Estimation of deformation in a walking orthosis for paraplegic patients

Although good results have already been achieved in reciprocal walking for paraplegic patients using mechanical orthoses (e.g. ORLAU ParaWalker), improvements in lateral stiffness of walking devices could increase significantly the efficiency of ambulation. For this reason a method for monitoring the structural properties of an orthosis during locomotion has been studied. A motion analysis system (ELITE system) able to detect automatically and accurately the positions of small retroreflective markers in a television field was used. Starting from marker positions, the angular variations between adjacent structural segments in the orthosis were computed and the areas in which maximum deformations occurred were identified. Experiments were performed on two paraplegic patients using their ORLAU ParaWalker orthoses and two different kinds of movements were analysed: lateral tilting and walking. The results show that this approach is able to detect the small deformations occurring in the orthotic structure and therefore to provide valuable information for orthotic design optimization.