December 2011

When diabetes complicates drop foot

Photo courtesy of Allard USA

By Larry Hand

In patients affected by both diabetes and drop foot, ankle foot orthoses (AFOs) can help restore a more normal gait pattern and reduce the mechanical risks of ulceration. But microtrauma caused by irritation and elevated pressure is also a significant concern in these patients, making device selection and fit critical concerns.

The prevalence of patients presenting with both diabetes and drop foot is unknown, and, like diabetes, may vary geographically.

Michael Relle, CPO, of Orthotic and Prosthetic Specialists in Coving­ton, LA, estimates that diabetes is present in 50% of his patients with drop foot, and that about 80% of those may also have neuropathy.

“However, we practice in south­ern Louisiana, where there is an extremely high prevalence of dia­betes,” he said.

For Thomas Current, CPO, of Hanger Prosthetics and Orthotics in Milwaukee, WI, the picture isn’t as clear.

“Of the patients I treat for drop foot, diabetes is the cause in only one to two percent of cases. Almost always the patient has another primary diagnosis that caused the drop foot, and I’d guess that 15 percent of those patients also have diabetes,” Current said. “You can be certain that if diabetes caused the drop foot there is some significant neuropathy in the limb.”

AFOs can facilitate exercise, improve balance, and reduce the risk of falls.

“These advantages are the same for diabetic patients as they are for any patient, and also include decreased stress on the hip and knee joints, a more energy-efficient gait, and correction or prevention of foot and ankle deformities,” Current said. “In addition to keeping the foot in good alignment, you can reduce the risk for Charcot’s joint deformity and ulcer formation.”

The right AFO and the right fit, however, are needed to ensure patients with diabetes gain these potential benefits.

“It is imperative that you look at the patient’s foot and check for bone structure and skin quality,” said Carey Jinright, LO, of Precision Medical Solutions in Montgomery, AL. “Many of these patients present with the triple threat: diabetes, drop foot, and edema. When I am treating a patient with the dual diagnosis of diabetes and drop foot, my first approach is to move outside the shoe with my structure. This allows the patient to have the full capacity of the shoe depth and width.”

Other features, such as removable pads, adjustable straps, and modifiable footplates, can also help accommodate edema and reduce the potential for irritation and pressure.

“Our industry spends much time debating the proper material for a diabetic foot orthotic. However, too often we fabricate thermoplastic and carbon fiber AFOs for the diabetic population with no padding,” Relle said.

Current said he bases device selection on the severity of the drop foot; for simple drop foot, for exam­ple, he typically pairs a carbon fiber AFO with a diabetic insert.

“These take up the least amount of room in the shoe and, because the foot is not in contact with the AFO, there is a much lower risk of pressure sores or skin breakdown,” he said.

For a more complex case, Current might use a plastic hinged or solid AFO. “I use liners, sheer band, molded inner boots, flexible liners, dorsal wraps, internal T-shapes, ankle X straps, and pretibial shells as needed to reduce the risk of ulceration,” he said. “I also like to use metal AFOs on my severe diabetics when appropriate. This, like the carbon graphite AFOs, offers zero skin contact at the foot and ankle and also can accommodate fluctuating edema.”

Shoe selection and fit are also important, he said.

Relle noted that an AFO’s risks only outweigh the benefits when the device creates an environment not conducive to rehabilitation, protection, or improving quality of life.

“Treating the diabetic patient with foot drop with AFOs is a risk worth taking,” Jinright concurred. “These patients suffer from decreased proprioceptive feedback that leads to an inability to detect where their foot is in space, leading to greater risk of falls or stumping their toes, which increases their risk of amputation. The fitting of an AFO is an ideal time to remind the patient of these important factors.”

Sponsored by an educational grant from Allard USA

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