Re: Adjustable Instantaneous Center & European Alignmen t musings

Re: Adjustable Instantaneous Center & European Alignmen t musings

Benveniste, David Mark

2/9/2001

Jack,
Please DO continue! This is exactly the kind of clear thinking and
experience that I think most of us would appreciate.
Mark Benveniste CP

> -----Original Message-----
> From: <Email Address Redacted> [SMTP: <Email Address Redacted> ]
> Sent: Friday, February 09, 2001 9:48 AM
> To: <Email Address Redacted>
> Subject: Re: [OANDP-L] Adjustable Instantaneous Center & European
> Alignment musings
>
> A couple of comments on Euopean alignment and stance brake knees.
> The increased toe clearance for the Euro alignment over the TKA alignment
> is
> due to the relative anterior placement of the knee. The foot is not
> dorsiflexed. In fact, if the bench alignment is done with a safety
> factor
> lift under the heel, the foot is plantarflexed. As pointed out by
> Radcliffe,
> this does not cause the leg to be too long or the toe to catch in swing
> because the distance from the ball of the foot to the hip is the same in
> both
> systems.
>
> Safety knees. In my opinion, they should be used much less than they are.
> Why, They cause the amputee to walk with an unnatural gait because they
> can't begin to flex the knee in late stance, while still in double
> support.
> If a good walker is fitted with a safety knee, they will likely complain
> of a
> popping when the knee begins to bend. This is because the brake is
> resisting knee flexion, the amputee is producing a knee flexion moment
> with
> active hip muscle action and when enough weight is transferred off of the
> prosthesis and the brake releases, they get that annoying pop.
> I prefer to fit all AK's who have adequate hip musculature with a knee
> that
> will allow and even encourage voluntary controlled knee flexion while
> still
> in double support.
>
> Hope this is useful and that this brief explanation gets my thoughts
> across.
> I would be happy to continue this if anyone likes.
>
> Regards,
> Jack Uellendahl, CPO
>
> In a message dated 2/9/01 6:45:44 AM Central Standard Time,
> <Email Address Redacted>
> writes:
>
> << Furthermore, it has been brought to my attention that single axis knees
> have
> improved toe clearance if aligned in the European alignment system.
> It is very possible that I am not understanding this correctly but it
> seems
> that the European alignment starts with bench alignment of the prosthesis
> with the foot in dorsiflexion.
>
> This would seem to create improved toe clearance but I wonder if this is
> effective with more flexible keels vs. hard sach keels or S/A feet that
> don't
> have front bumpers. Is there a problem with inadequate toe lever?
>
> Additionally, it seems to me that there is toe clearance with a single
> axis
> knee when there is adequate knee AND hip flexion at the appropriate time
> which may not happen with the slow or beginning or feeble ambulators
>
> So...it appears that a beginning and or feeble ambulator will have
> difficulty
> clearing the toe
> with a single axis knee, would have an easier time with a four bar, but
> wouldn't have the safety advantage of the single axis weight activated
> stance
> control type knee. >>
>
>