C-Leg responses
nathan keepers
Description
Collection
Title:
C-Leg responses
Creator:
nathan keepers
Date:
4/13/2004
Text:
Here are the responses I received to my question on C-leg and Adaptive
knees. Question followed by the responses. Thank you to all who responded.
I did talk to a practitioner who has worked with hundreds of C-Legs and he
indicated that the hardest patient to transition to a C-Leg is a Century 22
wearer, the next is 4, 5 bar knees, easier is the SNS single axis, the
easiest is a new amputee. The polycentric linkage appears to be the
difference.
Nathan Keepers, CPO
Hello,
We have a patient that has been wearing a Century XXII total knee until we
recently fit him with a C-leg. He likes many of the features, but feels
like there is a lot of terminal swing impact to him. In observing gait it
doesn't appear that way to us. We have discussed with Otto Bock at length
and made numerous adjustments to setting and alignments to no avail. We can
turn the extension dampening feature all the way up on its setting and he
feels little difference. We have sent the knee in for testing, came back
with clean bill of health and still had same issue. Another new knee was
tried and same problem. In his prior prosthesis, which he received
elsewhere, his socket was flexed significantly, with no hip flexor
tightness.
I believe that this may be part of the difference, that the extension
dampening on the old knee is slowing the knee in a more flexed position
earlier due to the alignment. Also, it may appear that the extension
dampening in the Cent 22 acts over a longer ROM arc than the C-Leg, and less
resistance overall (which I believe is one of the benefits of the C-Leg)
With the old knee, he is stable because it has a mechanical stance phase
lock even with the weight line more posterior than we'd like. There is no
adjustment available above the knee unit to straighten this alignment to see
if he would feel the same terminal swing.
That said, do you have any patients that you have tried the C-Leg on that
were previous Cent 22 wearers, did they have any of these issues? Other SNS
wearers?
Another question, What are your experiences with the Adaptive knee from
Endolite? Is it at all comparable to C-Leg? The patient is Young and
active, and does very well with previous knee, but likes the stair/slope
stability that the C-Leg offers.
Any thoughts would be appreciated.
I haven't had any negative experiences with C-leg wearers that have
previoulsy been wearing a C22. I do have one patient that I had to flex his
socket because his hip flexors were so strong that he intuitively
overpowered the knee unit and caused excessive extension impact. I flexed
his socket about 7 degrees which reduced the effect of his stength on the
C-leg.
About the Endolite Adaptive Knee, I have put two on and have recieved
two back from those patients. One patient was an older man that spent too
much time in stance phase while he was walking, and the Adaptive thought he
was stopping and standing which threw it into standing mode. I also tried
the Adaptive on a 28 year old woman. She rejected the knee because she
didn't feel comfortable having the knee think for her. I think that the
Adaptive is not a bad component, but it needs to be applied on the right
person, i.e. active with discernable varried cadences. It sounds like from
the information you provided, that your patient may be a decent candidate.
I don't know, It is tough to be absolutely sure about any one component.
This problem has a simple solution. His shoe is too heavy
I am writing with a comment to offer but honestly have no experience
with the C-leg, so forgive my eagerness. Have you considered referring
the patient to a physical therapist? Perhaps you are right on the money
with the socket flexion issue. Once an amputee gets used to certain
habits, they are difficult to break. Perhaps working with a therapist
will enable this patient to learn new methods of control (breaking those
old habits) and therefore better acceptance of the C-leg.
I am a C-leg wearer and previous wearer of the Total
knee, I did not experience any of the problems your
patient is having but I am a very short transfemoral.
There are two options I see that you could try and you
may have already.
1. Try increasing the Knee Angle Threshold to allow
more ROM before the dynamic factor kicks in but not so
much to allow excessive heel rise. you could also
decrease the dynamic factor as well both would give
the knee a more ROM arc to possibly absorb the hip
flexor strength this patient has.
2. You could try decreasing the initial swing flexion
damping to allow more heel rise during swing phase and
increase the Swing Extension Damping thus possibly
preventing the terminal impact he is experiencing.
Yes, to previous century 22 to C leg, No to terminal impact problem, No to
the SNS to cleg.
