The human forearm, a dynamically coordinated system of bones, muscles, and connective tissues, is central to upper limb function but poses significant chal

The intricate anatomical structure of talocalcaneal coalitions (TCCs) presents significant challenges for clinicians in both diagnosis and treatment. This study aimed to investigate the anatomy, imaging characteristics, and biomechanical properties of TCCs, providing essential references for contemporary clinical diagnosis, treatment, scientific research, and education regarding TCCs. The morphologies of TCCs were examined and classified in intact dry osseous specimens from 131 Asian adults. The imaging characteristics of TCCs were summarized by carefully observing the X-rays and CT scans. Additionally, finite element models of TCCs were established and validated, allowing for the simulation and analysis of stress and strain. The TCCs were primarily located in the region between the posterior end of sustentaculum tali (ST), the medial port of the tarsal canal, and the medial edge of the posterior talar articular surface (PTF). In comparison to specimens with cartilage and ligament connections, the medial tubercle of osseous connections exhibited significant inward and downward protrusion, while the ST was longer and thicker. Statistically significant differences were noted in the widths of the calcaneus and talus, as well as in the thickness and length of the ST (P < 0.05). CT imaging provided an accurate determination of TCCs' locations, while X-rays revealed the presence of the "C sign" and "duck beak sign" in all osseous connection specimens. Finite element model analysis indicated that stress was primarily concentrated at the osseous connection, which also reduced displacement of the subtalar joint. The comprehension of the precise location, anatomical morphological characteristics, imaging features and finite element mechanical properties of TCCs is instrumental in enhancing the diagnosis and treatment of TCCs.

Cranial sutures play critical roles in load distribution and neuroprotection, with their biomechanical performance intimately linked to morphological complexity. The purpose of this study was to investigate the effect of different morphologies of cranial sutures on their biomechanical behavior. Based on the different morphologies of the cranial sutures, six groups of finite element models (closed, straight, sine wave, tight sinusoidal wave, layered sinusoidal wave, and layered sinusoidal wave + sutural bone) of the bone–suture–bone composite structures that ranged from simple to complex were constructed. Each model was subjected to 50 kPa impact and 98 N bilateral tensile loads to evaluate von Mises stress and total deformation variations across all groups under combined loading conditions. Key findings reveal that morphological complexity directly governs stress dynamics and mechanical adaptation; layered sinusoidal configurations delayed peak stress by 19–36% and generated elevated von Mises stresses compared to closed sutures, with stress concentrations correlating with interfacial roughness. Under impact, sutures exhibited localized energy dissipation ( 0.05), underscoring their dual roles in localized energy absorption and global strain redistribution. Craniosacral therapy relevant forces produced sub-micron deformations far below pathological thresholds (≥1 mm), which implies the biomechanical safety of recommended therapeutic force. Staggered suture–bone in open sutures (31.93% closure rate) enhances shear resistance, whereas closed sutures prioritize rigidity. The findings provide mechanistic explanations for suture pathological vulnerability and clinical intervention limitations, offering a quantitative foundation for future research on cranial biomechanics and therapeutic innovation.