PIPSS

A Portable Instrument Postural Stability System

to Assess Dynamic Postural Stability

Michael Korostelev

, Li Bai

, Assaf Zoor

and Carole A. Tucker

1,2

Department of Electrical and Computer Engineering, Temple University, Philadelphia PA, U.S.A

Department of Physical Therapy, Temple University, Philadelphia PA, U.S.A.

Keywords: Balance Testing, Gaming Console, Portable Instrumentation.

Abstract: The most common method to assess postural stability involves the use of a force plate to measure changes

in center of pressure (COP)(Duarte et al 2010). The high cost of this technology limits practicality and

accessibility for widespread use outside of major clinical centers. There is an emerging trend toward video

game use as a means of increasing patient engagement in rehabilitation interventions. This trend is primarily

driven by the newest generation of consumer console systems which use motion-based controls (e.g.

Nintendo Wii and WiiFit). We have developed and tested PIPSS, a system that utilizes the Nintendo Wii

balance board to quantify COP during simple static and more complex dynamic balance tasks. This low

cost, accessible postural stability assessment system could be easily deployed in clinics, sport and athletic

centers, training rooms, schools or elderly care facilities to provide a quantitative metric of postural control.

Such information would allow for more timely assessment and intervention, improved return to play

guidelines in athletes, or balance and fall interventions in care centers for the elderly. Current work includes

analyses and interpretation of the PIPSS testing protocols with

existing balance measures in children

and adults with Cerebral Palsy, and concussion.

1 INTRODUCTION

The widespread use and societal acceptance of video

games within households, clinics, care and

rehabilitation centers, provides an exceptional

opportunity to quantitatively assess and monitor

balance training programs on a daily basis. The

capability to provide patient-specific therapeutic

programs using such devices, and simultaneous data

collection from these devices, supports efforts in

tele-rehabilitation. The ability to monitor clients at

home, obtaining frequent objective measures as well

as updating the intervention programs over the

internet extends the potential to provide such health

care services within a variety of settings.

In the past decade, there has been a recent focus

of attention towards concussion management in

athletes. The impact of concussion on health status

relies on a multifactorial approach that include self-

reported symptoms, neurocognition, and postural

control. Self-reported symptoms are typically

unreliable due to under-reporting and neurocognitive

testing has demonstrated good reliability. The most

effective and most common method to assess

postural stability involves the use of a force plate to

measure changes in center of pressure (COP)

(Duarte et al, 2010). The high cost of this

technology limits practicality and accessibility for

clinicians. A low technology alternative that is

commonly used to assess postural stability is the

Balance Error Scoring System (BESS). Although

the BESS test is commonly and easily used by

clinicians, it exhibits only moderate reliability

(Finoff 2009, Bell 2011) with a lack of normative

data to assess minimal detectable changes within the

population to determine indication of return to play.

1.1 Background

TheraWii was a software application developed as

an Engineering Senior Design Project at Drexel

University during the 2008-2009 academic year.

TheraWii can generate quantitative balance and

reaching assessments and interventions using the

Wii balance board, hand controllers, and a laptop

computer. In addition to the TheraWii software,

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Korostelev M., Bai L., Zoor A. and A. Tucker C..

PIPSS - A Portable Instrument Postural Stability System to Assess Dynamic Postural Stability.

DOI: 10.5220/0004934703120315

In Proceedings of the International Conference on Biomedical Electronics and Devices (TPDULL-2014), pages 312-315

ISBN: 978-989-758-013-0

 2014 SCITEPRESS (Science and Technology Publications, Lda.)

Excel and blue tooth capability on the laptop are the

primary requirements for data collection. TheraWii

software incldued a set of generic balance activities

that can be linked together to form balance or

reaching assessments or interventions. Patient- and

session-specific data, as well as the balance and

acceleration signals from the Wii devices during

sessions, were exported using Bluetooth technology

to a data file that could be analyzed and used to

quantify posture and movement. The software was

designed to record and display models of physical

motion using the Wii Remote and Balance Board

motion capturing interfaces as input.

