November 2017

Focus on biomechanics helps treat claudication

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Lower extremity clinicians say ankle foot orthoses, rocker-soled shoes, and other orthotic interventions can benefit patients with peripheral arterial disease and intermittent claudication by making it easier for them to exercise, and research is starting to demonstrate these benefits.

By Shalmali Pal

The treatment protocol for lower extremity providers consulting with patients with peripheral arterial disease (PAD) who complain of claudication is fairly straightforward, if somewhat counterintuitive: Don’t focus on the calf pain.

Instead, experts say, lower extremity clinicians should do what they do best and focus on the patient’s biomechanical issues.

“With this pathology, you are really treating the biomechanical deficits associated with the person, not so much the condition [of claudication],” noted Martin W. Buckner, CPO/L, a lecturer in prosthetics and orthotics in the Department of Physical Medicine & Rehab­ilitation at Northwestern University in Chicago. “The key to success with this patient population is a thorough assessment because the patient complains of pain … without any hint of what’s wrong biomechanically from that.”

Orthotic management

Studies on how lower extremity practitioners can manage claudication have focused predominantly on exercise-based treatments (see “Exercise helps reduce claudication symptoms,” March 2013). But clinicians say ankle foot orthoses (AFOs), rocker-soled shoes, and other orthotic devices can benefit patients with PAD by making it easier for them to exercise. Research is also starting to demonstrate these benefits.

Some benefits of orthotic devices in patients with PAD are similar to those seen in other patient populations, including the ability to ensure a safe gait.

Orthotic interventions that help patients with intermittent claudication to be active and avoid a sedentary lifestyle will lead to better health and well-being, experts say.

If an AFO and/or rockered shoes reduce the likelihood of falling or tripping, or allow a patient to walk farther without symptoms, that’s a positive outcome, said Linda Laakso MSc, CO(c), a staff orthotist at Custom Orthotic Design Group in Mississauga, Canada.

It makes sense, intuitively and clinically, that if orthotic devices can decrease the pain associated with exercise in these patients, their exercise participation should increase.

“If I can do something to mitigate pain, that makes the exercise prescription more worthwhile,” said Ryan Mizner, PhD, PT, an associate professor in the School of Physical Therapy and Rehabilitation Science at the University of Montana in Missoula.

Seamus Kennedy, CPed, BEng (Mech), president of Hersco Ortho Lab in Long Island City, NY, agreed orthotic devices can help in that regard.

“If they can improve their exercise level, going from say five minutes a day to ten minutes a day, that’s an increase of one-hundred percent,” Kennedy said.

But scientific data on the role of orthotic devices in this patient population are scarce, possibly because conducting such studies can be complicated.

“Claudication affects individuals differently, and may be accompanied by different biomechanical deficits,” Buckner pointed out. “The patient may present with hallux rigidus, posterior tibial tendon dysfunction, or neuropathy. The claudication is a comorbidity, and the diagnosis [of claudication] alone doesn’t lend itself to a specific presentation.”

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Background

Symptomatic PAD may present as intermittent claudication (IC), which is defined as “a reproducible discomfort in a specific muscle group that is induced by exercise and then relieved with rest. Although the calf muscles are most often affected, any leg muscle group, such as those in the thigh or buttock, also may be involved. This condition is caused by arterial obstruction proximal to the affected muscle bed, which impairs exercise-induced blood flow and leads to transient muscle ischemia.1 IC is often the first clinical symptom associated with PAD,” according to practice guidelines from the Society of Vascular Surgery (SVS).2

The risk factors for PAD risk are similar to those classically identified in the context of coronary artery disease, including advanced age, tobacco use, diabetes, hypertension, and hypercholesterolemia.3 In patients with type 2 diabetes in particular, PAD and claudication have been linked with peripheral neuropathy.

In an Italian study of 25 patients with diabetes and 12 without, only PAD patients without diabetes experienced increases in markers for muscular ischemia after a treadmill test, while those with diabetes and PAD (about half of whom had mild peripheral neuropathy) did not.4 “Mild peripheral neuropathy may have prevented them from reaching the point of muscular ischaemia during the treadmill test, because they stopped exercising with the early onset of pain,” the authors wrote.

