Search Results (211)

In physiological environments, several metallic alloys, including titanium, stainless steel, cobalt–chromium, and emerging biodegradable systems such as magnesium (Mg), zinc (Zn), and iron (Fe), offer mechanical properties and biocompatibility suitable for load-bearing implants. With the rapid advancement of 3D printing technologies, these alloys can now be fabricated into patient-specific, complex geometries that enhance both structural performance and functional integration. Beyond serving as structural supports, 3D-printed alloys are increasingly engineered as localized drug-delivery platforms to release anti-inflammatory, antibacterial, anticancer, and osteogenic agents at the implant–tissue interface, addressing the dual clinical needs of site-specific therapy and mechanical stabilization. Nevertheless, this field remains underexplored because studies differ widely in alloy chemistry, surface topography, porosity, coating strategy, drug-loading methods, and release profiles, as well as in how material degradation or passivation interacts with pharmacokinetics. For the first time, this review consolidates drug-loading and elution strategies across 3D-printed alloy platforms, compares therapeutic categories in relation to alloy and coating types, and critically evaluates how the surface microstructure or alloy geometry influences release behavior. Full article

Abdominal aortic aneurysm (AAA) is a dangerous disease and can cause sudden death if it ruptures. This study investigated blood flow behaviors and hemodynamic changes in three categories (small, medium and large diameters) of AAAs using computational fluid dynamics (CFD) based on patient geometry. Computed tomography images of patients with abdominal aortic aneurysms were used to construct a patient-specific AAA model. This study included one healthy subject and seven patients who had AAAs with a diameter larger than 3 cm. The results showed that the aortic aneurysms were highly turbulent in the diastolic phase, and there was an increase in turbulence as the aneurysm size increased. The time-averaged wall shear stress (TAWSS) in the artery was high at peak systole and decreased during diastole. The oscillating shear index (OSI) was higher at the middle and distal aortic aneurysm sac than in other areas. Low TAWSS and a high OSI in the aneurysm region may indicate a risk of wall rupture in AAA. This study suggests that CFD provides further insights by visualizing blood flow behaviors and quantitatively analyzing hemodynamic parameters. Full article

Background. Accurate anatomical assessment is essential for pre-procedural planning in structural heart disease. Advanced 3D imaging could offer improved visualization for more accurate reconstruction. We assessed the performance of a novel immersive 3D virtual reality (VEA) for the pre-procedural planning of transcatheter aortic valve implantation (TAVI) candidates. Methods. Measurement of cardiac-gated contrast-enhanced computed tomography (CT) scans was performed with the novel VEA and established tools: 3Mensio and Horos. Results. 50 consecutive patients were included. Annular and LVOT measurements obtained with VEA were strongly correlated with those derived from standard CT analysis. The intraclass correlation coefficient (ICC) confirmed excellent consistency for annular measurements (ICC = 0.93), while the concordance correlation coefficient indicated very good overall agreement (CCC = 0.83, 95% CI 0.73–0.90). Similarly, LVOT measurements obtained with VEA showed strong correlation with CT values, with good consistency (ICC = 0.90) and good overall agreement (CCC = 0.77, 95% CI 0.64–0.86). VEA-based planning improved prosthesis size selection accuracy, achieving higher concordance with implanted valves and a significant net reclassification gain over conventional CT. Conclusions. Given the increasing use of advanced 3D cardiac imaging technologies, understanding their diagnostic accuracy to guide pre-procedural planning of TAVI is paramount. In our study, VEA provided reliable assessment of aortic root anatomy for TAVI planning. This novel 3D software provides accurate, patient-specific reconstructions of the aortic root and surrounding structures that may optimize valve sizing, improve procedural safety and enhance procedural outcomes. This provides a rationale for future studies to assess the procedural benefit derived from a three-dimensional assessment of the aortic valve geometry. Full article

