Key Pearls For Prescribing AFOs

Clinical Editor: Howard Dananberg, DPM
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.” Q: Are there any specific problems you see with AFOs that could be considered areas to avoid during the fabrication process? A: Dr. Dananberg says he often finds the foot bed of the device is excessively long and ends in front of rather than behind the metatarsal heads. Although some who fabricate these AFOs may feel the increased length will better maintain the toes’ rectus position, Dr. Dananberg believes this increased length blocks metatarsophalangeal joint dorsiflexion and makes walking most difficult. By creating a device that ends behind the metatarsal heads and even incorporating a first ray cutout, you can achieve sufficient control of a dropfoot condition, according to Dr. Dananberg. The difference is patients can step efficiently and far more comfortably, notes Dr. Dananberg. He adds that designing a device this way “can often prevent the arch irritation so common with AFO use.” Dr. Richie says you must inform the lab about the specific limitations of the patient in terms of fixed structural deformity as well as muscle weakness or spasticity. “Patients with lateral ankle instability and high tibial varum should have their AFOs modified to fit the varus deformity of the leg. Otherwise, their lateral instability will get worse,” he contends. Dr. Richie says you cannot position a patient with dropfoot and severe equinus in a fixed solid AFO set at 90 degrees at the ankle. He also notes that one should not prescribe an articulated, full-motion AFO for a patient with spasticity. In summary, Dr. Richie says it is essential to give the lab as much biomechanical information about your patient as possible. “Certainly, this is much more important than the required information for the fabrication of standard custom foot orthoses,” he concludes. Dr. Dananberg (pictured) practices in Bedford, N.H. Dr. Richie is a Director of the American Academy of Podiatric Sports Medicine. Dr. Banks is the Director of Podiatric Medical Education and Residency Training at the Emory-Northlake Regional Medical Center in Tucker, Ga.

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