Feasibility study on a composite material construction technique for highly stressed components in reciprocal walking orthoses for paraplegic patients

Abstract

Reciprocal walking for thoracic level paraplegic patients using reciprocal walking orthoses has become a routine treatment option. Two general design options are currently deployed within an overall treatment regime. Research has shown that one has better walking efficiency but is cosmetically less acceptable to the patient. Design analysis and experimental data have shown that a major factor in improved walking efficiency is the lateral stiffness of the body brace section of the orthosis. This is the area where problems of cosmesis in the more efficient orthosis are perceived because of the employment of metallic structures. The use of composite material structures to achieve shapes which are more closely conforming to the patient is an attractive option. However the brittle nature of these materials makes it unlikely that the requirement for the ductile failure mode will be achieved from a straightforward moulding. A new construction technique has been devised which has the potential to provide a safe failure mode with greater stiffness and lighter weight. This feasibility study has been undertaken to demonstrate its potential so that further work can be justified which will provide sufficient evidence to support a patent application. The successful outcome of the study, in which stiffness was increased by 60 per cent with a weight reduction of 50 per cent and a failure mode comparable with the original metal structure, suggests that further work will enable the dilemma in the choice of orthosis to be resolved.