The increased incidence of respiratory diseases in the recent past has resulted in a growing number of respiratory failures and dependence on mechanical ventilation. The death rates in patients under long-term ventilator therapy are seen to be as high as 62%, with mortality often attributed to secondary bacterial infections originating in endotracheal tube (ETT) assemblies. The ETT connects the ventilator to the trachea, and the parameters selected by the clinician play important roles in determining the airflow dynamics and mucus transport. This study considers the influence of ETT cuff geometry and ventilator cycling on tracheal airflow behavior, comparing Taperguard- and Microcuff-type designs with respect to Pressure-Controlled Ventilation (PCV) and Assisted Volume-Controlled Ventilation (VCV) modes. Three-dimensional Unsteady Reynolds Averaged Navier–Stokes (URANS) simulations in an idealized intubated trachea were performed and complemented by flow visualization and flow rate measurements for model validation. The simulation results show that both the cuff geometry and ventilation mode affect flow asymmetry of air flow in the trachea and consequently the wall shear stresses and secondary flow development. Specifically, the Taperguard-style cuff under PCV conditions generated substantially elevated wall shear stress values—nearly twice those observed for the same cuff operating in VCV mode. In contrast, the Microcuff configuration paired with VCV produced lower gas flow velocities and reduced shear stress levels, reaching only about 80% of the peak values associated with the Taperguard case. These differences highlight the combined influence of cuff geometry and ventilation strategy on local airway loading. These findings highlight the coupled impact of cuff design and ventilatory mode, and provide a pathway for understanding flow physics in intubated trachea towards improved respiratory care and mechanical ventilation practices. Full article

Accurate and efficient simulation of airflows in human airways is critical for advancing the understanding of respiratory physiology, disease diagnostics, and inhalation drug delivery. Traditional computational fluid dynamics (CFD) provides detailed predictions but is often mesh-sensitive and computationally expensive for complex geometries. In this study, we explored the usage of physics-informed neural networks (PINNs) to simulate airflows in three geometries with increasing complexity: a duct, a simplified mouth–lung model, and a patient-specific upper airway. Key procedures to implement PINN training and testing were presented, including geometry preparation/scaling, boundary/constraint specification, training diagnostics, nondimensionalization, and inference mapping. Both the laminar PINN and SDF–mixing-length PINN were tested. PINN predictions were validated against high-fidelity CFD simulations to assess accuracy, efficiency, and generalization. The results demonstrated that nondimensionalization of the governing equations was essential to ensure training accuracy for respiratory flows at 1 m/s and above. Hessian-matrix-based diagnosis revealed a quick increase in training challenges with flow speed and geometrical complexity. Both the laminar and SDF–mixing-length PINNs achieved comparable accuracy to corresponding CFD predictions in the duct and simplified mouth–lung geometry. However, only the SDF–mixing-length PINN adequately captured flow details unique to respiratory morphology, such as obstruction-induced flow diversion, recirculating flows, and laryngeal jet decay. The results of this study highlight the potential of PINNs as a flexible alternative to conventional CFD for modeling respiratory airflows, with adaptability to patient-specific geometries and promising integration with static or real-time imaging (e.g., 4D CT/MRI). Full article

Additive manufacturing (AM) of polyetheretherketone (PEEK) offers a promising route for producing lightweight, biocompatible, and patient-specific medical implants with complex geometries. This study investigates and optimizes fused deposition modeling (FDM) parameters for fabricating small-scale PEEK medical components with improved dimensional accuracy and surface quality. PEEK’s high processing temperature and thermal contraction make precision printing of fine features challenging. A Taguchi design of experiments (L9 orthogonal array) was employed to assess the effects of nozzle temperature, layer height, printing speed, and extrusion width on dimensional deviation and surface roughness using 5 × 5 × 5 mm cube specimens. Dimensional accuracy was quantified along the horizontal and vertical axes, and surface roughness was measured using a stylus profilometer. Statistical analysis showed layer height was the most significant factor affecting horizontal accuracy (p = 0.0225), while printing speed most strongly influenced vertical deviation. The optimal parameters, 450 °C nozzle temperature, 0.06 mm layer height, 7.5 mm/s printing speed, and 0.4 mm extrusion width, achieved mean deviations of 0.013 mm (horizontal) and 0.049 mm (vertical) with a surface roughness of 4.01 µm. Validation using a benchmark model and micro-computed tomography confirmed improved reproduction of small features under these conditions. The results demonstrate that precise control of FDM parameters enables accurate fabrication of sub-millimeter PEEK structures suitable for medical device applications. Full article

