Muscle firing changes stump shape
Randy McFarland
Description
Collection
Title:
Muscle firing changes stump shape
Creator:
Randy McFarland
Date:
3/20/2012
Text:
ORIGINAL POST
We have a patient with a new transtibial amputation. Currently we have him
in a Pelite liner over a cushion liner. We put a vertical slit in the Pelite
liner to ease donning because the stump is slightly bulbous..
His stump significantly changes shape when he fires his calf and tibialis
anterior muscles, causing a bulge out and up, making the distal end even
larger than the proximal portion. After 5-10 minutes, these muscles start to
get uncomfortable from the weight bearing pressure on these muscles.
Have you had experience with this type of stump. where muscle bulging
causes a significant change in volume and contour of the stump? What
worked to achieve a comfortable fit? I'll post responses.
Thanks, Randy McFarland, CPO Fullerton, CA
RESPONSES
I have seen this once before, the patient never really got completely
comfortable, because of the bulbous nature of the limb the weight bearing
area is minimized. The best result that we found for the patient was to
accommodate the change in the limb and actually captured the change in shape
while making the impression and increased loading to other weight bearing
areas. Also we ended up using a joint and corset to reduce the overall axial
loading of the residual limb.
Summary:
PTB type socket.
Pelite type liner.
Joint and corset
Foot to promote knee extension to load thigh lacer.
Also, I would recommend a custom liner accommodating the change in shape and
filling in the undercut areas to give a more conical or cylindrical shape
and maximizing weight bearing areas. This was not option for this patient
when I was treating before.
That's a tough one. You need to be careful not to over-modify the mold. I
would make the liner by using leather, a layer of PPT and pelite on the
outside. The cushion should help. I had a patient like that once who could
suspend the prosthesis by stump contraction.
I have seen this before and have had the most success with a relatively
flexible inner socket and rigid frame. If necessary cut the frame away so
the flexible inner socket can accommodate the changes in muscle shape.
A large pare of success comes from the casting and modification or lack
there of. Casting should be done with circumferential wrap using the extra
fast setting rigid plaster bandage. Smooth and do what ever you normally
would but pay attention to how the plaster is setting. There is a magic
moment when the plaster bandage is just about to set. This is the point when
your patent should be flexing those muscles over and over. The idea is to
capture the shape changes the muscle goes through in the cast.
Glue a three or five ply sock into the cast before filling. The choice
depends on how your sockets usually fit. You can not wrap the cast super
tight or the muscle will not be able to deform the plaster as it sets
DO NOT OVER MODIFY fit the check socket with a one inch plastizote end
pad, that way you can modify the end contact without having to add more
socks. check and modify for any high pressure area and your done.
Any time have to split a liner I go to a custom silicone liner. These
stretch enough to go over Symes and KD so I am sure it would work for you.
Not only that, you can eliminate the cushion liner as the silicone will
provide excellent shock and torque absorption. Hope this helps.
I have seen this too, what worked was to have the Patient intermittently
fire those muscles during the casting procedure that way proper
accommodations are built into the cast. From there it was normal cast mods
and test sockets.
I have fit a few patients with this presentation. Have the patient fire and
hold the contraction throughout the casting procedure, this captures the
muscle contours when firing. Also, using a flexible socket and frame with
windows cut over large muscle bellies will allow the muscles to fire without
as much restriction. Make sure your mods are more TSB than PTB and leave the
limb contours as they are. Hope this helps.
I have a patient like this right now. Elongating the socket seems to help
but it doesn't get rid of it. If you find a good solution please share.
Remember the few designs for self suspending sockets. Those sockets and
still apply to some patients today who have a perfect anatomy for them. It
actually give the patient a natural sense of feel. I would want my
patient to exercise those muscles and keep his strength up. The adipose of
his limb will shrink, so the muscle is still active really can help this
patient control and feel his limb in space. So I think I would examine the
distal bulge and try to determine if the muscle underbelly is actually since
he is a new amputee, is the tissue bulge is caused by the muscle lifting up
the adipose. If that is the case I would encourage the patient to fire this
muscle in mid-stance to propel himself off the ground. I am assuming that
he only has activity in his gastrocnemeus flexor.
If he can extend and flex and you can acknowledge the value of his
voluntary propulsion he will have less cost of energy trying to balance on a
prosthetic foot all by itself, and relearning to be passive in a prosthetic
alignment.
I have had similar issues. When the muscle fires creating shape changes it
sets up our classic problem of making static devices for dynamic residual
limbs. I always remember something Raymond Frances said to me, total
contact does not have to be hard contact. We tend to make sockets for
transtibial amputations in either a specific load bearing manor (PTB), or
total surface bearing, hydrostatic-like. These methods work well most of the
time because the great majority of our clients are very passive, meaning
that they do not fire the residual muscles, leaving an amorphous blob for us
to do with as we choose. When presented with cases like you describe, I have
found that you have to fit them with a looser fitting device. The act of
firing the muscle grips the sides of the socket, keeping them off the distal
end making distal pressure less of a problem than impeding the firing
muscles. It really runs contrary to what most of us are taught because at
some point the muscle movement looks a whole lot like pistoning. Sometimes
comfortable must be replaced with tolerable.
Maybe there is not enough room for when his muscles fire causing
restriction? Could the socket be not as tight?
