POSITION AND ORIENTATION IN-SPACE OF BONES DURING MOVEMENT - EXPERIMENTAL ARTIFACTS

This paper deals with the experimental problems related to the reconst ruction of the position and orientation of the lower limb bones in spa ce during the execution of locomotion and physical exercises. The inac curacies associated with the relative movement between markers and und erlying bone are analysed. Quantitative information regarding this mov ement was collected by making experiments on subjects who had suffered fractures and were wearing either femoral or tibial external fixators . These latter devices provided frames that were reliably rigid with t he bone involved, and hence the possibility of assessing the relative movement between markers mounted on the skin and this bone, Anatomical frames associated with thigh and shank were reconstructed using techn ical frames based on different clusters of skin markers and their rota tion with respect to the relevant bone evaluated. Marker movement was also assessed in subjects with intact musculoskeletal structures using digital videofluoroscopy.