3-S Locking Pin Responses
Robert Schiff
Description
Collection
Title:
3-S Locking Pin Responses
Creator:
Robert Schiff
Text:
These are the responses so far. Thank you for your input and I will keep
posting the responses...
Robert
---
Robert,
I prefer to use Iceross' Ice-Cast System which allows me to obtain a total
surface bearing impression using pneumatic pressure over the residual limb.
I have found this system to be consistently accurate and am able to provide
my patients with comfortably fitted sockets, usually on the first fitting.
There is no need for all the extra steps involved that you mention in your
posting. No distraction, no build ups, no guesswork. Ask your clinical
coordinators what their opinions are on this method. This may be something
that would benefit everyone, including your patients.
Steven L. Fries, CPO, (L)
Fort Myers, FL
---
Robert,
This has worked for me since the advent of 3S about 12-13 years ago. I take
a conventional length measurement of the residual limb without the liner...I
then add one-half inch to that measurement (trying to measure over the liner
you can get all sorts of length readings). I cast over the liner (over a TEC
skin if I am using a TEC or Alpha) using whatever wrapping technique is
appropriate for the configuration of that specific limb. In my modification
I make sure the length coincides with my actual plus one-half AFTER I have
flattened a small area distally to perch the locking mechanism on. I
personally like to use the TEC modification technique, which includes a very
subtle patella bar area and popliteal shelf. With this technique pulling the
test socket directly over the mold generally produces about a 3-5 ply
stretch sock fit. Best of luck.
Jim Price, MEd, CPO
---
Robert,
My casting methods differs from each type of silicone / urethane liner and
the flabbiness of each residual limb.
I doubt it if you will get a true answer. Otto Bock and Iceross recommend
completely different types of casting methods for almost exactly the same
type of liner.
The truth is: There's so many different opinions concerning casting methods
over silicone sleeves, that I doubt it if someone has a answer for all the
problems and all your questions.
I had most success with custom-made silicone liners.
Regards
Marco
---
Since the prosthesis literally hangs from the distal attachment pin some
practitioners want the limb/liner or under tension or elongation to prevent
pistoning. Cutting the cast or check socket and elongating it before pouring
will achieve the same thing. I cast over the liner of choice, modify, and
during dynamic alignment observe if pistoning occurs to a great degree, then
take the appropriate steps to remedy the situation.
---
with a silicon liner i would cast under pressure using one of cascade's
casting chambers. luke richards
---
Robert
My casting Tech depends on the type of liner used. If I use a rigid silicone
I cast over the liner with pressure and slight distration (see Ossur casting
Tech.). If I am using Alpha, I cast over the liner doing very little
distortion of the cast and follow the OWW modifications. Check sockets are
needed for all types. My recommendation to you as a new prosthetist would be
to follow the manufactures modifications for a while and the create your own
technique.
good luck and have fun,
Steve Mersch CPO
---
Hi Robert,
I have always been a believer that you must cast with the liner on the
patient and pull some manual distal elongation to the limb while casting to
maximize the coupling stiffness between the limb and socket. How much
someone elongates when distracted is a very individual thing and retro
modifying it on a cast is a bit of an assumption. The IceCast Compact from
OSSUR works very well for liner casting and accomplishes proper compression
and elongating for you in the casting phase with minimal cast modification.
The other issue about the tissues being pushed proximally inside a socket
makes sense, but with the use of a pin lock the lock works to draw the distal
tissue down inside the socket. As the patient clicks or turns themselves
down with the locking mechanism in the socket the tissues are elongated
making what was a potentially flaccid presentation into a more solid one.
Combined w/a maxtrix based liner it gives superior results.
If you do not properly distract during casting you can run the risk of
developing an air noise each time the patient heel strikes. In a socket w/o
proper elongation during swing phase the prosthesis can tend to pull downward
on the limb/liner due to its weight and inertia causing the liner to slightly
pull away from the socket walls creating a slight gap. Each time they heel
strike, the limb compresses into the socket forcing the air out around the
pin thus the noise. If proper elongation is in the socket design during
casting, the limb is at full stretch mated against the socket wall and cannot
gap thus no air noise.
Some food for thought,
Gregory Michalov, C.P.
---
Hello Robert,
I have tried all three methods, except for alginating the bottom. I have
found that casting over the liner once it is donned onto the residual limb
gives the best results in most cases. I have also tried 2 or 3 stage
casting techniques, but once again have found it best to do a
circumferential wrap with plaster. You can also use the Iceross bladder to
achieve a total contact fit and slight distraction.
Regarding distracting while casting, it all depends on tissue type and how
much distraction is possible. It is a judgement call. A good rule of thumb
is to considering most AK limbs and to use a lanyard system and not a pin.
BK's that are short or not fleshy do not usually have to be distracted and a
pin is usually best.
Good luck,
Tyra Rikimaru, CPO
IPS (Innovative Prosthetic Solutions)
---
We have started using TEC's casting vacuum and a 2 stage method over patien's
liner. So far , our results are very good.
---
Robert,
I think you are very astute. You've obviously given this some thought.
I go by the first method (two stage casting technique with the locking liner,
and with no tissue distraction) and it works very well for me, although I
have a number of esteemed colleagues who stand by method number two. My
philosophy is, do what works best for you in your hands. If you get the
results you want, then you are doing it right.
Regards,
Barry Steineman, CPO
President, Ohio Chapter, AAOP
posting the responses...
