A new process to measure postural sway using a Kinect depth camera during a Sensory Organisation Test

Abstract

Posturography provides quantitative, objective measurements of human balance and postural control for research and clinical use. However, it usually requires access to specialist equipment to measure ground reaction forces, which are not widely available in practice, due to their size or cost. In this study, we propose an alternative approach to posturography. It uses the skeletal output of an inexpensive Kinect depth camera to localise the Centre of Mass (CoM) of an upright individual. We demonstrate a pipeline which is able to measure postural sway directly from CoM trajectories, obtained from tracking the relative position of three key joints. In addition, we present the results of a pilot study that compares this method of measuring postural sway to the output of a NeuroCom SMART Balance Master. 15 healthy individuals (age: 42.3 ± 20.4 yrs, height: 172 ± 11 cm, weight: 75.1 ± 14.2 kg, male = 11), completed 25 Sensory Organisation Test (SOT) on a NeuroCom SMART Balance Master. Simultaneously, the sessions were recorded using custom software developed for this study (CoM path recorder). Postural sway was calculated from the output of both methods and the level of agreement determined, using Bland-Altman plots. Good agreement was found for eyes open tasks with a firm support, the agreement decreased as the SOT tasks became more challenging. The reasons for this discrepancy may lie in the different approaches that each method takes to calculate CoM. This discrepancy warrants further study with a larger cohort, including fall-prone individuals, cross-referenced with a marker-based system. However, this pilot study lays the foundation for the development of a portable device, which could be used to assess postural control, more cost-effectively than existing equipment.

A Comparison among Different Strategies to Detect Potential Unstable Behaviors in Postural Sway

“…In the following, a brief review of the state of the art, addressing the development of solutions for postural sway monitoring, is given. The very first classification key among different solutions already available or under development consists of the two main classes: infrastructure-dependent devices and wearable systems [ 3 , 4 , 5 , 6 ]. The actual approaches adopted in diagnostic premises exploit force platforms and/or vision systems [ 3 , 4 ].…”

“…Recent works investigated the possibility to use a Kinect vision system to study postural stability features or to localize the center of mass (CoM) of an upright person [ 5 , 6 ]. Although very accurate, the main limit of such infrastructure-dependent solutions is represented by the need to perform periodic laboratory tests, which lead to a discontinuous monitoring of the patient.…”

“…Among wearable systems, the most popular devices are instrumented insoles [ 7 ] and inertial-sensor-based systems [ 8 , 9 , 10 ]. Insoles represent a valuable solution for the monitoring of the Centre of Pressure (CoP), although not always easy to use and to maintain [ 6 , 7 ].…”

Best Features Selection for the Implementation of a Postural Sway Classification Methodology on a Wearable Node

“…In particular, studies should focus on identifying early instrumental markers of instability among frailty people. Different solutions can be used for these purposes, being classified in infrastructure-dependent devices, mainly represented by computerized posturography [7][8] and lowcost vision systems [9][10], as well as wearable devices [11].…”

Detection of Postural Control in Young and Elderly Adults Using Deep and Machine Learning Methods with Joint–Node Plots

“…Microsoft Kinect is a popular human motion capture tool. Kinect cameras are useful, as they provide joint center position data directly without additional processing of depth or image data [ 6 ]. Recent evidence suggests that Kinect may enable low-cost balance assessments and gait analyses [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ].…”