Search Results (68)

Cerebral aneurysm clipping remains a key surgical approach despite advancements in endovascular techniques. However, training for this procedure is complex due to the variable and fragile nature of aneurysmal tissues. This study evaluates the mechanical behaviour of human basilar arteries during clipping and compares them to 3D-printed models used for neurosurgical training. Mechanical tests were performed on ten cadaveric basilar arteries, distinguishing between healthy and plaque-affected segments. Plaque-affected regions required significantly higher clipping force (1.73 ± 0.22 N) compared to healthy segments (0.45 ± 0.19 N), confirming that atherosclerosis markedly increases arterial stiffness. Six 3D-printed phantom materials were evaluated; none accurately replicated the biomechanical response of real arteries. The Flex Anatomical material showed the highest stiffness (44.51 ± 0.98 N), while Silicone 40A was the most compliant (1.05 ± 0.12 N), yet both deviated substantially from biological performance. These findings underscore the current limitations of anatomical models that lack realistic biomechanical properties. Full article

Hypertension, a leading factor for cardiovascular diseases (CVD), is a particularly heavy burden in women during middle age, when cardioprotective hormones begin to decline. The abnormal handling of calcium (Ca²⁺) in vascular smooth muscle cells (VSMCs) leads to increased vasoconstriction, remodeling, and altered arterial compliance during hypertension. The Spontaneously Hypertensive Rats (SHR) is a model of essential hypertension, and middle-aged females with hypertension represent a stage of disease where vascular dysfunction is prominent but understudied. Losartan, a widely prescribed angiotensin II (AngII) receptor (AT1R) blocker, exerts antihypertensive effects by affecting Ang II/Ca²⁺ signaling. However, whether it corrects the Ca²⁺ mishandling in the aorta of middle-aged female SHR has not been established. In this study, the thoracic aorta from 36-week-old female SHRs treated with losartan was assessed for Ca²⁺ mishandling using myography and biochemical assays. Meanwhile, biomechanical properties and stiffness were evaluated using Pulse Wave Velocity (PWV), Atomic Force Microscopy (AFM), and assessments of collagen and elastin contents. Compared with normotensive controls, SHR demonstrated disrupted Ca²⁺ handling, increased stiffness, and Extracellular Matrix (ECM) remodeling in middle-aged females. Treatment with losartan abrogated Ca²⁺ mishandling influx and efflux in the VSMC, decreased stiffness, and restored the aortic structural changes. These findings demonstrate that losartan abolishes Ca²⁺ mishandling and highlight a mechanistic role of AT1R blockade in restoring vascular function in the aorta of middle-aged females during hypertension. Full article

Caspases are known for their roles in cell death and inflammation. However, emerging evidence suggests they also mediate non-lethal processes, governed by a finely tuned balance of localization, activity, kinetics, and substrate availability. Given that many caspase substrates are implicated in mechanoadaptive processes, we investigated if caspases contribute to morphological adaptation of human pulmonary artery endothelial cells to fluid shear stress and other morphology-altering stimuli in vitro. Using selective inhibitors, we screened all major caspases for a role in endothelial cell adaptation to unidirectional laminar shear stress (15 dyn/cm², 72 h). Selective inhibition of caspase-6, but not other caspases, impaired morphological shear adaptation. Only 5.5% of caspase-6-inhibited cells shear-adapted vs. 75.2% of vector controls. Live-cell FRET imaging revealed progressive caspase-6 activation starting at 18 h of shear stress, coinciding with the onset of morphological remodeling. The active caspase-6 localized predominantly perinuclearly, while caspase-3 remained inactive throughout shear exposure. Caspase-6 inhibition did not affect elongation in response to alternative biomechanical or biochemical stimuli, including uniaxial cyclic stretch (5%, 1 Hz), spatial confinement on narrow micropatterned RGD-lines, or TNF-α stimulation, nor did it impair cell adhesion, directed migration, wound healing, or barrier recovery after wounding. Our study uncovers a previously unidentified role of caspase-6 as a non-apoptotic, mechanosensitive effector specifically required for shear-induced morphological adaptation of pulmonary artery endothelial cells, highlighting a novel regulatory axis in vascular mechanoadaptation. Full article

