralogous Human Silencing Hub (HuSH) Complexes in Regulating LINE-1 Element Silencing

The Human Silencing Hub (HuSH) complex silences retrotransposable elements in vertebrates. Here, we identify a second HuSH complex, designated HuSH2, which is centered around TASOR2, a paralog of the core TASOR protein in HuSH. Our findings reveal that HuSH and HuSH2 localize to distinct and non-overlapping genomic loci. Specifically, HuSH localizes to and represses LINE-1 retrotransposons, whereas HuSH2 targets and represses KRAB-ZNFs and interferon signaling and response genes. We use in silico protein structure predictions to simulate MPP8 interactions with TASOR paralogs, guiding amino acid substitutions that disrupted binding to HuSH complexes. These MPP8 transgenes and other constructs reveal the importance of HuSH complex quantities in regulating LINE-1 activity. Furthermore, our results suggest that dynamic changes in TASOR and TASOR2 expression enable cells to finely tune HuSH-mediated silencing. This study offers insights into the interplay of HuSH complexes, highlighting their vital role in retrotransposon regulation.

Reduction of material groups for vertebral bone finite element simulation: cross comparison of grouping methods

In patient-specific biomechanical modeling, the process of image-to-mesh-material mapping is important, and various strategies have been explored for assigning the number of groups of unique material properties to the mesh. This study aims to cross-compare different grouping strategies to identify the minimum number of unique groups necessary for accurately calculating the fracture load of vertebral bones. We analyzed 12 vertebral specimens by experimentally determining the biomechanical fracture load and acquiring corresponding CT scans. After geometry extraction and meshing, we applied commonly used fixed-value strategies for reducing the number of unique groups, such as Modulus Gaping and Percentual Thresholding. Additionally, we introduced a patient-specific adaptive grouping method based on K-means clustering, which allowed us to maintain a consistent number of groups of unique material properties across the study. A total of 204 simulations were performed, achieving a potential 98% reduction in the number of individual material parameters while maintaining a strong correlation with experimental results when utilizing Percentual Thresholding or Adaptive Clustering, compared to Modulus Gaping. The findings demonstrate the feasibility of significantly reducing simulation complexity while maintaining the accuracy of patient-specific models that strongly correlate with experimental results. This reduction enables efficient processing of patient-specific biomechanical models derived from image data, offering potential benefits for clinicians, particularly in resource-constrained settings.

First Valanginian (Early Cretaceous) ornithopod (Dinosauria, Ornithischia) from Patagonia

Here we describe a new ornithopod species, Emiliasaura alessandrii gen. et sp. nov. from Valanginian rocks (Early Cretaceous) of northwestern Patagonia. This new taxon exhibits affinities with the Rhabdodontomorpha and is primarily represented by two specimens of mid-sized ornithopods collected from different sites and stratigraphical levels of the Mulichinco Formation. The holotype specimen MLL-Pv-001 includes the coracoid, the proximal end of a scapula, a humerus and a complete right hind limb, whereas the paratype specimen MLL-Pv-006 preserves vertebral elements, haemal arches, an incomplete pelvis, and nearly complete hind limbs. The new taxon has an anteroposteriorly elongate ilium with a sigmoidal dorsal border and broad brevis shelf, a femur shaft with an extensive, mid-shaft positioned fourth trochanter, and a second pedal digit with a short, robust, blunt ungual phalanx similar to those in Ankylopollexia ornithopods. The new ornithopod taxon formed part of a diverse dinosaur association from the Mulichinco Fm that includes dicraeosaurid sauropods and carcharodontosaurid theropods, and represents the first South American record of a rhabdodontomorph, and the oldest and most primitive representative of this clade.

The evolution of ultraconserved elements in vertebrates.

