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

Total knee replacement (TKR) failure, low patient satisfaction and high revision surgery rates may stem from insufficient preclinical testing. Conventional joint motion simulators for preclinical testing of TKR implants manipulate a knee joint in force, displacement, or simulated muscle control. However, a rig capable of using all three control modes has yet to be described in literature. This study aimed to validate a novel platform, the muscle actuator system (MAS), that can generate gravity-dependent, quadriceps-controlled squatting motions representative of an Oxford rig knee simulator and is mounted onto a force/displacement-control-capable joint motion simulator. Synthetic knee joint phantoms were created that comprised revision TKR implants and key extensor and flexor mechanism analogues, but no ligaments. The combined system implemented a constant force vector acting from simulated hip-to-ankle coordinates, effectively replicating gravity as observed in an Oxford rig. Quadriceps forces and patellofemoral joint kinematics were measured to assess the performance of the MAS and these tests showed high levels of repeatability and reproducibility. Forces and kinematics measured at a nominal patellar tendon length, and with patella alta and baja, were compared against those measured under the same conditions using a conventional Oxford rig, the Pennsylvania State Knee Simulator (PSKS). There was disagreement in absolute kinematics and muscle forces, but similar trends resulting from changing prosthesis design or patellar tendon length.

Achilles tendon overuse injuries are common for long-distance runners. Ankle exos (exoskeletons and exosuits) are wearable devices that can reduce Achilles tendon loading and could potentially aid in the rehabilitation or prevention of these injuries by helping to mitigate and control tissue loading. However, most ankle exos are confined to controlled lab testing and are not practical to use in real-world running. Here, we present the design of an unpowered ankle exo aimed at reducing the load on the Achilles tendon during running while also overcoming key usability challenges for runners outside the lab. We fabricated a 500-gram ankle exo prototype that attaches to the outside of a running shoe. We then evaluated the reliability, acceptability, transparency during swing phase, and offloading assistance provided during treadmill and outdoor running tests. We found that the exo prototype reliably assisted 95-99% of running steps during indoor and outdoor tests, was deemed acceptable by more than 80% of runners in terms of comfort and feel, and did not impede natural ankle dorsiflexion during leg swing for 86% of runners. During indoor tests, the exo reduced peak Achilles tendon loads for most participants during running; however, reductions varied considerably, between near zero and 12%, depending on the participant, condition (speed and slope) and the precise tendon load metric used. This next-generation ankle exo concept could open new possibilities for longitudinal and real-world research on runners, or when transitioning into the return-to-sport phase after an Achilles tendon injury.

Measurement of internal intervertebral disc strain is paramount for understanding the underlying mechanisms of injury and validating computational models. Although advancements in noninvasive imaging and image processing have made it possible to quantify strain, they often rely on visual markers that alter tissue mechanics and are limited to static testing that is not reflective of physiologic loading conditions. The purpose of this study was to integrate high-frequency ultrasound and texture correlation to quantify disc strain during dynamic loading. We acquired ultrasound images of the posterior side of bovine discs in the transverse plane throughout 0-0.5 mm of assigned axial compression at 0.3-0.5 Hz. Internal Green-Lagrangian strains were quantified across time using direct deformation estimation (DDE), a texture correlation method. Median principal strain at maximal compression was 0.038±0.011 for E1 and -0.042±0.012 for E2. Strain distributions were heterogeneous throughout the discs, with higher strains noted near the disc endplates. This methodological report shows that high-frequency ultrasound can be a valuable tool for quantification of disc strain under dynamic loading conditions. Further work will be needed to determine if diseased or damaged discs reveal similar strain patterns, opening the possibility of clinical use in patients with disc disease.

