Influence of wheelchair footrest height on ischial tuberosity pressure in individuals with paraplegia

Abstract

Objective: To describe the effect of wheelchair footrest height on sitting pressures in persons with paraplegia. Methods: Seventeen manual wheelchair users with paraplegia underwent a seat pressure examination while footrests were elevated from the initial position with the thighs parallel to the seat (p0), by 10% (position p10) and by 20% of the fibula length (position p20). We analyzed average pressure (AP), the contact surface of the body with the seat (CS), pressures on the ischial tuberosities - left (LIP) and right (RIP) - and average pressure on both ischial tuberosities (AIP). Results: A gradual increase in footrest elevation was accompanied by significant increases in AP (p0: 57.24±14.31; p10: 60.65±14.85; p20: 62±15.3 mm Hg; Kendall coefficient of concordance W=0.962), AIP (p0: 159.35±54.95; p10: 176.35±53.3; p20: 184.26±54.09 mm Hg; W=0.896), LIP (p0: 165.24±54.05; p10: 183±52.08; p20: 193.18±56.32 mm Hg; W=0.751) and RIP (p0: 153.71±71.23; p10: 167.35±72.19; p20: 175.35±70.84 mm Hg; W=0.524) and a significant decrease in CS (p0: 1218.2±100.8; p10: 1131.8±134.6; p20: 1065±142.6 cm2; W=0.985). There was a moderate correlation between the relative increase in LIP and RIP between p0 and p10, and between p10 and p20 (Pearson's correlation coefficient for LIP r=0.66; P=0.04, for RIP r=0.77; P=0.003), and a high correlation between relative changes in AIP (r=0.87; P<0.0001). Conclusion: Wheelchair footrest elevation caused a steady rise in AIP; however, left to right side pressure differences changed variably, suggesting that the risk of pressure ulcers may increase disproportionately with footrest elevation.