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

Despite the increasing use of inertial measurement units (IMUs) and machine learning techniques for gait analysis, there remains a gap in which feature selection methods are best tailored for gait time series prediction. This study explores the impact of using various feature selection methods on the performance of a random forest (RF) model in predicting lower limb joints kinematics from two IMUs. The primary objectives of this study are as follows: (1) Comparing eight feature selection methods based on their ability to identify more robust feature sets, time efficiency, and impact on RF models' performance, and (2) assessing the performance of RF models using generalized feature sets on a new dataset. Twenty-three typically developed (TD) children (ages 6-15) participated in data collection involving optical motion capture (OMC) and IMUs. Joint kinematics were computed using opensim. By employing eight feature selection methods (four filter and four embedded methods), the study identified 30 important features for each target. These selected features were used to develop personalized and generalized RF models to predict lower limbs joints kinematics during gait. This study reveals that various feature selection methods have a minimal impact on the performance of personalized and generalized RF models. However, the RF and mutual information (MI) methods provided slightly lower errors and outliers. MI demonstrated remarkable robustness by consistently identifying the most common features across different participants. ElasticNet emerged as the fastest method. Overall, the study illuminated the robustness of RF models in predicting joint kinematics during gait in children, showcasing consistent performance across various feature selection methods.

Due to individual differences, accurate identification of tissue elastic parameters is essential for biomechanical modeling in surgical guidance for hepatic venous injections. This paper aims to acquire the absolute Young's modulus of heterogeneous soft tissues during endoscopic surgery with two-dimensional (2D) ultrasound images. First, we introduced a force-sensor-less approach that utilizes a precalibrated soft patch with a known Young's modulus and its ultrasound images to calculate the external forces exerted by the probe on the tissue. Second, we introduced a Kriging-based inverse algorithm to identify the relative Young's modulus (RYM) between the inclusion and the background tissue. The RYM was estimated based on 2D plane strain approximation and mapped to the RYM of three-dimensional (3D) soft tissue through a trained Kriging model. Finally, we developed a direct method to identify the background Young's modulus (BYM) based on calculated external forces and RYM. The simulation results demonstrate the high efficiency and robustness of the Kriging-based inverse algorithm in identifying RYM. Physical experiments on the three phantoms show that the errors of the identified BYM and RYM are all below 15%. The proposed methodology for Young's modulus identification is feasible and achieves satisfactory accuracy and computational efficiency in both simulations and physical experiments.

Hemodynamic variations influence the location of entry tears in aortic dissection. This study investigates whether variations in tear strength across the human aorta contribute to these clinical manifestations. Circumferential and axial strips were collected from nine axial and two circumferential sites along each autopsied aorta, yielding 1188 samples (11 aortas × 18 sites × 2 directions × 3 layers per site). These samples underwent tear testing to assess tear strength and tear energy, constituting resistance to tear propagation. Adventitial tear parameters were significantly higher than those of the intima and media, with no significant differences between the latter two, supporting the observation that entry tears typically occur in the inner wall. Tear propagation angles were approximately 15 and 75 deg for circumferential and axial medial strips, and 30 and 45 deg for circumferential and axial strips of the intima and adventitia, with minimal variation along the aorta. These findings indicate that the media, and to a lesser extent the other layers, have higher resistance to axial tearing compared to circumferential tearing, aligning with the clinical observation of circumferentially directed tears. Intimal and adventitial tear parameters increased modestly along the aorta, while medial parameters varied less, explaining why entry tears rarely originate in the abdominal aorta. Tear parameters in inner and outer quadrants were similar at most axial locations, except for dissimilar tear propagation angles of the intima and adventitia in the proximal aorta (especially the arch), explaining why entry tears seldom involve the entire circumference.

Estimating muscle forces is crucial for understanding joint dynamics and improving rehabilitation strategies, particularly for patients with neurological disorders who suffer from impaired muscle function. Muscle forces are directly proportional to muscle activations, which can be obtained using electromyography (EMG). EMG-driven modeling estimates muscle forces and joint moments from muscle activations. While surface muscles' activations can be obtained using surface electrodes, deep muscles require invasive methods and are not readily available for real-time applications. This study aims to extend our previously developed method for a single unmeasured muscle to a comprehensive approach for the simultaneous prediction of multiple unmeasured muscle activations in the upper extremity using muscle synergy extrapolation and EMG-driven modeling. By employing non-negative matrix factorization to decompose known EMG data into synergy components, the activations of unmeasured muscles are reconstructed with high accuracy by minimizing differences between joint moments obtained by EMG-driven modeling and inverse dynamics. This methodology is validated through experimentally collected muscle activations, demonstrating over 90% correlation with EMG signals in various scenarios.

