A New Design for a Drop-Foot Polypropylene Brace

Edward Rice

The drop-foot polypropylene brace or, as it is called in the new nomenclature, an AFO or ankle-foot orthosis, is a recent innovation in orthotics. It constitutes a great advance in the treatment of certain ankle-foot conditions. However, in all new appliances certain problems arise, and this is certainly true of this drop-foot brace, which has also been called the "shoe-horn" brace.

To accommodate the appliance, a high percentage of patients have to buy a shoe that is a size larger than they would ordinarily wear. However, as a polio victim with a flaccid foot, I find that I can wear this appliance with some self-designed modifications without the need for a larger shoe. I have found it to be more comfortable than previously worn designs.

The cast-taking procedure in making this orthotic appliance differs only slightly from standard techniques. However, the "cutting-out" stage is quite different.

In taking the cast, the leg is placed at 90 deg. to the foot and a block is placed under the heel to simulate the height of the shoe heel. This block is placed under the calcaneus before and during the wrapping of the foot. This elevation of the heel is done so that the appliance will have a better cosmetic appearance when the patient is sitting; that is, the foot will be flat on the floor rather then sticking up in the air at an 8 to 12 deg. angle.

In modifying the cast, just smoothing the surface and accenting the arch a little is all that is necessary for the majority of casts. The polypropylene is applied to the cast by any method typically used by the prosthetist-orthotist, i.e., either by draping or by vacuum forming.

This appliance differs from the "shoe-horn" device in three major respects: 1) The heel portion of the orthosis is eliminated (Fig. 1 ). The heel portion of the brace takes up the most space in the shoe, hence the toes are squeezed and all-around foot discomfort occurs. 2) The shortened distal end of the footplate (Fig. 2 ) also eliminates excessive shoe pressure on the foot. The lack of these two design modifications in other insert braces is the major reason for requiring a larger shoe size. The third design difference relates to the anterior projection of the medial and lateral bars (Fig. 3 ). Besides holding the footplate in position, these bars offer valgus or varus support-the wider the bars and the further forward they project, the greater the support, and vice versa.

The appliance is removed from the cast with a cast cutter and a sharp knife is used to trim the edges. Distally, the footplate is terminated just behind the head of the first metatarsal. The proximal end of the footplate is cut away midway through the calcaneus and extends on a radius that will end at least one inch above the top of the shoe counter. This trimline will eliminate the heel portion of the orthosis and provide more room for the foot in the shoe. Both the distal and proximal trimlines of the footplate should be skived, so that the plate fits snugly against the bottom of the foot.

The top of the appliance is closed by Velcro tape. This means of closing is very handy for stroke patients who may only have the use of one hand.

Sometimes the patient may prefer a sock (nylon) over the foot to prevent the polypropylene from making contact with his/her skin. Then a second sock is placed over the brace, thus completely hiding the appliance (Fig. 4 ).

Edward Rice is a Prosthetist at Sunnybrook Medical Center, Toronto, Ontario, Canada