Re: Extension Assist Joints

Re: Extension Assist Joints

Jim Thelen

8/15/2001

Thank you all for your responses concerning an extension assist knee
joint. My original post and reponses follow:

I have a patient with a repaired torn quad who the doctor wants in a
kafo with firm extension assist and near 0 flexion resistance so the quads do
not have to fire and full flexion is easily attainable. He does not want a
locked knee. Any suggestions as to available joints would be
appreciated.

Thanks
Jim Thelen
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Otto Bock offset knee joints with extension assists. Two strengths
available. It will work for you very well. Neither you nor your
patient will be disappointed.
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Utra Flex Knee joints. Depending on the size of the person and limb you
may only need one power unit and thir single axis joint on the medial side
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Check with Otto Bock. I'm not sure which joint but there is one that
you can add an elastic ext assist. I've gotten good reports from another
orthotist but haven't used it myself.
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Becker sell the Scott knee extension assist, I have used these and they
work well.

A knee extension joint was developed at OTS and is marketed by Becker as the
Model 1016. If that has been d/c'd, you can fashion your own with a section
of surgical tubing that spans the joint and is fastened on the AK & BK uprights.

Have you considered using an Ultraflex joint or orthosis? They sell their
joints individually if you were to make the brace in-house. The joint is
primarily used for resisting contractures, but the resistance is variable
and may be a thought for this application. There is also the option for
setting range of motion in the joint, which may be useful to the patient for
long periods of walking (can lock it to 0-30 degress) or standing (can lock
it to 0-10 maybe). Of course, that would depend on compliance of patient
and whether you felt he could adjust these ROMs. Otherwise, it could just
be free with the spring resistance. Nice joints; not too bulky for the
power they are capable of. They can fax you info on the joints. Their
phone: 800-220-6670

Call Scott Orthotic Labs, They have a couple of different models of K.O.'s
with extension assist, the SKO-437, and the SKO-438. One with polycentric
free knee joints, and one with drop locks with a ball retainer. They work
well, utilizing surgical tubing, the tension on the tubing can be increased
to allow greater extension assist, and it runs through a midsection piece
they fabricate. They have pre-fab sizing, and do custom to cast. Tell them
I sent you there, hope this helps sounds like exactly what your looking for.
I have used it on a couple of people with no to fair quadricep strength.

The trick knee joint will allow about 20 degrees of assisted knee flexion
during gait (but it is a locking joint). When new they work reasonably
well, but durability is an issue--particularly with large/active patients--I
believe that most of the major distributors carry them.

Check Otto Bock. They used to have an extension mechanism for their KAFO
uprights.

i know of 3 systems, the UTX, ultraflex system and a company in france make
an orthosis called the CDO

floor reaction AFO, or we sometimes use the CAMP toe off brace, email me if
you want to know any more info about either

Jane Marlor here...you may be able to obtain enough stability with a Becker
Posterior offset knee joint, it has an extension moment that stops flexion.

You might want to look at Becker's Trick Knee joints. They provide an
adjustable extension moment while allowing flexion. They also come with
drop locks if needed for positive locking. I have used them very
successfully for patients/clients with polio/post polio syndrome but they
(the patients/clients) were relatively small and lightweight.

Sounds as if you need a UCLA, functional KAFO. It's never been a very
popular orthosis, but it will fill your needs to a T
It was taught at UCLA throughout the 1960s. I don't know if the ball
bearing, offset knee joints are still in production. Maybe you could find a
pair at U.S. Mfg. or Hosmer Dorrance. They were the only manufacturers of
that joint that I know of. Tim Staats, who teaches at U. Cal. Dominguez
Hills, might still have a copy of the manual, as he was the last director of
the UCLA program.

Otto Bock makes/made a knee extension assist attachment for their 18mm
offset knee joints. I have used it on a woman with a similar condition that
you describe. My patient had partial extensors but lacked the final 30 degrees
of extension. The offset joints will allow knee stability during stance and the
extension assist mechanism will help extend the knee during swing. I've also
used the combination on polio patients.
There isn't much to choose from commercially. I have used criss-cross
elastic webbing attached above and below the knee joints anterior to the
knee, but these get very tight when sitting. A bale to hold the elastic off
the knee helped somewhat but caused cosmetic problems.

I have worked with a knee orthosis from Scott Orthotic labs. It is
available from them directly of from Becker Orthopedic. I would say that it
is functional, although a bit bulky. It uses latex surgical tubing as the
extension assist. It does not lock in extension, and it does allow full
flexion. I use this more as a diagnostic tool than a definitive orthoses,
however, when appropriate, I find that it can work long term. As long as
the patient/client is content or at least accepting of the size and shape.
I have custom fabricated similar devices in an attempt to reduce the bulk of
the orthoses, but none of these worked quite as well as I would have liked.

Just from my gait analysis experience, couldn't you try to aply a
GRF-AFO in order to stabilse the knee in extension during stance,
herefore removing any need to use knee extensors?

Otto Bock used to make 22mm offset knee joints with extensist rubber (or
synthetic) bands. The joint provides stance stability because of the
offset. The bands provide extension assist and attach to the exterior of the
joints using the normal mounting screws. You should be able to use
aluminium uprights but guard against rapid flexion (such as could occur in a
fall). Be sure the design won't cause a fracture of the femur if violently
flexed. I generally used an anterior thigh section with straps in the
posterior for attachment and security.

You may wish to consider a KAFO with unlocked posterior offset knee joints
and free ROM ankle. The posterior offset knee joints will provide excellent
stability in stance by the patient maintaining his center of gravity
anterior to the mechanical joint. Additional stability at the knee will be
provided by the hip extensors and plantar flexors. As an example of this
compensatory gait pattern will be found in the post polio patient with a
functional ambulation pattern in spite of absent knee extensors. I have
tried and rejected any number of extension assist mechanisms over the years.