Einat Kedar

Otolith organs are specialized structures of the vertebrate inner ear that provide the inertial mass required for maintaining equilibrium. Mammals possess two otolithic organs, the utricle and the saccule, whereas birds and other non-mammalian vertebrates also retain a third one, the lagena, whose development remains poorly understood and whose function is still debated. In birds, the lagena contains thousands of calcium carbonate biomineral particles, termed otoconia. Here, we reconstruct the developmental crystallization of lagena otoconia in the Japanese quail ( Coturnix japonica ) throughout embryogenesis. We combine multiscale imaging with structural, compositional, and crystallographic analyses across length scales. We show that lagena mineralization precedes cranial bone formation and proceeds predominantly through the growth of existing otoconia rather than continued nucleation. Otoconia develop through progressive particle growth, alignment, and fusion within a pre-existing organic compartment while maintaining a persistent central core, ultimately forming magnesium calcite biominerals. This maturation is accompanied by progressive nanoscale densification, transforming early mineral deposits into mature hierarchical crystals. This work establishes a developmental model of avian otoconia formation and provides new insights into how hierarchical calcium carbonate crystals are assembled during vertebrate development. Statement of significance: Otoliths are the only calcite based biomineral in our body that has a physiological function, yet their developmental assembly remain incompletely understood. While the utricle and saccule have been extensively investigated across vertebrates, the lagena, a third otolithic organ lost during mammalian evolution, has received comparatively little attention. Here, we combine multiscale imaging and materials characterization to reconstruct the developmental crystallization of lagena otoconia in the Japanese quail. We establish how hierarchical magnesium calcite biominerals emerge through coordinated mineral growth, structural maturation, and crystallization, providing a developmental framework for avian otoconia formation and new insights into the assembly of vertebrate calcium carbonate crystals.

It is widely accepted that modern humans display distinctive vertebral and intervertebral disc (IVD) morphologies that evolved to meet the biomechanical demands of habitual terrestrial bipedalism. This study synthesizes macro- and microstructural differences in the lumbar spine to clarify how human specializations compare with those of extant apes. The skeletal sample consisted of 240 humans, 20 chimpanzees, and 25 gorillas. The CT scan sample comprised 180 humans and eight chimpanzees. Histological analysis of the IVD was performed on 10 humans and four ape specimens. Vertebral bodies and discs were measured. Histological analyses employed hematoxylin–eosin, Von Kossa, and Van Gieson staining. Statistical analyses included ANOVA with Bonferroni-corrected t-tests or Welch’s ANOVA and Games–Howell post hoc tests. Regression analyses were performed using ordinary least-squares estimation, and differences between regression lines were assessed using ANCOVA. Humans and chimpanzees differed significantly in vertebral body proportions, bone volume fraction, IVD thickness, apophyseal ring thickness, annulus fibrosus lamellar organization, endplate and subchondral bone thickness, and vascularization at the bone–endplate interface. These results indicate substantial evolutionary modification of the human vertebral body and IVD, enhancing rotational mobility and resistance to axial loading, key functional requirements for maintaining upright posture and efficient bipedal locomotion.

Aims: The development of lumbar lordosis has been traditionally examined using angular measurements of the spine to reflect its shape. While studies agree regarding the increase in the angles during growth, the growth rate is understudied, and sexual dimorphism is debated. In this study, we used a novel method to estimate the shape of the lumbar curve (LC) using the landmark-based geometric morphometric method to explore changes in LC during growth, examine the effect of size and sex on LC shape, and examine the associations between angular measurements and shape.Methods: The study population included 258 children aged between 0 and 20 years (divided into five age groups) who underwent a CT scan between the years 2009 and 2019. The landmark-based geometric morphometric method was used to capture the LC shape in a sagittal view. Additionally, the lordosis was measured via Cobb and sacral slope angles. Multivariate and univariate statistical analyses were carried out to examine differences in shape between males and females and between the age groups.Results: The overall shape of the LC overlapped between males and females in most age groups, except for the nine- to 12-year age group. However, size did not affect LC shape. LC shape changed significantly during growth from straight to curved, reaching its mature shape earlier in females. This corresponded with the results obtained by the lordosis and sacral slope angles. A significant positive correlation was found between the LC shape and angles, although the angles demonstrated poor distinction between age groups, as opposed to the LC shape.Conclusion: New insights into LC shape development were achieved using the geometrical morphometric method. The LC shape was sex-independent in most age groups. However, the LC reached its mature shape earlier in females than males. The method and data of this study are beneficial for future studies examining aetiological factors for spinal pathologies and maldevelopment.Cite this article: Bone Joint Res 2025;14(1):58–68.

The cervical spine manifests a wide shape variation. However, the traditional methods to evaluate the cervical spine curve were never tested against its actual shape. The study's main aim was to determine whether the shape classification of the cervical spine, based on traditional angular measurements, coincides with each other and with the shape captured by the 2D landmark‐based geometric morphometric method. The study's second aim was to reveal the associations between the cervical spine shape and the demographic parameters, the head's position, and the spine's sagittal balance. CT scans of the cervical spine of 163 individuals were evaluated to achieve these goals. The shape was assessed by measuring the C2–C7 Cobb angle (CA), the C2–C7 posterior tangent angle (PTA), the curvedness of the arch, and by a 2D landmark‐based geometric morphometric method. The position of the head and the sagittal balance of the spine were evaluated by measuring the foramen magnum‐C2 Cobb angle (FMCA) and the T1 slope angle (T1SA), respectively. Based on the size of the angle measured, each individual was classified into one of the three cervical ‘shape groups’ (lordotic, straight, and kyphotic). We found that cervical lordosis was the dominant shape regardless of the measuring methods utilized (46.6%–54.6%), followed by straight neck (28.2%–30.1%), and kyphosis (15.3%–25.2%); however, about a third of the 163 individuals were classified into a different shape group using the CA and PTA methods. The cervical spine angle was sex‐independent and age‐dependent. The T1SA was significantly correlated with CA and PTA (r = 0.640 and r = 0.585, respectively; p < 0.001). In conclusion, the cervical spine shape evaluation is method‐dependent and varies with age.

This CT-based study aimed to characterize and explain the existence of two anatomical structures positioned near the maxillary sinuses, which are of clinical relevance in rhinology and maxillofacial surgery. A total of 182 head scans (92 males and 90 females) were inspected for infraorbital ethmoid cells (IECs) and for the type (route) of infraorbital canal (IOC). The maxillary sinuses were segmented, and their volumes were measured. Statistical analysis was conducted to reveal the associations between the two anatomical variations, namely, sex and the maxillary sinus volume. Infraorbital ethmoid cells were noted in 43.9% of the individuals studied; they were more frequent in males (53.3%) than in females (34.4%). The descending infraorbital nerve (type 3 IOC) was found in 13.2% of individuals and was independent of sex. Infraorbital ethmoid cells were associated with the IOC types. The maxillary sinus volume was found to be sex-dependent. A large sinus volume is significantly associated with IOC Type 3 (the descending canal) and the presence of IEC. Dentists, radiologists, and surgeons should be aware that individuals with extensive pneumatization of the maxillary sinuses are more likely to display a descending IOC and IEC. These findings should be studied, along with CT scans, before treatment and surgery.