Stresses and deformations of an osteosynthesis plate in a lateral tibia plateau fracture

This study has the aim to investigate the strain and stress in an anterolateral locking plate applied for the fixation of a lateral split fracture. To simulate a complex fracture situation, three segments were separated. With a FEM analysis, representative places for strain and stress measurement were determined. A locked osteosynthesis plate was instrumented with strain gauges and tested on a fractured and a non-fractured Saw Bone model. To simulate different loading situations, four different points of force application, from the center of the condyles to a 15 mm posterior position, were used with a medial-lateral load distribution of 60:40. The simulations as well as the biomechanical tests demonstrated that two deformations dominate the load on the plate: a bending into posterior direction and a bulging of the plate head. Shifting the point of application to the posterior direction resulted in increasing maximum stress, from 1.16 to 6.32 MPa (FEM analysis) and from 3.04 to 7.00 MPa (biomechanical study), respectively. Furthermore, the comparison of the non-fractured and fractured models showed an increase in maximum stress by the factor 2.06–2.2 (biomechanical investigation) and 1.5–3.3 (FEM analysis), respectively.

Postural Instability after Stepping on a Stair in Older Adults: A Pilot Study

This study aimed to examine how older adults (OA) control their postural stability after stepping on a stair in comparison to young adults (YA). Ten OA and 10 YA participated in this study. Participants ascended a single stair (15 cm high by 30 cm wide) which was secured atop one of the force plates. Ground reaction forces (GRFs) and center of pressure (COP) motion data were obtained from the force plate under the stair. After standing on the stair with both feet, GRFs and COP data for a 3 s duration were analyzed to assess postural variables, including time to stabilization (TTS), COP velocity (COPVEL), and COP sway area (COPSWAY). A significant difference in TTS in the anterior–posterior direction between OA and YA (p = 0.032) was observed, indicating that OA had difficulty stabilizing their body posture after the stair ascent compared to YA. For COP postural variables, no significant differences in COPVEL (p = 0.455) and COPSWAY (p = 0.176) were observed between OA and YA. Study findings indicate that older adults have less capacity to regain postural stability compared to young adults following a challenging dynamic movement.

Static Balancing Ability and Lower Body Kinematics Examination of Hungarian Folk Dancers: A Pilot Study Investigating the “Kalocsai Mars” Dance Sequence

Folk dance is a collection of traditional dances that requires years of practicing to perform correctly. The aim of the present study was to develop a complex biomechanical measurement procedure that investigated Hungarian folk dancers’ balancing ability and lower body kinematics through a dance movement called “Kalocsai mars”. Therefore, 11 dancers’ motion (5 female and 6 male; age: 20.5 ± 2.5 years; height: 173.82 ± 7.82 cm; weight: 64.77 ± 8.67 kg) was recorded with an optical-based motion capture system and force platforms simultaneously. Before and after the dancing session, static balancing tests were performed, examining bipedal stance with eyes opened and closed conditions. The ANOVA results showed that the values of the range of motions of the knee joint flexion-extension angles and hip flexion averaged for sessions increased significantly (p=0.044, p=0.003, p=0.005) during the dancing sessions. The deviation in the joint angle was greater in the nondominant legs, suggesting that the nondominant side requires more attention to execute the dance steps correctly. The results of the balance tests showed that the oscillation in the posterior direction increased significantly after dancing (p=0.023). In comparison, the visual feedback had no significant effect on the dancers’ balancing ability.

The role of attainability and external focus of attention on standing long jump performance

BACKGROUND: External focus of attention (FOA) promotes enhanced performance and learning in comparison to internal FOA; however, several dimensions associated with external FOA appear to have varying influence on motor skill performance. AIM: The purpose of this study was to investigate whether an attainability aspect of external FOA elicits enhanced standing long jump performance. METHOD: Fifteen healthy males performed standing long jumps in the following conditions: without a visual target (Tno), target placed at maximum distance (Tmax), and a target placed 10% beyond maximum distance (Tmax+10). Jump distances were measured, and kinetic data were recorded using a force platform. RESULTS: One-way ANOVA showed significantly greater jump distances for Tmax+10 compared to Tno and Tmax (p < 0.01). Additionally, the impulse of the ground reaction force (GRFimpulse) in the anterior-posterior direction was significantly greater for Tmax and Tmax+10 compared to Tno (p < 0.05). CONCLUSION: Thus, an external FOA tailored to individual ability benefits standing long jump performance. Overall, the findings support the approach of adopting an external FOA with an emphasis on targets that are specific to the individual and based on attainability.

Age differences in adaptation of medial-lateral gait parameters during split-belt treadmill walking

The split-belt treadmill (SBT) has been used to examine the adaptation of spatial and temporal gait parameters. Historically, SBT studies have focused on anterior-posterior (AP) spatiotemporal gait parameters because SBT is primarily a perturbation in the anterior-posterior direction, but it is important to understand whether and how ML control adapts in this scenario. The medial-lateral (ML) control of balance must be actively controlled and adapted in different walking environments. Furthermore, we seek to determine whether ML balance adaptation differs in older age. We analyzed SBT-induced changes in gait parameters including variables which inform us about ML balance control in younger and older adults. Our primary finding is that younger adults showed sustained asymmetric changes in these ML balance parameters during the split condition of the SBT. Specifically, younger adults sustained a greater displacement between their fast stance foot and their upper body, relative to the slow stance foot, in the ML direction. This finding suggests that younger adults may be exploiting passive dynamics in the ML direction during the SBT, which may be more metabolically efficient. Additionally, the ML parameters did not show any aftereffects despite large adjustments during the split condition, which may indicate higher level neural control than AP parameters.