The Portable Instrumented Postural Stability

System (PIPSS) extends the original TheraWii

project with enhanced testing and training protocols

as well as a web-based interface.

1.2 Clinical Significance

PIPSS provides the technology of a force plate with

a mass-produced, low cost device that demonstrates

good validity and reliability in assessing postural

stability via COP measures (Clark et al). TheraWii

can provide quantitative measures of balance and

acceleration in a software platform that is

economical, easily accessible for home and clinic

use. TheraWii is open-source software released

under the GNU General Public License Version 3

(GPLv3), and the copyright is retained by the

original TheraWii project personnel. A detailed

software guide, project description and User manual

are available, and the intention is to provide the

TheraWii system as an open-source platform for

clinical, non-profit applications. The use of

TheraWii as an objective measure that can be used

to objectively capture in movement and posture

outside of a laboratory environment on a frequent

basis is unparalleled, particularly coupled with

existing videogame technology.

2 METHODS

2.1 Subjects

The data from a sample of convenience of ten

participants (6 female, height=162.3cm±17.0,

weight=67.8kg±23.6, leg length=86.2cm±5.4, ages

25±2.5 collected as part of a study are used to

demonstrate the PIPSS as a dynamic balance

measure for this report. All subjects had no history

of concussion or neuromusculoskeletal issues within

6 months of testing.

2.1.2 Procedures

All subjects completed the BESS test and the

Random Positioning Test on the PIPSS as well as

clinical measures of postural stability. The BESS

was performed on the TheraWii balance board to

ensure coincident COP and BESS scores for each

condition. The BESS consists of 6 conditions

performed for 20sec with eyes closed: 1) double leg

standing, 2) non-dominant single leg standing, 3)

tandem stance, 4) double leg standing on foam

(AIREX Balance Pad Elite, Power Systems Inc,

Knoxville, TN), 5) non-dominant single leg standing

on foam, and 6) tandem standing on foam (4). The

investigator scored the BESS based on the following

criteria: 1) moving hands off iliac crests, 2) opening

the eyes, a step, 3) stumble or fall, 4) abduction or

flexion of the hip beyond 30 degrees, 5) lifting the

forefoot or heel off the testing surface or 6)

remaining out of the testing position for greater than

five seconds. Each error counted as 1 point with a

maximum score of 10 points per condition. Anterior-

Posterior (A-P) and medial-lateral (M-L) COP data

was acquired at 30Hz from the Wii balance board.

Custom Matlab programs were written to analyze

the data. COP was averaged across A-P and M-L

values and log transformed for the purpose of this

report

The Random Positioning Test is a test where

subjects stand barefoot (standardized foot position)

and look straight ahead at a screen on which a red

dot representing their real-time COP is visible. A

target shape appears on the screen in a random

position (position specifications controlled by the

software) and the subjects are instructed to move

their COP within the target and maintain it there for

2 seconds. After 2 seconds in the target, the target

moves to a new random position, and the subject

again moves as fast as possible to that target. This

process is repeated for a total of 10 random target

positions. Hence the total trail length varies

depending on how fast and accurate the individual is

in moving to the target and remaining in the target.

Though many performance metrics are available in

the PIPSS software, for the purposes of this report

we have focused only on the COP trajectory and

average path efficiency.

3 RESULTS

Quantitative measures for each BESS score showed

appropriate directionality (Table 1) with a BESS

score of 1 having a mean COP path efficiency of

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.04cm±.02 and a BESS score of 10 having a mean

COP path efficiency of .01cm±.01. Average COP

range and path efficiency for each BESS score had

overlapping ranges across scores (Figure 1). A score

of zero on the BESS varied in average COP from

0.13 to 0.58cm for range with path efficiency spread

from 0.016 to 0.11cm. A BESS score of five also

had high variation for range (0.51-3.7cm) where a

BESS score of eight had a high path efficiency

variation (0.01-0.44cm). The BESS score of ten had

the highest variation in both range and path

efficiency (0.51-8.1cm, 0.01-0.02cm), respectively.

Figure 1: BESS COP measures of range and path

efficiency.