Lipid-rich atheromas are linked to plaque rupture in stented atherosclerotic arteries. While fibrous cap thickness is acknowledged as a critical indicator of vulnerability, it is likely that other morphological features also exert influence. However, detailed quantifications of their contributions and intertwined effects in stenting are lacking. Therefore, our goal is to assess the impact of plaque characteristics on the fibrous cap stress and elucidate their underlying mechanisms. We analyzed the stent deployment in a three-dimensional patient-specific coronary artery reconstructed from intravascular optical coherence tomography (IVOCT) data using the finite element method. Additionally, we performed sensitivity analysis on 78,000 distinct plaque geometries of two-dimensional arterial cross section for verification. Results from the three-dimensional patient-specific model indicate strong correlations between maximum fibrous cap stress and lipid arc (r=0.769), area stenosis (r=0.550), and lumen curvature (r=0.642). Plaques with lipid arcs >60 deg, area stenosis >75%, and lumen curvatures >5 mm-1 are at rupture risk. While we observed a rise in stress with thicker lipid cores, it was less representative than other features. Fibrous cap thickness showed a poor correlation, with the sensitivity analysis revealing its significance only when high stretches are induced by other features, likely due to its J-shaped stress-stretch response. Contrary to physiological pressure, the stent expansion generates unique vulnerable features as the stent load-transferring characteristics modify the plaque's response. This study is expected to prompt further clinical investigations of other morphological features for predicting plaque rupture in stenting.

Community ambulation is essential for maintaining a healthy lifestyle, but it poses significant challenges for individuals with limb loss due to complex task demands. In wearable robotics, particularly powered prostheses, there is a critical need to accurately estimate environmental context, such as walking speed and slope, to offer intuitive and seamless assistance during varied ambulation tasks. We developed a user-independent and multicontext, intent recognition system that was deployed in real-time on an Open Source Leg (OSL). We recruited 11 individuals with transfemoral amputation, with seven participants used for real-time validation. Our findings revealed two main conclusions: (1) the user-independent (IND) performance across speed and slope was not statistically different from user-dependent (DEP) models in real-time and did not degrade compared to its offline counterparts, and (2) IND walking speed estimates showed ∼0.09 m/s mean absolute error (MAE) and slope estimates showed ∼0.95 deg MAE across multicontext scenarios. Additionally, we provide an open-source dataset to facilitate further research in accurately estimating speed and slope using an IND approach in real-world walking tasks on a powered prosthesis.

This study investigated the effect of collagen fiber tortuosity distribution on the biomechanical failure and prefailure properties of arterial wall tissue. An in-silico model of the arterial wall was developed using data obtained from combined multiphoton microscopy imaging and uni-axial tensile testing. Layer-dependent properties were prescribed for collagen, elastin, and ground substance. Collagen fibers were modeled as discrete anisotropic elements, while elastin and ground substance were modeled as homogeneous isotropic components. Our parametric analysis, using a finite element approach, revealed that different parameters of collagen fibers tortuosity distribution significantly influence both prefailure and failure biomechanical properties. Increased fiber tortuosity improved the tissue strength whereas the dispersion in the tortuosity distribution reduced it. This study provides novel insights into the structural-mechanical interdependencies in arterial walls, offering potential targets for clinical assessments and therapeutic interventions aimed at mitigating rupture risks.

The aim of this work is to improve musculoskeletal-based models of the upper-limb wrench feasible set (WFS), i.e., the set of achievable maximal wrenches at the hand for applications in collaborative robotics and computer aided ergonomics. In particular, a recent method performing wrench capacity evaluation called the iterative convex hull method (ICHM) is upgraded in order to integrate nondislocation and compression limitation constraints at the glenohumeral (GH) joint not taken into account in the available models. Their effects on the amplitude of the force capacities at the hand, glenohumeral joint reaction forces and upper-limb muscles coordination in comparison to the original iterative convex hull method are investigated in silico. The results highlight the glenohumeral potential dislocation for the majority of elements of the wrench feasible set with the original iterative convex hull method and the fact that the modifications satisfy correctly stability constraints at the glenohumeral joint. Also, the induced muscles coordination pattern favors the action of stabilizing muscles, in particular the rotator-cuff muscles, and lowers that of known potential destabilizing ones according to the literature.

