Can static interface pressure mapping be used to rank pressure-redistributing cushions for active wheelchair users?

Interface pressure mapping (IPM) is a clinical tool that assists the selection of seat cushions for pressure management for wheelchair users. Clinical pressure measurements are almost always made under static sitting conditions, although this does not consider the time-dependent properties of some cushion materials that may behave differently under the dynamic conditions of self-propulsion. This study investigated the potential for such differences by collecting seat IPM measurements from eight wheelchair users using four different seat cushion designs during static sitting and self-propulsion. Mean pressure corresponding to the approximate anatomical location of the ischial tuberosities was used to rank the four cushions under the two conditions. The two sets of rankings for each participant were then compared using correlation. Dynamic data from four participants was judged too inconsistent to be interpreted reliably and demonstrates the practical difficulties associated with dynamic IPM measurement when variations in individual propulsion technique cannot be controlled. Strong correlations were observed between rank orders for the remaining four participants and suggest that the statically derived pressure measures can be used for clinical decision making when selecting cushions for self-propelling wheelchair users.