Ultraconserved elements (UCEs) were discovered two decades ago, arbitrarily defined as sequences that are identical over a length ≥200 bp in the human, mouse and rat genomes. The definition was subsequently extended to sequences ≥100 bp identical in at least three of five mammalian genomes (including dog and cow), and shown to have undergone rapid expansion from ancestors in fish and strong negative selection in birds and mammals. Since then, many more genomes have become available, allowing better definition and more thorough examination of UCE distribution and evolutionary history. We developed a fast and flexible analytical pipeline for identifying UCEs in multiple genomes, dedUCE, which allows manipulation of minimum length, sequence identity, and number of species with a detectable UCE according to specified parameters. We suggest an updated definition of UCEs as sequences ≥100 bp and ≥97% sequence identity in ≥50% of placental mammal orders (12813 UCEs). By mapping UCEs to ∼200 species we find that placental UCEs appeared early in vertebrate evolution, well before land colonisation, suggesting the evolutionary pressures driving UCE selection were present in aquatic environments in the Cambrian-Devonian periods. Most (>90%) UCEs likely appeared after the divergence of gnathostomes from jawless predecessors, were largely established in sequence identity by early Sarcopterygii evolution - before the divergence of lobe-finned fishes from tetrapods - and became near fixed in the amniotes. UCEs are mainly located in the introns of protein-coding and non-coding genes involved in neurological and skeletomuscular development, enriched in regulatory elements, and dynamically expressed throughout embryonic development.

Extensive Loss and Gain of Conserved Noncoding Elements During Early Teleost Evolution.

Conserved noncoding elements in vertebrates are enriched around transcription factor loci associated with development. However, loss and rapid divergence of conserved noncoding elements has been reported in teleost fish, albeit taking only few genomes into consideration. Taking advantage of the recent increase in high-quality teleost genomes, we focus on studying the evolution of teleost conserved noncoding elements, carrying out targeted genomic alignments and comparisons within the teleost phylogeny to detect conserved noncoding elements and reconstruct the ancestral teleost conserved noncoding elements repertoire. This teleost-centric approach confirms previous observations of extensive vertebrate conserved noncoding elements loss early in teleost evolution, but also reveals massive conserved noncoding elements gain in the teleost stem-group over 300 million years ago. Using synteny-based association to link conserved noncoding elements to their putatively regulated target genes, we show the most teleost gained conserved noncoding elements are found in the vicinity of orthologous loci involved in transcriptional regulation and embryonic development that are also associated with conserved noncoding elements in other vertebrates. Moreover, teleost and vertebrate conserved noncoding elements share a highly similar motif and transcription factor binding site vocabulary. We suggest that early teleost conserved noncoding element gains reflect a restructuring of the ancestral conserved noncoding element repertoire through both extreme divergence and de novo emergence. Finally, we support newly identified pan-teleost conserved noncoding elements have potential for accurate resolution of teleost phylogenetic placements in par with coding sequences, unlike ancestral only elements shared with spotted gar. This work provides new insight into conserved noncoding element evolution with great value for follow-up work on phylogenomics, comparative genomics, and the study of gene regulation evolution in teleosts.

Biomechanical study of different bone cement distribution on osteoporotic vertebral compression Fracture-A finite element analysis

PurposeThis study aimed to compare the biomechanical effects of different bone cement distribution methods on osteoporotic vertebral compression fractures (OVCF). Patients and methodsRaw CT data from a healthy male volunteer was used to create a finite element model of the T12-L2 vertebra using finite element software. A compression fracture was simulated in the L1 vertebra, and two forms of bone cement dispersion (integration group, IG, and separation group, SG) were also simulated. Six types of loading (flexion, extension, left/right bending, and left/right rotation) were applied to the models, and the stress distribution in the vertebra and intervertebral discs was observed. Additionally, the maximum displacement of the L1 vertebra was evaluated. ResultsBone cement injection significantly reduced stress following L1 vertebral fractures. In the L1 vertebral body, the maximum stress of SG was lower than that of IG during flexion, left/right bending, and left/right rotation. In the T12 vertebral body, compared with IG, the maximum stress of SG decreased during flexion and right rotation. In the L2 vertebral body, the maximum stress of SG was the lowest under all loading conditions. In the T12-L1 intervertebral disc, compared with IG, the maximum stress of SG decreased during flexion, extension, and left/right bending and was basically the same during left/right rotation. However, in the L1-L2 intervertebral discs, the maximum stress of SG increased during left/right rotation compared with that of IG. Furthermore, the maximum displacement of SG was smaller than that of IG in the L1 vertebral bodies under all loading conditions. ConclusionsSG can reduce the maximum stress in the vertebra and intervertebral discs, offering better biomechanical performance and improved stability than IG.

