The standard manual wheelchair is an effective, but inefficient means of transport. Hemiplegic users face cognitive, perceptual and physical difficulties. Although the cognitive and perceptual difficulties are difficult to address, the physical difficulties can be ameliorated by improvements in wheelchair design. Current provision includes two different types of propulsion: the ratchet arm or lever-drive mechanism and the dual-handrim mechanism. Lever arm design, such as the NuDrive (Watford, Hertfordshire, UK) or Pivot (Pivot Rio Mobility, San Francisco, CA), involves a pushing or pulling action on the end of a lever mechanism.
The second type of design is the dual handrim where the two handrims are mounted on the same side of the wheelchair. Propulsion involves gripping and rotating both rims at the same time in order to move forward in a straight line. This can be difficult for users with a small hand span or with impaired hand function. Alternatively each rim may be used in turn to propel the wheelchair forwards but this can result in a snake-like movement, which is inefficient and requires significant effort.
Literature reports that nearly 70 per cent of wheelchair users experience upper extremity pain or overuse injury at some point. Anecdotally, clinicians report that the current one-arm drive wheelchairs do not meet the needs of hemiplegic users, which may explain the high level of wheelchair abandonment.
The study was designed as a controlled, same-subject study that measured the force generated by each user during propulsion in three different one-arm drive wheelchairs.
The data being measured were vertical reaction forces at the buttock/seat interface in Newtons. These were measured using the CONFORMat® Pressure Measurement System, a portable interface pressure mapping system, which records pressure distribution under the contact area. The system includes pressure-sensing hardware and software.
The study was designed to compare the measurements taken in each wheelchair for each individual participant, with each user acting as their own control. This was considered to be an appropriate approach due to the heterogeneity of hemiplegia within the user group and the bespoke postural and pressure equipment that they used in the wheelchairs during the study.