Responses to the Medi OP4
Michael Arnette
Description
Collection
Title:
Responses to the Medi OP4
Creator:
Michael Arnette
Date:
1/28/2013
Text:
Hello List,
I have included the replies which I have gotten on this knee and others, it
looks like it is worth a try for my patient. I have tried the 3R80 (a
really nice knee) but my more elderly patients have cussed it because it
won't lock unless fully extended. (maybe it's just my adjustment of the
knee?) It's also a bit heavy for many in this population. I will also be
trying the 3R106 in the future for these patients.
Here they are:
1)
I have one on a 88 year old woman. She is a pistol and weighs 95 lbs
soaking wet. So far I am pleased with the knee. This was her first
prosthesis and she is doing well with no issues. I'm not a huge fan of Medi
but like you the weight and simplicity were hard to beat. I tend to use
pneumatic on lighter patients (less than say 160) but have found that I
must stay hydraulic on heavier patients.
2)
I have used a number of the OP4 knees, and I think that it is an excellent
knee for the population you are referring to. I don't use a lot of
pneumatic knees generally, as I have found that the only advantages they
have over hydraulic are reduced force required to initiate knee flexion and
usually lower weight, and I don't think they do nearly as good a job at
regulating knee flexion across a range of walking speeds. And many of them
have no stance control of any kind. But for those folks that do have a
variable cadence, but not over a wide range, like active seniors, the
pneumatic works very well, and the reduced knee flexion force is better for
them. A few too many of my patients that were on the edge between pneumatic
and hydraulic spent too much time walking with reduced knee flexion when
using hydraulic knees, which kind of defeats the purpose. They were the
ones for whom I usually used the OP4.
The OP4 is one of only two non-MP knees I know of with a true variable
cadence knee control and a true stance phase lock. There are hydraulic
knees with geometric locks (Total Knee, 3R60), and one hydraulic knee with
a stance phase lock (3R80), but the geometric locks don't seem to inspire
the same confidence as the stance phase lock in this population. It is
really easy to have the patients test the stance phase lock in parallel
bars to get that immediate feel of the lock activating.
My patients have found the stance phase lock of the OP4 much more positive
than other non-MP stance flexion systems, except of course a standard
safety knee and its variants. I have transitioned patients to the OP4 from
both directions, from a safety knee (3R90/3R92) as their gait velocity and
gait variability increased, and from a (typically) 4-bar or 6-bar knee for
a more definitive stance phase lock.
Chosen for the right patient, I think it is a very good knee. Active
seniors can cover quite a range of patients. The limitation of the OP4,
and pneumatics in general, are that if the patient tends to ambulate over a
wider velocity range than the knee can manage, you will have gait problems
with excessive swing phase knee flexion and excessive terminal impact,
which will in turn result in a lower quality gait, in my opinion from
compromised confidence. My general evaluation approach is to first evaluate
them with a safety knee, and see how close I can tweak it to match their
gait. If I can get reasonably close, but not quite there (excessive swing
flexion, terminal impact, asymmetric step length), then the OP4 is usually
a good choice. If I can't get it very close, then I will choose hydraulic.
Of the Medi knees, I have only used the OP4 and a few of the OH5. The ones
I have use have been durable and reliable, but I can't comment on any of
the others.
*3)*
It is a good knee with one hitch. I feel like the pneumatics are too weak.
For a average K3 it is hard to stop terminal impact ant not get the spring
back from the air compressing.
I would put this knee at a low K3 walker. Had a pt in one, but as her gait
improved she out walked it. Ended up putting her in a 3r60 pro.
4)
I've used this knee since its inception 7 years ago.. I just looked after 2
elderly ladies who've had other knees and like this one the best. Generally
I've not been a fan of safety knees but this one is definitely a good one!
5)
I've used that knee successfully on several pts. So far so good.
6)
I can't find this one, but someone mentioned that they have never found a
pneumatic knee that has held air pressure for an exceptable amount of time.
7)
It sounds like this active senior would suit the Ultimate Knee perfectly.
<URL Redacted>
As discussed last year this knee is a weight activated, free swinging
hydraulic knee that providing 120 deg's of flextion, It also has a custom
discontinuous knee cover available.
We would be happy to send you a trial knee.
