The effect of seat shape on the risk of pressure ulcers using discomfort and interface pressure measurements

Background: It is clinically known that shape is important when selecting or designing a wheelchair support surface for the prevention of pressure ulcers (a £2 billion annual cost to the National Health Service, UK); however, the effect of different levels of shape contouring has not been adequately studied. Objectives: To investigate the effect of seat shape on the risk of pressure ulcers using discomfort and interface pressure measurements. Study design: Randomised, repeated trial. Methods: Thirty able-bodied participants sat with restricted movement for 30 min in three sessions to evaluate two cushion shapes against a flat baseline surface. Visual Analog Scaling and pressure mapping were used to measure surrogates for pressure ulcer risk, discomfort and interface pressures, respectively. Results: Linear regression revealed a reduction in discomfort (p < 0.05) on the custom contoured shapes. Interface pressures measured were also lower (p < 0.05) on the custom contoured shapes, and a negative Pearson’s correlation (p < 0.05) indicated an association between smaller hip widths and increased discomfort for the commercially shaped cushion. Conclusions: The results of this study confirm that custom contoured shapes were effective at reducing pressure ulcer surrogate measures in the participants of this study and therefore suggests that the contribution of a cushion’s three-dimensional contours on pressure ulcer risk should be further researched. Clinical relevance The measurement of seat shape, discomfort and interface pressure in surrogate participants can help inform the design of wheelchair seating for individuals who are insensate or otherwise at risk of developing pressure ulcers. This knowledge can now be implemented using modern three-dimensional shape acquisition, analysis and fabrication technologies.