Background/Objectives: Patients suffering from fractures are often treated with clopidogrel during the phase of bone healing due to multiple comorbidities. Studies indicate that clopidogrel suppresses osteoblast proliferation and the formation of trabecular bone. However, it is unknown whether clopidogrel also affects fracture healing under ischemic conditions, as they may occur in multimorbid patients. Methods: To test this in the present study, a murine ischemia model was performed in CD-1 mice by ligating the right deep femoral artery to induce mild ischemia of the right lower limb. A closed fracture of the femur was then stabilized by inserting an intramedullary lag screw. The animals received either 3 mg/kg body weight clopidogrel daily per os or vehicle (control). Bone healing was assessed by biomechanical, radiological, histomorphometrical and Western blot analyses 2 and 5 weeks postoperatively. Results: The fractured femurs in the clopidogrel group exhibited no increase in biomechanical stiffness throughout the observation period in contrast to controls. While the radiological analysis showed no differences between both groups, histomorphometric analyses demonstrated a significantly reduced bridging score, less bone and more connective tissue within the callus of clopidogrel-treated animals. Western blot analyses revealed a significantly reduced expression of the osteogenic marker bone morphogenetic protein (BMP)-4 and an increased expression of the blood vessel marker CD31. Conclusions: These results show that clopidogrel may impair fracture healing under challenging ischemic conditions, which is associated with a shift in angiogenic and osteogenic expression markers in the callus tissue. Therefore, clopidogrel treatment may not be recommended in fracture patients with tissue ischemia. Full article

Tricuspid regurgitation (TR) represents a significant, often silently progressing, valvular heart disease with historically suboptimal management due to perceived high surgical risks. Transcatheter tricuspid valve interventions (TTVI) offer a promising, less invasive therapeutic avenue. Central to the success of TTVI is Right Ventricular Reverse Remodelling (RVRR), defined as an improvement in RV structure and function, which strongly correlates with enhanced patient survival. The right ventricle (RV) undergoes complex multi-scale biomechanical maladaptations, progressing from adaptive concentric to maladaptive eccentric hypertrophy, coupled with increased stiffness and fibrosis. Molecular drivers of this pathology include early failure of antioxidant defenses, metabolic shifts towards glycolysis, and dysregulation of microRNAs. Accurate RV function assessment necessitates advanced imaging modalities like 3D echocardiography, Cardiac Magnetic Resonance Imaging (CMR), and Computed Tomography (CT), along with strain analysis. Following TTVI, RVRR typically manifests as a biphasic reduction in RV volume overload, improved myocardial strain, and enhanced RV-pulmonary arterial coupling. Emerging molecular biomarkers alongside advanced imaging-derived biomechanical markers like CT-based 3D-TAPSE and RV longitudinal strain, are proving valuable. Artificial intelligence (AI) and machine learning (ML) are transforming prognostication by integrating diverse clinical, laboratory, and multi-modal imaging data, enabling unprecedented precision in risk stratification and optimizing TTVI strategies. Full article

Background/Objectives: Fluid dynamic models of the cerebral vasculature are being developed to evaluate intracranial vascular pathology. Fluid–structure interaction modeling provides an opportunity for more accurate simulation of vascular pathology by modelling the vessel wall itself in conjunction with the fluid forces. Accuracy of these models is heavily dependent on the parameters used. Of those studied, elastin has been considered a key component used in aortic and common carotid artery modeling. We studied elastin thickness to determine if there was significant variation between cerebral artery territories to suggest its importance in cerebral blood vessel biomechanical response and provide reference data for modeling intracranial elastin. Elastin thickness was compared to vessel location, thickness, diameter, and laterality within human intracranial arteries. Methods: Tissue was taken from five human cadaveric heads preserved in formaldehyde from each intracranial vessel distribution bilaterally and stained with Van Gieson stain for elastin. A total of 160 normal cerebral vascular artery specimens were obtained from 17 different cerebrovascular regions. Two reviewers measured elastin thickness for each sample at five different locations per sample using Aperio ImageScope (Leica Biosystems, Deer Park, IL, USA). Statistical analysis of the samples was performed using mixed-models repeated measures regression methods. Results: There was a significant difference between anterior circulation (6.01 µm) and posterior circulation (4.4 µm) vessel elastin thickness (p-value < 0.05). Additionally, two predictive models of elastin thickness were presented, utilizing a combination of anterior versus posterior circulation, vessel diameter, and vessel wall thickness, which demonstrated significance for prediction with anterior versus posterior combined with vessel diameter and wall thickness. Conclusions: Elastin thicknesses are significantly different between anterior and posterior circulation vessels, which may explain the differences seen in aneurysm rupture risk for anterior versus posterior circulation aneurysms. Additionally, we propose two potential models for predicting elastin thickness based on vessel location, vessel diameter, and vessel wall thickness, all of which can be obtained using preoperative imaging techniques. These findings suggest that elastin plays an important role in cerebral vascular wall integrity, and this data will further enable fluid–structure interaction modeling parameters to be more precise in an effort to provide predictive modeling for cerebrovascular pathology. Full article