According to the SVS guidelines,2 the diagnosis of IC involves:

  • Cramping, aching discomfort in the calf muscles
  • Reproducible onset with exercise
  • Quickly relieved with rest
  • May have atypical limb symptoms on exercise

Treatment for claudication most often involves medications that reduce the pain by widening the arteries and improving the flow of blood and oxygen to the legs, or medications that decrease the viscosity of blood to improve flow through the arteries, also boosting blood and oxygen to the muscles. Surgical revascularization may be necessary if a patient does not respond to medications.3

Finally, as mentioned, exercise rehabilitation can be designed to improve claudication pain symptoms. A 1995 meta-analysis concluded walking for at least 30 minutes per session, at least three times weekly, and for more than six months were associated with the best results for improving claudication symptoms in patients with PAD.5 Successful protocols also used near-maximal pain during training as the claudication pain end point, according to the authors.

Rocker soles

Much of the research on the use of devices in this patient population has focused on rocker soles. For instance, a study from the early 1990s compared walking distances in patients with calf claudication using rocker-soled shoes and a placebo shoe insert.6 The total distance walked and the distance at which patients were initially bothered by symptoms were both significantly longer for the rocker-sole condition (by 37% and 91%, respectively).

A 2012 pilot study from the UK compared a therapeutic shoe (used for baseline trials) and the same shoe outfitted with a three-curve rocker sole in patients with intermittent claudication.7 During a single clinical trial session, the rocker-soled shoe was associated with increased pain-free walking distance and reduced intensity of claudication calf pain, compared with baseline.

“A specifically designed rocker sole has the potential to offer a reduction in the intensity of calf pain experienced by claudicants,” the authors wrote.

A recently completed UK study (results unpublished, according to clinicaltrials.gov)8 used an unloading shoe with an incorporated rocker sole “designed to influence the line of action of the ground reaction force to pass close to the anatomical joint centres and so reduce the moments needed to be generated for ambulation by the muscles acting across those joints in the lower limb. Additionally, it is designed to place the ankle into a relatively plantar flexed position where the ankle plantar flexors use less energy than for instance when placed in dorsiflexion.” The trial design called for 40 patients with IC to complete several walking tests while wearing experimental shoes and control shoes, which do not have a rocker sole but are otherwise similar in appearance to the experimental shoes.

Kennedy called both of the published studies “encouraging.”

“Their underlying premise is that utilizing rocker soles reduces the amount of work performed by leg muscles, which in turn allows the patients to walk for longer before symptoms arise,” he said.

Ankle foot orthoses

As for the role of AFOs in this patient population, research is in the works, such as the effect of a lightweight low-profile carbon fiber AFO on the primary outcome of peak walking time in patients with PAD. One of the secondary study outcomes is claudication onset time. The study, led by Ryan Mays, PhD, MPH, a research assistant professor of exercise physiology at the University of Montana in Missoula, will be completed this December, according to clinical trials.gov.9

A second study, being conducted at the University of Nebraska, Omaha, will determine whether use of an off-the-shelf carbon composite AFO can boost walking performance in patients with PAD.10 For study inclusion, patients must demonstrate a positive history of chronic claudication and limitations to their ability to exercise because of that claudication. The estimated primary completion date for the study is April 2022.

Mays and colleagues offered some insights into how AFOs performed in patients with claudication. At the 2017 American College of Sports Medicine (ACSM) meeting in Denver, they presented results from a study in 15 patients with PAD and IC who were fitted with bilateral carbon fiber AFOs to supplement a community walking program.11

AFO use was associated with significantly less peak ankle plantar flexion power during the propulsion phase of walking at initial testing (mean 1.5 W/kg with AFO vs 2.6 W/kg without). The reduced propulsion power was also associated with 4.5° less dorsiflexion during the terminal phase of stance, a significant difference. Peak ankle plantar flexion moment and calf muscle recruitment did not differ significantly between conditions. A similar pattern of results was observed at 12 weeks.

The authors underscored the finding that calf muscle recruitment was not adversely affected by AFO use, contrary to the belief among some clinicians that AFO use is associated with muscle
atrophy.

