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AFO Trim Lines for Ankle Varus/Valgus Issues: High vs. Low
By Brady Delander
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Kevin C. Matthews, CO/LO |
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Every practitioner wants a happy patient. But to what end? Orthotists need compliance or all of the time and brainpower spent making a diagnosis and eventually a fitting are wasted, so it's only natural that a compromise be sought. In some cases, that concession may not do the user harm, but it may not do them any good either.
Kevin C. Matthews, CO/LO, owner of Advanced Orthopedic Designs in San Antonio, Texas, has waged minor battles with some fellow practitioners over high vs. low trim lines on AFOs when dealing specifically with talo-calcaneal valgus and varus conditions. "There is a difference of logic between orthotists and podiatrists," Matthews says. "I like to discuss the rationale as I see it and why I feel typical orthotist-recommended designs are better.
"The Richie Brace® and Arizona-type orthoses are great for treating some foot maladies, but to get the best control of talocalcaneal valgus and varus conditions, more proximal trim lines offer the best chance for success. Once you tie in the calf you tie in the knee much more. The knee is inherently resistant to valgus and varus movement. That is one reason more proximal trim lines can be more effective and another reason why more orthotists prefer them. It's all about leverage and distribution of pressure."
Few respondents argued with that logic on the OANDP-L listserv. However, a well-meaning practitioner may have a patient with comfort issues, and a brace that rides up toward the knee may not be agreeable. Or a patient with aesthetic concerns might not understand why such a tall brace must be used when the problem is with the foot and/or ankle. Or a conservative podiatrist may not want to restrict motion in the foot. Suddenly a low-profile AFO looks awfully appealing.
"In this case, if you end up making them a lower-profile AFO, it's all about [the patient's] wishes and desires," says John N. Billock, CPO/L, FAAOP, clinical director at Orthotics & Prosthetics Rehabilitation Engineering Centre, Warren, Ohio.
Matthews and Billock agree that it is not effective to yield to the patient in this instance, and the reason is, as Billock points out, Newton's Second Law of Motion—the net force on an object is equal to the mass of the object multiplied by its acceleration. In this case, a longer lever arm is needed or the necessary leverage simply isn't there. Also, a low trim line can put extra pressure on the "less-meaty" part of the lower calf. "Ideally you'd like to have the brace go equidistant above and below the ankle you are trying to control. But you can only go from the ankle down to the floor. To get a little bit of leverage then, you are forced into a higher profile," Billock says. Then he adds the caveat: "In my personal experience, [patients] don't accept that."
Matthews does not compromise in this situation, however. He hears the line of reasoning when issuing a low profile—the patient simply won't want to wear a taller, more unwieldy brace-but he does not buy it.
"That basic argument is not biomechanically accurate in my opinion," Matthews says. "In patients with talo-calcaneal valgus/varus conditions there is most often more going on than that. These instabilities tend to be triplanar in nature, and even when they're not, if you consider the amount of force generated by just walking, more proximal trims make sense.
"I take the time to explain basic biomechanics to the patient. I talk them through the phases of gait and what goes on with their foot and ankle. I then explain how I plan on attacking the problem and my rationale behind it. This makes my evaluations and casting longer than most, but I truly want the patient to understand their problem and buy into the treatment. I take the time to answer all of their questions before casting."
Matthews has been practicing for more than 25 years in 12 different facilities, and he says that he has yet to find an orthotist who prefers or regularly recommends the lower-profile design in this case. "As orthotists we want to make what is best for the patient and what will lead to fewer follow-up visits for adjustments and fewer complaints," he says. "Over the years we have experimented with many designs and have, for good reason, settled on designs with the higher trim lines."
Kevin C. Matthews, CO/LO, provided technical assistance for this article. Brady Delander can be reached at 303.255.0843 or
Table Of Contents - June 2008
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