New theropod remains from the late Barremian (Early Cretaceous) of Eastern Iberian Peninsula

ABSTRACT In the last decade, the Iberian Peninsula has become a hot spot in the understanding of the early evolutionary history of large-bodied theropods from the Early Cretaceous, especially for the Spinosauridae and Carcharodontosauridae families. To date, at least five species of spinosaurids and one species of carcharodontosaurid inhabited the Iberian region during the Barremian. However, the discovery of new fossil remains suggests that such a diversity of medium- to large-sized theropods could be even higher. Here, we describe an unpublished large theropod tooth and two caudal vertebrae collected in the late 70s in the upper Barremian strata of the Arcillas de Morella Formation (Morella, eastern Spain). The tooth element displays a series of features that allow its identification as cf. Protathlitis, while the vertebral elements are tentatively attributed to an indeterminate carcharodontosaurid. Interestingly, these last remains are different from those of Concavenator, allowing speculation about the occurrence of another species of carcharodontosaurid allosauroids in the Iberian Peninsula during the Early Cretaceous apart from the famed humpbacked dinosaurs and with some reminiscence to Acrocanthosaurus. Therefore, the new findings clearly illustrate the significance of any new theropod remains in depicting the theropod diversity before the final break-up of Pangea in the Iberian Peninsula.

Posterior Column Reconstruction of the Lumbar Spine Using En Bloc Resected Vertebral Arch in Spinal Tumor and Deformity Surgeries.

In high-grade spinal osteotomy involving large anterior column resection, restoration of the structural integrity of the posterior column at the osteotomy site can reduce postoperative instrumentation failure (IF). This study aimed to describe our technique of posterior strut bone grafting using an en bloc resected vertebral arch, which is useful for posterior column reconstruction after high-grade osteotomies during surgeries for spinal tumor and deformity in the lower lumbar spine. Using a posterior approach, en bloc resection of the targeted vertebral arch was performed in accordance with the surgical technique for total en bloc spondylectomy (TES). The posterior elements in the upper and lower adjacent vertebrae were separated by a significant space after vertebral body resection followed by cage insertion in TES or anterior column osteotomy followed by correction in deformity surgery. To create a new posterior column, the en bloc resected vertebral arch was placed at 90° rotation to bridge the upper and lower vertebral arches. Using this technique, an abundant amount of bone chips made from the resected vertebral elements were placed over the en bloc resected posterior arch as an additional bone graft. The technique was used in three patients who underwent TES for spinal tumors and in one patient who underwent grade 4 osteotomy for adult spinal deformity in the lower lumbar spine. One year after surgery, computed tomography showed that the structural integrity of bony fusion was successfully achieved between the en bloc resected arch and the posterior elements of the adjacent vertebrae in all patients and showed no postoperative IFs. This bone graft technique created new continuity of the posterior column after high-grade osteotomies in the lower lumbar spine. Bone fusion was achieved in the posterior elements to prevent IF after surgery.

