Ankle-foot orthoses of various designs are widely considered an important aid in managing young patients with spastic cerebral palsy; indeed, they are prescribed for cerebral palsy (C.P.) management more than any other orthotic device. Primary goals include contracture prevention, improved function and ambulation and tone reduction in proximal muscles to improve function at higher levels.
Ankle-Foot Orthoses (AFOs)
The chief role of the AFO in this application is to limit unwanted ankle and subtalar movement, primarily ankle plantarflexion, and indirectly to affect knee and hip function. Children with spastic C.P. often acquire a dynamic equinus deformity, which prevents them from putting their foot flat and attaining a stable base for stance and walking. Assuming the ankle can be placed in a neutral position at rest, i.e. the deformity is not fixed, a correction can be applied through one of several AFO constructions, depending on the capabilities of and goals for the patient.
Reviewing the different types of AFOs that may be appropriate for C.P. patients:
With a shorter profile than a full AFO, the supra malleolar orthosis (SMO) maintains a desired ankle position and provides support for the dynamic arches of the foot. Due to its shortened lever-arm, an SMO allows ankle movement, beneficial for ambulation and sit-to-stand transitions. The basic SMO is not very effective for managing equinus, however when constructed as part of a two-piece AFO with an extended footplate, this design can address that deformity as well.
A leaf-spring AFO
Helps overcome mild equinus spasticity and can improve ground clearance during ambulation swing phase. It is not normally rigid enough to control stance phase equinus, however. Its low profile and thin footplate allow it to fit in normal shoes, providing improved cosmesis over some other designs.
The solid-ankle AFO,
One of the most commonly used designs for the C.P. population, essentially prevents dorsiflexion and plantarflexion as well as varus or valgus deviations of the ankle and hindfoot. It can be designed to hold the ankle in a neutral position or at a predetermined degree of plantarflexion or dorsiflexion depending on the needs of the patient. This design is a primary choice for controlling equinus in both stance and swing phase and for contracture prevention.
An articulating AFO,
Which typically incorporates medial and lateral joints to allow plantarflexion-dorsiflexion, can be beneficial for C.P. patients who require increased ankle motion for higher-level balance and functional activities, including walking and sit-to-stand transitions. Stops can be incorporated to restrict plantarflexion and/or dorsiflexion beyond optimal limits. With a plantarflexion stop, for example, the ankle can be maintained in neutral from heelstrike through midstance, then allowed to dorsiflex from midstance through toeoff.
Floor Reaction Orthosis (FRO)
This solid-ankle design incorporates a broad, rigid anterior wall, which applies a knee extension moment during stance phase. The FRO can be a welcome improvement over a heavy knee-ankle-foot orthosis for addressing C.P. crouch gait and other sources of knee instability.
Tone-inhibiting characteristics can be built into many of these designs to address hypertonicity in proximal muscles.
Donning and wearing an AFO can be a challenge for C.P. patients with deformities, abnormally stretched muscles, pressure-sensitive feet and other tolerance issues. A fabrication option that provides relief in appropriate instances is a two-piece or combination construction featuring a flexible molded inner boot of thin thermoplastic, which wraps around the foot and can be donned separately from, then joined to, the outer AFO. Because the two components are custom-fabricated from the same mold, they fit together intimately and are held snugly in place by closure straps.
Available research is inconclusive on the relative merits of different AFO options, so selection of a particular design is a combination of art and science. However, the value of AFOs for improving gait function in spastic cerebral palsy patients, relative to no orthosis, is well established. Properly prescribed and custom-fabricated AFOs have been shown to increase stride length, reduce energy expenditure, and give patients a more natural look while walking.
When prescribing an AFO for a patient with spasticity, bear in mind that while AFOs can prevent or delay development of a deformity, they are not valid for overcoming pre-existing fixed deformities. Therefore, any existing fixed deformities should be corrected by surgery, therapy, serial casting or other means, if possible before orthotic application.
In summary, AFOs serve as a positive tool in managing spasticity associated with cerebral palsy. They will delay or prevent development of fixed deformities but not overcome an existing fixed deformity. They can prevent contractures, improve gait parameters, and often give patients a more natural appearance while ambulating.
Our orthotic staff is well prepared to assist in the selection and fabrication of AFOs for C.P. patients. We welcome your inquiries and referrals. Offices located in Beaumont, Nederland and Jasper, Texas.