A Guide To Conservative Stabilization Of The Neuromuscular Foot

Author(s): 
Dennis Janisse, CPed, and Erick Janisse, CPed, CO

     In regard to bracing for ankle instability, one may utilize either a solid AFO or a hinged AFO. If the ankle medial-lateral instability is the primary problem, then a hinged AFO is sufficient. The hinged AFO will prevent motion in the
front while allowing free dorsiflexion and plantarflexion. Appropriate hinged AFOs include: the Richie Brace®, an articulated molded thermoplastic AFO, a metal and thermoplastic hybrid AFO or a metal single or double upright AFO attached to the shoe.

     If the goal is to control motion in more than just frontal plane motion, then one may prescribe a solid ankle molded thermoplastic AFO or Arizona Brace®.

Pertinent Insights On Treating Dropfoot

One basic function of any AFO is to maintain the foot in a plantigrade position. During stance phase, the brace provides a stable base of support and reduces tone. During swing phase, however, the primary function of the AFO is to prevent foot drop.

     There are several devices providers may employ to assist the patient with foot drop. Of course, there are many different styles of braces, both prefabricated and custom-made. There are also other devices such as elastic cords that run from a calf band to the top of the shoe that aid in dorsiflexing the foot. A relatively new development is the emergence of small electrical stimulation devices that send electrical signals that cause the foot and ankle dorsiflexors to fire and lift the foot in swing phase.

     Foot orthoses and shoe modifications alone are inadequate to treat dropfoot. Usually some sort of AFO is indicated.

     A number of manufacturers offer prefabricated carbon fiber composite dropfoot AFOs. These braces are lightweight — with some weighing only a few ounces — and are easily hidden under clothing. One style consists of a thin full-length footplate, a molded calf band and a posterior strut that can be as narrow as 1½ inches. There are also rear-entry models and spiral, wrap around designs. These styles of braces allow for significant heel compression at initial contact, energy return from midstance to terminal stance and toe-off assistance. These benefits allow for a longer and easier stride.

     It is quite common to use thermoplastic leaf spring-style prefabricated AFOs for mild to moderate dropfoot. They are usually available in several sizes and many can be heated and easily modified for a more comfortable fit.

     The posterior leaf spring AFO has a narrow posterior shell. The ankle region trimlines are substantially posterior to the malleoli. The posterior leaf spring AFO does an adequate job compensating for mild to moderately weak ankle dorsiflexors. It provides no medial-lateral control whatsoever. Since this device flexes with every step, it needs to be fabricated from a plastic with good fatigue resistance such as copolymer polypropylene.

     Many off-the-shelf dropfoot AFOs can fit into regular shoes as long as the shoe has some sort of closure system such as laces, a strap and buckle, or Velcro®.

     If there is increased tone, an additional strap at the ankle is required to keep the heel seated snugly in the brace. The shoe alone is not usually sufficient.

     Custom AFOs for dropfoot can fit into two categories: hinged and solid ankle. If there is no increased tone — merely a lack of dorsiflexion strength — then one may utilize a hinged AFO that allows motion. The hinges of either a metal bracing system or a metal-plastic hybrid AFO can either block motion with a pin or assist motion with a spring. Double-action joints stop motion one way and assist it in the opposite direction. There are also semi-flexible plastic hinges with offset tension cables molded inside of them that assist with dorsiflexion.

     If one desires dorsiflexion above neutral, one can set the hinges with a 90-degree plantarflexion stop. This will not assist with toe-off but will prevent foot drop.

     Using hinges that allow the full range of ankle motion but actively assist with dorsiflexion allows the patient without increased tone to walk normally as well as drive a car. Driving a car is certainly possible but more difficult when the patient is wearing an AFO that allows no plantarflexion.

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