Robert
---
Robert,
I prefer to use Iceross' Ice-Cast System which allows me to obtain a total
surface bearing impression using pneumatic pressure over the residual limb.
I have found this system to be consistently accurate and am able to provide
my patients with comfortably fitted sockets, usually on the first fitting.
There is no need for all the extra steps involved that you mention in your
posting. No distraction, no build ups, no guesswork. Ask your clinical
coordinators what their opinions are on this method. This may be something
that would benefit everyone, including your patients.
Steven L. Fries, CPO, (L)
Fort Myers, FL
---
Robert,
This has worked for me since the advent of 3S about 12-13 years ago. I take
a conventional length measurement of the residual limb without the liner...I
then add one-half inch to that measurement (trying to measure over the liner
you can get all sorts of length readings). I cast over the liner (over a TEC
skin if I am using a TEC or Alpha) using whatever wrapping technique is
appropriate for the configuration of that specific limb. In my modification
I make sure the length coincides with my actual plus one-half AFTER I have
flattened a small area distally to perch the locking mechanism on. I
personally like to use the TEC modification technique, which includes a very
subtle patella bar area and popliteal shelf. With this technique pulling the
test socket directly over the mold generally produces about a 3-5 ply
stretch sock fit. Best of luck.
Jim Price, MEd, CPO
---
Robert,
My casting methods differs from each type of silicone / urethane liner and
the flabbiness of each residual limb.
I doubt it if you will get a true answer. Otto Bock and Iceross recommend
completely different types of casting methods for almost exactly the same
type of liner.
The truth is: There's so many different opinions concerning casting methods
over silicone sleeves, that I doubt it if someone has a answer for all the
problems and all your questions.
I had most success with custom-made silicone liners.
Regards
Marco
---
Since the prosthesis literally hangs from the distal attachment pin some
practitioners want the limb/liner or under tension or elongation to prevent
pistoning. Cutting the cast or check socket and elongating it before pouring
will achieve the same thing. I cast over the liner of choice, modify, and
during dynamic alignment observe if pistoning occurs to a great degree, then
take the appropriate steps to remedy the situation.
---
with a silicon liner i would cast under pressure using one of cascade's
casting chambers. luke richards
---
Robert
My casting Tech depends on the type of liner used. If I use a rigid silicone
I cast over the liner with pressure and slight distration (see Ossur casting
Tech.). If I am using Alpha, I cast over the liner doing very little
distortion of the cast and follow the OWW modifications. Check sockets are
needed for all types. My recommendation to you as a new prosthetist would be
to follow the manufactures modifications for a while and the create your own
technique.
good luck and have fun,
Steve Mersch CPO
---
Hi Robert,
I have always been a believer that you must cast with the liner on the
patient and pull some manual distal elongation to the limb while casting to
maximize the coupling stiffness between the limb and socket. How much
someone elongates when distracted is a very individual thing and retro
modifying it on a cast is a bit of an assumption. The IceCast Compact from
OSSUR works very well for liner casting and accomplishes proper compression
and elongating for you in the casting phase with minimal cast modification.
The other issue about the tissues being pushed proximally inside a socket
makes sense, but with the use of a pin lock the lock works to draw the distal
tissue down inside the socket. As the patient clicks or turns themselves
down with the locking mechanism in the socket the tissues are elongated
making what was a potentially flaccid presentation into a more solid one.
Combined w/a maxtrix based liner it gives superior results.
If you do not properly distract during casting you can run the risk of
developing an air noise each time the patient heel strikes. In a socket w/o
proper elongation during swing phase the prosthesis can tend to pull downward
on the limb/liner due to its weight and inertia causing the liner to slightly
pull away from the socket walls creating a slight gap. Each time they heel
strike, the limb compresses into the socket forcing the air out around the
pin thus the noise. If proper elongation is in the socket design during
casting, the limb is at full stretch mated against the socket wall and cannot
gap thus no air noise.
Some food for thought,
Gregory Michalov, C.P.
---
Hello Robert,
I have tried all three methods, except for alginating the bottom. I have
found that casting over the liner once it is donned onto the residual limb
gives the best results in most cases. I have also tried 2 or 3 stage
casting techniques, but once again have found it best to do a
circumferential wrap with plaster. You can also use the Iceross bladder to
achieve a total contact fit and slight distraction.
Regarding distracting while casting, it all depends on tissue type and how
much distraction is possible. It is a judgement call. A good rule of thumb
is to considering most AK limbs and to use a lanyard system and not a pin.
BK's that are short or not fleshy do not usually have to be distracted and a
pin is usually best.
Good luck,
Tyra Rikimaru, CPO
IPS (Innovative Prosthetic Solutions)
---
We have started using TEC's casting vacuum and a 2 stage method over patien's
liner. So far , our results are very good.
---
Robert,
I think you are very astute. You've obviously given this some thought.
I go by the first method (two stage casting technique with the locking liner,
and with no tissue distraction) and it works very well for me, although I
have a number of esteemed colleagues who stand by method number two. My
philosophy is, do what works best for you in your hands. If you get the
results you want, then you are doing it right.
Regards,
Barry Steineman, CPO
President, Ohio Chapter, AAOP
Citation
Robert Schiff, “3-S Locking Pin Responses,” Digital Resource Foundation for Orthotics and Prosthetics, accessed November 22, 2024, https://library.drfop.org/items/show/217034.
