Journal of Biomechanical Engineering-Transactions of the Asme最新文献

Multiscale coupling between cell-scale biology and tissue-scale mechanics is a promising approach for modeling disease growth. In such models, tissue-level growth and remodeling (G&R) are driven by cell-level signaling pathways and systems biology models, where each model operates at different scales. Herein, we generate multiscale G&R models to capture the associated multiscale connections. At the cell-scale, we consider systems biology models in the form of systems of ordinary differential equations (ODEs) and partial differential equations (PDEs) representing the reactions between the biochemicals causing the growth based on mass-action or logic-based Hill-type kinetics. At the tissue-scale, we employ kinematic growth in continuum frameworks. Two illustrative test problems (a tissue graft and aneurysm growth) are examined with various chemical signaling networks, boundary conditions, and mechano-chemical coupling strategies. We extend two open-source software frameworks-febio and fenics-to disseminate examples of multiscale growth and remodeling simulations. One-way and two-way coupling between the systems biology and the growth models are compared and the effect of biochemical diffusivity and ODE versus PDE-based systems biology modeling on the G&R results are studied. The results show that growth patterns emerge from reactions between biochemicals, the choice between ODEs and PDEs systems biology modeling, and the coupling strategy. Cross-verification confirms that results for febio and fenics are nearly identical. We hope that these open-source tools will support reproducibility and education within the biomechanics community.

This paper predicts the optimal motion for a repetitive lifting task considering muscle fatigue. The Denavit-Hartenberg (DH) representation is employed to characterize the two-dimensional (2D) digital human model with 10 degrees-of-freedom (DOFs). Two joint-based muscle fatigue models, i.e., a three-compartment controller (3CC) muscle fatigue model (validated for isometric tasks) and a four-compartment controller with augmented recovery (4CCr) muscle fatigue model (validated for dynamic tasks), are utilized to account for the fatigue effect due to the repetitive motion. The lifting problem is formulated mathematically as an optimization problem, with the objective of minimizing dynamic effort and joint acceleration subjected to both physical and task-specific constraints. The design variables include joint angle profiles, discretized by quartic B-splines, and the control points of the profiles of the fatigue compartments associated with major body joints (spinal, shoulder, elbow, hip, and knee joints). The outcomes of the simulation encompass profiles of joint angles, joint torques, and the advancement of joint fatigue. It is notable that the profiles of joint angles and torques exhibit distinct periodic patterns. Numerical simulations and experiments with a 20 kg box reveal that the maximum predicted lifting cycles are 11 for the 3CC fatigue model and 13 for the 4CCr fatigue model while the experimental result is 13 cycles. The results indicate that the 4CCr muscle fatigue model provides enhanced accuracy over the 3CC model for predicting task duration (number of cycles) of repetitive lifting.

Topological features of time-dependent, three-dimensional (3D) vector flow fields, such as wall shear stress (WSS) fixed points, are considered surrogates of pathological blood flow dynamics in cardiovascular diseases. Fixed-point visualizations are typically constrained to two-dimensional (2D) spaces, yet they aim to display complex spatiotemporal (four-dimensional (4D)) dynamics. There is a need for visualization strategies to reduce occlusion and reliance on animations to allow the detection of holistic flow patterns. Using intracranial aneurysms as a use case, we present the fixed-point carousel, a novel approach to visually depicting the "4D" nature of WSS fixed points via (1) topographic mapping of the 3D aneurysm sac to overcome occlusion while preserving fixed-point distances and sac morphological features; and (2) arranging these into a carousel model to present with temporal dimension holistically. Examples are presented for image-based computational fluid dynamic (CFD) models of intracranial aneurysms, illuminating the intricate and distinct fixed-point trajectories and interactions, a necessary step toward understanding the volumetric flow manifolds that drive them for this and other cardiovascular-and potentially nonbiomedical-fluid dynamics applications.

