Measurement of changes in the physiological cycle-to-cycle variability in gait kinematics using the ELLIS approach holds promise as a new tool for quantitative evaluation of gait adaptability. Adaptability is arguably one of the most crucial factors of gait function. However, functional limitations in adaptability have not been well documented, presumably due to the inability to accurately measure this aspect. For this purpose, we developed a new method to quantify subtle changes in cycle-to-cycle physiological variability in gait kinematics; a technique designated as the entropy of leg-linkage inertial signals (ELLIS) analysis. A previous study (Tochigi et al., JOR 2012) found that the ELLIS outputs in an asymptomatic cohort) became lower with greater age, and that subjects with symptomatic knee osteoarthritis exhibited lower values compared to age-matched asymptomatic subjects. In addition, highly consistent speed-dependent increases in ELLIS outputs (in the asymptomatic subjects) were also documented. This speed-dependency is consistent with the fact that stable walking at a faster pace places higher demands on the neuromuscular control systems. Complex interactions across multiple controlling factors presumably increase perturbations to gait kinematics within the “normal” range (i.e., increase in physiological variability). To advance understanding of the degree of speed dependence, the present study aimed to test whether or not the ELLIS outputs would linearly increase with increase in walking speed.Summary
Introduction
When performing the Scandinavian Total Ankle Replacement (STAR), the positioning of the talar component and the selection of mobile-bearing thickness are critical. A biomechanical experiment was undertaken to establish the effects of these variables on the range of movement (ROM) of the ankle. Six cadaver ankles containing a specially-modified STAR prosthesis were subjected to ROM determination, under weight-bearing conditions, while monitoring the strain in the peri-ankle ligaments. Each specimen was tested with the talar component positions in neutral, as well as 3 and 6 mm of anterior and posterior displacement. The sequence was repeated with an anatomical bearing thickness, as well as at 2 mm reduced and increased thicknesses. The movement limits were defined as 10% strain in any ligament, bearing lift-off from the talar component or limitations of the hardware. Both anterior talar component displacement and bearing thickness reduction caused a decrease in plantar flexion, which was associated with bearing lift-off. With increased bearing thickness, posterior displacement of the talar component decreased plantar flexion, whereas anterior displacement decreased dorsiflexion.