Table 1: Range and Path Efficiency Across BESS Scores,

mean (SD). BESS Scores represent the min and max

values awarded for each condition.

BESS Scores

Condition 0 1 2 3 4

Range

.32(.13) .33(.06) .80(.13) .31(.) .67(.35)

Path

.04(.02) .03(.02) .03(.02) .04(.) .02(.01)

Condition 5 6 7 8 9 10

Range

1.3(1.45) .45(.) .70(.07) .51(.11) .72(.) 1.9(3.0)

Path

.02(.01) .02(.) .01(.01) .02(.01) .02(.) .01(.01)

The PIPSS random positioning test was completed

by all subjects with an average time for completion

of 32.2+14.3 (range 35.6 – 84.1 seconds). Examples

of 2 COP relative to target positions are displayed in

Figures 1 & 2. of (range for simply.

4 DISCUSSION

PIPSS can be used simply as an input device that

quantifies COP during simple static balance tasks, but

more importantly as demonstrated in this report, can be

used to implement dynamic postural tasks. This low cost,

accessible postural stability assessment system could be

easily deployed on clinics, sport and athletic centers,

training rooms, schools or elderly care facilities to provide

a quantitative metric of postural control. Such information

would allow for more timely assessment and intervention,

improved return to play guidelines in athletes, or balance

and fall interventions in care centers for the elderly.

Current work includes analyses and interpretation of the

PIPSS testing protocols with existing balance measures

Table 2: Center of Pressure (COP) variables during standing eyes open (SEO) baseline trial, Total Time (TT) on the random

positioning (RP) test, and BESS firm surface sub-score (out of 30 points).

Figure 2: Of the COP and target positions for 2 exemplar subject performing the PIPSS random positioning test.

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and improved definition to the relevant PIPSS output

variable that are more sensitive to changes in

postural control.

5 CONCLUSIONS

The PIPSS provides a portable, instrumented system

that captures center of pressure like data that can be

used to provide improved quantification of balance

and postural stability during quiet and dynamic

standing tests. We are currently continuing our

validation of the PIPSS measures in children and

adults in a variety of conditions including typically

developing, individuals post-concussion, and

individuals with cerebral palsy.

Our current technological work is focused on the

integration of a software design pattern for this new

style of PIPSS with Model-View-Controller (MVC)

pattern at its core. In order to facilitate

interoperability and further system extension a

component based MVC should be implemented

where raw server API is abstracted and the

gathering, validation and conversion of parameters

for data models should be made easy and server

based.

The emerging concept of the Internet of Things

provides a foundation for this relationship with some

advanced telemetry methodologies. Until recently,

connection of edges of networks has been

problematic, particularly if devices are limited in

their computation power. The Message

QueuingTelemetry Transport protocol alleviates

many issues with remote telemetry. With it’s

publish/subscribe pattern, it is a great candidate for

the PIPSS application. We will create a centralized

entry point for PIPSS telemetry and simple hardware

drivers for computing and mobile devices that will

enable device level MQTT communication with the

MVC architecture. A standard API along with

MQTT will enable further development of drivers

for other diagnostic devices to seamlessly enter this

ecosystem and support the collection of data. This

idea of an openly available API facilitates

dissemination of results as well as broadly impacting

the field and enable clinicians to make the steps

needed for standardizing return-to-sport criteria

through collaborative data collection and analytics

ACKNOWLEDGEMENTS

The authors would like to thank the original

TheraWii software developers from Drexel

University: Dr David Breen, Timothy Chagnon,, Joe

Kokinda, Andrew Meinert and Don Naegel.

REFERENCES

Bell, D. et al. (2011) Sports Health, 3(3): 287-295.

Clark, R et al. (2010) Gait and Posture, 31:207-310.

Duarte, M et al. (2010) Rev Bras Fisoter, 14(3):183-192.

2. 3.

Finoff, J. et al (2009) Physical Medicine and

Rehabilitation, 1(1):50-54.

Iverson, G. et al (2008) Brain Injury, 22(2):147-152.

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