Three-dimensional, six-degrees-of-freedom kinematics of the human hindfoot during the stance phase of level walking

The goal of this study was to develop a technique to measure the unconstrained, six-degrees-of-freedom motion of the hindfoot during level walking and to apply this technique to characterize this motion in a young healthy population. The motion was described using a joint coordinate system which provided a description of motion in terms of three angular displacements and three linear displacements. The accuracy of the technique was first determined using a six-degrees-of-freedom linkage, The motion of the hindfoot was then measured during level walking on ten young healthy volunteers. For this purpose, a motion analysis system was used to record the motion of eight reflective skin markers attached over bony landmarks on the tibia-fibula and calcaneus. The results indicate that the baseline accuracy of the technique (not including skin motion) was 1 degree for rotations and 1.4 mm for translations. From the gait data it was concluded that the patterns of hindfoot motion are similar amongst individuals in some joint parameters but not in others. Specifically, dorsiflexion/plantarflexion had a very consistent pattern, followed by inversion/eversion and to a lesser extent by compression/distraction. The other parameters (axial rotation, anterior/posterior displacement and medial/lateral displacement) demonstrated a highly variable pattern amongst the individuals tested. In terms of the range of motion of the six joint parameters it was found that angular excursions were smaller than 20 degrees and that linear displacements in both anterior/posterior direction and medial/lateral direction was smaller than 3.5 mm.