According to medical statistics, sacroiliac joints (SIJs) appear to be the source of low back pain in 15 - 30% of cases. The SIJs are located at the junction between the sacrum and the ilium, supported by strong ligaments and with low mobility. Due to unexpected external force or repeated impact, pain may arise from the SIJ region (SIJ dysfunction). The treatment to cure SIJ dysfunction includes nonsurgical approaches as well as surgery with implants (SIJ fixation). Previous studies have assessed the consequences of SIJ fixation, but no simulation study so far has been performed during walking. The SIJ is burdened with variant loads during walking. In this given study, walking conditions were replicated in a finite element model of the pelvis combined with 3D walking analysis data. The simulation mimicked two types of unilateral SIJ fixation: anterior fixation with a plate implant and screws (model A) and posterior fixation with a rod, a cage and screws (model P). Equivalent stress of the SIJ and the loading of the SIJ ligaments decreased in the fixed models. In these fixed pelves, the slight motion on the SIJ decreased. The reduction rates on equivalent stress, ligament loads and equivalent stress were low during the swing phase. In addition, the efficiency of fixations was mostly same on anterior and posterior fixations. It can be concluded that the stronger fixation reduces the loading but also may have a greater impairment effects on walking.

Micro/nanoplastics (MPs/NPs) in the environment exhibit various effects on ecosystems as well as living organisms, such as immune system toxicity. To understand the effects of MPs/NPs experimentally, preparing synthetic MPs/NPs with their geometrical morphology closely similar to the MPs/NPs present in natural environments and with specific material composition is necessary. A pin-on-disc method with plastic pins and micro-textured glass discs has been employed to generate MPs/NPs with defined composition for biological tests. However, these previous studies did not clarify the repeated elastic deformation and stress distribution inside the pin causing the fatigue of degraded areas. Accordingly, in this study, MPs/NPs were generated using a pin-on-disc method, and the interfacial pressure of the pin and disc and the micro-texture pattern were assessed as factors that could change the elastic deformation and the stress distribution inside the pin; additionally, how these factors affect the MP/NP geometrical morphology were investigated. Polyethylene, polypropylene, polyvinyl chloride, polystyrene, and polyethylene terephthalate were used as test materials. Almost all the MPs/NPs of these materials had a fragmented morphology. Further, these MPs/NPs were compared to those identified and they showed almost the same geometrical morphology as the fragmented MPs/NPs in the environment. The equivalent circle diameters of the generated MPs/NPs were suggested to be affected by micro-textures on the discs, which promoted fatigue failure. Additionally, by increasing the interfacial pressure, the stress was distributed deeper inside the pin depending on the plastic materials, which accelerated the crack propagation and generated a large amount of MPs/NPs. From these results, the fragmented morphology of MP/NP which is similar to those present in environments is expected to be generated with defined morphology and material composition for application to biological tests.

The global demand for assistive devices to support individuals with disabilities is increasing, yet their accessibility remains limited. Self-help devices (SHDs), particularly for handwriting tasks, play a pivotal role in enhancing independence. This study presents a semi-automated method for producing personalized handwriting SHDs, thereby reducing the need for occupational therapists (OTs) to possess advanced technical skills and enabling them to concentrate on patient care. Ten healthy participants, simulating upper limb dysfunctions by restricting their finger joint mobility with bandages, are recruited for the study. OTs assess measurements that encompass manual measurements, automatic joint recognition, and 3D scanning for digital representation. This process facilitates the development of a personalized SHD 3D model, utilizing 3D CAD software. The SHD model is designed to be adaptable, allowing adjustments based on the individual's unique hand measurements. The 3D model, composed of six primary components, is then fabricated using 3D printing technology. The streamlined process, from measurement to production, reduces design and printing time to approximately two hours. Testing focuses on handwriting speed and letter legibility, with participants reporting enhanced comfort and a significant increase in handwriting speed using our SHD compared to conventional SHDs. Furthermore, users experienced improved letter legibility in addition to a significant increase in handwriting speed with our SHD. The study's innovation promises to broaden the reach of personalized assistive devices and allows OTs to better focus on patient care, improving therapy outcomes.

Recent advancements in motion measurement systems have facilitated the analysis of kinematic techniques in sports, emphasizing the importance of motion control for performance enhancement. Ground reaction forces and moments are crucial in biomechanical analysis, and are typically measured using force plates. However, conventional force plates pose limitations in winter sports due to their impracticality on ice. To address this, various methods have been explored, including skates equipped with strain gauges and pressure-sensitive insoles. Despite advancements, simultaneous measurement of forces and moments in three axes remains a challenge. In this study, we developed a new wearable system capable of comprehensively measuring the forces and moments during skating by attaching three wearable force plates between the boot and the blade. The precision of this measurement system was validated through an experiment employing a conventional force plate, demonstrating its high accuracy. On-ice trials confirmed the system's efficacy in capturing dynamic movements like forward sliding and half-turn jumps. The six-component force was successfully measured during skating motions, a task that is challenging with conventional systems. This system offers a promising avenue for nuanced biomechanical analysis in figure skating, facilitating insights into performance optimization and injury prevention.

In the fall accident on stairs, a human body receives a multiple impact on the body including on the head in a short time, as a result it often results in being unidentified which impact gives what kind of damage in the human body. However, it is important in addition to emergency treatment to know the process of the accident when brain may be injured to predict prognostic process. In this paper, the fatal accident by the fall on the stairs is analyzed, in which the cause of death was cerebral contusion, and plural damage traces were observed on a body including the head. In the first stage of the accident analysis, possible fall motions are reproduced repeatedly based on multibody dynamics, and the fall motion that the physical damage trace fitted the reported position of the blow is chosen from them. In the next stage, finite element analyses are performed in which the initial condition in a posture and the initial velocity for each impact obtained from the fall motion are given as initial condition, and the possibility of the head injuries are evaluated. The analysis results indicates that in the case, there is a high likelihood of falling during descending the stairs, followed by sliding down with rotation. During this sequence, the head experiences three impacts, each impact indicated the potential for causing specific types of injuries.

This paper studies a 2D, spring-loaded inverted pendulum (SLIP) passive dynamic biped with two degrees of freedom (stance leg only) to find the existence of symmetric periodic walking and jogging gaits. These gaits are differentiated by vertical ground reaction force (vGRF) patterns. The double-support phase is considered to be instantaneous, and jogging has no airborne phase. We consider the initial leg compression an additional model parameter compared to earlier studies with symmetric gaits. Different gaits are obtained through numerical optimization with various combinations of model parameters -- initial leg compression, spring stiffness, and touchdown angle; with the gait speed as the resultant parameter. Initial compression of the leg spring is found to be an important parameter in transitioning between walking and jogging gaits. This approach can capture the vertical ground reaction force and center of mass (CoM) trajectories of human gaits for both walking and jogging while providing additional control over peak vGRF and the amplitude of CoM oscillation. In comparison, existing SLIP walking models employ an asymmetric single support phase (SSP), and jogging gaits incorporate an aerial phase. Overall, we present a common approach to finding both slow walking and jogging gaits without significant changes in resulting gait speeds.