Responses to: Plantarflexion weakness

Responses to: Plantarflexion weakness

Thanks to all for your input. Here is a posting of the responses I received:

I assume that her problem is excessive dorsiflexion beyond 90*. To replace
her
plantar flexors for inclines and stair you could try one of the following: an
articulated ground reaction AFO with 90* dorsi stop; a regular articulated AFO
with reversed tamarack dorsi assist joint (to provide dorsiflexion
resistance); a
regular articulated free motion tamarack AFO with some type of posterior,
adjustable, dorsiflexion limiter. My brother has the same type of problem 2*
to
Achilles tendon rupture that he did not have repaired. He wears cowboy or
wellington boots and no orthosis. What was the rational behind her other
orthosis, i.e.: the carbon plate and posterior trim?

Try a floor reaction AFO with an anterior section on the proximal tibia and
open the posterior down to just proximal to the heel. Use a wide (4)
elastic strap at the proximal posterior opening. This will allow PF at
heel strike but block DF at heel-off and give a more rigid lever to push-off
with.

I would not conisder a dorsiflexion assisting orthosis for someone with
plantarflexion weakness; this is probably de-stabilizing her. Basically,
when you have plantarflexion weakness you cannot roll over becuse you will
collapse forward as soon as the center of gravity crosses in front of the
ankle joint. So you take short steps and keep all your weight on your
heel, walking as if you do not have a forefoot. We use ground reaction
AFOs that block dorsiflexion or full wrap SMOs that limit it and sort of
hold the foot down, diffusing weight from the heel a little (works on some
of our L4 spina bifida patients who get calcaneal sores). I would suspect
the GRAFO owuld be the better choice, even though any solid AFO makes
steps and inclines difficult especially if bilateral. You may even
need to climb stairs sideways; or if unilateral go up with the unbraced
foot first and down with the braced foot first. The GRAFO for this
purpose should be set in slight dorsiflexion.


Your functional concerns here are the ability for the PF group to
eccentrically
contract to and slow anterior tibial progression.
Yes the quads will assist in countering this, but looking at it from a foot
and
ankle issue you have to take it into consideration.
A leaf spring design will not provide this resistance needed, in fact its
quite
the opposite, it lacks dorsiflexion control which is what
is needed. She can actively dorsiflex her foot which prevents toe drag in
swing
and foot slap at heel contact. You can approach
a design of an orthosis with these possibilites:
1) Reverse the leaf spring design to have it go on the anterior aspect and
(like
the CAMP Toe Off) encompass the lower extremity.
2) Use an articulated with free plantarflexion and limit the dorsiflexion
with a
posterior strap.


I can make some really good arguments for for an orthosis that should help
this situation. In reality though I doubt that she will wear anything. This
lady has too many other muscles working for her that she can substitute with,
I would be very interested in hearing from you in three months from now. You
might come up with something for this lady but the real test is will she
continue to use it once all the interventions are not part of her daily
routine. Please get back with me.


      Have you considered a ground reaction orthosis with a dorsiflexion
stop?
  It sounds like it may be appropriate for this lady.


Possibilities are:

Floor Reaction AFO
Posterior entry AFO with anterior panel and dorsiflexion stop

You may get by with less depending on the degree of plantarflexion weakness
and what might be going on at the knee or hip.


Interesting that she was given a PLS previously as one of the
prescription criteria for this would of course be normal plantarflexion
power.
Anyway, I would suggest a jointed AFO with free plantarflexion and
dorsiflexion stops to act with the Tibia in neutral (ie set for her
shoe). If this is not enough then perhaps a rocker sole to help reduce
the dorsiflexion moment.


How about an AFO that has joints with free dorsiflexion, but either has
plantar-flexion stops or perhaps a plantar-flexion assist? One could make a
plastic AFO with a plantar-flexion stop but I'm not sure about finding a
joint that has an assist, unless he or she used a metal AFO. Hope this helps.


Your patient will have trouble on inclines and stairs if she is not given
enough dorsiflexion range. This is true for any patient that is limited in
dorsiflexion. Does the reinforcement make the leaf spring rigid or less
flexible? Just a thought. Let me know if you still need bracing suggestions.


The Ground Reaction Force (GRF) will be anterior to the ankle joint at
mid-stance and heel off during ambulation. That is when the plantarflexors
are really active to move the body forward and up in normal locomotion. If
her plantarflexors are 3- (manual muscular test) she will not be able to stop
the tibia from moving anteriorly on the talus. Most likely she will present
increased cadence, and short steps on the contralateral side. That is to
prevent the load line to fall anterior to the ankle on the affected side.
Mr. Supan has a good recommendation regarding the AFO Ground Reaction.
However, I would allow 5 degrees of dorsiflexion to the AFO anterior stop.
This is for two reasons: 1. Because during heel off at least 10 degrees are
needed. 2. Because walking up a ramp she will need more dorsiflexion. Her
ability to go up stair won't improve substantially because, again, she will
need more dorsiflexion when the affected side goes up first. But it will be
safe.

Thanks again for your responses.
William C. Earles, CO
Beacon Prosthetics and Orthotics