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

The optic nerve head (ONH) is subjected to both intra-ocular pressure (IOP) and intracranial pressure (ICP). The translaminar pressure difference (TLPD) is defined as the difference between IOP and ICP. A change in TLPD, whether from changes in IOP or ICP, could subject the lamina cribrosa (LC) to altered deformation, potentially damaging the axons, activating the mechanosensitive glial cells, and promoting remodeling of the connective tissue structures in the ONH. In this study, we applied spectral domain optical coherence tomography (SD-OCT) and digital volume correlation (DVC) to calculate the deformation response of the LC in 7 eyes of 7 patients with normal pressure hydrocephalus (NPH). Radial SD-OCT scans centered on the ONH were acquired prior to and after therapeutic extended cerebrospinal fluid (CSF) drainage. IOP was measured immediately before imaging, and ICP was measured at the beginning and end of the drainage procedure. The procedure led to a mean ICP decrease of 11.24±1.84 mmHg and a small, nonsignificant mean IOP increase of 0.67±2.56 mmHg. ICP lowering produced a significant Ezz=-0.50%±0.47%, Err=0.53%±0.48%, and Eθz=0.35%±0.21% (p≤0.031). A larger compressive Ezz was associated with a larger ICP decrease (p=0.007). Larger Err, Erθ, maximum principal strain, Emax and maximum shear strain, Smax in the plane of the radial scans were associated with a larger increase in a calculated TLPD change (p≤0.035).

Interlobar sliding has long been suspected to help the lungs adapt to changes in thoracic cavity shape by reducing parenchymal distortion. Our previous controlled computational experiment tested the hypothesis that lung lobar sliding reduces parenchymal distortion during breathing, but only the left lung was studied. The goal of this study was to extend this analysis to the right lung which has three lobes and two fissures compared to the left lung's two lobes and single fissure. Finite elastic contact mechanics models of the right lung were used to perform paired subject-specific simulations of lung deformation with and without lobar sliding from end inhale to end exhale at both tidal breathing volumes (n = 8) and breath hold volumes near total lung capacity and functional residual capacity (n = 6). Consistent with the hypothesis, we found that parenchymal distortion, quantified with the spatial mean of the anisotropic deformation index (ADI) throughout each lung model, was lesser in the models with lobar sliding than their nonsliding counterparts (p = 0.008, 13% median difference for tidal breathing and p = 0.03, 19.6% median difference for breath holds). This effect was several times larger than was previously observed in the left lung (p = 0.008, 5.3% median difference for tidal breathing and p = 0.03, 3.2% median difference for breath holds), likely due to the greater number of sliding interfaces in the right lung than the left which better allow the right lung to adapt to the thoracic cavity.

Robot-assisted gait rehabilitation is an increasingly common therapeutic intervention for enhancing locomotion and improving quality of life for children with lower-limb mobility impairments. However, there are few systems specifically designed for pediatric use, and those that do exist are largely cumbersome, bulky, and noncustom devices that ultimately reduce therapy effectiveness. This paper introduces the Cable-Driven Joint System (CDJS), a novel approach for pediatric gait rehabilitation that addresses these shortcomings in a lightweight and compact robotic device using the patient's professionally fitted orthosis. The CDJS consists of a 2.1 kg actuation unit that is held by a clinician which delivers assistive torques through a Bowden cable transmission to a 0.3 kg joint mounted to user-custom bracing. This work details an actuator benchtop evaluation, demonstrating a peak torque of 20 N·m, peak velocity of 7.2 rad/s, bandwidth of 9.7 Hz, and a mass moment of inertia of 58.38 kg cm2. An actuator model was developed and evaluated in simulation, showing a strong correlation with the experimental torque data (R-squared = 0.95) and indicating a transmission efficiency of 72%. In-air gait tracking experiments on an emulated subject showed that the CDJS assisted the subject to track a nominal knee trajectory with an average root-mean-squared error of 2.56 deg at a continuous torque of 1.37 N·m. These results suggest that the cable-driven actuator meets the design requirements for use in pediatric gait rehabilitation and is ready for implementation in clinical device trials.

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.