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Our team asked if adding a toe joint to a passive prosthesis would alter unilateral BK user biomechanics, O2 rate, or be preferred (over no toe joint) during level walking. The summary answer is below + there's an intriguing surprise!
https://www.nature.com/articles/s41598-021-81565-1
(1/n)
https://www.nature.com/articles/s41598-021-81565-1
(1/n)
But first, here’s our modified prosthesis. It allowed us to quickly transition from a Locked to a Flexible toe joint during data collection (taking our fastest undergrad <25s!). Max toe DF angle confirmed the design works well (~1 vs. ~21deg). So how do people respond?
(2/n)
(2/n)
Intact limb mechanics don't change much with a Flexible toe prosthesis. But on the prosthetic limb, +ve Push-off work DECREASED by 16 & 10% at the prosthesis & center of mass, respectively. Maybe you're thinking all users preferred a Locked toe but they didn’t!
(3/n)
(3/n)
Despite lower Push-off work with a Flexible toe joint we don’t see a ubiquitous increase in O2 rate. In fact, there was no clear trend. Lit is also divided on the relationship btwn Push-off work & metabolics. Importantly our O2 data didn’t appear to drive preference either
(4/n)
(4/n)
User preference was a mystery to us at first. It didn’t align biomech/O2 data. BUT, interestingly, it did align with limb dominance. People who lost their dominant limb (N=4) preferred a Flexible toe joint & everyone else (N=5) preferred a Locked toe!! But why?!
(5/n)
(5/n)
Hard to tell (& perhaps results=coincidence) but one idea we’ve had: in able-bodied ppl, the dominant limb seems to engage in the more dynamic aspect of an asymmetric, bilateral task, with joints moving through high ROM, while non-dominant limb joints stabilize (eg kicking)
(6/n)
(6/n)
Gait data is less conclusive re lower limb dominance & biomech symmetry. But maybe prosthesis users who have lost their dominant limb prefer the extra DoF provided by the Flexible toe joint & those who have lost their non-dominant limb prefer the stability of a Locked toe?
(7/n)
(7/n)
Broadly though, a link between limb dominance & prosthesis user preference could have BIG implications to device prescription and is an important avenue of future research.
(8/n)
(8/n)
. @rachelteater21, @KarlZelik and I are also exploring prosthetic toe joints on uneven terrain & slopes so watch this space!
(9/9)
(9/9)