Capillary-driven microfluidic chips have emerged as promising platforms for point-of-care diagnostics, offering portable, inexpensive, and pump-free operation. Accurate tracking of cell flow in these systems is vital for quantitative applications such as on-chip cytometry, cell counting, and biomechanical analysis. However, tracking in capillary-driven devices is challenging due to rapid cell displacements, flow instabilities, and visually similar cells. Under these conditions, conventional tracking algorithms such as TrackPy, TrackMate, SORT, and DeepSORT exhibit frequent identity switches and trajectory fragmentation. Here, we introduce FloCyT, a robust, high-speed centroid tracking tool specifically designed for capillary-driven and microfluidic flow. FloCyT leverages microchannel geometry for tracking and uses anisotropic gating for association, global flow-aware track initialisation, and channel-specific association. This enables precise tracking even under challenging conditions of capillary-driven flow. FloCyT was evaluated on 12 simulated and 4 real patient datasets using standard multi-object tracking metrics, including IDF1 and MOTA, ID switches, and the percentage of mostly tracked objects. The results demonstrate that FloCyT outperforms both standard and flow-aware-modified versions of TrackPy and SORT, achieving higher accuracy, more complete trajectories, and fewer identity switches. By enabling accurate and automated cell tracking in capillary-driven microfluidic devices, FloCyT enhances the quantitative sensing capability of image-based microfluidic diagnostics, supporting novel, low-cost, and portable cytometry applications. Full article

This study presents a computational framework for the topology optimization of a patient-specific femoral component used in the total knee endoprosthesis. The motivation stems from the growing need to enhance implant longevity and biomechanical compatibility by optimizing internal structural design according to physiological loading conditions. A finite element–based density optimization method was employed to determine the optimal material distribution within the femoral component while maintaining anatomical geometry and functional constraints. The model was developed using realistic boundary conditions derived from knee joint mechanics, and the resulting design was compared with a conventional reference geometry. The optimized configuration exhibited more uniform stress distribution, reduced peak von Mises stresses, and improved mass efficiency without compromising mechanical stiffness. These findings demonstrate that the proposed method can significantly improve the structural performance and reliability of knee prostheses. The study concludes that integrating patient-specific modeling with topology optimization offers a promising pathway for developing advanced, individualized orthopedic implants and supports future experimental validation through 3D printing and biomechanical testing. Full article

Mg-based alloys are one of the most promising materials used in regenerative medicine for bone tissue engineering. Considering the increasing prevalence of a continuously aging population, as well as the high incidence of accidents and bone cancers, it is crucial to explore biomaterials that can serve as bone substitutes. After carefully analyzing the literature in the introduction section, we proposed two Mg-based alloys as suitable for obtaining biodegradable structures for bone defect treatment. To achieve trustworthy results, the alloys’ microstructure was investigated using microscopic techniques coupled with energy-dispersive spectroscopy and X-ray diffraction. The obtained results were comparable with those described in references on similar Mg alloys. Then, the mechanical compression properties were highlighted, and the in vitro corrosion behavior proved that Mg-Zn exhibited a reduced corrosion rate compared to the Mg-Nd alloy, as tested using electrochemical methods. However, the in vivo tests showed good biocompatibility for both magnesium alloys. In conclusion, both alloys are suitable for use as potential bone substitute applications, but it must be taken into consideration that Mg-Zn alloys present lower biodegradation and mechanical properties. For future investigations, we aim to develop bone substitutes made from these materials, specifically designed for small bone defect treatment and with patient-adapted geometry. Due to the differences mentioned above, various designs will be tested. Full article

Background: Osteoid osteoma (OO) is a benign osteogenic tumor that causes severe pain despite its small size. Minimally invasive image-guided thermal ablation has replaced surgery as the treatment of choice. While radiofrequency ablation (RFA) is considered the gold standard, microwave ablation (MWA) offers faster and more homogeneous heating, though comparative evidence remains limited. Methods: We retrospectively analyzed 53 patients with OO treated with RFA (n = 27) or MWA (n = 26) between 2014 and 2023. All procedures were CT-guided. Technical success, clinical success, recurrence, complications, and prognostic factors—including the nidus diameter and eccentricity index—were evaluated over a minimum 24-month follow-up period. Results: Technical success was achieved in all cases. Overall clinical success was 94.3% (96.2% MWA vs. 92.6% RFA, p = 1.000). Two recurrences (4%) occurred, unrelated to device type. One major complication (1.9%, third-degree skin burn after MWA) was noted. Median nidus diameter was 7 mm; lesions ≥10 mm were significantly linked to failure (p = 0.009). Logistic regression identified nidus size as the strongest outcome predictor, with the eccentricity index showing a borderline effect. Conclusions: Both RFA and MWA are safe and effective for OO, with comparable outcomes and low recurrence rates. Treatment selection should prioritize lesion-specific factors—particularly nidus size ≥ 10 mm and geometry—rather than device type. Lesion size (≥10 mm) and geometry—not ablation modality—were the principal determinants of treatment success. Individualized modality selection based on these features may optimize outcomes. Full article

