Abstract
Toe joints play an important functional role in able-bodied walking; however, for prosthesis users, the effect of adding a toe joint to a passive prosthetic foot remains largely unknown. The current study explores the kinematics, kinetics, rate of oxygen consumption and user preference of nine individuals with below-knee limb loss. Participants walked on a passive prosthetic foot in two configurations: with a Flexible, articulating toe joint and with a Locked-out toe joint. During level treadmill gait, participants exhibited a decrease in Push-Off work when using the Flexible toe joint prosthesis versus the Locked toe joint prosthesis: 16% less from the prosthesis (p = 0.004) and 10% less at the center of mass level (p = 0.039). However, between configurations, participants exhibited little change in other gait kinematics or kinetics, and no apparent or consistent difference in the rate of oxygen consumption (p = 0.097). None of the traditional biomechanical or metabolic outcomes seemed to explain user preference. However, an unexpected and intriguing observation was that all participants who wore the prosthesis on their dominant limb preferred the Flexible toe joint, and every other participant preferred the Locked configuration. Although perhaps coincidental, such findings may suggest a potential link between user preference and limb dominance, offering an interesting avenue for future research.
Highlights
Toe joints play an important functional role in able-bodied walking; for prosthesis users, the effect of adding a toe joint to a passive prosthetic foot remains largely unknown
We observed a significant increase in maximum angle from 1.1 ± 1.6° in the Locked configuration, to 20.8 ± 3.0° in the Flexible configuration (p = 0.008), confirming our experimental design was effective in varying toe joint articulation
Lower limb prosthesis users walking with the Flexible toe joint exhibited a decrease in Push-Off work: approximately 16% less from the prosthesis and 10% less at the center of mass level
Summary
Toe joints play an important functional role in able-bodied walking; for prosthesis users, the effect of adding a toe joint to a passive prosthetic foot remains largely unknown. A small sample of prostheses with toe joints have recently entered the commercial market (e.g., Ottobock Meridium, ST&G ToeFlex) Whether this feature is preferable and/or beneficial relative to a fully rigid/stiff keel, and how this may vary according to locomotor task, remains unclear. Together, these prior research findings and contemporary commercial devices motivated us to explore the effects and implications of toe joint dynamics on lower limb prosthesis users, most of whom walk on commercially-available prosthetic feet that do not include an articulating toe joint. It remains unknown whether these aesthetic toes behave functionally as a toe joint, or if the stiffness properties of the cosmesis provide auxiliary benefits during walking and other locomotor tasks
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