Furcatoceratops elucidans, a new centrosaurine (Ornithischia: Ceratopsidae) from the upper Campanian Judith River Formation, Montana, USA

Although ceratopsian dinosaurs have been excavated from the Judith River Formation for more than a century, their diversity within the formation remains poorly understood due to the fragmentary nature of those specimens. Here, we describe Furcatoceratops elucidans gen. et sp. nov., a new centrosaurine ceratopsid, based on a nearly complete skeleton found in the upper Judith River Formation. F. elucidans is diagnosed by several unique characters such as anteriorly oriented supraorbital horncores with slight medial curvature and anteroventral process of the nasal that laterally covers the premaxilla. Cladistic analysis recovered F. elucidans as an early-diverging centrosaurine closely related to Nasutoceratops. The holotype is inferred to be a subadult individual based on its surface textures, histological features, size and suture obliteration patterns among bones, thus providing insights into the ontogeny of ceratopsid dinosaurs. The inferred ontogenetic sequence of F. elucidans suggests that the supracranial elements co-ossified earlier than narial elements, as in the chasmosaurine Triceratops but possibly unlike in derived centrosaurines. Because most bones such as cranial and vertebral elements are disarticulated and well preserved, the holotype will serve as a useful comparative specimen for future ceratopsian research.

A new herrerasaurid dinosaur record from southern BrazilL (Upper Triassic) and its faunal association

The Predebon Site, located in São João do Polêsine, Quarta Colônia region (Rio Grande do Sul, Brazil) has a Triassic fauna, including footprints and traces of small vertebrates and abundant remains of rhynchosaurs. This fauna is typical of the Hyperodapedon Assemblage Zone, which is correlated to the late Carnian Ischigualasto Formation (Ischigualasto-Villa Unión Basin) in Argentina. The present study records new fossil remains for the Predebon Site collected in 2001 that consists of two dorsal and two sacral vertebrae referred to the same individual (MCN-PV 10344), and two isolated, serrated blade-shaped teeth (MCN-PV 10425 and 10426). The trunk vertebrae were identified as between 11th and 15th. The sacral vertebrae are fully fused, with no indication of another fused vertebral element, not even signs suggestive of dorsosacral and caudosacral vertebrae, also because the ilia are not preserved. The general characteristics observed are: (i) lateral fossa in the vertebral body; (ii) concave ventral face of the vertebral body; (iii) neural spine high and wide at the top, subquadrangular in shape, in both dorsal and sacral vertebrae; (iv) infrapre- and infrapostzygapophyseal ridges on the dorsals; (v) presence of hyposphene and hypantrum; and (vi) first sacral vertebra larger than the second, with transverse processes and broad sacral ribs, triangular in shape in dorsal view. This set of features in the vertebral elements is similar to that present in Herrerasaurus ischigualastensis from the Ischigualasto Formation and allows us to consider MCN-PV 10344 as a member of the Herrerasauridae clade. It differs from Staurikosaurus pricei, which has three smaller and more slender sacral vertebrae and a low neural spine without subquadrangular platform at the top, and from Gnathovorax cabreirai, which has subrectangular platforms, slightly more elongated anteroposteriorly, suggesting the presence of a new herrerasaurid morphotype. The two isolated, serrated blade-shaped teeth were attributed to Archosauriformes indet., because this morphotype is observed in several groups within this clade. Keywords: Dinosauria, Hyperodapedon Assemblage Zone, late Carnian, Predebon Site, Rio Grande do Sul, Brazil.

Biomechanical effect of proximal multifidus injury on adjacent segments during posterior lumbar interbody fusion: a finite element study

