B D Ashton | PubMed Health

PubMed1996

Adding loads to occupied wheelchairs: effect on static rear and forward stability.

OBJECTIVE: To determine the extent to which loads added in different positions affect the static rear and forward stability of an occupied wheelchair. DESIGN: Controlled, cross-over study. INTERVENTION: Loads from 0 to 10kg (in 1-kg increments) were added to five positions: high rear (HR), low rear (LR, beneath the seat and behind the crossbrace), on the lap (LAP), low anterior (LA, beneath the seat and anterior to the crossbrace), and on the footrests (FR). We also used a computer model to evaluate the relationship between stability and load, with a range of loads (0 to 100kg, in 10-kg increments) beyond the loads that were practical to test empirically. OUTCOME MEASURE: On a tilting platform, we measured the static stability (in degrees) of a wheelchair occupied by an anthropomorphic test dummy (ATD). RESULTS: The greatest increase in rear stability was with FR loads, changes of 64% and 227% for 10-kg and 100-kg loads, respectively. Only HR loads reduced rear stability, by 32% and 64%. The greatest increase in forward stability was with LR loads, by 13% and 92%. The greatest reduction in forward stability was with FR loads, by 10% and 149%. To minimize the effect of added loads on stability, the LAP and LA positions would be preferred. CONCLUSION: Added loads affect wheelchair stability as a function of the load magnitude. The extent and direction of the effect is profoundly influenced by load position.

Accidents↗

PubMed1994

Wheelchair stability and maneuverability: effect of varying the horizontal and vertical position of a rear-antitip device.

Although properly adjusted rear-antitip devices on wheelchairs prevent rear-tipping accidents, many wheelchair users do not use them because they limit manueverability. This study evaluated the use and effectiveness of antitip devices, particularly the effect of the devices' position on rear stability and maneuverability. In an epidemiologic study of the use of antitip devices, using a database of noninstitutionalized users of manually propelled chairs, we found no significant difference in the incidence or nature of rear-tipping accidents between the 167 who used antitip devices and the 399 who did not. We also evaluated seven common manually propelled wheelchairs, occupied by an anthropomorphic test dummy, with and without antitip devices. The added stability provided by the antitip devices varied considerably (from -1.0 to 27.1 degrees) depending on the type of chair, the configuration of the chair and the position of the antitip device. A representative wheelchair was then equipped with an adjustable antitip device that allowed us to test 68 combinations of vertical and horizontal positions. The relationships between the position of the antitip device and both the measured rear-stability and maneuverability values could be expressed by significant regression equations, and correlated highly with the values predicted by a theoretical model that we developed. These relationships should assist clinicians, users and wheelchair designers in finding appropriate compromises between safety and maneuverability.

Accidental Falls↗