How a Toe Joint on a Prosthetic Leg Can Transform Walking
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In a biological leg, the toe joints flex and extend when walking. This movement influences how the muscles and bones in the foot and ankle work together, as well as how the entire body moves while walking. As prosthetic design improves to mimic the biological design, researchers sought to find out if adding a flexible toe joint to an otherwise stiff prosthetic foot would make a difference.
Context
A previous study on the effect of toe joint stiffness on walking was done in 2018. The researchers found that changing the stiffness substantially affects how the body keeps its balance during push-off when walking, making it easier to push off the ground and keep moving forward smoothly. In this study, nine out of 10 participants preferred walking on a prosthetic foot with a moving toe joint to one without.
Furthermore, this need for more data comes with the commercial release of prostheses with toe joints, such as Ottobock’s Meridium and ST&G’s ToeFlex.
If you’re considering getting a prosthesis with a moving toe joint, the findings in this study might help you decide.
The study
Although previous research (like the one mentioned above) has found favorable outcomes for having a toe joint in prosthetic feet, the researchers noted that there are still knowledge gaps. So, this study set out to examine the biomechanics, metabolic or energy cost, oxygen consumption rates, and user preferences among individuals with one-sided below-knee limb loss while walking on prosthetic feet equipped with and without a toe joint.
The study involved nine participants with below-knee limb loss who tested a passive prosthetic foot in two different configurations: one with a flexible toe joint and the other with a fixed toe joint. The research protocol included training and trial sessions, including level walking trials.
Results
While walking on a flat treadmill, participants using a flexible toe joint prosthesis produced less push-off power than those using a locked toe joint prosthesis. Push-off is the moment when the ankle joint produces a burst of energy to help move the body forward.
Other aspects of walking mechanics changed only slightly, and oxygen use was not significantly different between the two types of prostheses.
Interestingly, the researchers found a possible connection between users' preferences for toe joint types and which leg they had lost. Participants who had lost their dominant leg tended to favor the flexible toe joint, while those who had lost their non-dominant leg preferred the locked version.
These results suggest that personal preferences for toe joint styles do not always align with what might save the most energy while walking.
The bottom line
While the researchers found no significant difference between flexible and fixed toe joints regarding metabolic demands or biomechanics, the study highlighted the need to consider limb dominance and individual choices when designing, prescribing, or choosing prosthetic feet.
In the future, additional studies may investigate the long-term impacts on user comfort and mobility.
What do you think of the study’s findings?
