Questioning Conventional wisdom-responses
Benveniste, David Mark
Description
Collection
Title:
Questioning Conventional wisdom-responses
Creator:
Benveniste, David Mark
Date:
10/18/2005
Text:
Colleagues,
There was a limited response to this post but no one defended their use of
the 3R49 over the advantages of the 3R36 (or equivalent)
I assume that means everybody agrees or has been converted, and that the
market for 3R49's will shrink precipitously..........?
Original post
Our primary concern for AK amputees and new amputees in particular, is to
prevent falls.The major problems seem to be clearing the toe and getting
sufficient extension quickly enough to place the heel on the ground and
prevent buckling.
For a long time, I believe the standard practice in developed countries has
been the use of weight activated stance control knees for beginning AK pts,
less active pts, and for patients needing a greater degree of safety in
general.
Otto Bock's 3R49 has been the standard with other companies duplicating it
to varying degrees.The 3R49 is a single axis knee and if the pt doesn't
clear his toe and stumbles, the pressure will activate the braking
mechanism, IF it's within a certain number of degrees of flexion.
Pts were encouraged to swing their leg and firmly plant their heel to gain
stability. So, the beginning pt needed to clear his toe and to make sure the
knee was in extension. In addition, the pt needed to unload the knee in
order to initiate flexion.
Instead of using the 3R49, I am now frequently using the Otto Bock 3R36.I
would also include any similar lightweight 4bar knees with strong extension
assists and a knee cap.
Short of active dorsiflexion, which I would like to see more of, the 4 bar
knee contributes to toe clearance and has inherent stability with its
posterior-superior instantaneous center of rotation. There is also no need
to unload the brake mechanism to gain flexion. (One of the reasons Otto Bock
created the 3R90/92)
In the Otto Bock 3R36 knee, there is a very strong extension assist which
assures rapid knee extension and therefore initial heel contact. With time,
and increased pt strength and control, you can reduce the strength of the
extension assist if desired.
Any flaws to this line of thinking? Anyone converted?
Mark Benveniste RN BS CP
Responses:
You bring up a great topic. Early in my career (1994) I was working for a
rehab hospital in central Canada. I was fortunate to work with a very
forward thinking prosthetist (Curtis Issell, CP(c)) who began doing just
what you mentioned. He noticed increased gait deviations and therefore
decreased efficiency due to the unnatural late stance unloading of the
knee's friction brake. We were also very concerned with our remote patients
(most lived many miles away) relying on the friction brake, only to have it
wear out and risk a fall...
He started converting all (within reason) over to the 3R36. As a result, I
have (happily) very little experience with the 3R49, other than repairing
them. He was also great at converting our pricribing doc's over to the 3R36
- for the reasons you mention, as they were very keen on the Safety Knee.
He was able to effectively show them the inadequacies, and earned some well
deserved respect while doing it!
Your logic has definitely stood the test of time in central Canada!!
Keep up the stimulating posts.
Regards,
Jason Goodnough, CPO(c), Msc.P.O. (candidate)
Program Head, Prosthetics & Orthotics
Faculty of Health Sciences
British Columbia Institute of Technology
While I prefer the four-bar knees from Proteor over those from Otto Bock, I
am in full agreement on the advantages of toe clearance, RELIABLE stability,
and ending the requirement for hip hiking to unload the knee in order to
initiate knee flexion. I've been practicing for 24 years now and have used
the 3R49 only two or three times, always for an amputee who had worn it
previously and was not interested in trying something different.
The idea of the safety knee seems to be deeply ingrained and I'm not
optimistic that it will leave us any time soon. .
Intellectual inertia is a powerful force!
Ted A. Trower C.P.O.
A-S-C Orthotics & Prosthetics
Jackson, Michigan, USA
Have a look at the TechGUIDE for the 3R36
<URL Redacted>
< <URL Redacted>>
you'll find a link to knee characterisation data which is information
derived courtesy of Professor Radcliff's software.
( <URL Redacted>
tm
< http://rehabtech.eng.monash.edu.au/techguide/4barwebpages/OB3r36etallMain.h
tm> )
In the prescription of the knee you'll also find an indication of toes
clearance and see that between 45 and 65 degrees knee flexion (typical swing
phase) you will achieve betwen 18mm and 21.5 mm of toe clearance as
compared to a single axis knee.
So from the engineering perspective, yes you are quite correct that
significant toe clearance and therefore safety for the client can be
achieved....
Have fun!
Bill Contoyannis
I have used that approach with almost all my primary and most of my
geriatric type fittings for some time...
