Key Pearls For Prescribing AFOs
- Volume 16 - Issue 2 - February 2003
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“The most usual patient accommodation for this is a steppage-type gait,” says Dr. Dananberg. “In these cases, AFOs can be quite effective.”
Dr. Richie notes that when you employ the device to treat conditions such as dropfoot and lateral ankle instability, the AFO can control sagittal plane ankle rotation and also resist unwanted subtalar and midtarsal joint inversion instability if the orthotic footplate is properly contoured and balanced. Historically, bracing has been used to treat patients with dropfoot and is still “a reasonable conservative alternative for this condition,” according to Dr. Banks.
However, Dr. Banks also points out that “the need for bracing of the foot and ankle has, in many circumstances, been obviated with the advancement of surgical techniques that allow patients to undergo repair of their deformities and/or with tendon transfers to provide dorsiflexion.”
There are also clinical situations in which prescribing an AFO may not be the best course of action. Dr. Banks says a common problem is physicians prescribing an AFO for a patient who has a spastic equinus following a stroke. In this circumstance, the foot is often fixed in equinus and therefore the AFO is “of little benefit, except to possibly counteract some additional degree of contracture.”
That said, Dr. Banks says using an AFO may be an acceptable means of controlling patients with tibialis posterior tendon dysfunction who are not surgical candidates or are waiting for a more convenient time to undergo surgery. In some instances, patients who have chronic tendonopathy at this level (or involving the Achilles tendon) may benefit from a more sustained form of immobilization which you may achieve with the AFO. Dr. Banks also notes that the AFO may provide some symptomatic relief for patients who have chronic pain secondary to arthritis and typically works better than a functional orthotic alone.
Dr. Richie says one of the key benefits of the AFO is it can provide a force system both above and below the axis of rotation of the major joints of the ankle-rearfoot complex. The device also can help control position of the foot during the swing phase of gait.
“These are significant advantages over standard custom functional foot orthoses,” notes Dr. Richie. “In the adult acquired flatfoot, secondary to posterior tibial tendon insufficiency, you should consider the AFO when standard foot orthoses fail or in any patient who has lost integrity of the spring ligament and deltoid ligament complex.”
Q: When taking an impression for an AFO, what do you consider most important?
A: When taking an impression, Dr. Dananberg says he usually makes sure the foot is positioned at 90 degrees to the lower leg. However, he cautions there are times when this is either not possible or a 90-degree device would not be appropriate due to the height of the heel the patient wears.
“Several years ago, I did have a female patient who wanted to wear a high-heeled shoe,” recalls Dr. Dananberg. “She was cast in the position (mildly plantarflexed) that her foot would be in the shoe and she was very pleased with the device she received.”
For Dr. Richie, the most important consideration in casting and prescribing an AFO is performing a stance evaluation of the patient and determining position of the tibia relative to the foot and floor. He emphasizes a careful assessment of ankle range of motion and reducibility of deformity when placing the foot in a corrected, “neutral” position. The cast must accurately capture the corrected foot position, according to Dr. Richie.
While Dr. Banks usually refers patients to a prosthetist for molding and fabrication of the device, he will advise the prosthetist as to whether or not he wants a rigid device or one with some degree of flexibility. For the majority of patients, Dr. Banks will recommend a more rigid device in order to “maximize the level of immobilization and protection.”