Foot and ankle strategies for patients at risk for falls

As a result of limitations in the fall prevention research to date, investigators and clinicians are often left to make their best guesses about the effect of foot and ankle interventions based on the effect such strategies have on issues related to falls, rather than on falls themselves.

By Cary Groner

As the population ages, the prevention of falls is assuming an ever more prominent role, both for saving lives and for improving their quality. Fall prevention is critical not only in older patients, of course, but also in those with neuromuscular impairments, balance and sensory deficits, and other factors such as amputation that contribute to fall risk.¹ The stakes are high: in 2007 more than 21,700 people in the US died as a result of falls, and each year a third of adults older than 65 years suffers a fall.^2,3

Research into fall prevention must consider the whole person, but those who specialize in lower extremity issues naturally focus on their own areas of expertise. This makes sense for other reasons, too: of the risk factors for falls in older people that are part of the multifactorial risk assessment recommended by the American Geriatrics Society, three—muscle weakness, gait deficit, and feet/ footwear—pertain directly to lower extremity clinicians.⁴

Reflecting these priorities, the November-December 2013 issue of the Journal of the American Podiatric Medical Association (JAPMA) focused on the role of footwear and lower extremity interventions in preventing falls in older people. And, though the journal examined a comprehensive array of issues related to falls—individuals’ perceptions of an intervention program, footwear selection, nonslip socks, the relationship between neuropathy severity and fear of falling, whether surgical interventions improve gait and balance, making lower extremity exercises more gamelike, perceptions of footwear and balance, and the effect of footwear interventions—only one study, of foot and ankle exercises, looked directly at their effect on fall risk.⁵ In that review, moreover, the authors reported that only one of the studies included had demonstrated significant benefit.⁶

As a result of such limitations in the research, investigators and clinicians are often left to make their best guesses about the effect of foot and ankle interventions based on the effect such strategies have on issues related to falls, rather than on falls themselves. It turns out that there are reasons for this, however, and that knowing something is better than knowing nothing.

“It is inherently difficult to ascertain the actual mechanism of falls, as almost all studies rely on self-report by older people themselves,” said Hylton Menz, PhD, a senior research fellow and head of the Lower Extremity and Gait Studies program at La Trobe University in Melbourne, Australia. “In many cases, people are uncertain as to what occurred when they fell, so are likely to attribute the fall to tripping or slipping. Falls are clearly multifactorial, and it is essential to consider well-established risk factors such as impaired vision, peripheral sensory loss, slowed reaction time, and muscle weakness.⁷ However, our work^8,9 has shown that foot and ankle risk factors are independently associated with falls after these well-established risk factors are accounted for in statistical models.”

Doug Richie, DPM, owner of Seal Beach Podiatry in Seal Beach, CA, and associate clinical professor in the Department of Applied Biomechanics at the California School of Podiatric Medicine in Oakland, agreed.

“There appears to be a big difference between identifying fall risk factors and verifying that interventions prevent falls,” he said. “Fall prevention studies are costly and difficult to conduct. Measurement requires a strict control of variables, lots of subjects, and long-term observation.”

Footwear interventions

One interesting study in the special issue of JAPMA reviewed the effects of footwear interventions on balance and gait in older adults.¹⁰ The article evaluated the results of 14 studies of a variety of interventions (eg, textured insoles, custom orthoses) on several measures of static or dynamic balance. The authors concluded that the interventions significantly altered both static and dynamic performance and gait, and appeared to alter movement patterns through a combination of mechanical and sensorimotor mechanisms. It was particularly relevant to the study of fall risk that some interventions improved lateral stability measures during standing and walking, given the established relationship between lateral sway and falls.¹¹

“Sway, in general, is a predictor of fall risk,” commented Richie. “Older people don’t slip or trip more than young people; they simply cannot recover as well.¹² Sway may measure a delayed motor response to perturbation, which would cause a delayed or ineffective recovery.”

The JAPMA study’s lead author, Anna Hatton, PhD, is cautious not to overstate the paper’s conclusions given the study population.

“People who have investigated the healthy population—whether younger or older—have found a limited effect [for such interventions],” she told LER. “But if you look at a clinical population, one with neurological problems such as multiple sclerosis or Parkinson’s, the effects seem to be more prominent.”

Hatton, a lecturer in physiotherapy at the University of Queensland in Brisbane, Australia, noted that one of her previous studies found textured insoles were detrimental to older fallers’ balance and walking ability.¹³ In that study, 30 individuals who had fallen two or more times in the previous year were tested wearing either textured (intervention) insoles or smooth (control) insoles in their usual shoes. The participants had a few minutes to get used to the insoles; they then wore one type for a variety of standing and walking tests, then switched to the other type. It turned out that textured insoles were associated with significantly lower gait velocity, step length, and stride length. Hatton, however, expressed concern that the participants may simply have needed more time to get used to the different insoles—a common problem in such research, she said.