BackgroundAdjacent segment degeneration (ASD) is a common complication of lumbar interbody fusion; the paraspinal muscles significantly maintain spinal biomechanical stability. This study aims to investigate the biomechanical effects of proximal multifidus injury on adjacent segments during posterior lumbar interbody fusion (PLIF).MethodsData from a lumbosacral vertebral computed tomography scan of a healthy adult male volunteer were used to establish a normal lumbosacral vertebral finite element model and load the muscle force of the multifidus. A normal model, an L4/5 PLIF model (PFM) based on a preserved proximal multifidus, a total laminectomy PLIF model (TLPFM), and a hemi-laminectomy PLIF model based on a severed proximal multifidus were established, respectively. The range of motion (ROM) and maximum von Mises stress of the upper and lower adjacent segments were analyzed along with the total work of the multifidus muscle force.ResultsThis model verified that the ROMs of all segments with four degrees of freedom were similar to those obtained in previous research data, which validated the model. PLIF resulted in an increased ROM and maximum von Mises stress in the upper and lower adjacent segments. The ROM and maximum von Mises stress in the TLPFM were most evident in the upper adjacent segment, except for lateral bending. The ROM of the lower adjacent segment increased most significantly in the PFM in flexion and extension and increased most significantly in the TLPFM in lateral bending and axial rotation, whereas the maximum von Mises stress of the lower adjacent segment increased the most in the TLPFM, except in flexion. The muscle force and work of the multifidus were the greatest in the TLPFM.ConclusionsPLIF increased the ROM and maximum von Mises stress in adjacent cranial segments. The preservation of the proximal multifidus muscle contributes to the maintenance of the physiological mechanical behavior of adjacent segments, thus preventing the occurrence and development of ASD.

Direct BMP signaling to chordoblasts is required for the initiation of segmented notochord sheath mineralization in zebrafish vertebral column development.

The vertebral column, with the centra as its iteratively arranged building blocks, represents the anatomical key feature of the vertebrate phylum. In contrast to amniotes, where vertebrae are formed from chondrocytes and osteoblasts deriving from the segmentally organized neural crest or paraxial sclerotome, teleost vertebral column development is initiated by chordoblasts of the primarily unsegmented axial notochord, while sclerotomal cells only contribute to later steps of vertebrae formation. Yet, for both mammalian and teleostean model systems, unrestricted signaling by Bone Morphogenetic Proteins (BMPs) or retinoic acid (RA) has been reported to cause fusions of vertebral elements, while the interplay of the two signaling processes and their exact cellular targets remain largely unknown. Here, we address this interplay in zebrafish, identifying BMPs as potent and indispensable factors that, as formerly shown for RA, directly signal to notochord epithelial cells/chordoblasts to promote entpd5a expression and thereby metameric notochord sheath mineralization. In contrast to RA, however, which promotes sheath mineralization at the expense of further collagen secretion and sheath formation, BMP defines an earlier transitory stage of chordoblasts, characterized by sustained matrix production/col2a1 expression and concomitant matrix mineralization/entpd5a expression. BMP-RA epistasis analyses further indicate that RA can only affect chordoblasts and their further progression to merely mineralizing cells after they have received BMP signals to enter the transitory col2a1/entpd5a double-positive stage. This way, both signals ensure consecutively for proper mineralization of the notochord sheath within segmented sections along its anteroposterior axis. Our work sheds further light onto the molecular mechanisms that orchestrate early steps of vertebral column segmentation in teleosts. Similarities and differences to BMP's working mechanisms during mammalian vertebral column formation and the pathomechanisms underlying human bone diseases such as Fibrodysplasia Ossificans Progressiva (FOP) caused by constitutively active BMP signaling are discussed.

A review of small-bodied theropod dinosaurs from the Upper Cretaceous of India, with description of new cranial remains of a noasaurid (Theropoda: Abelisauria)

