Measurement of Load Redistribution Properties of Wheelchair Cushions Using a Compliant Cushion Loading Indenter

The aim of this project was to develop and validate a compliant cushion loading indenter (CCLI) capable of evaluating wheelchair cushion performance by measuring internal pressures and deflection. The design of the CCLI consists of 3 subsystems: 1) an internal substructure with medial and lateral protuberances to mimic the load-bearing ischial tuberosities and trochanters, 2) an elastomeric shell to mimic soft tissue and 3) instrumentation to measure internal pressures at both protuberances and deflection of the elastomer at 7 locations. It is parametrically designed so can be scaled larger or smaller to represent different body sizes. To assess the repeatability and sensitivity of measurements, the model was loaded onto two wheelchair cushions, 3″ flat foam and Jay3, using two loads, 44kgf and 53kgf, representing the average upper body mass of 70kg and 83kg persons, respectively. The results showed a high precision of pressure and deflection measurement across two different cushions and loads. Under both loads, pressure measurements exhibited a standard error of < 1 mm and <3 mmHg. The standard deviations of deflection values were less than 2.5 mm (0.1 in.). The pressures and absolute deflection differed significantly across load and cushion type indicating sensitivity to change.