We have a patient with a new transtibial amputation. Currently we have him
in a Pelite liner over a cushion liner. We put a vertical slit in the Pelite
liner to ease donning because the stump is slightly bulbous..
His stump significantly changes shape when he fires his calf and tibialis
anterior muscles, causing a bulge out and up, making the distal end even
larger than the proximal portion. After 5-10 minutes, these muscles start to
get uncomfortable from the weight bearing pressure on these muscles.
Have you had experience with this type of stump. where muscle bulging
causes a significant change in volume and contour of the stump? What
worked to achieve a comfortable fit? I'll post responses.
Thanks, Randy McFarland, CPO Fullerton, CA
RESPONSES
I have seen this once before, the patient never really got completely
comfortable, because of the bulbous nature of the limb the weight bearing
area is minimized. The best result that we found for the patient was to
accommodate the change in the limb and actually captured the change in shape
while making the impression and increased loading to other weight bearing
areas. Also we ended up using a joint and corset to reduce the overall axial
loading of the residual limb.
Summary:
PTB type socket.
Pelite type liner.
Joint and corset
Foot to promote knee extension to load thigh lacer.
Also, I would recommend a custom liner accommodating the change in shape and
filling in the undercut areas to give a more conical or cylindrical shape
and maximizing weight bearing areas. This was not option for this patient
when I was treating before.
That's a tough one. You need to be careful not to over-modify the mold. I
would make the liner by using leather, a layer of PPT and pelite on the
outside. The cushion should help. I had a patient like that once who could
suspend the prosthesis by stump contraction.
I have seen this before and have had the most success with a relatively
flexible inner socket and rigid frame. If necessary cut the frame away so
the flexible inner socket can accommodate the changes in muscle shape.
A large pare of success comes from the casting and modification or lack
there of. Casting should be done with circumferential wrap using the extra
fast setting rigid plaster bandage. Smooth and do what ever you normally
would but pay attention to how the plaster is setting. There is a magic
moment when the plaster bandage is just about to set. This is the point when
your patent should be flexing those muscles over and over. The idea is to
capture the shape changes the muscle goes through in the cast.
Glue a three or five ply sock into the cast before filling. The choice
depends on how your sockets usually fit. You can not wrap the cast super
tight or the muscle will not be able to deform the plaster as it sets
DO NOT OVER MODIFY fit the check socket with a one inch plastizote end
pad, that way you can modify the end contact without having to add more
socks. check and modify for any high pressure area and your done.
Any time have to split a liner I go to a custom silicone liner. These
stretch enough to go over Symes and KD so I am sure it would work for you.
Not only that, you can eliminate the cushion liner as the silicone will
provide excellent shock and torque absorption. Hope this helps.
I have seen this too, what worked was to have the Patient intermittently
fire those muscles during the casting procedure that way proper
accommodations are built into the cast. From there it was normal cast mods
and test sockets.
I have fit a few patients with this presentation. Have the patient fire and
hold the contraction throughout the casting procedure, this captures the
muscle contours when firing. Also, using a flexible socket and frame with
windows cut over large muscle bellies will allow the muscles to fire without
as much restriction. Make sure your mods are more TSB than PTB and leave the
limb contours as they are. Hope this helps.
I have a patient like this right now. Elongating the socket seems to help
but it doesn't get rid of it. If you find a good solution please share.
Remember the few designs for self suspending sockets. Those sockets and
still apply to some patients today who have a perfect anatomy for them. It
actually give the patient a natural sense of feel. I would want my
patient to exercise those muscles and keep his strength up. The adipose of
his limb will shrink, so the muscle is still active really can help this
patient control and feel his limb in space. So I think I would examine the
distal bulge and try to determine if the muscle underbelly is actually since
he is a new amputee, is the tissue bulge is caused by the muscle lifting up
the adipose. If that is the case I would encourage the patient to fire this
muscle in mid-stance to propel himself off the ground. I am assuming that
he only has activity in his gastrocnemeus flexor.
If he can extend and flex and you can acknowledge the value of his
voluntary propulsion he will have less cost of energy trying to balance on a
prosthetic foot all by itself, and relearning to be passive in a prosthetic
alignment.
I have had similar issues. When the muscle fires creating shape changes it
sets up our classic problem of making static devices for dynamic residual
limbs. I always remember something Raymond Frances said to me, total
contact does not have to be hard contact. We tend to make sockets for
transtibial amputations in either a specific load bearing manor (PTB), or
total surface bearing, hydrostatic-like. These methods work well most of the
time because the great majority of our clients are very passive, meaning
that they do not fire the residual muscles, leaving an amorphous blob for us
to do with as we choose. When presented with cases like you describe, I have
found that you have to fit them with a looser fitting device. The act of
firing the muscle grips the sides of the socket, keeping them off the distal
end making distal pressure less of a problem than impeding the firing
muscles. It really runs contrary to what most of us are taught because at
some point the muscle movement looks a whole lot like pistoning. Sometimes
comfortable must be replaced with tolerable.
Maybe there is not enough room for when his muscles fire causing
restriction? Could the socket be not as tight?
Citation
Randy McFarland, “Muscle firing changes stump shape,” Digital Resource Foundation for Orthotics and Prosthetics, accessed November 5, 2024, https://library.drfop.org/items/show/233549.