ABSTRACT Small-bodied theropod dinosaurs are rare on southern landmasses but have been known from India for a century. Excavations by Charles Matley and Durgansankar Bhattacharji in uppermost Cretaceous sediments at Bara Simla, central India in 1917–1919 recovered small theropod vertebral and limb elements originally interpreted as coelurosaurians and separated into at least three species (Compsosuchus solus, Laevisuchus indicus, Jubbulpuria tenuis) based on features that can now be attributed to their serial position in the vertebral column. The comparatively recent discoveries of Noasaurus leali and Masiakasaurus knopfleri from similar-aged rocks in South America and Madagascar, respectively, and advances in basal theropod systematics led to a revised interpretation of most small-bodied Indian theropods as noasaurid abelisauroids. Here we review and redescribe Laevisuchus, Jubbulpuria, and Compsosuchus, including several elements that until now were thought lost, and describe a new partial noasaurid dentary from central India. The dentary bears the characteristic procumbent dentition of Masiakasaurus, which apparently is absent in Noasaurus. Likewise, cervical vertebrae of Laevisuchus more closely resemble those of Masiakasaurus than those of Noasaurus. Despite these similarities, phylogenetic analyses indicate that the balance of character data supports the Indian noasaurid species outside the sister-taxon pairing of South American and Malagasy species. Bones of small-bodied theropods have been recovered exclusively from the youngest Mesozoic localities in India (e.g., Pisdura, Bara Simla); to date they have not been reported from the slightly older localities in western and central India, from southern Indian sites in the Cauvery Basin, nor from the Vitakri Formation of Pakistan.

First biostratigraphic dating for a Cretaceous ichthyosaur from the Apennine Chain (Italy)

We report a new fossil-bearing locality from the “Chaotic Complex” units in the Northern Apennine Chain of the Emilia-Romagna Region (northern Italy). The material collected includes an articulated series of nine caudal vertebrae referable to a large-bodied ichthyosaur. Based on the nannofossil assemblage sampled from the matrix encasing the vertebrae, we refer the specimen to the early Aptian: this is the first accurate chronostratigraphic dating of a Cretaceous ichthyosaur from the Apennine Chain. The discovery of this new fossil-bearing locality is also significant because of the rather poor record of Aptian ichthyosaurs worldwide. Compared to the large majority of vertebrate remains from the “Chaotic Complex” units, usually represented by isolated or damaged skeletal elements, the specimen retains several vertebral elements in articulation and is associated to ichnological traces left by possibly saprophagous invertebrates, a taphonomic pattern which might indicate depositional conditions less destructive than those usually assumed for the genesis of the “Chaotic Complex’’ vertebrate fossils. The presence of both ichthyosaurs and thalattosuchians in the Aptian of Italy supports the persistence in the Western Tethys of the large-bodied pelagic reptile clades typical of the Middle and Late Jurassic along the first half of the Early Cretaceous.

Morphological modularity in the anthropoid axial skeleton

Previous research has found that hominoids have stronger modularity between limb elements than other anthropoids, suggesting that there is less constraint on morphological diversification (e.g., limb proportions) in hominoids in terms of evolutionary independence. However, degrees of modularity in the axial skeleton have not been investigated across a broad range of anthropoid taxa. Thus, it is unknown whether hominoids also have stronger modularity in the axial skeleton than other anthropoids, which has implications for the evolution of diverse torso morphologies in Miocene apes as well as the evolution of novel characteristics in the skull and vertebrae of fossil hominins. In this study, 12 anthropoid genera were sampled to examine degrees of modularity between axial skeletal elements (i.e., cranium, mandible, vertebrae, and sacrum). Covariance ratio coefficients were calculated using variance/covariance matrices of interlandmark distances for each axial skeletal element to evaluate degrees of modularity. The results showed that Alouatta, Hylobates, Gorilla, Pan, and Homo showed generally stronger modularity than other anthropoid taxa when considering all axial skeletal elements. When only considering the vertebral elements (i.e., vertebrae and sacrum), Alouatta, Hylobates, Gorilla, and Pan showed generally stronger modularity than other anthropoid taxa. Humans showed stronger modularity between the skull and vertebrae than other hominoids. Thus, the evolution of novel characteristics in the skull and vertebral column may have been less constrained in fossil hominins due to the dissociation of trait covariation between axial skeletal elements in hominoid ancestors, thus fostering more evolutionary independence between the skull and vertebral column.

