Lumbar support thickness: effect on seated buttock pressure in individuals with and without spinal cord injury.

We compared the effects of different lumbar support thicknesses on seated buttock pressure in individuals with and without spinal cord injury (SCI). Eighteen subjects with SCI (SCI group) and 18 subjects without SCI (control group) were seated on a pressure-sensing transducer incorporated into an adjustable chair. The output was calibrated so that eight pressure intervals (colors) were displayed. The lumbar support thickness was adjusted to 0, 2.5, 5, and 7.5 cm, and the highest and lowest seated buttock pressures were analyzed. External measurements of the hip angle were taken for each lumbar support condition. High reliability of repeated seated test positions was found (intraclass correlation coefficient = .93). The 5- and 7.5-cm-thick lumbar supports caused a decrease in the highest pressure areas in the control group, but no change in the SCI group. The hip angle was increased with each increment in lumbar support thickness in both groups, but the SCI group's hip angle was consistently less than that of the control group for each lumbar support condition. The results of this study suggest that in individuals with chronic paralysis (greater than or equal to 3 years), the use of a wheelchair lumbar support has a negligible effect on seated buttock pressure.