Responses to 3S Locking Liner Question

Responses to 3S Locking Liner Question

Robert Schiff

Thank you for all your responses. Some of them are quite interesting. Here
are the results...

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Hey Rob,

I caught your original post and thought it was a good question. As far as
distracting a RL with lots of excess tissue. That is the only time I do
distract. I do this because pin only suspension will piston quite a bit
with these types of RL. Now I'm using shuttle locks with expulsion valves.
The suction and pin work really well together. Try it and you'll like what
you see. These redundant RL stop pistoning. However, you have to seal the
proximal brim. Sometimes the liner alone will work, but this is not
completely reliable. I use a sleeve, but hypobaric sock or so sort of a
ring seal in the socket are options.

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Robert,
Two solutions to your honest question, use a clutch lock for the slightly
redundant patient once the pin is engaged they can proceed to ratchet the
liner down, use a lanyard lock for the more fleshy, redundant patient.
I've had good luck with both if care is taken in choosing the proper system.

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the patient will slowly sink into the socket distally as he walks. to speed
up the process you can pull them in by turning the locking mechanism(assuming
you use an alps gear type lock or comparable)

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Hey Robbie:

It doesn't seem to matter what you do in your casting techniques for the pin
system, the fact is when the pt is ambulating there is a draw on the distal
aspect of the limb. You're right, there never really is total contact or
total surface bearing in this system. IF the limb has distal contact
within the socket (& that's a big IF from what I've seen of these sockets),
it is sitting in the little umbrella of the liner (not custom to the pt's
RL). Usually there is lack of distal contact w/in the socket so they are wt
bearing through whatever modifications the practitioner felt like putting in
the socket (i.e., monster MPT bars, pretib depressions and popliteal
walnuts...all natural modifications, I'm sure!). The distal aspect of the
limb then is under continuous stress. They get a pulling effect with every
swing through of the prosthesis, continual distraction in sitting (unless the
pt REMEMBERS to release the pin alittle) and then weird wt bearing surfaces
in stance with skin movement w/in the liner to get back in place after being
distracted in non-wt bearing.

Our facility is moving totally away from the pin system of any kind. In
fact, the pts who formally worn these systems are now very happy with BK
suction sockets. Hey, the work silicone on their skin before, now it goes
just alittle higher on the leg. But now there IS total surface bearing, the
distal aspect of the socket is custom made to the pt (not some umbrella/pin
attachment), and there is NO movement w/in the system unless they get a hole
in their knee sleeve. We are also beginning this coming week beginning to
use the new TEC Harmony system. This is added to the V3 BK suction system
for what sounds like a very healthy limb environment.

Hope this helps.

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Robert,
People are telling you to distract the tissues because it is felt that this
technique will reduce pistoning, which it probably does.
However, if you have an airtight shuttle lock and a sleeve suspension in
addition to the pin, you have zero pistoning.
This was brought up again at the last academy meeting in the seminar about
gel liners. The engineering professor says that it make the most sense to not
pull on the distal tissues as a pin suspension liner does for suspension
alone.
If the liner can be fixed to the hard wall of the socket, then you have
suspension on the whole residuum. Glueing it is impractical but
vacuum/suction is easily achieved.
There are a few shuttle locks that incorporate this airtight feature now, and
you can achieve the same results with most shuttle locks if certain measures
are taken.

Your concerns are rightfully taken and are most significant in AK's when the
pt is trying to get into the socket and is pushing down that redundant tissue
mass and trying to get it into the narrower distal end created by distracting
during casting.
Often this is the reason for the clutch type lock that allows the pt to draws
the residuum down by turning the shuttle lock and pulling the pin down if it
can be initially engaged.

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If you use a clutch lock, ratcheting the pin back after donning the socket
should help restore the original configuration resulting from distraction
during casting and provide total contact. If this isn't done, then the
tissues may hang up and prevent total contact. Or, a lanyard might be used
instead of a clutch lock. But to have total contact there first has to be
good containment of the tissue prior to casting. Some AK liners tend to be
loose distally when redundant tissue is present, in which case a cup may
need to be applied first.

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Hi Robert.

It's a fair question you ask.

When you roll an interface on to the residual limb, you will displace the
soft tissue a little and you will also take some loose movement out of the
skin. If you take a cast like this, you will get a reasonable result.

Now the next time you do this, before you cast, take a pin or a lanyard to
the interface - and pull. There will, to a greater or lesser degree, some
loose movement of the interface. The more the movement, the less stable the
interface/soft tissue combo is. The less movement, the more stable
everything is, which is good and a good platform on which to start thinking
about replicating that shape.

Now you have choices. The type of interface you use can affect this
stability issue significantly. Personally, I feel it's preferable to have a
liner that is longitudinally stiff, so it is the interface that provides
longitudinal stability, not the skin and soft tissues reaching their limit
of stretch. Try pulling a few different liners on, do the smae thing with a
pin or lanyard and see the differences.

Next thing is sizing. The job of the interface is, as I suggest, to act as
an interface, not necessarily an influence on the soft tissues. An
accurately and correctly sized interface should almost just lie on the
surface of the skin. Note: a tighter interface does not make a tighter
socket! Try some different sized interfaces, do the pin and lanyard thing
again and see the effect. In most cases a tighter interface actually makes
the longitudinal stability worse!

Now we come to your final choice. You have an appropriate and correclty
sized interface, that still exhibits a little movement when you pull the
end. If you wish, you can further improve the longitudinal stability by
pulling the interface until you feel a little resistance. There will be a
relatively loose movement that you can effect upon the sleeve, with little
load. When this begins to stiffen up, stop pulling. If you capture that
shape, then you have a very stable combination of interface/soft tissue.
You are trying to further stabilise the interface, which in turn stabilses
the soft tissues.

If you pressure cast, the the result can be a socket that exhibits minimal
displacement between the socket and the skeleton, both during loading and
non loading.

When the socket is donned, it should and will find it's way all they way to
the bottom of the socket - else it doesn't fit as you intend. In you have a
socket with a pin that has 13 clicks on it, then 13 clicks is what you're
looking for. In some cases, if the soft tissue is really mobile, like on a
transfemoral amputee, then a ratchet pin is inappropriate, because it just
can't pull itself in. Then you should consider using a wind-in or 'clutch'
lock, or if space is an issue - a lanyard. This way you are ensuring that
the interface is pulled all the way down into the socket. You can not get
'too far' into these sockets. It 's either correct, or not in far enough!

It's the socket that does the job here, and part of that job is to optimise
the functional properties of the interface, which if you chose, you can
optimise by further displacing the interface prior to casting. Try to use
the word 'displace' rather than words that suggest load, like distraction
and so on. 'Stretch' is also inappropriate as stretching is not what we
want to do.

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