[Improving seating comfort in wheelchairs for the prevention of pressure sores]

The risk factors for occurrence of pressure sores--pressure, temperature and humidity--were measured in extensive tests on commercially available wheelchair designs. The effects of different chair positions on the strain and pressure distribution on the backrest, seat surface and foot rests were recorded on a universally adjustable experimental chair. In order to appraise the influence of various types of handicaps, the experiments were conducted with paraplegic, spastic and hemiplegic subjects. It became evident from the results obtained that the currently used suspension belt chairs display serious deficiencies, inherent in their construction principle. Above all, they do not offer an adequately large support area to handicapped persons with severe atrophy of the gluteal muscle. Also, a backrest shape with lumbar pad, as requested by physiologists and orthopaedic surgeons, is technically difficult to realize. Considerable improvements with respect to pressure distribution and orthopaedically correct support of the seated patient can be achieved by using a shell seat construction. In order to enable the handicapped person to use various sitting postures, the backrest should be provided with a rotary joint to the sitting surface.