I have had ample experience with the adaptive knee. I have had ample
experience with the c leg. They are both great knees.
In my experience, the ideal cleg user is an old sns user, gait pattern is
the same and transition to c leg takes minimal adjustment. Any other knee
to c leg is a bit more adventurous. The heel and toe sensor in shin seems
to be the culprit, on both accounts. Sns users are used to the hyperext
needed to mechanically switch the valve in the hydraulic cylinder. As a
result you get very good sensor input on shin. Users of other knees, seem
to have a bit more difficulty adjusting to the heel toe input.
My thoughts, are due to the change in configuration, four bar/five bar to
single axis, may be contributing to the patients perception of terminal
impact. I have noticed in some of the four/five bar knee setups the
mechanical bias of all the rotation points create a more progressive
terminal impact dampening effect.
The adaptive on the other hand is a bit more user friendly in the
programming and I think it can be adapted (clever eh?) to a larger patient
population more successfully.
Three points I love about the adaptive
1.pnuematic swing, hydraulic stance - by separating these it is easier to
overlap settings and accommodate patient gate. Nothing is smoother for
swing phase control than pneumatic.
2 Battery life and options - rechargable batteries last from 3 - 8 days
between charges, and if the patient is going on vacation, the battery packs
can be swapped out with lithium battery packs that require no charging and
will last 3 - 12 weeks.
3 remote control programming - You can adjust the knee while patient is
walking, they do not have to be still while programming changes are made, it
is much easier to get the swing settings correct while the patient just
walks, and the wireless rf controller means no wires plugged into the knee.
I think the adaptive would be an excellent knee for a young active patient.
I have a friend of mine who is jumping outta planes with his.
You did not mention anything about the 5 bar linkage the Century XXII
employs. Since the C-Leg is a single axis knee unit the variable you have
introduced with these two different centers of rotation may very well be
causing the confusion.
Before I'd try a C-Leg on a patient I would see if they have the ability to
successfully operate a knee unit with a true hydraulic swing and stance
function...i.e. 3R80 or Mauch SNS or CaTech. Going from a 5 Bar knee like
the total knee with just a hydraulic swing phase function and a geometric
lock is to much of a variable to make any sort of comparison. I would
suspect that the total knee terminal impact is what you say it is....the
flexed socket along with the 5 bar linkage has dampened terminal impact
purely by means of the mechanical disadvantage the flexed socket provides in
the acceleration of the foot/shank below the knee.
I have one gentleman who has moved from a Total Knee to the C-Leg. He had
buckling problems in the Total Knee, loves his C-Leg. We did have to
increase the extension dampening slightly over the default setting, but that
was adequate.
I have significant experience with this specific situation and would be
pleased to share this information with you�please feel free to call and
discuss�
Get an Adaptive from Endolite. They're jumping out planes with it!
i am an A/K and have been using the XX11 for around 5-7 yrs(i think). i have
been an A/K now for 50+ yrs. i have always had socket fitting problems
which required me to start making my own limbs in my garage, which i have
been doing for the last 15yrs. ( i might add that they are state of the art
vacuumed formed plus i do all my own laminations and cast modifications).
i also just recently switched over to the c-leg and have experienced the
same terminal impact when the foot extends out while walking. the xxll has
an adjustment for this which makes the foot come out in a nice soft motion
which i don't think the c-leg has.
having said all this, i find that i can adjust to this with the c-leg as
long as i don't try to almost run with it.( which i think the xii is still
the best for running since you can adjust for heel raise and walking fast).
which is probably what your patient is used to now.
i still like the xxll but have gone to the c-leg for another reason. i have
on occassion had the xxll knee disengage out from under me and it has put me
in the hospital. so i am trying out the c-leg to see if this problem can be
eliminated since i am also very active.
i have also found that the bench alienment of the attachment plate has to be
set more posterier for the c -leg than on the XXll. (by posterier i mean the
center line of body weight has to be brought much more forward over the
knee). however this will still not stop the terminal impact of the foot.
just thought i would give you my thoughts and experience that i have had
with your existing problem
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knees. Question followed by the responses. Thank you to all who responded.
