Designs Enhance Ankle-Foot Orthosis (AFO) Function
01 Aug 2017
Is an ankle-foot orthosis incorporating tone-inhibiting features effective in managing patients with spastic cerebral palsy and other upper motor neuron disorders?
There is considerable evidence that abnormal tone in proximal muscle groups can be influenced by joint position and cutaneous stimulation. For cerebral palsy management, maintaining a neutral position of the ankle and subtalar joint and stimulating key reflexogenous areas of the plantar surface (see drawing) can inhibit deforming reflexes and/or stimulate desirable antagonist reflexes to counter a dynamic equinus deformity, overcome toe grasp, and control foot pronation-supination and inversion-eversion issues, thereby enhancing function.
Tone-inhibiting features can be built into different AFO designs to accommodate the needs of both children and adults with neuromuscular deficiencies. An approach particularly suited to young C.P. patients is the dynamic AFO (DAFO), so named because its flexible assembly intentionally permits some degree of ankle motion. This flexible supra malleolar orthosis can be designed with a custom-contoured soleplate that evokes the desired reflex response.
Key to the effectiveness of the dynamic AFO is its thin wraparound construction, which is particularly brief over the dorsum of the foot. In creating a DAFO, an orthotist can incorporate a set degree of plantarflexion or dorsiflexion as necessary and combine tone-reduction with other features, such as plantarflexion stops and three-point pressure systems, to address unique patient needs.
A DAFO is sometimes constructed around an inner boot, usually made of thermoplastic but sometimes fabricated of very thin foam material. The boot is formed first over the patient’s mold followed by the remainder of the AFO structure so the two pieces align correctly.
With its lightweight flexible construction, the dynamic AFO is generally well tolerated by young patients. The total-contact, soft plastic assembly largely eliminates skin breakdown, even in children unable to tolerate other types of AFOs because of breakdown or pressure sores.
Dynamic AFOs can be worn under any type of clothing and will fit inside shoes with a wide toe box. They can be rendered in bright colors and finished with popular children’s designs. Assuming the patient does not grow out of them, DAFOs typically need to be replaced after about a year of wear.
Note: The terms “dynamic AFO” and “DAFO” are sometimes associated with a particular company that fabricates finished orthoses from patient molds.
Other providers fabricate these devices as well, sometimes under different product names. In using the dynamic AFO and DAFO terms, we are referring to the concept, not a particular company’s product.
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