Validation of the BESTest for Measuring Balance in People With Multiple Sclerosis

Background: Evaluation of balance disorders and differentiation of the populations with deficits is necessary for treatment and rehabilitation. The BESTest is used to evaluate balance and posture in various populations and has been shown to distinguish between different neurological populations. This study investigated the validity of the BESTest in measuring balance in the people with multiple sclerosis (PwMS). Methods: A cross-sectional study conducted with 34 participants including 17 PwMS (42.64 ±7.8 years old, score 1-5 on the Expanded Disability Status Scale) and 17 healthy controls (42.33±8.65 years old). After a comprehensive medical history, subjective clinical balance assessment (via BESTest) was performed. Then objective measures of balance domains of Anticipatory Postural Adjustments (APAs) and Sensory Orientation were assessed using a force plate, with sway, velocity and the area of sway outcomes calculated. Correlations between the subjective and objective measures of balance were computed. Results: The anterior-posterior and the medio-lateral sway, sway velocity in the AP direction, and area of displacement were significantly different between the two groups (P<0.005). Significant correlations were found between the BESTest scores with anterior-posterior and medio-lateral sway, sway velocity in anterior-posterior direction, and area of displacement in anterior-posterior direction (p<0.005). Conclusions: Results indicated that the BESTest assessment tool has a high accuracy and sensitivity to assess balance function in PwMS. It can be used as an outcome measure to test postural balance disorders in these people.

Using mastoid vibration can detect the uni/bilateral vestibular deterioration by aging during standing

BACKGROUND: The mastoid vibration (MV) has been used to investigate unilateral vestibular dysfunction by inducing nystagmus. Additionally, this MV can be used to quantify the effect of deterioration by aging on the vestibular system during walking. Could such MV be used to assess the uni/bilateral vestibular deterioration by aging during standing? OBJECTIVE: This study attempted to determine the feasibility of using MV for identifying the uni/bilateral vestibular deterioration by aging during standing. METHODS: Fifteen young and ten old adults’ balance control patterns were assessed by three random MV conditions: 1) No MV; 2) Unilateral MV; 3) Bilateral MV. The dependent variables were the 95% confidence ellipse areas and the sample entropy values, which were calculated based on the center of gravity displacement within each condition. RESULTS: Significant main effects of MV and aging were found on all outcome variables. A significant interaction between aging and different MV types was observed in the 95% confidence ellipse area (p = 0.002) and the length of the short axis (anterior-posterior direction, p = 0.001). CONCLUSIONS: We concluded that the MV could be used to identify different vestibular dysfunctions, specifically in old adults.

Morphological mechanism allowing a parasitic leech, Ozobranchus jantseanus (Rhynchobdellida: Ozobranchidae), to survive in ultra-low temperatures

Ozobranchus jantseanus is the largest metazoan known to survive in liquid nitrogen without pretreatment to date, however, the mechanism underlying this tolerance remains unclear. In this study, the first analyses of histological and morphological changes in normal, frozen, and dehydrated states were performed. Adults survived after direct placement in liquid nitrogen for 96 h, with a survival rate of approximately 86.7%. The leech could withstand rapid desiccation and its survival rate after rehydration was 100% when its water loss was below about 84.8%. After freezing, desiccation, and ethanol dehydration, the leech immediately formed a hemispherical shape. Particularly during drying, obvious transparent glass-like substance was observed on surface. Scanning electron microscopy revealed many pores on the surface of the posterior sucker, creating a sponge-like structure, which may help to rapidly expel water, and a hemispherical shape may protect the internal organs by contraction and folding reconstruction in the anterior-posterior direction. A substantial amount of mucopolysaccharides on the surface and acid cells and collagen fibers in the body, all of which contained substantial polysaccharides, may play a key protective role during freezing. Our results indicate that the resistance of leeches to ultra-low temperatures can be explained by cryoprotective dehydration/vitrification strategies.

Ability of a Set of Trunk Inertial Indexes of Gait to Identify Gait Instability and Recurrent Fallers in Parkinson’s Disease

The aims of this study were to assess the ability of 16 gait indices to identify gait instability and recurrent fallers in persons with Parkinson’s disease (pwPD), regardless of age and gait speed, and to investigate their correlation with clinical and kinematic variables. The trunk acceleration patterns were acquired during the gait of 55 pwPD and 55 age-and-speed matched healthy subjects using an inertial measurement unit. We calculated the harmonic ratios (HR), percent recurrence, and percent determinism (RQAdet), coefficient of variation, normalized jerk score, and the largest Lyapunov exponent for each participant. A value of ≤1.50 for the HR in the antero-posterior direction discriminated between pwPD at Hoehn and Yahr (HY) stage 3 and healthy subjects with a 67% probability, between pwPD at HY 3 and pwPD at lower HY stages with a 73% probability, and it characterized recurrent fallers with a 77% probability. Additionally, HR in the antero-posterior direction was correlated with pelvic obliquity and rotation. RQAdet in the antero-posterior direction discriminated between pwPD and healthy subjects with 67% probability, regardless of the HY stage, and was correlated with stride duration and cadence. Therefore, HR and RQAdet in the antero-posterior direction can both be used as age- and-speed-independent markers of gait instability.