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 degrees 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 degrees increments between 0 degrees and 50 degrees, 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 degrees 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 degrees 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. Spinal Cord (2011) 49, 827-831; doi: 10.1038/sc.2010.194; published online 18 January 2011