Evaluating the contribution of microstructure to overall bone strength is tricky since it is difficult to control changes to pore structure in human or animal samples. We developed an open-source program that can generate three-dimensional (3D) models of micron-scale cortical bone. These models can be highly customized with a wide array of variable input parameters to allow for generation of samples similar to micro-computed topography scans of cortical bone or with specific geometric features. The program can generate samples with specific desired porosities and minor deviations in pore diameter from human samples: 1.67% (±4.90) using literature values, and 1.36% (±2.39) with optimized values. When coupled with finite element analysis, this open-source program could be a useful tool for evaluating stress distributions caused by microstructural changes.

Crash avoidance vehicle maneuvers are known to influence occupant posture and kinematics which consequently may influence injury risks in the event of a crash. In this work, a generic buck vehicle finite element (FE) model was developed which included the vehicle interior and the front passenger airbag (PAB). Seat position and occupant characteristics including anthropometry, sex, and age were varied in a design of experiments. Two pre-crash maneuvers representing (1) a generic 1 g braking and (2) turning-and-braking scenarios were simulated. Rigid-body human models with active joints (GHBMCsi-pre models) obtained by morphing a 50th male model to selected anthropometries were used in pre-crash simulations. The kinematics data of belted GHBMCsi-pre models at the end of the pre-crash phase were transferred using a developed switch algorithm to the corresponding morphed Global Human Body Model Consortium (GHBMC) occupant simplified (OS) models to predict occupant injury risks. Finally, an FMVSS-208 pulse was applied to simulate the in-crash phase. During both pre-crash maneuvers, the occupant's head and thorax moved forward toward the dashboard. Therefore, the head and thorax contacted the PAB earlier, leading to lower head accelerations when the pre-crash phase was considered. Overall, it was concluded that pre-crash braking decreased the severity of injury sustained by the passenger. Seat track position and seat recline angle showed the highest influence on the head injury criterion (HIC). The brain injury criterion (BrIC) and neck injury criterion (Nij) were most sensitive to pre-crash maneuver type, seat recline angle, and occupant size.

This study presents a comprehensive finite element (FE) model for the human wrist, constructed from a CT scan of a 68-year-old male (type 1 wrist). This model intricately captures the bone and soft tissue geometries to study the biomechanics of wrist axial loading through tendon-driven simulations and grasping biomechanics using metacarpal loads. Validation is carried out by assessing the radial and ulnar axial loading distribution, radiocarpal articulation contact patterns, and other standard finite element metrics. The results show radial transmission of the load, consistent with results from wrist finite element models conducted in the last decade and other experimental studies. Our results confirm the model's efficacy in reproducing key known biomechanical aspects, laying the groundwork for future investigations into ongoing wrist biomechanics challenges and pathology mechanism studies.

The carotid arteries (CAs) and vertebral arteries (VAs) are principal conduits for cerebral blood supply and are common sites for atherosclerotic plaque formation. To date, there has been extensive clinical and hemodynamic reporting on carotid arteries; however, studies focusing on the hemodynamic characteristics of the VA are notably scarce. This article presents a systematic analysis of the impact of VA diameter and the angle of divergence from the subclavian artery (SA) on hemodynamic properties, facilitated by the construction of an idealized VA geometric model. Research indicates that the increase in the diameter of the VA is associated with a corresponding increase in the complexity of the vortex structures at the bifurcation with the SA. When the VA diameter is constant, a 30 deg VA-SA angle yields better hemodynamic capacity than 45 deg and 60 deg angles, and the patterns of blood flow and helicity values are consistent across different angles. Elevated oscillatory shear index (OSI) zones are mainly at the origin of the VA, with an elliptical low OSI region within. As the diameter increases, the high OSI region spreads downstream. Increasing the bifurcation angle decreases OSI values in and below the elliptical low OSI region. These findings are valuable for studying the physiological and pathological mechanisms of VA atherosclerosis.

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.