(1) Background: Peripheral artery disease (PAD) and related conditions significantly impair walking ability. Previous studies demonstrated that passive lightweight exosuits can improve walking biomechanics. However, most of these devices focus on assisting hip flexion. The aim of this study was to investigate the effects of flexion and extension assistance on joint kinetics and muscle activation. We hypothesized that there would be an optimal combination of flexion and extension assistance for measured parameters. (2) Methods: Four patients with PAD and six healthy individuals walked on a treadmill while wearing a passive exosuit with adjustable hip flexion and extension assistance. Lower limbs’ power, moment, and muscle activation were recorded. (3) Results: We found that passive hip assistance effectively reduced hip kinetics in both healthy and PAD participants. We also found different effects between the groups, with the PAD group utilizing the exosuit to reduce plantarflexion kinetics and gastrocnemius activity. (4) Conclusions: These findings suggest that patients with PAD can leverage the exosuit to ameliorate impairment-specific deficits. Future research should explore more real-world applicability of passive exosuits. Full article

Aortic dissection (AD) is a highly lethal cardiovascular emergency, and clinical studies have found that a high percentage of AD patients are hypertensive. In previous studies, the AD model was simplified, such as by treating the vessel wall as a single-layer rigid material, ignoring the complex biomechanical factors of the vascular lumen. This study elucidates key biomechanical mechanisms by which hypertension promotes primary AD progression using multiscale modeling. First, based on experimental data from longitudinal and circumferential uniaxial tensile testing of porcine aortic walls (5–7-month-old specimens), a constitutive model of the aortic wall was developed using the Holzapfel–Gasser–Ogden (HGO) framework. The material parameters were calibrated via inverse optimization in ABAQUS-ISIGHT, achieving close alignment with mechanical properties of the human aorta. Using this validated model to define the hyperelastic properties of the aortic wall, a multiphysics coupling platform was constructed in COMSOL Multiphysics 6.2, integrating computational fluid dynamics (CFD) and fluid–structure interaction (FSI) algorithms. This framework systematically quantified the effects of blood pressure (bp) fluctuations on compressive stresses, von Mises stresses, and deformation of the intimal flap within the AD lesion region. With constant blood rheology, elevated blood pressure enhances wall stresses (compressive and von Mises), and intima-media sheet deformation, this can trigger initial rupture tears, false lumen dilation, and branch arterial flow obstruction, ultimately deteriorating end-organ perfusion. Full article

Isolated popliteal artery (PA) lesions account for around 1% of lower limb revascularisations. Whatever treatment modality is chosen, the effects on the artery during knee flexion must be considered. The decision between a less invasive endovascular treatment (EVT) and traditional open interventions remains complex due to anatomical, biomechanical, and pathophysiological considerations and the varying aetiology of PA lesions. Available data remain limited, making it more challenging to decide on the most effective and durable treatment approach. Nowadays, when EVT is planned, several non-stenting techniques are available, making a “leave-nothing-behind strategy” possible after adequate vessel preparation. If stent implantation is required, self-expanding vasculomimetic stents are preferred due to their ability to provide flexibility and resist compression during motion. This narrative review discusses the available treatment options, challenges, and specific considerations for isolated PA disease, highlighting the need for large-scale, high-quality studies to provide more robust evidence on the optimal treatment approach. Full article

