Agreement between the inertial measurement unit and optoelectronic system to measure postural sway

BACKGROUND: Optoelectronic systems and force platforms represent the gold standard for postural sway assessment, but pose disadvantages in terms of equipment, cost and preparation time. OBJECTIVE: Wearable inertial measurement units (IMUs) have been proposed to overcome these issues, but have never been compared to an optoelectronic system. The study aim was therefore to investigate agreement between inertial measurement unit and optoelectronic system in postural sway assessment. METHODS: Thirty healthy volunteers performed four balance tasks. IMU was placed on the sacrum (S2) with a retroreflective marker over the sensor and subjects’ performance was simultaneously recorded by both systems. Total (TOT), anterior-posterior (AP) and medial-lateral (ML) length of trace, range, speed, root mean squared (RMS), and confidence ellipse were computed. RESULTS: ICCs revealed excellent correlations for Length-TOT, Length-AP and Speed-AP, good correlation for Length-ML, Speed-ML, Confidence Ellipse, Range-AP and RMS-AP, and moderate correlation for range-ML and RMS-ML. Bland-Altman plot showed greater estimation for Length-TOT, Length-AP, Speed-AP, confidence ellipse and RMS-AP using optoelectronic system, and for Length-ML, Range-AP, Range-ML, Speed-ML, RMS-ML using IMU. Both systems revealed the same differences among tasks. CONCLUSION: The excellent to good agreement of IMU for length of trace and speed parameters and its user-friendly application suggest its potential implementations in clinical practice.

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.

The resting coronal and sagittal stance position of the torso in adolescents with and without spinal deformity

The purpose of this work is to identify the resting stance of the torso, defined as the position of the C7 vertebral body relative to the sacrum in a ‘birds eye view’, as the coronal and sagittal offset, in those without spinal deformity, those with pre and post-operative AIS, and those with Scheuermann's kyphosis (SK). Using ISIS2 surface topography, the coronal and sagittal offset were measured in a prospective manner in all groups. With bivariate ellipses, a mean and 95% confidence ellipse of the data was developed. Statistical analyses was performed to examine the distribution of the data from the groups. A graphical representation of the data was developed. There were 829 without spinal deformity, 289 in both the pre and post-operative with AIS and 59 with SK. The results showed that the mean coronal offset for all groups was between 2 and 6 mm and the sagittal offset was 12 and 26 mm. Statistically significance was seen for both measures between the non-scoliotic and both AIS groups, along with the pre-operative AIS coronal offset and post-operative AIS sagittal offset and the SK measures. However, all mean values were within the 95% confidence ellipse for all of the groups. Regardless of the size or type of spinal deformity, the position of the C7 vertebral body and sacrum remain within the 95% confidence ellipse of that seen in those without spinal deformity. This work defines the Minimally Clinically Important Difference for all of the groups.

A blazar as the likely counterpart to 4FGL J0647.7−4418 instead of a gamma-ray binary

ABSTRACT The persistent gamma-ray source 4FGL J0647.7−4418 is tentatively associated in the latest Fermi catalogue with the subdwarf O-type X-ray binary HD 49798. However, an active galactic nucleus (AGN) candidate is also mentioned as an alternative identification in updated versions of the catalogue accompanying paper. If the first association were correct, this would add HD 49798 to the handful of currently known gamma-ray binaries, and therefore represent a significant breakthrough not only because of a new member addition, but also because of the apparent white dwarf companion in this system. Despite these perspectives, here, we show that the stellar association is likely wrong and that the proposed AGN object, well inside the Fermi 95 per cent confidence ellipse, is a more conceivable counterpart candidate to the Fermi source due to its strong blazar similarities.

Proposal of standardization of Horus® computerized posturography in adults

ABSTRACT Purpose: To propose a normalization model of a posturography platform in adults without changes in body balance, through descriptive analysis by age group and sex. Methods: Cross-sectional observational study. Adults, with no changes in body balance and no vestibular complaints were submitted to 6 sensory conditions on the Horus® posturography platform. The following variables were analyzed: stability limit area and confidence ellipse area, trajectory length and average velocity for each condition tested. The variables were analyzed by age group and sex. The equilibrium score, the sensory integration test and the equilibrium index were calculated on the conditions. Results: Sixty-one subjects (38.3%) and 23 (37.7%) were male, 40 (65.57%) between the ages of 20 and 40 and 21 (34.43). %) between 41 and 59 years. The area of the stability limit and pressure center variables for 6 sensory conditions tested - confidence ellipse area, trajectory length, total mean velocity and confidence ellipse ratio by the area of the stability limit were described. There was a statistically significant difference in the comparison between the area of the stability limit between sexes and between age groups, being a higher value in males and in younger patients. Regarding the analysis of the variables by each condition, there was no difference of results between the sexes and age groups. Conclusion: Subjects of different sexes and age groups should be considered separately only in the analysis of the stability limit.

Bipedal and unipedal stance in Brazilian football 7-a-side athletes with cerebral palsy

ABSTRACT To compare postural control between Football 7-a-side players with cerebral palsy (CP) and active non-athletes without neurologic impairments, 28 individuals (15 to 35 years old) were selected and divided into the Non-Athletes Group (NAG), consisting of 14 individuals without neurologic or musculoskeletal injury; and the CP Group (CPG), composed of 14 athletes from the regional football team. A force platform was used to measure anteroposterior displacement of center of pressure (COPap), velocity (COPvel), mediolateral displacement (COPml), and 95% confidence ellipse area (AREA95) on bipedal and unipedal stance. On bipedal stance, there was no difference between groups in anteroposterior displacement of center of pressure (COPap) and velocity (COPvel). On unipedal stance with the dominant leg, the NAG presented better postural control, statistically significant in mediolateral displacement (COPml), 95% confidence ellipse area (AREA95) and COPap (p = 0.003; p = 0.001; p = 0.018, respectively). Our results showed that both groups have similar postural control on bipedal stance, but NAG demonstrated better postural control with unipedal stance than Football 7-a-side players with CP.

Manual and Cognitive Dual Tasks Contribute to Fall-Risk Differentiation in Posturography Measures

Falls occur in 33% of older adults each year, some leading to moderate to severe injuries. To reduce falls and fall-related injuries, it is important to identify individuals with subtle risk factors elevating their likelihood of falling. The objective of this study was to determine how postural sway measures differed between fallers and nonfallers under standard and dual-task conditions. Quietstanding posturography measures were collected from 150 older adults during standard, cognitive, manual, and cognitive+manual tasks, and analyzed through traditional and nonlinear analyses. Of the traditional measures, M/L sway range and 95% confidence ellipse sway area showed statistically significant differences in all 4 test conditions between fallers and nonfallers. Although the manual dual task showed the most stable balance, effect sizes demonstrated larger differences between fallers and nonfallers. Nonlinear analysis revealed M/L sample entropy and M/L α-scaling exponent differentiating between fallers and nonfallers, with the cognitive task demonstrating larger differences. Based on the results, it is recommended to: (1) apply M/L sway range and 95% confidence ellipse area, (2) use the manual task to differentiate between fallers and nonfallers when using traditional analyses, and (3) use the cognitive task and M/L alpha and M/L sample entropy when using nonlinear analyses.