“Maintenance of calf muscle recruitment when using the AFO was an unexpected but favorable finding that contradicts conventional wisdom,” the authors wrote. “Patients maintained normal values of ankle motion using AFO and sustained their gait velocity over time. The AFO reduces power demands on the calf muscle, which has the potential to reduce [intermittent claudication] while still maintaining muscle integrity and walking function.”11

Coauthor Mizner, who presented the findings at the ACSM meeting, explained to LER that because an AFO limits ankle motion, “it restricts some of the mechanical demands on the calf muscles when they walk … I thought [the AFO] might augment their calf muscle performance and we might actually have more calf muscle power; it appears to have been actually quite a bit less.”

But the lack of calf muscle power was not a negative, Mizner emphasized, noting that despite the decrease in how much the ankle contributed to walking, there was no decrease in the neural recruitment.

“There are two factors that contribute to power. One is the velocity of the movement, and the second is the torque demand at the joint,” he said. “What made the power go down is that the ankle didn’t move at the same velocity; it slowed its movement. The brain’s response to that was not to turn the muscle off. The muscle still got the same message from the brain to contract; it was just working slower and in less motion.”

Mizner said the group plans to continue building on this research, including a randomized controlled trial, a placebo controlled trial, and qualitative data based on patient feedback about the value of the devices. Anecdotally, he said, the results are promising.

“We had one lady in her forties who could walk two minutes before she had calf pain,” Mizner said. “She didn’t want to participate in any life activities. She put the braces on, and could walk for twenty minutes. As far as I know she’s still using them. That’s the ideal story of how [device intervention] works.”

In practice

Outside the lab, clinicians say their emphasis is on diagnosing and treating the biomechanical deficiencies first as a way to address, or resolve, the claudication. Indeed, patients are generally seeing a lower extremity practitioner for another condition.

“We do see many people who complain of claudication, but are referred to us for other complaints such as drop foot due to diabetic peripheral neuropathy,” Laakso said.

She added that when patients do complain of calf pain, it’s because she makes a point to ask about general pain during the initial assessment.

The degree of rocker would depend on the individual biomechanics of the patient, Laakso noted. She said she’d start with a rocker device-based strategy that would make the gait smoother and reduce the requirement for plantar flexion (push-off).

“That would most likely be more of a forefoot rocker,” she said.

Kennedy noted different rocker-sole designs benefit different patients in different ways.

“My approach in general is to begin by providing a commercially available off-the-shelf solution. This may be a shoe with a mild rocker sole and an orthotic inlay,” he said. “If you see benefits that can be gained, then you might introduce a customized shoe or
custom orthotics.”

Kennedy added he’d like to see more research on how subgroups of patients might benefit from particular rocker sole designs.

“For example, patients with PAD and limited ankle range of motion could be separated from patients with restrictions of the first metatarsophalangeal [MTP] joint [hallux limitus or hallux rigidus],” he said. “That’s where a good biomechanical exam helps you focus your therapy.”

Similarly, a biomechanics-based approach to AFO prescription in patients with IC means matching the type of AFO—rigid, semirigid, dynamic—to the right patient, Mizner stressed. For the University of Montana study, patients all received the same style of carbon fiber brace.

“What’s nice about this is the carbon fiber is so light, it’s so strong, that when you put it on the lower leg you can get much bigger impact on the torque loads,” he said of the study brace. “So I think there’s more potential for using a carbon fiber AFO than just a rocker bottom.”

Still, some of the feedback from study participants included comments that the brace felt like a ski boot. In future studies, the group will look at the possibility of customizing AFOs to patients’ clinical needs as well as their preferences, he said, adding the goal is to maximize load sharing without compromising safe and comfortable mobility.

Maintaining movement

So how do lower extremity professionals go about assessing the biomechanics of a patient with PAD and calf pain?

“As part of the assessment of this patient population, you must determine what treatment the patient is going through. If one of those happens to be an exercise program, as is often the case, the primary goal is to allow for improved participation in that program,” Buckner said. “If there is a biomechanical phenomenon that is preventing them from participating, then that biomechanical deficit is what you’re treating.”

Kennedy said his assessment focuses on range of motion—at the ankle, the first MTP joint, the subtalar joint, and so on.

“What’s abnormal with the patient? Begin to build your case through a thorough assessment and then employ specific modalities to address the findings,” he said. “A complete biomechanical evaluation should be conducted in three ways. With the patient seated, take their foot in your hand and manipulate the joints. Then, with the patient standing. Finally, with the patient walking.”

