December 2010

Gait speed in AFOs: Results may vary

By Cary Groner

Numerous studies, and significant clinical experience, suggest that ankle foot orthoses help increase gait speed in post-stroke patients with hemiplegia or drop foot. Not all research supports this conclusion, however. A 2003 consensus report from the International Society for Prosthetics and Orthotics cited C- and B-grade evidence for use of nonarticulated and articulated AFOs, respectively, to improve walking speed. Scientists and clinicians alike have begun to discuss why results vary and whether gait speed may, in fact, be the best measure of function in such patients.

A 2009 article by researchers at Northwestern University reported that three variations of articulated AFOs, with slight adjustments to alignment and foot-plate length, failed to affect walking speed in subjects with post-stroke hemiplegia.

Lead author Stefania Fatone, PhD, a research assistant professor in physical medicine and rehabilitation at the university, said the study should be interpreted with care. This is partly because for research purposes the AFOs were standardized across the study’s subjects, whereas in the clinic each patient would receive a customized device. The necessity for measurable cohort statistics may have washed out the nuances of individual results.

“When I look at our individual subjects’ responses, I see that [walking speed with] the AFO is slightly faster than the no-AFO condition,” Fatone said. “It’s just that this doesn’t occur with the same AFO in each subject.”

Also, Fatone said, it could be that articulated AFOs don’t allow the same level of tibial control as nonarticulated devices do.

“We think that if you control the tibia—not only at the beginning of stance, as the plantar-flexion stop in articulated AFOs does, but at the end of stance—then you can potentially alter the dynamics of gait so that you affect walking speed more dramatically,” she said.
Fatone noted that walking speed is merely a convenient index.

“The orthosis doesn’t necessarily create a normal gait,” she said. “When a stroke patient walks without an AFO and can’t pick the foot up for swing phase, they might circumduct or hip hike. You hope that the AFO will decrease those compensations, but it’s not always the case because the compensation may have become a habitual gait pattern.”

Other compensations may develop as a result of the AFO itself. According to Carey Jinright, CO, owner of Precision Medical Solutions in Montgomery, AL, some patients experience an abnormal, mid-stance quadriceps firing because to get from heel strike to foot flat with an AFO may require excessive knee flexion.

“The patient may be faster, but that’s not a pattern we’d choose to promote,” he said. “We should be looking at the patient’s stability and gait, and be sure we’re not making an AFO so rigid we force them to compensate.”

Fatone agreed.

“Walking normally is not always the goal,” said Fatone. “You have to set priorities and find the balance for each patient.

A 2009 study in Physical Medicine & Rehabilitation concluded that AFOs did increase walking speed, particularly for patients who started out with more impaired walking ability. Lead author Karen Nolan, PhD, noted that even so, gait speed may not be an optimal metric for assessing results. Nolan is a researcher at the Kessler Foundation in West Orange, NJ, and an assistant clinical professor of physical medicine and rehabilitation at the University of Medicine and Dentistry of New Jersey.

“It’s useful, because in the clinic you may only have ten minutes,” she said. “But my goal is to find measures that make more sense, are easily obtainable, and correlate to walking speed, because an improvement in speed isn’t necessarily an improvement in biomechanics.”

Like Fatone, Nolan believes that individualized treatment is paramount.

“Someone with good ankle stability and strength may be able to maximize walking using a hinged brace,” she said, “whereas someone with less strength and a flaccid foot could be hindered by a hinge because the AFO doesn’t stabilize the ankle enough.”

Sponsored by an educational grant from Allard USA

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.