I did talk to a practitioner who has worked with hundreds of C-Legs and he
indicated that the hardest patient to transition to a C-Leg is a Century 22
wearer, the next is 4, 5 bar knees, easier is the SNS single axis, the
easiest is a new amputee. The polycentric linkage appears to be the
difference.
Nathan Keepers, CPO
Hello,
We have a patient that has been wearing a Century XXII total knee until we
recently fit him with a C-leg. He likes many of the features, but feels
like there is a lot of terminal swing impact to him. In observing gait it
doesn't appear that way to us. We have discussed with Otto Bock at length
and made numerous adjustments to setting and alignments to no avail. We can
turn the extension dampening feature all the way up on its setting and he
feels little difference. We have sent the knee in for testing, came back
with clean bill of health and still had same issue. Another new knee was
tried and same problem. In his prior prosthesis, which he received
elsewhere, his socket was flexed significantly, with no hip flexor
tightness.
I believe that this may be part of the difference, that the extension
dampening on the old knee is slowing the knee in a more flexed position
earlier due to the alignment. Also, it may appear that the extension
dampening in the Cent 22 acts over a longer ROM arc than the C-Leg, and less
resistance overall (which I believe is one of the benefits of the C-Leg)
With the old knee, he is stable because it has a mechanical stance phase
lock even with the weight line more posterior than we'd like. There is no
adjustment available above the knee unit to straighten this alignment to see
if he would feel the same terminal swing.
That said, do you have any patients that you have tried the C-Leg on that
were previous Cent 22 wearers, did they have any of these issues? Other SNS
wearers?
Another question, What are your experiences with the Adaptive knee from
Endolite? Is it at all comparable to C-Leg? The patient is Young and
active, and does very well with previous knee, but likes the stair/slope
stability that the C-Leg offers.
Any thoughts would be appreciated.
I haven't had any negative experiences with C-leg wearers that have
previoulsy been wearing a C22. I do have one patient that I had to flex his
socket because his hip flexors were so strong that he intuitively
overpowered the knee unit and caused excessive extension impact. I flexed
his socket about 7 degrees which reduced the effect of his stength on the
C-leg.
About the Endolite Adaptive Knee, I have put two on and have recieved
two back from those patients. One patient was an older man that spent too
much time in stance phase while he was walking, and the Adaptive thought he
was stopping and standing which threw it into standing mode. I also tried
the Adaptive on a 28 year old woman. She rejected the knee because she
didn't feel comfortable having the knee think for her. I think that the
Adaptive is not a bad component, but it needs to be applied on the right
person, i.e. active with discernable varried cadences. It sounds like from
the information you provided, that your patient may be a decent candidate.
I don't know, It is tough to be absolutely sure about any one component.
This problem has a simple solution. His shoe is too heavy
I am writing with a comment to offer but honestly have no experience
with the C-leg, so forgive my eagerness. Have you considered referring
the patient to a physical therapist? Perhaps you are right on the money
with the socket flexion issue. Once an amputee gets used to certain
habits, they are difficult to break. Perhaps working with a therapist
will enable this patient to learn new methods of control (breaking those
old habits) and therefore better acceptance of the C-leg.
I am a C-leg wearer and previous wearer of the Total
knee, I did not experience any of the problems your
patient is having but I am a very short transfemoral.
There are two options I see that you could try and you
may have already.
1. Try increasing the Knee Angle Threshold to allow
more ROM before the dynamic factor kicks in but not so
much to allow excessive heel rise. you could also
decrease the dynamic factor as well both would give
the knee a more ROM arc to possibly absorb the hip
flexor strength this patient has.
2. You could try decreasing the initial swing flexion
damping to allow more heel rise during swing phase and
increase the Swing Extension Damping thus possibly
preventing the terminal impact he is experiencing.
Yes, to previous century 22 to C leg, No to terminal impact problem, No to
the SNS to cleg.
I have had ample experience with the adaptive knee. I have had ample
experience with the c leg. They are both great knees.
