Seat-interface pressures on various thicknesses of foam wheelchair cushions: A finite modeling approach  Robert Ragan, PhD, Thomas W. Kernozek, PhD, Mani Bidar, BS, J.W. Matheson, MSPT  Archives of Physical Medicine and Rehabilitation  Volume 83, Issue 6, Pages 872-875 (June 2002) DOI: 10.1053/apmr.2002.32677 Copyright © 2002 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions

Fig. 1 Contour map of seat-interface pressure. For modeling purposes, the area of high pressure around the ischial tuberosity was treated as a radial pressure distribution centered at the ischial tuberosity. To put the pressure data into radial form, the pressure was recorded as a function of distance from the ischial tuberosity along the 8 radial lines shown and then averaged at each distance for input to the computational model. Archives of Physical Medicine and Rehabilitation 2002 83, 872-875DOI: (10.1053/apmr.2002.32677) Copyright © 2002 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions

Fig. 2 Cross-section of the axisymmetric, seat-interface, finite-element model using 408 elements. The black area represents ischial tuberosity, the dark gray represents subcutaneous tissue, and the light gray represents the cushion. Archives of Physical Medicine and Rehabilitation 2002 83, 872-875DOI: (10.1053/apmr.2002.32677) Copyright © 2002 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions

Fig. 3 The radial distribution of the seat-interface pressures for a soft foam cushion (cushion thickness, 8cm) and hard flat seat (no cushion) is depicted. The points are the radial pressure data measured (meas.) as in figure 1. The curved lines are the model calculations (calc.) fitted to the measured points. Archives of Physical Medicine and Rehabilitation 2002 83, 872-875DOI: (10.1053/apmr.2002.32677) Copyright © 2002 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions

Fig. 4 Contour plot of the compressive subcutaneous stress under load with a 16-cm cushion. The arrows indicate the areas of high subcutaneous compressive (bottom arrow) and subcutaneous shear (top arrow) stress. The black area represents ischial tuberosity, the dark gray represents subcutaneous tissue, and the light gray represents the cushion. Archives of Physical Medicine and Rehabilitation 2002 83, 872-875DOI: (10.1053/apmr.2002.32677) Copyright © 2002 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions

Fig. 5 Maximum subcutaneous stress, seat-interface pressure, and subcutaneous shear stress for various foam cushion thicknesses. Archives of Physical Medicine and Rehabilitation 2002 83, 872-875DOI: (10.1053/apmr.2002.32677) Copyright © 2002 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions