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

Multidirectional load transmission ability by annulus fibrosus (AF) requires substantial mechanical stability. Additionally, AF exhibits a unique biochemical concentration gradient with outer AF (OA) dominated by type I collagen (COL-I) and inner AF dominated by type II collagen (COL-II) with higher water and proteoglycan concentration. This indicates an intricate relationship between biochemistry and mechanical stability, which remains unclear. This study uses molecular dynamics (MD) simulations to investigate the impact of water, COL-I and COL-II, concentration gradients on mechanical stability of AF's collagen-hyaluronan (COL-HYL) nano-interfaces during tensile and compressive deformation. For this, COL-HYL atomistic models are created by increasing COL-II concentrations from 0% to 75% and water from 65% to 75%. Additional tensile and compressive deformation simulations are conducted for COL-I-HYL interface (COL-HYL interfaces with 0% COL-II) by increasing water concentration from 65% to 75% to segregate the effects of increasing water concentration alone. Results show that increasing water concentration alone to 75% results in marginal changes in local hydration indicating increase in bulk water. This enhances HYL and COL segment sliding-leading to reduction in mechanical stability in tension, indicated by drop in stress-strain characteristics. Additionally, increase in bulk water shifts load-bearing characteristics toward water-leading to reduction in modulus from 3.7 GPa to 1.9 GPa. Conversely, increasing COL-II and water concentration facilitates stable water bridge formation which impedes sliding in HYL and COL-enhancing mechanical stability. These water bridges further improve compressive load sustenance leading to lower reduction in compressive modulus from 3.7 GPa to 2.8 GPa.

High tibial osteotomy is a common procedure for knee osteoarthritis during which the surgeon partially opens the tibia and must stop impacting when cortical bone is reached by the osteotome. Surgeons rely on their proprioception and fluoroscopy to conduct the surgery. Our group has developed an instrumented hammer to assess the mechanical properties of the material surrounding the osteotome tip. The aim of this ex vivo study is to determine whether this hammer can be used to detect the transition from cortical to trabecular bone and vice versa. Osteotomies were performed until rupture in pig tibia using the instrumented hammer. An algorithm was developed to detect both transitions based on the relative variation of an indicator derived from the time variation of the force. The detection by the algorithm of both transitions was compared with the position of the osteotome measured with a video camera and with surgeon proprioception. The difference between the detection of the video and the algorithm (respectively, the video and the surgeon; the surgeon and the algorithm) is 1.0±1.5 impacts (respectively, 0.5±0.6 impacts; 1.4±1.8 impacts), for the detection of the transition from the cortical to trabecular bone. For the transition from the trabecular to cortical bone, the difference is 3.6±2.6 impacts (respectively, 3.9±2.4 impacts; 0.8±0.9 impacts), and the detection by the algorithm was always done before the sample rupture. This ex vivo study demonstrates that this method could prevent impacts leading to hinge rupture.

Ultrasonically assisted cutting (UAC), a process characterized by high-performance material removal and enhanced surface finish, is widely employed in orthopedic surgery. However, variability in the mechanical properties of cortical bone may lead to unstable fractures and fluctuating cutting force during material removal, particularly under high-frequency vibration cutting. This study introduces a transient shear strength model that utilizes strain rate fluctuations to estimate cutting forces in the UAC process. The impact of varying osteon orientations and strain rate ranges on the yield strength of cortical bone is analyzed to elucidate changes in its mechanical properties under UAC conditions. Additionally, strain rates from conventional cutting (CC) and UAC, measured through digital image correlation (DIC), are compared with model predictions. The results demonstrate that the proposed model accurately predicts cutting forces and associated changes in thrust. This research offers a fresh insight into the dynamics of fluctuating forces during UAC, potentially inspiring advancements in orthopedic surgical instruments.