“A lot of studies test interventions on one occasion only, so it isn’t clear whether there is an initial deterioration in balance which may be followed by an improvement, once the individual becomes accustomed to the intervention,” she said.

As a further example of the sometimes contradictory findings inherent in such research, Hatton noted another study of hers, which showed that, when older adults stood on a textured surface, their lateral balance was improved.¹⁴

“Because lateral balance is a strong predictor of falls, this suggests that you could have a significant impact on falls rate and incidence,” she said.

She acknowledged, nevertheless, that dynamic measures are more important than static ones.

“Falls occur when people are moving, so an intervention has more clinical relevance if it improves dynamic balance,” she said. “A custom orthotic is strongly related to the ability to change biomechanical alignment, which is probably why you see more stark changes in balance performance during gait in those cases.”

In fact, the diverse geometric patterns of textured insoles seem to have surprisingly varied effects, according to Hatton.

“They have very different underlying mechanisms for altering sensory information, and I think that’s why there can be such disparate results,” she explained. “I think the way forward is to try to pinpoint which clinical populations are most likely to benefit from which geometric patterns, though that’s difficult to do.”

Keith Rome, PhD, DPM—Hatton’s previous mentor and a frequent coauthor of her papers, including the recent JAPMA study—agreed that the situation is complicated.

“The traditional view of the custom foot orthosis is that it’s all about motion control, cushioning, and support,” said Rome, a professor of podiatry at the Auckland University of Technology in New Zealand. “But, by introducing a material under the plantar surface of the foot, you’ve got to do more than simply control motion. If you stimulate in such a way that mechanoreceptors are more effective, then you may be decreasing postural sway. From a clinical perspective, when you prescribe foot orthoses, you have to ask whether you are enhancing balance or whether it’s detrimental to that person. You want to be sure your patients are safe and stable in their everyday activities.”

According to Doug Richie, orthoses form an important part of a more comprehensive approach to fall prevention.

“Muscle strength and reaction time, as well as a coordinated whole-body response, should be emphasized in any program,” he said. “Foot orthoses may improve sensory feedback on the proprio­ceptive side, but they also facilitate muscle activity and improved patterns of firing.”

Exercise programs

Regarding approaches that incorporate conditioning, one intriguing paper in the JAPMA special issue had to do with exercise programs and fall risk.⁵ In this case, the authors reviewed eight studies but in most cases found only small to moderate effects for balance and ankle flexibility; moreover, there were no significant effects for ankle plantar flexor strength and walking performance. Falls were not typically reported as an outcome measure, mainly due to small sample sizes.

“Overall, the effects were surprisingly low,” said Michael Schwenk, PhD, the paper’s lead author.

Schwenk, a postdoctoral research associate at the Interdisciplinary Consortium on Advanced Motion Performance (iCAMP) at the University of Arizona in Tucson, noted there is limited consensus in the field as to the most reliable outcomes to measure.

“This is a limitation you find in many systematic reviews,” he said. “There are so many different outcomes, it’s difficult to compare the studies.”

Ideally, every study should report on an intervention’s effects on balance, functional performance, strength, and flexibility, according to Schwenk.

“They should also be assessed objectively using biomechanical instrumentation—for instance, wearable sensors,” he continued. “They should also report established balance endpoints such as hip and ankle sway, center of mass, reciprocal compensatory index, and gait—including speed, cadence, stride length, and variability.” (Wearable sensors and reciprocal compensatory index—a method of assessing postural compensation strategies involving the hips and ankles—are described in a 2010 paper¹⁵ in the Journal of Diabetes Science and Technology by Schwenk’s colleague, Bijan Najafi, PhD, director of iCAMP.)

“The interplay between ankle sway and hip sway is a very important outcome measure,” Schwenk explained. “For example, if someone doesn’t anticipate hip sway by changing the ankle sway, he may be at a higher risk of falling. That’s the reciprocal compensatory index that Dr. Najafi proposed.”

Echoing the point made earlier by Richie, Schwenk noted that most of the studies in his review didn’t actually evaluate fall risk because they didn’t have enough participants enrolled.

“If you just want to prove reduction in sway, or improvement in gait, you power your study for that particular outcome measure,” he said. “But then you may not report falls because they’re fairly rare, and you’d need a much larger sample size to show a reduction. That’s why most studies don’t show any effect on falls; but if that same intervention had been used in a much larger sample, they could have potentially found a reduction.”

The one study in the review that did report a reduction in falls was published in the British Medical Journal in 2011.⁶ Australian researchers studied 305 individuals, mean age 74 years, who had disabling foot pain and an increased risk of falling. Of those, 153 received a multifaceted podiatry intervention consisting of foot orthoses, footwear advice, a footwear subsidy of AUS$100, a home-based program of foot and ankle exercises, a booklet about fall prevention, and routine podiatry care. The control group (n = 152) received only routine podiatry care.