Biplane videoradiography (BVR) is the preferred 3D imaging modality for investigating the relationship between sub-millimeter knee kinematic abnormalities and posttraumatic osteoarthritis risk following anterior cruciate ligament (ACL) injury and surgery. Activity-specific BVR system geometries maximize BVR’s limited field of view which, in turn, influences downstream accuracy. The present work aimed to quantify the accuracy, bias, and precision of the reconstructed 3D tibiofemoral kinematics within a BVR system configured to capture the landing phase of a one-leg hop-for-distance activity. Radio-opaque beads were implanted into the femurs and tibiae of three cadaveric knees to provide the gold-standard kinematics. The specimens were moved through the BVR field of view simulating hop and drop landing motions such that the motion trajectories could better approximate dynamic in vivo velocities. The motions were tracked using both marker- and model-based methods. The mean absolute difference in kinematics between the two tracking methods was used to describe accuracy. Bland–Altman tests were used to quantify bias and precision. Kinematic accuracy ranged from 0.30 to 0.39° for rotations and from 0.34 to 0.50 mm for translations. The magnitudes of absolute difference, bias, and precision were similar regardless of the amount of soft tissue present or velocity of the simulated movement. Our results indicate that our approach for capturing BVR-derived kinematics for a one-leg hop-for-distance is sufficiently accurate to capture the magnitude of differences we expect to observe in a clinical population of ACL-reconstructed patients at long-term follow-up and will be useful to other investigators who may wish to record the hop-for-distance activity using the system geometry and image capture settings described here. Full article

Background and Clinical Significance: Tandem pathology at the dominant-hemisphere middle cerebral artery (MCA)—combining a wide-neck bifurcation aneurysm that shares the neck with both M2 origins and a short dorsal M1 fusiform dilation embedded in the lenticulostriate belt—compresses the therapeutic margin and complicates device-first pathways. We aimed to describe an anatomy-led, microscope-only sequence designed to secure an immediate branch-definitive result at the fork and to remodel dorsal M1 without perforator compromise, and to place these decisions within a pragmatic perioperative framework. Case Presentation: A 37-year-old right-handed man with reproducible, load-sensitive cortical association and capsulostriate signs underwent high-fidelity digital subtraction angiography (DSA) with 3D rotational reconstructions. Through a left pterional approach, vein-respecting Sylvian dissection achieved gravity relaxation. Reconstruction proceeded in sequence: a fenestrated straight clip across the bifurcation neck with the superior M2 encircled to preserve both M2 ostia, followed by a short longitudinal clip parallel to M1 to reshape the fusiform segment while keeping each lenticulostriate mouth visible and free. Temporary occlusion windows were brief (bifurcation 2 min 30 s; M1 < 2 min). No neuronavigation, intraoperative fluorescence, micro-Doppler, or intraoperative angiography was used. No perioperative antiplatelets or systemic anticoagulation were administered and venous thromboembolism prophylaxis followed institutional practice. The bifurcation dome collapsed immediately with round, mobile M2 orifices, and dorsal M1 regained near-cylindrical geometry with patent perforator ostia under direct inspection. Emergence was neurologically intact, headaches abated, and preoperative micro-asymmetries resolved without new deficits. The early course was uncomplicated. Non-contrast CT at three months showed structurally preserved dominant-hemisphere parenchyma without infarction or hemorrhage. Lumen confirmation was scheduled at 12 months. Conclusions: In dominant-hemisphere tandem MCA disease, staged, perforator-sparing clip reconstruction can restore physiologic branch and perforator behavior while avoiding prolonged antiplatelet exposure and device-related branch uncertainty. A future-facing pathway pairs subtle clinical latency metrics with high-fidelity angiography, reports outcomes in branch- and perforator-centric terms, and, where available, incorporates patient-specific hemodynamic simulation and noninvasive lumen surveillance to guide timing, technique, and follow-up. Full article