This paper presents a novel hip trajectory error (HTE) framework for designing prosthetic feet specifically for people with an above-knee amputation. Finding a high-performance prosthetic foot for people with an above-knee amputation can greatly improve mobility and prosthesis satisfaction of a user and provide a predictable interaction with the knee prosthesis. The HTE framework accounts for the lack of early and midstance knee flexion, a common gait deviation in people with above-knee amputation compared to people with a below-knee amputation and able-bodied subjects. The goal of the HTE framework is to design prosthetic feet that closely replicate able-bodied hip motion, a kinematic target that is correlated with sufficient shock absorption lost due to the lack of knee flexion during early and midstance. This paper presents a design process to optimize HTE prosthetic feet and shows that the performance of the foot is not constrained by ankle height determined by the prosthetic knee choice. In simulation, HTE feet also demonstrate a closer replication of able-bodied hip motion compared to lower leg trajectory error framework, which designs prosthetic feet specifically for people with a below-knee amputation. The HTE framework may provide the above-knee amputee population around the world with high-performance prosthetic feet designed specifically for their needs, which could improve the overall function of the prosthetic limb and user satisfaction.

A systematic literature search and meta-analysis were performed to evaluate the variability in biomechanical testing of murine long bones, specifically focused on point-bending tests of mice femora. Due to the lack of standardized protocols for these tests, the assessment quantifies the heterogeneity in reported mechanical properties across existing literature. This study followed preferred reporting items for systematic reviews and meta-analyses (PRISMA) and strengthening the reporting of observational studies in epidemiology (STROBE) guidelines to search publicly available databases for relevant studies. After title and abstract screening, full-text reviews identified 73 articles meeting the inclusion criteria. Data was extracted from these studies, including stiffness, maximum load, modulus, and ultimate stress values for both three-point and four-point bending tests. The data were analyzed through ANOVA and metaregression to assess variability caused by age, sex, and genetic strain. The reviewers also assessed the quality of the included studies. The meta-analysis revealed significant heterogeneity in reported mechanical properties, with I2 values ranging from 72% to 100% in the three point-bend tests of pooled genetic strains. This heterogeneity persisted even after accounting for age, sex, and genetic strain differences. The review concludes that nonstandardized testing setups are the likely major source of the observed variability in reported data more than the population characteristics of the mice, highlighting the need for more consistent testing methodologies in future studies.

The periprosthetic acetabular osteotomy (PAO) is a commonly used technique in orthopedics for treating developmental hip dysplasia and hip dislocation, as the most effective treatment for developmental dysplasia of the hip (DDH). However, performing PAO can be challenging for surgeons due to limited visibility and difficulty in detecting any deformations of osteotome chisels when they are deeply immersed in the pelvis. These challenges can result in serious complications, such as excessive bleeding and nerve injuries. We propose a novel precision tracking system to mitigate these risks by acquiring the chisel deformation in real-time. This system consists of a newly designed osteotome chisel with five built-in microsensors, which are finely chosen with the help of Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). We propose a fast finite element method (FFEM) model to calculate the deformation of the chisel from flexibility information collected by these five sensors, where the model deformation can be predicted from a well-designed light deep neural network (DNN) model. Our model has achieved an impressive R2 value of 0.98781 and an average deformation error of only 0.07 mm in nodes compared to the experiment. The prediction time of FFEM model has been shortened to 0.33 s, and the total time including three-dimensional reconstruction and visualization has been shortened to 3.84 s. Implementing such an osteotome chisel with a deformation tracking system has shown immense potential in increasing surgical accuracy and reducing medical negligence for PAO operations.

The geometry and motility of the stomach play a critical role in the digestion of ingested liquid meals. Sleeve gastrectomy, a common type of bariatric surgery used to reduce the size of the stomach, significantly alters the stomach's anatomy and motility, which impacts gastric emptying and digestion. In this study, we use an imaging data-based computational model, StomachSim, to investigate the consequences of sleeve gastrectomy. The pre-operative stomach anatomy was derived from imaging data, and the postsleeve gastrectomy shapes were generated for different resection volumes. We investigate the effect of sleeve sizes and motility patterns on gastric mixing and emptying. Simulations were conducted using an immersed-boundary flow solver, modeling a liquid meal to analyze changes in gastric mixing and emptying rates. The results reveal that different degrees of volume reduction and impaired gastric motility have complex effects on stomach's mixing and emptying functions, which are important factors in gastric health of the patient. Specifically, the total gastric liquid emptying rates increased by 21% with a 30% volume reduction and by 51% with reductions exceeding 50%, due to altered intragastric pressure. Additionally, impaired motility functions resulted in slower mixing, leading to delayed food emptying. These findings provide insights into the biomechanical effects of sleeve gastrectomy on gastric digestion and emptying functions, highlighting the potential of computational models to inform surgical planning and postoperative management.

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.