MODIFICATION OF HYBRID III TEST DUMMY FOR USE IN WHEELCHAIR STUDIES

Michael J. Dvorznak, Rory A. Cooper & Thomas A. Corfman
Human Engineering Research Laboratories
University of Pittsburgh

Slide 1
MODIFICATION OF HYBRID III TEST DUMMY FOR USE IN WHEELCHAIR STUDIES

Michael J. Dvorznak, Rory A. Cooper & Thomas A. Corfman

Human Engineering Research Laboratories
University of Pittsburgh

Slide 2
Introduction

Two million full-time wheelchair users ~3.3%/year experience a serious wheelchair related accident

70% attributable to tips and falls

Test dummies provide an ethical/practical alternative to subjects

Only as enlightening as they are similar to population for which they represent

Slide 3
Objective

To develop a low speed, low impact test dummy for use in the study of the prevention of tips and falls from wheelchairs

Slide 4
Organization

Modifications to Hybrid III test dummy (HTD)

HTD validation

Robust test device

Slide 5
HTD Modifications

50th percentile HTD

Seated pelvis w/curved lumbar spine

to standing “pedestrian” pelvis w/straight lumbar spine

Abdomen removed

Slide 6
HTD Mod. (Cont.)

Hypothesis: bending in a forward fall occurs mostly from flexion in hips

Foam/rubber buttocks removed

Low density polyurethane foam – mimic flaccid tissue

Simulate a person with lower extremity paralysis

Slide 7
HTD Mod. (Cont.)

Abdomen removed
Standing pelvis
Straight lumbar spine

Graphic description:

Slide 8
HTD Validation

One wheelchair user with T8 paraplegia due to traumatic SCI served to validate modifications

Kinematic analysis of the trunk bending during a braking trial used to endorse modifications

Slide 9
Experimental Protocol

Study designed to maximize kinematic similarities between test pilot and test dummies

Emergency power off braking used

Test cases seated in Quickie P100

One test operator, drove wheelchair at maximum speed

Braking condition initiated when front caster crossed line on floor

OPTOTRAK 3020 motion measurement system recorded kinematic data

Slide 10
Exp. Protocol (Cont.)

Graphic description:

Slide 11
Statistical Analysis

Outcome Measures: trunk angular displacement, velocity, and acceleration

Wheelchair speed when braking was initiated was compared to ensure consistent input

10 repeated samples from each wheelchair rider

Analysis of Variance (ANOVA); α=.05

Tukey post hoc analysis

Slide 12
Results

Graphic description:

Slide 13
Results

No statistical differences in wheelchair speed when braking was initiated

Strong differences present (p<<.001) in angular displacement & velocity between test pilot and both HTDs

No significant differences in trunk angular acceleration

Slide 14
Discussion

800% increase in trunk motion after alterations

Simple modifications had positive influence

Bio-mechanically based flexion at hips

Differences attributable to anthropometrics and lumbar stiffness

Test Pilot only represents one population of wheelchair users, one level of SCI

Design for high risk population

Slide 15
Conclusions

Custom mold and shape polyurethane foam around hips to allow for a more robust, realistically responsive test dummy

Accurate dummy enhance understanding of how the user, wheelchair, and environment interact, and may lead to greater mobility with less risk of injury

Slide 16
Acknowledgements

This project was partially funded by the Centers for Disease Control and Prevention, Center for Injury Research & Control (R49/CCR310285-04), and the Paralyzed Veterans of America.

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Updated: March 7, 2002