Effect of Rear Wheel Suspension on Tilt-in-Space Wheelchair Shock and Vibration Attenuation.

ABSTRACT

BACKGROUND: Suspension systems are designed to reduce shock and vibration exposure. An aftermarket rear-wheel suspension system is now available for manual tilt-in-space wheelchairs. OBJECTIVE: To compare quantifiable shock and vibration on a rigid manual tilt-in-space wheelchair to published data on manual wheelchairs and to determine whether aftermarket rear suspension system will significantly decrease shock exposure when traversing common obstacles. DESIGN: Cross-sectional. SETTING: Research laboratory. PARTICIPANTS: Ten healthy non-wheelchair users. METHODS: Subjects seated in a manual tilt-in-space wheelchair were pushed over 4 different obstacles (an exterior door threshold, truncated domes, 2-cm descent, and 2-cm ascent) with the chair as manufactured and with the suspension system installed. MAIN OUTCOME MEASUREMENTS Superior/inferior and anterior/posterior accelerations were assessed at the seat pan with and without the use of ISO 2631-1 standards. Peak accelerations were analyzed from the door threshold, 2-cm descent and 2-cm ascent. Root mean square acceleration (RMSa) values were analyzed from the truncated domes, and vibration dose value (VDV) was analyzed for all surfaces. RESULTS: There were no differences in time spent over the 4 obstacles between rigid and suspended conditions (P≥.064). Suspension decreased the peak acceleration at the rear wheel when it initially impacted the door threshold, and when the rear wheel traversed the 2-cm descent and ascent (P≤.043). ISO 2631-1 frequency weighting, placing emphasis on frequencies most harmful to humans, also supports suspension reducing peak accelerations at the rear wheel both when it initially impacted and left the door threshold, and when the rear wheel descended 2 cm (P≤.049). Suspension also reduced the truncated dome RMSa as well as the door threshold, 2-cm descent, and total VDV (P≤.041). CONCLUSIONS: The results indicate that rigid manual tilt-in-space wheelchairs respond to rough surfaces in a similar fashion to previously studied rigid wheelchairs. Furthermore, the aftermarket suspension system reduces some aspects of shock and vibration exposure, also consistent with previously studied suspension systems. LEVEL OF EVIDENCE NA.