Background: The occurrence of ALL rupture during posterior correction of adult spinal deformity (ASD) was rare before the introduction of lateral lumbar interbody fusion (LLIF) but has become more frequent recently. It remains unclear whether this phenomenon is unique to LLIF-combined procedures or primarily related to enhanced corrective ability. Methods: The research method used in this study is finite element analysis (FEA). Using preoperative computed tomography images, LLIF cage (L group) or posterior lumbar interbody fusion (PLIF) cage (P group) were placed in the disc space with identical lordotic angles and distances from the anterior vertebral body edge for the same patients’ samples. Finite element simulations of corrective procedures were conducted. A spring simulating the ALL was introduced into the FEA, and the load on the ALL was evaluated with either LLIF or PLIF cage placement. Spring elongation directly measured the load on the ALL, while the location of the rotation center served as an indirect evaluation. Two different types of corrective procedures were created, one of which is mimicking ASD correction. For both procedures, the load to ALL was measured using abovementioned parameters when either LLIF cage (L group) or PLIF cage (P group) was used. The load to ALL was compared between L group and P group. Results: The degree of spring elongation during the simulation of a corrective procedure significantly decreased in the L group compared to the P group only in the model which is mimicking ASD correction (p = 0.006, Cohen’s d = 2.33, Power (1−β) = 0.956). The rotation center was significantly more posteriorly located in the P group than that in the L group in both models. These differences were more obvious in the model mimicking ASD correction (p = 0.0013, Cohen’s d = 2.00, Power (1−β) = 0.891). Conclusions: Our findings suggest that the use of a PLIF cage, which has a longer anterior–posterior cage length, caused the posterior edge of the cage to act as a pivot point. This configuration places greater leverage on the ALL, potentially leading to rupture during posterior correction procedures. This phenomenon, ALL rupture during posterior correction for ASD, is thought to be associated with increased corrective capabilities rather than being specific to the geometry of the LLIF cage. Full article

Background/Objective: Precise preprocedural planning is essential for the safety and efficacy of structural heart interventions. Conventional imaging modalities, while informative, do not allow for direct and accurate visualization, limiting procedural predictability. We aimed to develop and validate a high-resolution micro-computed tomography (microCT)-based reverse modeling workflow that integrates digital reconstructions of metallic cardiac devices into patient imaging datasets, enabling accurate, patient-specific virtual simulation for procedural planning. Methods: Clinical-grade transcatheter heart valves, septal defect occluders, patent ductus arteriosus occluders, left atrial appendage closure devices, and coronary stents were scanned using microCT (36.9 μm resolution). Agreement was assessed by intra-class correlation coefficients (ICC) and Bland–Altman analyses. Device geometries were reconstructed into 3D stereolithography files and virtually implanted within multislice CT datasets using dedicated software. Results: Devices were successfully reverse-modeled with high geometric fidelity, showing negligible dimensional deviations from manufacturer specifications (mean ΔDistance range: −0.20 to +0.20 mm). Simulated measurements demonstrated excellent concordance with postprocedural imaging (ICC 0.90–0.96). The workflow accurately predicted clinically relevant parameters such as valve-to-coronary distances and implantation depths. Notably, preprocedural simulation identified a case at high risk of coronary obstruction, confirmed clinically and managed successfully. Conclusions: The microCT-based reverse modeling workflow offers a rapid, reproducible, and clinically relevant method for patient-specific simulation in structural heart interventions. By preserving anatomical fidelity and providing detailed device–tissue spatial visualization, this approach enhances preprocedural planning accuracy, risk stratification, and procedural safety. Its resource-efficient digital nature facilitates broad adoption and iterative simulation. Full article

Background/Objectives: Screw loosening and vertebral fractures remain common after vertebral body tethering (VBT). Because tightening torque sets screw preload, its biomechanical effect warrants explicit modeling. In this paper, a Finite Element (FE) model, supported by ex vivo porcine vertebral tests, was developed and validated that incorporates torque-induced pre-tension to quantify vertebral stress, aiming toward customizable VBT planning. Methods: An FE model with pre-tension and axial extraction failure was parameterized using ex vivo tests on five porcine vertebrae. A laterally inserted surgical screw in each specimen was tightened to $5.9\pm 0.80$ Nm. Axial extraction produced failure loads of $2.1\pm 0.31$ kN. This is also considered in the FE model to validate the failure scenario. Results: Torque alone generated peak von Mises stresses of $16.1\pm 0.86$ MPa (cortical bone 1) and $2.1\pm 0.13$ MPa (trabecular), lower than prior reports. With added axial load, peaks rose to $141.1\pm 0.70$ MPa and $19.7\pm 0.23$ MPa, exceeding typical ranges. However, predicted failure agreed with experiments, showing $0.58$ mm displacement and a conical displacement distribution around the washer. Conclusions: Modeling torque-induced pre-tension is essential to reproduce realistic stress states and anchor failure in VBT. The framework enables patient-specific assessment (bone geometry/density) to recommend safe tightening torques, potentially reducing screw loosening and early fractures. Full article