CLINICAL MEASUREMENT OF NORMAL AND SHEAR STRESSES ON A TRANS-TIBIAL STUMP - CHARACTERISTICS OF WAVE-FORM SHAPES DURING WALKING

Stresses on the surface of a stump within a prosthetic socket during w alking can potentially traumatise stump tissues. To gain insight into stresses and design parameters that affect them, normal and shear inte rface stresses were measured on three unilateral trans-tibial amputee subjects during walking trials. During stance phase repeated character istics in wave-form shapes from different subjects were apparent. They included ''loading delays'', ''high frequency events (HFE's)'', ''fir st peaks'', ''valleys'', ''second peaks'', and ''push-off''. Character istics did not necessarily occur at the same time from one step to the next but their timings matched well with events in shank force and mo ment data which were collected simultaneously. For ''plantarflexion'' and ''dorsiflexion'' alignment changes, the above wave-form characteri stics were still pesent but their timings within the stance phase chan ged. The physical meaning and relevance of the characteristics to stum p tissue mechanics are discussed.