Measuring the effect of incremental angles of wheelchair tilt on interface pressure among individuals with spinal cord injury

Study design:This study was a repeated measures study.Objectives:The objective was to systematically measure the relative reduction in interface pressure (IP) at the ischial tuberosities (IT) and sacrum through 10° increments of tilt in a manual wheelchair among individuals with motor complete spinal cord injury (SCI).Setting:This study was carried out in Manitoba, Canada.Methods:A total of 18 adults with ASIA A or B level of injury were recruited through an out-patient SCI clinic. Using a standardized protocol, participants were tilted in 10° increments between 0° and 50°, and IP readings were obtained at the IT and sacrum using pressure mapping technology. Relative pressure reduction from baseline was calculated and compared between tilt angles.Results:Tilt angle had a highly significant effect on pressure reduction at the IT (P=0.000) and the cosine relationship between these variables was expressed as quadratic. Reduction in sacral pressure did not occur until 30° tilt, with increased loading at smaller tilt angles. Pressure reduction at the IT and sacrum was not significantly different for tetraplegic and paraplegic participants.Conclusion:Small tilt angles are more suitable for postural control than pressure management. A minimum tilt of 30° is required to initiate unloading the sacrum and to achieve a clinically important reduction in pressure at the IT. Larger tilt angles resulted in more substantial pressure reduction than previously reported. Tilt-in-space appears to have similar benefits for individuals with paraplegia and tetraplegia.