Seat interface pressures of individuals with paraplegia: influence of dynamic wheelchair locomotion compared with static seated measurements.
OBJECTIVE: To provide a comparison of the seat interface pressures between static seating and dynamic seating during wheelchair locomotion of individuals with paraplegia. DESIGN: Repeated measures multivariate analysis of variance (MANOVA) comparing two conditions: static seat and dynamic seat interface pressures. SETTING: University campus and clinic. PARTICIPANTS: Fifteen participants, each of whom propelled a manual wheelchair for at least 5 hours per week over the previous 6 months and functioned with a spinal cord injury/ disability level of T1 or below. MAIN OUTCOME MEASURES: Peak pressure (PP) and pressure time integral (PTI) as measured by the Novel Pliance System, which consists of a flexible 32 x 32 capacitive sensor mat (each sensor 1.5 cm2) interfaced with a PC, was sampled at 10Hz. The participants were measured in their own wheelchair with a new Jay Active seat cushion. RESULTS: The repeated measures MANOVA showed a difference in the PP and PTI between the static and dynamic measurements (Wilk's = .00, p < .05). Follow-up dependent t tests yielded a difference in PP (t = 5.40, p < 0.025) and no difference in the PTI between static and dynamic conditions (t = 1.45, p > 0.025). The PP during static seating (mean = 16.2 +/- 5.0 kPa [121 +/- 37.5 mmHg]) was less than during dynamic seat interface pressures during wheelchair locomotion (20.03 +/- 6.6 kPa [152.3 +/- 49.5 mmHg]). PP varied by up to 42% during the wheelchair locomotion cycle. The PTI was similar between static (30.1 +/- 9.3 kPa [225.75 +/- 69 mmHg]) and dynamic conditions (36.2 +/- 18.1 kPa [271 +/- 135.7 mmHg]). CONCLUSIONS: The results from this study are consistent with some of the previous work on the nondisabled and a single case study, but with greater external validity because of the nature of the sample chosen and the methodology employed. PPs were greater during dynamic wheelchair locomotion compared with static seating interface pressures, with the peak varying up to 42% during the wheelchair locomotion cycle. The PTI indicates that the cumulative effect of the loading was comparable between conditions. The question that remains is whether this dynamic loading, resulting in a change in PP throughout the cycle, has a significant effect on tissue health.