Minimal facet and lateral mass fractures of the subaxial cervical spine (C3–C7) are a distinct subset of spinal injuries that present diagnostic and therapeutic challenges. These fractures often result from low-energy trauma or hyperextension mechanisms. They are frequently stable. However, subtle fracture instability and associated soft tissue injuries may lead to delayed instability, neurological compromise, and/or chronic severe pain if not properly identified. Accurate diagnosis relies on a combination of plain radiography, high-resolution computed tomography (CT), and magnetic resonance imaging (MRI) to assess bony and ligamentous integrity. Treatment strategy is determined based on fracture stability, neurological status, and radiographic findings. Most stable fractures can be effectively treated with conservative treatment, allowing for natural healing while minimizing complications. However, when instability is suspected—such as those with significant disc and ligamentous injuries, progressive deformity, or neurological deficits—surgical stabilization may be considered. The presence of vertebral artery injury (VAI) can further complicate management. To mitigate the risk of stroke, a multidisciplinary approach that includes neurosurgery, vascular surgery, and interventional radiology is needed. Surgical treatment aims to restore spinal alignment, maintain stability, and prevent further neurological deterioration with approaches tailored to individual fracture patterns and patient-specific factors. Advances in surgical techniques, perioperative management, and endovascular interventions for VAI continue refining treatment options to improve clinical outcomes while minimizing complications. Despite increasing knowledge of these fractures and associated vascular injuries, optimal treatment strategies remain unclear due to limited high-quality evidence. This review provides a comprehensive analysis of the anatomy, biomechanics, classification, imaging modalities, and treatment strategies for minimal facet and lateral mass fractures in the subaxial cervical spine, highlighting recent advancements in diagnostic tools, therapeutic approaches, and managing vertebral artery injuries. A more precise understanding of the natural history and optimal management of these injuries will help spine specialists refine clinical decision-making and improve patient outcomes. Full article

Coronary heart disease, a leading global cause of mortality, has witnessed significant advancement through robotic coronary artery bypass grafting (CABG), with the internal mammary artery (IMA) emerging as the preferred “golden conduit” for its exceptional long-term patency. Despite these advances, robotic-assisted IMA harvesting remains challenging due to the absence of force feedback, complex surgical maneuvers, and proximity to the beating heart. This study introduces a novel virtual simulation platform for robotic IMA harvesting that integrates dynamic anatomical modeling and real-time haptic feedback. By incorporating a dynamic cardiac model into the surgical scene, our system precisely simulates the impact of cardiac pulsation on thoracic cavity operations. The platform features high-fidelity representations of thoracic anatomy and soft tissue deformation, underpinned by a comprehensive biomechanical framework encompassing fascia, adipose tissue, and vascular structures. Our key innovations include a topology-preserving cutting algorithm, a bidirectional tissue coupling mechanism, and dual-channel haptic feedback for electrocautery simulation. Quantitative assessment using our newly proposed Spatial Asymmetry Index (SAI) demonstrated significant behavioral adaptations to cardiac motion, with dynamic scenarios yielding superior SAI values compared to static conditions. These results validate the platform’s potential as an anatomically accurate, interactive, and computationally efficient solution for enhancing surgical skill acquisition in complex cardiac procedures. Full article

Background/Objectives: Peripheral artery disease (PAD) is a significant global health challenge, affecting millions worldwide. Among its various manifestations, femoropopliteal atherosclerotic disease presents a unique challenge due to the biomechanical stresses on the superficial femoral artery (SFA) and popliteal artery (PA). Despite advancements in endovascular interventions, restenosis and stent fractures remain critical issues, particularly in complex and long lesions. Biomimetic stents, such as the SUPERA interwoven nitinol stent, have been developed to address these challenges by closely replicating the natural mechanical properties of the femoropopliteal arteries. This study evaluates the clinical and procedural outcomes of biomimetic stent implantation in patients with femoropopliteal atherosclerotic disease, focusing on patency rates, procedural success, and major adverse limb events (MALE). Methods: A cohort study was conducted at the University Clinical Center of Serbia, including 294 patients with femoropopliteal stenosis or occlusion treated with the SUPERA stent from January 2017 to December 2024. Patients were stratified by lesion complexity using the GLASS classification and procedural success, patency rates, and MALE incidence were assessed. Kaplan–Meier survival analysis was used to evaluate long-term outcomes, and Cox regression analysis identified predictors of MALE. Results: Primary patency rates at 1, 6, 12, and 24 months were 95.6%, 90.1%, 84.2%, and 77.7%, respectively. Primary-assisted patency and secondary patency rates remained high over time. Patients with GLASS IV lesions exhibited significantly lower patency rates and higher MALE incidence compared to GLASS I-III patients (p = 0.002). Occlusion length (≥16 cm) and lesion complexity (GLASS IV) were independent predictors of MALE (p = 0.015). The stent demonstrated high procedural success and durability, with minimal complications. Conclusions: Biomimetic SUPERA stents provide high patency rates and favorable clinical outcomes in complex femoropopliteal lesions. However, lesion complexity and occlusion length significantly impact long-term success. The findings highlight the importance of careful patient selection and lesion assessment for optimizing endovascular treatment strategies in PAD management. Full article

