Quantification of the Balance Error Scoring System with Mobile Technology

Abstract

Purpose The aim of this project was to develop a biomechanically based quantification of the Balance Error Scoring System (BESS) using data derived from the accelerometer and gyroscope of a mobile tablet device. Methods Thirty-two healthy youth and adults completed the BESS while an iPad was positioned at the sacrum. Data from the iPad data was compared to position data gathered from a 3D motion capture system. Peak-to-peak (P2P), normalized path length (NPL), and root mean squared (RMS) were calculated for each system and compared. Additionally, a 95% ellipsoid volume, iBESS volume, was calculated using center of mass (COM) movements in the anterior-posterior (AP), mediolateral (ML), and trunk rotation planes of movement to provide a comprehensive, 3-dimensional metric of postural stability. Results Across all kinematic outcomes, data from the iPad were significantly correlated with the same outcomes derived from the motion capture system (Rho range: 0.37- 0.94, p<0.05). The iBESS volume metric was able to detect a difference in postural stability across stance and surface, showing a significant increase in volume in increasingly difficult conditions, while traditional error scoring was not as sensitive to these factors. Conclusions The kinematic data provided by the iPad is of sufficient quality relative to motion capture data to accurately quantify postural stability in healthy young adults. The iBESS volume provides a more sensitive measure of postural stability than error scoring alone, particularly in conditions 1 and 4, which often suffer from floor effects, and condition 5, which can experience ceiling effects. The iBESS metric is ideally suited for clinical and in the field applications in which characterizing postural stability is of interest.

Quantification of postural control deficits in patients with recent concussion: An inertial-sensor based approach

“…Alberts et al (14) subsequently developed an objective and quantitative scoring system for the BESS on the basis of an IMU placed on the posterior aspect of the sacrum in a group of healthy participants; data from the accelerometer and gyroscope were used to calculate a 3D 95% ellipsoid volume of sway during task completion. This 'sway-volume' metric was deemed more sensitive of BESS performance than errors alone, but could not be used to determine how many errors occurred, thus limiting any ability to make inferences of the…”

“…Importantly, neither Brown et al nor Alberts et al evaluated their technology in a cohort of concussion patients (13,14).…”

“…Finally combining the two linear accelerations (ML and AP) and one angular acceleration (V), the 3D volume of sway was established as described by Alberts et al (14).…”

“…For instance, participants will rarely incur any errors in the bilateral stance position. As such, the diagnostic accuracy of this component for concussion using the traditional clinical outcome is belied by a floor-effect (14). Despite this, a minutiae of postural corrections are necessary in the maintenance of any upright posture (26).…”

“…To resolve this issue, Alberts et al developed the volume of sway metric adopted in the current study (14). We have developed on the findings of these groups by using the same metric to both quantify postural control performance and identify task errors.…”