The Norwood procedure creates a reconstructed neo-aorta to provide unobstructed systemic cardiac output for hypoplastic left heart syndrome patients. We used patient-specific computational fluid dynamics (CFD) simulations incorporating physiologic boundary conditions to quantify hemodynamics for reconstructed aortic arch geometries versus native aortic arches from a control group of single ventricle patients. We hypothesized that reconstructed arches from Norwood patients (n = 5) would experience significant differences in time-averaged wall shear stress normalized to body surface area (TAWSSnBSA), oscillatory shear index (OSI), energy efficiency (Eeff), and energy loss (EL) versus controls (n = 3). CFD simulations were conducted using 3 T cardiac magnetic resonance imaging, blood flow, and pressure data. Simulations incorporated downstream vascular resistance and compliance to replicate patient physiology. TAWSSnBSA and OSI were quantified axially and circumferentially. Global differences in Eeff and EL were compared. Significance was assessed by Mann-Whitney U test. Norwood patients had higher TAWSSnBSA distal to the transverse arch at locations of residual narrowing presenting following coarctation correction, as well as higher OSI within ascending aorta and transverse arch regions (p < 0.05). EL correlated with patient features including cardiac output (r = 0.9) and BT-shunt resistance (r = -0.63) but did not correlate with arch measurements or morphology. These results indicate reconstructed arches from Norwood patients are exposed to altered wall shear stress and energy indices linked to cellular proliferation and inefficiency in prior studies. These results may help clinicians further understand what constitutes an optimally reconstructed arch after confirmation in larger studies.

A lumbar spine statistical shape model (SSM) was developed to explain morphological differences in a population with adolescent idiopathic scoliosis (AIS). Computed tomography (CT) was used to collect data on the lumbar spine vertebrae and curvature of 49 subjects. The CT data were processed by segmentation, landmark identification, and template mesh mapping, and then SSMs of the individual vertebrae and entire lumbar spine were established using generalized Procrustes analysis and principal component analysis (PCA). Scaling was the most prevalent variation pattern. The weight coefficient was optimized using the Levenberg-Marquardt (LM) algorithm, and multiple regression analysis was used to establish a prediction model for age, sex, height, and body mass index (BMI). The effectiveness of the SSM and prediction model was quantified based on the root-mean-square error (RMSE). An automatic measurement method was developed to measure the anatomical parameters of the geometric model. The lumbar vertebrae size was significantly affected by height, sex, BMI, and age, with men having lower vertebral height than women. The trends in anatomical parameters were consistent with previous studies. The vertebral SSMs characterized the shape changes in the processes, while the lumbar spine SSM described alignment changes associated with translatory shifts, kyphosis, and scoliosis. Quantifying anatomical variation with SSMs can inform implant design and assist clinicians in diagnosing pathology and screening patients. Lumbar spine SSMs can also support biomechanical simulations of populations with AIS.

Evaluation of patients with neck pain often relies on end-range flexion and extension radiographs that do not capture mid-range or multiplanar motion. The purpose of this study was to determine if end-range flexion/extension range of motion (ROM) predicts axial rotation ROM or mid-range ROM during either flexion/extension or axial rotation in patients with neck pain or in asymptomatic controls. It was hypothesized that end-range flexion/extension ROM would predict mid-range flexion/extension ROM, but not mid-range or end-range axial rotation ROM. Dynamic flexion/extension and axial rotation were performed by 75 patients prior to surgery and 71 asymptomatic controls, while synchronized biplane radiographs were collected at 30 images per second. Intervertebral motion from C2 to C7 was tracked using a validated volumetric model-based tracking process that matched subject-specific computed tomography (CT)-based bone models to the radiographs. The main findings were that intervertebral end-range flexion/extension ROM is a strong to very strong predictor of mid-range flexion/extension at all subaxial motion segments of the cervical spine (all r = 0.61 to 0.91), but, in general, a weak to moderate predictor of axial rotation mid-range (all ρ = 0.002 to 0.50) and end-range (all r = 0.2 to 0.68) ROM. This study suggests that the current standard of care end-range flexion/extension ROM is not sufficient to characterize the multiplanar motion that occurs in the cervical spine during activities of daily living.