It’s important to keep in mind, however, that even when biomechanical issues have been identified, patients still may not be willing to get on board with a device for all the usual reasons (see “Improving compliance with diabetic footwear,” LER Foot Health, July 2015, page 15).

“I spend a lot of time before starting any sort of treatment talking about treatments as a tool for the person to use—if they choose to wear the device, they will get benefit from it, and if they don’t wear it, they will not get the benefit,” Laakso explained. “I provide information about the reason for the treatment so that the person understands why it is recommended, so it is their decision to wear it rather than me telling them they must. The internal drive [from the patient] to wear the brace works much better than an external reason [eg, a healthcare professional telling them].”

The ultimate objective is to keep patients moving, in and out of any rehabilitation program.

“For this pathology, the main goal is to allow them to participate in their prescribed exercise program,” Buckner said. “In cases when the patient has completed their [clinical] exercise program, the secondary goal is to assist them in increasing their self-selected activity level.”

Any orthotic intervention that keeps a patient active and helps them avoid a sedentary lifestyle will lead to better health and well-being, Kennedy said.

“Providing well-fitting shoes with a total-contact orthotic can help keep them walking,” he said. “There is an entire range of extra-depth shoes that have been developed for the diabetic market that will work very well for PAD patients. The shoes have firm counters, elevated heels, and snug closures, and, importantly, they come in a range of widths. They also have a removable depth inlay, so there is plenty of room for an orthotic if prescribed.”

While participation in an exercise program is important, Kennedy said, he also wants to ensure that the patient will use the device for all of their activities.

“You’re always looking to provide a device that will help a patient as frequently as possible,” he said. “By extending the time they can tolerate the device, it will have the most effect for them. I’m not always looking for maximum benefit, I’m looking for sufficient benefit so they’ll incorporate it into their daily lives.”

Shalmali Pal is a freelance writer in Tucson, AZ.

REFERENCES
  1. Vascular diseases: claudication/rest pain/ulcer/gangrene. Center for Vascular Awareness. V-Aware website. http://www.myvascularhealth.org/pad/legs-arms/claudication.html. Accessed November 13, 2017.
  2. Conte MS, Pomposelli FB, Clair DG, et al. Society for Vascular Surgery practice guidelines for atherosclerotic occlusive disease of the lower extremities: management of asymptomatic disease and claudication. J Vasc Surg 2015;61(3 Suppl):2S-41S.
  3. Cunha JP, Shiel WC Jr. Claudication. Medicine.net website. http://www.medicinenet.com/claudication/article.htm. Accessed November 13, 2017.
  4. Piarulli F, Sambataro M, Minicuci N, et al. Mild peripheral neuropathy prevents both leg muscular ischaemia and activation of exercise-induced coagulation in Type 2 diabetic patients with peripheral artery disease. Diabet Med 2007;24(10):1099-1104.
  5. Gardner AW, Poehlman ET. Exercise rehabilitation programs for the treatment of claudication pain: A meta-analysis. JAMA 1995;274(12):975-980.
  6. Richardson JK. Rocker-soled shoes and walking distance in patients with calf claudication. Arch Phys Med Rehabil 1991;72(8):554-558.
  7. Hutchins SW, Lawrence G, Blair S, et al. Use of a three-curved rocker sole shoe modification to improve intermittent claudication calf pain –a pilot study. J Vasc Nurs 2012;30(1):11-20.
  8. Tew G. York study of unloading shoes for Vascular Intermittent Claudication (YORVIC). Clinicaltrials.gov. https://clinicaltrials.gov/ct2/show/NCT02505503. Last verified September 2016. Accessed November 13, 2017.
  9. Mays RJ. Ankle-foot orthoses for peripheral artery disease. Clinicaltrials.gov website. https://clinicaltrials.gov/ct2/show/NCT02280200. Last verified December 2016. Accessed November 13, 2017.
  10. Myers S. Improving mobility in peripheral artery disease using an ankle foot orthosis. Clinicaltrials.gov. https://clinicaltrials.gov/ct2/show/NCT02902211. Last verified September 2016. Accessed November 13, 2017.
  11. Mizner RL, Mays AA, Mays RJ. Mechanical adaptations in walking performance using ankle foot orthoses for patients with peripheral artery disease. Med Sci Sports Exerc 2017;49(Suppl 1):S441.
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