An Ankle-Foot Orthosis Providing Mediolateral Stabilization While Allowing Free Plantar and Dorsiflexion of the Foot
Lucia Klemmt, CO
Fritz Klemmt
The development of an ankle-foot orthosis (AFO) providing mediolateral stabilization while allowing free plantar and dorsiflexion of the foot was prompted by a patient (W. F.) seen some months ago, who was wearing a posterior solid ankle-foot orthosis (PSAFO). However, rather than providing ankle stability, it was ineffective and an irritant during stance. W. F. was unhappy with it, and discouraged.
In evaluating his condition, he was found to have good plantar and dorsiflexion, but suffered from medio-lateral ankle instability. He was shown a conventional AFO with a metal stirrup and metal uprights, demonstrating the mediolateral protection the orthosis provides, while allowing free motion at the ankle. The fact that it was less cosmetic than a plastic orthosis did not concern the patient, if it allowed him to walk normally again and not with a stiff ankle. But considering his physician's preference for plastic over a metal orthosis, with its advantages, e.g., free choice of shoes, better appearance, etc., it occurred to us to combine mediolateral protection of the ankle with free ankle flexion-extension in a plastic orthosis.
This idea was realized by incorporating an ankle joint similar to that used in fracture bracing in a PSAFO (Fig. 1). From a plaster mold of the patient's limb, a PSAFO was fabricated with an anterior section for added tibial support. The distal aspect of the calf section was trimmed to clear the Achilles tendon. The proximal edge of the footplate was trimmed so as to include the malleoli (Fig. 2). A contoured bar was riveted to the lateral aspect of the posterior calf portion and joined with the footplate over the malleoli, creating a pivot point allowing, rotation necessary for flexion or extension (Fig. 3). Two velcro straps provided an intimate fit around the limb. The patient was pleased with the function and support provided by this orthosis.
The second patient fitted with this type of orthosis (R. R.) had a similar ankle problem. A slight change in the design was made. A separate ankle joint as with W. F.'s orthosis was not used. Rather, the proximal edges of the footplate were extended to the proximal aspect of the malleoli. The distal edges of the posterior calf section were then made to overlap the malleoli portions of the foot plate (Fig. 4a and Fig. 4b). This joint system works smoothly and is more cosmetic, although it requires a little more work. R. R. was delighted with the orthosis since he can wear it with regular Oxfords or boots (Fig. 5 and Fig. 6).
A third patient (P. B.) with a similar problem of ankle instability was fitted with the same type of orthosis made for R. R., but eliminating the anterior portion. This patient, too, was happy with the freedom of motion it allowed (Fig. 7).
In these three cases, free plantar and dorsiflexion were allowed while mediolateral ankle stability was achieved. Though it involves extra work and time during fabrication of this type of ankle joint on a posterior solid ankle foot orthosis, the security of the ankle on weight bearing, the freedom of movement while walking, and the satisfaction of the patients wearing the orthosis are achievements justifying the extra effort and expense.