Although diabetes is associated with alterations in the structural and functional properties of soft tissue, the response of the human Achilles tendon to location-dependent variations in both quasi-static and dynamic loading is unclear. This study aimed to characterize the elastic, viscoelastic, hysteresis, and failure properties of the distal, midsubstance, and proximal Achilles tendons in diabetic and nondiabetic patients and to investigate the relationship between biomechanical and clinical observations. Tendons were obtained from patients who underwent above- or below-knee amputation. Dumbbell-shaped specimens were harvested from the three sites. Relaxation tests were performed to determine viscoelastic characteristics. Cyclic loading tests at various frequencies were deployed to determine the dynamic modulus and phase angles. Incremental cyclic loading tests were carried out to investigate the backbone curve and energy dissipation due to hysteresis. Additionally, monotonic loading tests were performed to determine the elastic and failure properties. The results show that biomechanical parameters are not significantly different among the three sites. However, the midsubstance site exhibits significantly higher energy dissipation compared to other sites. Additionally, an increase in cyclic frequency enhances the phase angle, indicating that higher energy dissipation may protect the tendon from high loading rates. Furthermore, an increase in body mass index (BMI) and hemoglobin A1c (HbA1c) is significantly and negatively correlated with stiffness and viscoelasticity, suggesting that improving metabolic health may prevent tendon impairment. These findings may assist in creating more effective therapeutic strategies for tendon repair.

Given the increasing complexity of revision total hip arthroplasty, ensuring optimal stability of acetabular revision cups (ARCs) is crucial, especially in cases of bone stock loss. In this study, the primary stability of ARCs was investigated by modeling various configurations of screw placements, including all standard, all locking, and mixed setups, under different load scenarios. Finite element (FE) models were implemented to evaluate the stress distribution and micromotions at the bone-prosthesis interface, simulating three primary load cases: "walking," "stairs-down," and "stand-up." The results indicated that the stairs-down load case generated the highest von Mises stresses and sliding distances, marking it as the most critical load scenario. Configurations using all standard screws showed higher peak stresses and reduced stable areas, compared to those utilizing locking screws. While the locking screws provided a stiffer connection, the mixed screw configuration offered a balanced performance by combining the compression benefits of standard screws with the rigid fixation of locking screws. Configurations with a single standard screw complemented by locking screws showed enhanced stability, suggesting this combination could be advantageous in clinical applications. This study underscores the importance of screw type and placement in ensuring the primary stability of ARCs. Locking screws are recommended for use when feasible. For ARCs allowing both screw types, a mixed configuration starting with a standard compression screw followed by locking screws appears optimal. Future research should further explore various combinations of screw geometries and lengths to refine these findings and enhance surgical outcomes in acetabular revisions.

This study measured the strain response to intraocular pressure (IOP) change in the sclera, choroid, and retina of glaucoma patients whose optic nerve head region was imaged by optical coherence tomography (OCT) before and after IOP-lowering by laser suturelysis following trabeculectomy surgery. The strain response was calculated from digital volume correlation of the prior and after images. The strain response of the sclera, choroid, and retina were compared to those previously published for the anterior lamina cribrosa (ALC). Mean strains were lowest in the retina and highest in the prelaminar neural tissue (PLNT). Maximum principal and maximum shear strains were significantly increased with greater IOP decrease in all five eye regions. Maximum principal and maximum shear strains in the anterior lamina cribrosa and the sclera were significantly related (p = 0.0094). Strain in the radial direction was negative in the ALC and PLNT, but positive in the sclera (p = 0.017). In conclusion, the strain response of the sclera, choroid, and retina is related to the magnitude of IOP change and is smaller than those of the ALC. The strain response of the ALC and sclera are significantly related to each other.

Total talar replacement (TTR) with an additively manufactured personalized total talar prosthesis (TTP) is an emerging treatment for ankle disorders. However, how to enhance the ankle stability after TTR, which usually raises the ankle instability, has not been explored. This study constructed a set of specific numerical models to investigate the effects of TTR and oversized TTPs on the ankle stability, including inversion, eversion, and anterior stability. The oversized TTPs include TTP-FP1.5 and TTP-FP3 scaled the identical TTP0 by 1.5% and 3.0% along the frontal axis, and TTP-VP1.5 and TTP-VP3 scaled TTP0 by 1.5% and 3.0% along the vertical axis. The numerical results identify that under varus/valgus force, the TTP-FP1.5 and TTP-FP3 produce smaller talar tilt angles compared with that of TTP0, as the inversion and eversion stability are significantly enhanced. Furthermore, TTP-VP1.5 and TTP-VP3 can provide larger contact force to the tibia, providing better anterior stability under anterior drawer force. Additionally, the increased contact force of TTP-VP1.5 and TTP-VP3 with the tibial cartilage enhances the eversion stability. Besides, the increase of TTP size along the vertical axis will weaken the inversion stability under low loads, as this scaling might have compromised the stability of the subtalar joint. The present numerical study systematically investigates the effect of different ways of increasing TTP size on ankle stability after TTP.