Physical Properties of a New Orthopaedic Supporting Material for Posture Control in Wheelchairs

Providing a support surface with an even pressure distribution for wheelchair occupants is one of the primary objectives in clinical practice. Consequently a new warp-knit fabric has been developed with the aim to provide a more ideal orthopaedic support. The fabric, which hasbeen described in a US patent, comprises a lock-knit stitch with a laid-in yarn and is made by using three guide bars with nylon and elastic yarns. In a clinical trial it was observed that users found this new fabric system to be more comfortable than a conventional wheelchair material.The relationship between relevant fabric properties (including the supporting characteristics of the fabric) and the findings of the clinical trial were investigated. Comparisons of interface pressure were made on 5 nondisabled subjects sitting on a hard surface, a conventional wheelchair seat and the new fabric under different pre-stressed tension loading. Preliminary results indicated that the average pressure under the ischial tuberosities was reduced by 34% for the new fabric system and 17% for the conventional wheelchair seating material as compared to the hard surface. In the case of the fabric system, there appears to be little effect on the interfacial pressure under the ischial tuberosities due to variation in the pre-stressed tension loading. A consideration of the physical properties of the two supporting systems under investigation revealed that the new fabric system had a number of advantages in addition to the reduction of the average pressure under ischial tuberosities and that these advantages supported the findings ofthe clinical trial.