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lmiller69
07-20-2006, 11:18 PM
Following the definitions taught in most prosthetic texts, this is actually
backwards.

Flexion of the socket = dorsiflexion of the foot
Extension of the socket = plantarflexion of the foot

To visualize it, imagine holding the connection of the socket to the
prosthesis fixed and moving the top of the socket forward. Then the
person's knee would be "flexed". In that position, the toes of the
prosthetic foot are closer to the anterior-proximal border of the socket
(the foot has been dorsiflexed). Another way to see it is to take the
prosthesis in that position and move the whole device back to where the
socket previously fit, allowing the distal components to move. The foot
would then be standing on the heel and the toes would be up in the air
(again, dorsiflexed). In the "old" days, before endoskeletal components,
when the prostheses fit were all exoskeletal and alignment was done with a
Berkeley alignment fixture, there was no adjustment at the ankle (sold ankle
cushioned heel, SACH, feet). So there really was only one adjustment. Now,
with endoskeletal components, dorsiflexion at the ankle and flexing the
socket at the distal end of the socket have similar effects on alignment but
there is a linear difference.

As for dorsiflexion being the "most" important, it certainly is important
but the A-P placement of the foot as well as the foot characteristics (heel
and keel stiffness) also have a significant affect that should not be
disregarded. And, from teaching for a while, I can say that recognition of
frontal plane alignment seems to be the one that students struggle with the
most.

Laura

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Laura Miller, PhD, CP
Rehabilitation Institute of Chicago
312-238-2810 clinical services
312-238-1932 fax

-----Original Message-----
From: * Biomechanics and Movement Science listserver
[mailto:BIOMCH-L@NIC.SURFNET.NL] On Behalf Of Tan Chi Wei
Sent: Thursday, July 20, 2006 10:04 AM
To: BIOMCH-L@NIC.SURFNET.NL
Subject: [BIOMCH-L] Prosthetic foot alignment

Hi All :



I am a student and am new here. I learnt about Biomch-L after one of my
professors sent me an email regarding a topic of interest.



I am writing in today to find out how many people would agree with me in
the following:



In the alignment of the prosthetic foot, dorsiflexion was the most
important alignment change (ref: Fridman, Ona and Isakov; P&O
International 2003, 27. 17-22)

Would you agree if I say extension of a BK socket is actually equivalent
to dorsiflexion of the prosthetic foot and that flexion of the BK socket
is equal to plantar flexion of the prosthetic foot? I say this because
during mid stance, the shank is to be perpendicular ( or close to) to
the floor. Therefore, if a BK socket is flexed, shank perpendicular to
the floor, then the foot will have to be plantar flexed. Vice versa.



Open for comments.



Thanks

Chi Wei TAN