After 12 months, there had been 264 total falls; those in the intervention group experienced 103 whereas controls had 161. The mean number of falls per person per year was .67 for the intervention group and 1.06 for controls—a 36% lower rate for those who received the intervention. In terms of secondary outcomes, the intervention group also showed significant improvements, versus controls, in strength (ankle eversion), range of motion (ankle dorsiflexion and inversion/eversion), and balance (barefoot postural sway and maximum balance rage when shod).

Study coauthor Hylton Menz told LER in an email that the study was the only one so far sufficiently powered to detect an effect on falls, and that part of this entailed following participants for a full year.

“When it comes to designing interventions to prevent falls, I believe that the inclusion of those targeted to the foot and ankle could enhance the effectiveness of interventions such as exercise, improving vision, home modifications, and medication review,” Menz said.

Despite the fact that Schwenk et al’s JAPMA study found only small to moderate effects for balance, ankle flexibility, and other measures, Menz doesn’t discount the relevance of research into their relationship to falls.

“I don’t agree that the link between these variables and falls is tenuous,” he wrote. “Increased postural sway has repeatedly been associated with future falls.¹¹ Reduced ankle flexibility has been associated with poor balance and functional ability,^6,16 and in our 2006 study⁸ was also associated with prospectively documented falls.”

He noted, moreover, that just because lateral sway is associated with future falls, that doesn’t necessarily mean that any given fall will involve a lateral loss of balance.

“It could simply be that measures of lateral sway provide a useful overall indicator of postural stability,” he said.

As noted earlier, Menz said falls are difficult to track and categorize under any circumstances, including in clinical trials. One 2013 study, in BMC Geriatrics,¹⁷ addressed the problem by installing video cameras in a care facility for older people.

“They were able to capture twenty-six falls, and most occurred during transition from a bed or chair (35%) or walking (27%),” Menz wrote. “Most involved a backward (54%) or sideward (23%) fall.”

A holistic approach

Aside from the exercise, orthotic, and footwear interventions described here, some practitioners have proposed ankle foot orthoses (AFOs) for fall prevention, but, as described in a previous LER article, their effectiveness depends on a number of factors including the condition (eg, dropfoot) affecting the individual patient.¹⁸

“There is debate about poor toe clearance as a predictor of falls,” said Doug Richie. “While elderly patients may exhibit this trait, they do not necessarily trip more frequently than younger patients; they just can’t recover as well. Recovery requires maximum range of motion and proper firing of muscles, and, in a non-neurologically impaired individual, there is a question whether an AFO can improve any of these parameters.”

Richie also noted that, by limiting ankle joint range of motion, AFOs may inhibit the muscle spindles and tendon stretch receptors that provide important feedback for balance and postural control, hence increasing fall risk.¹⁸

“In the absence of a significant loss of muscle or tendon function in the foot and ankle, a foot orthosis, rather than an AFO, would be a better bet,” he said.

“To my knowledge, there are no trials that have demonstrated reductions in falls with AFOs in an older population,” agreed Menz. “Although there is evidence that externally applied devices can enhance postural stability by providing additional sensory feedback,¹⁰ this needs to be balanced against the possibility of restricting motion in the ankle-subtalar joint complex. Indeed, we have previously shown^6,8,16 that reduced ankle joint motion is associated with impaired balance and an increased risk of falls.”

Looking ahead, practitioners increasingly advocate a holistic approach.

“Muscle reaction time, muscle strength, as well as overall coordinated whole-body response should be emphasized in a falls prevention program,” Richie said.

David Armstrong, MD, DPM, PhD, one of the coauthors of the JAPMA special issue, agreed with the idea of a comprehensive approach. Armstrong, a professor of surgery and codirector of the Southern Arizona Limb Salvage Alliance (SALSA) at the University of Arizona College of Medicine in Tucson, told LER that the aging of the population is likely to lead to an epidemic of falling if researchers and clinicians don’t develop adequate interventions.

“When most people think of falls in the elderly, they think of the late-night infomercial—‘I’ve fallen and I can’t get up,’” Armstrong said. “Through efforts like this, we need to get out in front of this problem, so we can get to something better. Instead of the infomercial, how about this: ‘You’re about to fall, Mrs. Jones, and here’s what you can do. Take two of these exercises and call me in the morning. Or two of these footwear interventions, or two of these game-based interventions that improve postural stability.’”

Armstrong was kidding about the form, but he was quite serious about the content.

“Moving forward, clinicians who focus on the lower extremities and the feet can make a big difference in this population,” he said. “It’s exciting.”

Cary Groner is a freelance writer in the San Francisco Bay Area.