Biomechanics optimisation of the laminoplasty groove size and position: A numerical study

BackgroundThis study is focused on the opening technique of the cervical vertebrae during laminoplasty which serves to substantially reduce the most severe adverse effects of the simple resection of posterior vertebral elements. This computational study aims to clarify by an optimisation approach what shape and position upon the lamina the groove should have. MethodsThe computational model was developed in the computational software COMSOL Multiphysics 5.6a based on a computer tomography data obtained from the C4 vertebra. For finding the optimal minimum or maximum of a function (surface), optimisation algorithms are developed following the Nelder-Mead algorithm. ResultsThe reaction-opening force increases with a decreasing groove radius and an increasing position from the vertebra body. The created area increases with a decreasing groove radius and a decreasing position. As the opening happens mostly only above the groove, the opening area increases only in this location. Moreover, the von Mises stress peak value is almost twice as large as in the case of maximization of the opening area, which might result in breaking of the lamina as the thickness of the lamina would be reduced to its minimum. ConclusionThe groove radius and position can affect the opening force and the opening area in case of double door laminoplasty. The opening force is highly influenced by the groove position and radius. The best position for placing the groove is in the middle of the lamina and the radius of the groove should be as large as possible.

Taxonomic and palaeobiological implications of a large, pathological sabretooth (Carnivora, Felidae, Machairodontinae) from the Lower Pliocene of South Africa

AbstractWe describe the most complete postcranial remains of a pathological, large‐bodied sabretooth from the Lower Pliocene site of Langebaanweg ‘E’ Quarry (South Africa). The skeleton consists of hind limb and vertebral elements that exhibit distinctive exostoses, osteophytes and eburnation. We performed a quantitative morphological comparison of the new postcranial remains found in Langebaanweg, with other Neogene and Quaternary sabretooth and non‐sabretooth felids, consisting of the genera Amphimachairodus, Machairodus, Lokotunjailurus, Dinofelis, Panthera, Homotherium and Smilodon from several sites in Africa, Europe and North America, using principal component analysis and Mosimann transformations. Although the pathological deformation of the remains distorted some of the linear measurements, most of the analysed variables do not contain pathological features, and strongly indicate that the Langebaanweg sabretooth is morphologically closer to Machairodus aphanistus and Lokotunjailurus emageritus than it is to Amphimachairodus giganteus. This indicates that the remains could belong to an undetermined sabretooth species from the Langebaanweg locality. The observed pathologies in the foot and lumbar spine are consistent with diagnostic criteria for severe osteoarthritis (due to maturity), which would have limited limb mobility with severe consequences for hunting success.

Imaging of Spine Infections.

The incidence of spondylodiskitis has increased over the last 20 years worldwide, especially in the immunodepressed population, and it remains a complex pathology, both in terms of diagnosis and treatment. Because clinical symptoms are often nonspecific and blood culture negative, imaging plays an essential role in the diagnostic process. Magnetic resonance imaging, in particular, is the gold standard technique because it can show essential findings such as vertebral bone marrow, disk signal alteration, a paravertebral or epidural abscess, and, in the advanced stage of disease, fusion or collapse of the vertebral elements. However, many noninfectious spine diseases can simulate spinal infection. In this article, we present imaging features of specific infectious spine diseases that help radiologists make the distinction between infectious and noninfectious processes.

Vertebral anomalies in a natural population of Taricha granulosa (Caudata: Salamandridae)

Developmental plasticity, a common pattern in lissamphibian evolution, results in numerous alternative morphologies among species and also within populations. In the present study, a natural population of the salamander Taricha granulosa (Salamandridae) was examined to detect variation in the vertebral count and to identify potential deformities of their vertebral column. The number of trunk vertebrae varied between 11 and 13 and we recorded 58 individuals with 69 anomalous vertebral elements. These anomalies range from congenital malformations (block vertebrae, unilateral bars, hemivertebrae), extra ossifications in the haemal region, to posttraumatic pathologies. Most osseous pathologies were encountered in the caudal region of the axial skeleton. Our data suggest a high frequency of vertebral malformations in salamanders; however, the identification of the exact causes remains challenging.