--
Michael Arnette BOCPO, LPO
Progressive Orthotic and Prosthetic Services
www.progressiveoandp.com
9511 E. 46th St.
Tulsa OK, 74145
(918) 663 7077
(918) 724 6256
I have included the replies which I have gotten on this knee and others, it
looks like it is worth a try for my patient. I have tried the 3R80 (a
really nice knee) but my more elderly patients have cussed it because it
won't lock unless fully extended. (maybe it's just my adjustment of the
knee?) It's also a bit heavy for many in this population. I will also be
trying the 3R106 in the future for these patients.
Here they are:
1)
I have one on a 88 year old woman. She is a pistol and weighs 95 lbs
soaking wet. So far I am pleased with the knee. This was her first
prosthesis and she is doing well with no issues. I'm not a huge fan of Medi
but like you the weight and simplicity were hard to beat. I tend to use
pneumatic on lighter patients (less than say 160) but have found that I
must stay hydraulic on heavier patients.
2)
I have used a number of the OP4 knees, and I think that it is an excellent
knee for the population you are referring to. I don't use a lot of
pneumatic knees generally, as I have found that the only advantages they
have over hydraulic are reduced force required to initiate knee flexion and
usually lower weight, and I don't think they do nearly as good a job at
regulating knee flexion across a range of walking speeds. And many of them
have no stance control of any kind. But for those folks that do have a
variable cadence, but not over a wide range, like active seniors, the
pneumatic works very well, and the reduced knee flexion force is better for
them. A few too many of my patients that were on the edge between pneumatic
and hydraulic spent too much time walking with reduced knee flexion when
using hydraulic knees, which kind of defeats the purpose. They were the
ones for whom I usually used the OP4.
The OP4 is one of only two non-MP knees I know of with a true variable
cadence knee control and a true stance phase lock. There are hydraulic
knees with geometric locks (Total Knee, 3R60), and one hydraulic knee with
a stance phase lock (3R80), but the geometric locks don't seem to inspire
the same confidence as the stance phase lock in this population. It is
really easy to have the patients test the stance phase lock in parallel
bars to get that immediate feel of the lock activating.
My patients have found the stance phase lock of the OP4 much more positive
than other non-MP stance flexion systems, except of course a standard
safety knee and its variants. I have transitioned patients to the OP4 from
both directions, from a safety knee (3R90/3R92) as their gait velocity and
gait variability increased, and from a (typically) 4-bar or 6-bar knee for
a more definitive stance phase lock.
Chosen for the right patient, I think it is a very good knee. Active
seniors can cover quite a range of patients. The limitation of the OP4,
and pneumatics in general, are that if the patient tends to ambulate over a
wider velocity range than the knee can manage, you will have gait problems
with excessive swing phase knee flexion and excessive terminal impact,
which will in turn result in a lower quality gait, in my opinion from
compromised confidence. My general evaluation approach is to first evaluate
them with a safety knee, and see how close I can tweak it to match their
gait. If I can get reasonably close, but not quite there (excessive swing
flexion, terminal impact, asymmetric step length), then the OP4 is usually
a good choice. If I can't get it very close, then I will choose hydraulic.
Of the Medi knees, I have only used the OP4 and a few of the OH5. The ones
I have use have been durable and reliable, but I can't comment on any of
the others.
*3)*
It is a good knee with one hitch. I feel like the pneumatics are too weak.
For a average K3 it is hard to stop terminal impact ant not get the spring
back from the air compressing.
I would put this knee at a low K3 walker. Had a pt in one, but as her gait
improved she out walked it. Ended up putting her in a 3r60 pro.
4)
I've used this knee since its inception 7 years ago.. I just looked after 2
elderly ladies who've had other knees and like this one the best. Generally
I've not been a fan of safety knees but this one is definitely a good one!
5)
I've used that knee successfully on several pts. So far so good.
6)
I can't find this one, but someone mentioned that they have never found a
pneumatic knee that has held air pressure for an exceptable amount of time.
7)
It sounds like this active senior would suit the Ultimate Knee perfectly.
<URL Redacted>
As discussed last year this knee is a weight activated, free swinging
hydraulic knee that providing 120 deg's of flextion, It also has a custom
discontinuous knee cover available.
We would be happy to send you a trial knee.
--
Michael Arnette BOCPO, LPO
Progressive Orthotic and Prosthetic Services
www.progressiveoandp.com
9511 E. 46th St.
Tulsa OK, 74145
(918) 663 7077
(918) 724 6256
Citation
Michael Arnette, “Responses to the Medi OP4,” Digital Resource Foundation for Orthotics and Prosthetics, accessed November 1, 2024, https://library.drfop.org/items/show/234582.
