Low vs. high trimlies in AFO's replies

Low vs. high trimlies in AFO's replies

Kevin Matthews

4/3/2008

Thanks to all who offered opinions and expertise. Following are replies and my original post:
   
  Original Post:
   
  Hello All. While trying to compose an e-mail to a local podiatrist arguing the benefits of more proximal trimlines I came up with this brief description of leverage.
   
  The Ritchie and Arizona type orthoses are great for treating some foot maladies, but to get the best control of talo-calcaneal valgus and varus conditions more proximal trimlines offer the best chance for success. Once you tie in the calf you tie in the knee much more. The knee is inherently resistant to valgus and varus movement. That is why orthotists typically include the calf in their designs. It's all about leverage and distribution of pressure.
   
  Do you agree?
  
Replies:
   
   
  Kevin... I definitely agree with your description! Newton's Laws regarding equal and opposite forces still, and always will, apply in the Orthotic management and control of lower limb deformities. When treating talo-calcaneal valgus and varus, maximizing leverage forces and understanding how to best use them are essential in controlling the force of the mass above the the ankle and foot!

John N. Billock, CPO/L, FAAOP
Orthotics & Prosthetics Rehabilitation Engineering Centre
   
   
  pls post replies - i heard somewhere recently that the description of an AFO includes a trim line at the fib head - & if this is the case, we shouldn't be billing for 'short afo's' using the L1940/L1960/L1970 range of codes
   
  
Kevin;

    Despite all the claims for improved cosmesis and the efficacy of
short ankle designs, there is no substantive argument against basic
mechanics. The longer lever arm, the more force available to redirect
against deviations. In mild deformities with the lack of spasticity an
SMO or short ankle design may be effective, but these are typically
prescribed in situations that require more control. Patient assessment
and a precise mold impression yield the best result, but you are often
at a disadvantage to counter other allied health workers who decide the
treatment goal and subsequent orthotic design for you. Unfortunately
when things don't work they will then expect you to eat the cost of a
re-do. The best course is exactly what you are doing: objective
education with third party references directed to your prescriber. Good
luck.

David L. Benson CO

  This rationale seems way off mark: in coronal plane trimlines have
 little influence on Knee varus/valgus (unless you include in your design
 rock-solid rigid materials, PTB/triangular shape and serverly ad/ab-duct
 the forefoot in relation to hindfoot i.e. Oregon Orthotic concepts).
  More proximal trimline (i.e. longer lever/less pressure) is only
 indicated if you wish to STOP talo-crural dorsi-flexion which creates high
 forces and is the primary destructive force for many moderate to severe
 plano-valgus deformities. This is problem with Arizona designs: they do
 not permit dorsiflexion in design but have grossly short lever, they are
 solid by design AND description but are too short which creates
 excessive pressure and/or does not sufficiently limit talo-crural
 dorsi-flexion. Get off the fence: if you wish to stop dorsiflexion then use
 sufficient lever (i.e. standard solid AFO). If however you don't wish to
 stop dorsi and only wish to limit coronal plane (as to some extent
 transverse) plane movement then shorter levers are acceptable (i.e. Short
 Articulated AFO from Yanke Bionics or Articulated Arizona or the
 completely suspect and amusing Ritchie Brace). Basically, the more severe the
 plano-valgus deformation, the more indication to restrict
 dorsi-flexion (often plantarflexion contractures). For the mild to moderate
 deformations you may not wish to limit talo-crural dorsi (let them move a
 joint which is often non-pathologic). My 2 cents.


   
  Some thoughts:

1. Leverage is good, but the more proximal the trim lines, the more you are depending on soft tissue to gain the leverage with. Not sure I'm convinced that if you tie in the calf at the proximal calf level it will be more effective.

2. Your statement about the knee being inherently resistant to v/v movement is true for a non pathological knee, but you can't assume that a patient with v/v instability at the ankle will be inherently stable. I would even expect some v/v laxity or instability at the knee.

3. What prompts your email? Do you have a referring source that wants to put patients in a Ritchie or Arizona type orthosis? Are you wanting to put them in something else?

Keever Wallace, LO

   
  
 
  Yes we all agree, and in the instance of upper motor neuron disorders
 with increased tone the shorter braces actually increase tone and are
 counteractive. Do some actual biomechanical calculations and the
 actual
 lever-arm advantage and decrease in unit pressure speaks for itself.

Seth Locke
Orthotics & Prosthetics
Queen Alexandra Centre
Victoria CANADA
250-721-6732


  Kevin - I agree with the statement, but I think you could also add that
 the
higher trimlines allow the plastic to terminate at an area that is more
tolerant to forces generate while walking. The proximal calf is more
 fleshy
than the lower leg, particularly on a thin patient or a very heavy
 patient.
Some patients aren't able to tolerate the short AFO's for this reason.

Amelia K Denton, CPO


  I would go along the lines of way we need ther lnserts as aposed to making them wish they were orthotist.
  I am not sure of the answer but would like to here the replys
   
   
   
  You are right about it being about leverage and pressure distribution, but why involve the knee in the issue? Leverage is increased by applying the force further away from the axis of rotation (subtalar joint), and force applied over a larger area = less localized pressure. That is why we go higher with the trims.
               Karen Lynch, CPO

   
  Thanks All.
   
   


Kevin C. Matthews, CO/LO
Certified/Licensed Orthotist
   
  Advanced Orthopedic Designs
12315 Judson Rd. Suite 206
San Antonio, TX 78233

  Phone: 210-657-8100
Fax: 210-657-8105
  www.AdvancedOrthopedicDesigns.com