In my experience, the ideal cleg user is an old sns user, gait pattern is
the same and transition to c leg takes minimal adjustment. Any other knee
to c leg is a bit more adventurous. The heel and toe sensor in shin seems
to be the culprit, on both accounts. Sns users are used to the hyperext
needed to mechanically switch the valve in the hydraulic cylinder. As a
result you get very good sensor input on shin. Users of other knees, seem
to have a bit more difficulty adjusting to the heel toe input.
My thoughts, are due to the change in configuration, four bar/five bar to
single axis, may be contributing to the patients perception of terminal
impact. I have noticed in some of the four/five bar knee setups the
mechanical bias of all the rotation points create a more progressive
terminal impact dampening effect.
The adaptive on the other hand is a bit more user friendly in the
programming and I think it can be adapted (clever eh?) to a larger patient
population more successfully.
Three points I love about the adaptive
1.pnuematic swing, hydraulic stance - by separating these it is easier to
overlap settings and accommodate patient gate. Nothing is smoother for
swing phase control than pneumatic.
2 Battery life and options - rechargable batteries last from 3 - 8 days
between charges, and if the patient is going on vacation, the battery packs
can be swapped out with lithium battery packs that require no charging and
will last 3 - 12 weeks.
3 remote control programming - You can adjust the knee while patient is
walking, they do not have to be still while programming changes are made, it
is much easier to get the swing settings correct while the patient just
walks, and the wireless rf controller means no wires plugged into the knee.
I think the adaptive would be an excellent knee for a young active patient.
I have a friend of mine who is jumping outta planes with his.
You did not mention anything about the 5 bar linkage the Century XXII
employs. Since the C-Leg is a single axis knee unit the variable you have
introduced with these two different centers of rotation may very well be
causing the confusion.
Before I'd try a C-Leg on a patient I would see if they have the ability to
successfully operate a knee unit with a true hydraulic swing and stance
function...i.e. 3R80 or Mauch SNS or CaTech. Going from a 5 Bar knee like
the total knee with just a hydraulic swing phase function and a geometric
lock is to much of a variable to make any sort of comparison. I would
suspect that the total knee terminal impact is what you say it is....the
flexed socket along with the 5 bar linkage has dampened terminal impact
purely by means of the mechanical disadvantage the flexed socket provides in
the acceleration of the foot/shank below the knee.
I have one gentleman who has moved from a Total Knee to the C-Leg. He had
buckling problems in the Total Knee, loves his C-Leg. We did have to
increase the extension dampening slightly over the default setting, but that
was adequate.
I have significant experience with this specific situation and would be
pleased to share this information with you�please feel free to call and
discuss�
Get an Adaptive from Endolite. They're jumping out planes with it!
i am an A/K and have been using the XX11 for around 5-7 yrs(i think). i have
been an A/K now for 50+ yrs. i have always had socket fitting problems
which required me to start making my own limbs in my garage, which i have
been doing for the last 15yrs. ( i might add that they are state of the art
vacuumed formed plus i do all my own laminations and cast modifications).
i also just recently switched over to the c-leg and have experienced the
same terminal impact when the foot extends out while walking. the xxll has
an adjustment for this which makes the foot come out in a nice soft motion
which i don't think the c-leg has.
having said all this, i find that i can adjust to this with the c-leg as
long as i don't try to almost run with it.( which i think the xii is still
the best for running since you can adjust for heel raise and walking fast).
which is probably what your patient is used to now.
i still like the xxll but have gone to the c-leg for another reason. i have
on occassion had the xxll knee disengage out from under me and it has put me
in the hospital. so i am trying out the c-leg to see if this problem can be
eliminated since i am also very active.
i have also found that the bench alienment of the attachment plate has to be
set more posterier for the c -leg than on the XXll. (by posterier i mean the
center line of body weight has to be brought much more forward over the
knee). however this will still not stop the terminal impact of the foot.
just thought i would give you my thoughts and experience that i have had
with your existing problem
_________________________________________________________________
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Citation
nathan keepers, “C-Leg responses,” Digital Resource Foundation for Orthotics and Prosthetics, accessed November 26, 2024, https://library.drfop.org/items/show/222887.