Capillary refill time (CRT) is a widely used noninvasive measure of cardiovascular health. Despite its widespread diagnostic utility, it has several limitations, particularly its low sensitivity for certain conditions, because factors such as the contraction and relaxation of distal blood vessels can influence CRT readings. This study was performed to explore the relationships between CRT and distal blood flow. The right hand of each of ten healthy adult volunteers was cooled to induce blood vessel contraction. CRT, fingertip temperature, and blood flowrate were measured using a custom device, a thermometer, and a laser Doppler blood flowmeter, respectively, before and after cooling. Hand cooling significantly decreased blood flowrate and increased CRT. A robust inverse correlation was observed between blood flowrate and CRT, supporting a model where CRT is the time required for blood to flow through a cylindrical pipe. Furthermore, CRT showed a significant negative correlation with fingertip temperature. Most participants had high correlation coefficients, although two showed lower values. However, all data points exhibited a linear relationship, with the slopes of the regression lines between CRT and temperature varying among participants. These results suggested that the slope between CRT and fingertip temperature indicates individual differences in arterial contractility. These findings could improve the diagnostic utility of CRT in assessing vascular health, including arterial age and Raynaud's phenomenon, based on the contractility of peripheral arteries.

The interlamellar matrix (ILM), located between the annular layers of the intervertebral disc (IVD), is an adhesive component which acts to resist delamination. Investigating the mechanical properties of the ILM can provide us with valuable information regarding risk of disc injury; however given its viscoelastic nature, it may be necessary to conduct preconditioning on tissue samples before measuring these ILM properties. Therefore, the aim of this study was to optimize mechanical testing protocols of the ILM by examining the effect of preconditioning on stiffness and strength of this adhesive matrix. Eighty-eight annular samples were dissected from 22 porcine cervical discs and randomized into one of four testing conditions consisting of ten cycles of 15% strain followed by a 180 deg adhesive peel test. The four testing groups employed a different strain rate for the ten cycles of preconditioning: 0.01 mm/s (n = 23); 0.1 mm/s (n = 26); 1 mm/s (n = 23); and no preconditioning employed (n = 16). Samples preconditioned at 0.01 mm/s were significantly less stiff than those that had not received preconditioning (p = 0.014). No other results were found to be statistically significant. Given the lack of differences observed in this study, preconditioning is likely not necessary prior to conducting a 180 deg peel test. However, if preconditioning is employed, the findings from this study suggest avoiding preconditioning conducted at very slow rates (i.e., 0.01 mm/s) as the long testing time may negatively affect the tissue.

Sickle cell disease (SCD) is a genetic condition characterized by an abundance of sickle hemoglobin in red blood cells. SCD patients are more prone to intracranial aneurysms (ICA) compared to the general population, with distinctive features such as multiple intracranial aneurysms: 66% of SCD patients with ICAs have multiples ICAs, compared to 20% in nonsickle patients. The exact mechanism behind these associations is not fully understood, but there is a hypothesized link between hypoxic conditions in blood vessels and impaired synthesis of extracellular matrix, which may weaken the vessel walls, favoring aneurysm formation and rupture. SCD patients experience reduced oxygen levels in their blood, potentially exacerbating hypoxia in intracranial aneurysms, and potentially creating a feedback loop that could contribute to aneurysm development and early onset in these patients. In this work, we performed a series of computational studies (Fluent) using idealized geometries to investigate the key differences in the oxygen transport and blood flow dynamics inside an aneurysm formation for sickle and nonsickle cases. We found that using sickle cell disease parameters resulted in a 14% to 68% reduction in blood flow and a 37% to 70% reduction in oxygen availability within the aneurysm, depending on the vessel curvature and the aneurysm throat diameter, due to factors including oxygen-dependent viscosity and alteration in the oxygen transport. The results indicate that depending on geometry and flow characteristics, some degree of hypoxia maybe present in aneurysm bulb and would be more severe in sickle-cell disease patients. This study hopes to bring into attention the potential presence of hypoxic environment in the aneurysm bulb.