Brad van Lenthe C.P.(c)
There was a limited response to this post but no one defended their use of
the 3R49 over the advantages of the 3R36 (or equivalent)
I assume that means everybody agrees or has been converted, and that the
market for 3R49's will shrink precipitously..........?
Original post
Our primary concern for AK amputees and new amputees in particular, is to
prevent falls.The major problems seem to be clearing the toe and getting
sufficient extension quickly enough to place the heel on the ground and
prevent buckling.
For a long time, I believe the standard practice in developed countries has
been the use of weight activated stance control knees for beginning AK pts,
less active pts, and for patients needing a greater degree of safety in
general.
Otto Bock's 3R49 has been the standard with other companies duplicating it
to varying degrees.The 3R49 is a single axis knee and if the pt doesn't
clear his toe and stumbles, the pressure will activate the braking
mechanism, IF it's within a certain number of degrees of flexion.
Pts were encouraged to swing their leg and firmly plant their heel to gain
stability. So, the beginning pt needed to clear his toe and to make sure the
knee was in extension. In addition, the pt needed to unload the knee in
order to initiate flexion.
Instead of using the 3R49, I am now frequently using the Otto Bock 3R36.I
would also include any similar lightweight 4bar knees with strong extension
assists and a knee cap.
Short of active dorsiflexion, which I would like to see more of, the 4 bar
knee contributes to toe clearance and has inherent stability with its
posterior-superior instantaneous center of rotation. There is also no need
to unload the brake mechanism to gain flexion. (One of the reasons Otto Bock
created the 3R90/92)
In the Otto Bock 3R36 knee, there is a very strong extension assist which
assures rapid knee extension and therefore initial heel contact. With time,
and increased pt strength and control, you can reduce the strength of the
extension assist if desired.
Any flaws to this line of thinking? Anyone converted?
Mark Benveniste RN BS CP
Responses:
You bring up a great topic. Early in my career (1994) I was working for a
rehab hospital in central Canada. I was fortunate to work with a very
forward thinking prosthetist (Curtis Issell, CP(c)) who began doing just
what you mentioned. He noticed increased gait deviations and therefore
decreased efficiency due to the unnatural late stance unloading of the
knee's friction brake. We were also very concerned with our remote patients
(most lived many miles away) relying on the friction brake, only to have it
wear out and risk a fall...
He started converting all (within reason) over to the 3R36. As a result, I
have (happily) very little experience with the 3R49, other than repairing
them. He was also great at converting our pricribing doc's over to the 3R36
- for the reasons you mention, as they were very keen on the Safety Knee.
He was able to effectively show them the inadequacies, and earned some well
deserved respect while doing it!
Your logic has definitely stood the test of time in central Canada!!
Keep up the stimulating posts.
Regards,
Jason Goodnough, CPO(c), Msc.P.O. (candidate)
Program Head, Prosthetics & Orthotics
Faculty of Health Sciences
British Columbia Institute of Technology
While I prefer the four-bar knees from Proteor over those from Otto Bock, I
am in full agreement on the advantages of toe clearance, RELIABLE stability,
and ending the requirement for hip hiking to unload the knee in order to
initiate knee flexion. I've been practicing for 24 years now and have used
the 3R49 only two or three times, always for an amputee who had worn it
previously and was not interested in trying something different.
The idea of the safety knee seems to be deeply ingrained and I'm not
optimistic that it will leave us any time soon. .
Intellectual inertia is a powerful force!
Ted A. Trower C.P.O.
A-S-C Orthotics & Prosthetics
Jackson, Michigan, USA
Have a look at the TechGUIDE for the 3R36
<URL Redacted>
< <URL Redacted>>
you'll find a link to knee characterisation data which is information
derived courtesy of Professor Radcliff's software.
( <URL Redacted>
tm
< http://rehabtech.eng.monash.edu.au/techguide/4barwebpages/OB3r36etallMain.h
tm> )
In the prescription of the knee you'll also find an indication of toes
clearance and see that between 45 and 65 degrees knee flexion (typical swing
phase) you will achieve betwen 18mm and 21.5 mm of toe clearance as
compared to a single axis knee.
So from the engineering perspective, yes you are quite correct that
significant toe clearance and therefore safety for the client can be
achieved....
Have fun!
Bill Contoyannis
I have used that approach with almost all my primary and most of my
geriatric type fittings for some time...
Brad van Lenthe C.P.(c)
Citation
Benveniste, David Mark, “Questioning Conventional wisdom-responses,” Digital Resource Foundation for Orthotics and Prosthetics, accessed November 5, 2024, https://library.drfop.org/items/show/225623.