The convergence of 3D printing and auxetic materials is paving the way for a new era of adaptive structures. Auxetic materials, known for their unique mechanical properties, such as a negative Poisson’s ratio, can be integrated into 3D-printed objects to enable them to morph or deform in a controlled manner, leading to the creation of 4D-printed structures. Since the first introduction of 4D printing, scientific interest has spiked in exploring its potential implementation in a wide range of applications, from deployable structures for space exploration to shape-adaptive biomechanical implants. In this context, the current paper aimed to develop 4D-printed arterial stents utilizing bioinspired architected auxetic materials made from biocompatible and biodegradable polymeric material. Specifically, three different auxetic materials were experimentally examined at different relative densities, under tensile and compression testing, to determine their mechanical behavior. Based on the extracted experimental data, non-linear hyperelastic finite element material models were developed in order to simulate the insertion of the stent into a catheter and its deployment in the aorta. The results demonstrated that among the three examined structures, the ‘square mode 3’ structure revealed the best performance in terms of strength, at the same time offering the necessary compressibility (diameter reduction) to allow insertion into a typical catheter for stent procedures. Full article

The haptic fidelity of biomimetic materials used in the design of procedural task trainers is of growing interest to the medical community. Shore hardness has been proposed as a method for assessing tissue biomechanics and replicating the results as a way to increase the fidelity of biomimetics to tissues. However, there is limited research on the reliability of human tissue measurements using Shore scales. Using human tissues (internal carotid artery [ICA], internal jugular vein [IJV], vagus nerve [VN], sternocleidomastoid muscle [SCM], and overlying skin [skin]), this study evaluates (1) the inter-rater reliability of Shore hardness measurements, (2) examines the relationship between tissue thickness and hardness, and (3) investigates the impact of a measurement method (freehand vs. durometer stand). Preserved tissues, specifically a liver and components of the anterior triangle of the neck, were extracted from cadavers and measured by three independent raters using digital Shore durometers. Testing revealed that although Shore A demonstrated better inter-rater reliability compared to Shore OO, both scales exhibited poor-to-moderate reliability. ICC values for Shore A ranged from 0.21 to 0.80 and were statistically significant (p < 0.05) for all tissue types except the SCM. In contrast, Shore OO demonstrated poorer reliability, with ICC values ranging from 0.00 to 0.41. The ICC values were only significant for the ICA, IJV, and VN (p < 0.05). An inverse correlation between tissue thickness and hardness on the Shore A scale was found for all tissues and was significant (p < 0.05) for ICA, VN, and skin. There were mixed results for the correlation between tissue thickness and hardness on the Shore OO scale (−0.06–0.92), and only IJV had a statistically significant correlation (p < 0.05). Finally, the median hardness values on the Shore OO scale were significantly greater when measured using a durometer stand vs. freehand (Z = 4.78, p < 0.05). In summary, when using appropriate standards and addressing the challenges of tissue thickness and variability in freehand measures, Shore hardness has the potential to be used by clinicians in the clinical setting and in the selection of biomimetic materials in the design of task trainers. Full article

Background: The generation and perfusion of complex vascularized tissues in vitro requires sophisticated perfusion techniques. For multiscale arteriovenous networks, not only the arterial, but also the venous, biomechanical and biochemical conditions that physiologically exist in the human body must be accurately emulated. For this, we here present a modular arteriovenous perfusion system for the in vitro culture of a multi-scale bioartificial vascular network. Methods: The custom-built perfusion system consisted of two circuits: in the arterial circuit, physiological arterial biomechanical and biochemical conditions were simulated using a modular set-up with a pulsatile peristaltic pump, compliance chambers, and resistors. In the venous circuit, venous conditions were emulated accordingly. In the center of the system, a bioartificial multi-scale vascularized fibrin-based tissue was perfused by both circuits simultaneously under biomimetic arteriovenous conditions. Culture conditions were monitored continuously using a multi-sensor monitoring system. Results: The physiological arterial and venous pressure- and flow-curves, as well as the microvascular arteriovenous oxygen partial pressure gradient, were accurately emulated in the perfusion system. The multi-sensor monitoring system facilitated live monitoring of the respective parameters and data-logging. In a proof-of-concept experiment, vascularized three-dimensional fibrin tissues showed sustained cell viability and homogenous microvessel formation after culture in the perfusion system. Conclusions: The arteriovenous perfusion system facilitated the in vitro culture of a multiscale vascularized tissue under physiological pressure-, flow-, and oxygen-gradient conditions. With that, it presents a promising technique for the in vitro generation and culture of complex large-scale vascularized tissues. Full article