Ankle foot orthoses, AFOs, can help compensate for muscle weakness and accommodate related structural deformities in patients with Charcot-Marie-Tooth disease, but practitioners are constantly looking for ways to improve suboptimal compliance rates.
by Cary Groner, Lower Extremity Review May 2013
Lower extremity practitioners who specialize in orthotic management of patients with Charcot-Marie-Tooth disease (CMT) face a host of unique challenges, and many express professional differences about the best strategies to pursue. At the heart of the discussion lies the need to find a balance between correcting and accommodating the weaknesses and deformities associated with the disease.
It turns out to require an elusive alchemy of patient feedback, clinical experience, and dead reckoning. And when clinicians get it wrong, patients simply won’t wear their orthoses.[1,2]
“I think compliance is low in these patients because we don’t listen to their needs,” said Sean McKale, CO, practice manager at Midwest Orthotics & Technology Center in Chicago. “I also think compliance is low when clinicians do a poor job of managing the patient’s triplanar deformity. We get better outcomes when we find a solution that fits both lifestyle and functionality, and match the best tools we have to the individual patient.”
Charcot-Marie-Tooth disease was first described by French and English physicians in 1886 and presumably existed long before it was named, eponymously, for them. The disease is a hereditary demyelinating sensorimotor neuropathy; it is marked by progressive muscular atrophy, beginning with the intrinsic muscles of the foot and then including the peroneus brevis and longus, the tibialis anterior, the extensor digitorum longus, and the extensor hallucis longus. It affects men more often than women, in a roughly 5:3 ratio, and has a US incidence of about 1 in 2000, though mild cases are probably underreported.[3-5]
Clinical presentation depends to some extent on how advanced the disease is. Lower-leg atrophy is common, and because some muscles weaken more rapidly than others, the resulting imbalances between dorsiflexors and plantar flexors lead to contracture of the Achilles tendon and problems such as cavus feet, calcaneal inversion, forefoot adduction, and claw toes. When the anterior tibialis becomes weak, the peroneus longus, inserting into the plantar aspect of the first ray, often plantar flexes the ray and the rest of the forefoot, creating a semirigid equinus.[3,5]
There are three subtypes of CMT: When it is caused by an autosomal dominant gene, it typically manifests at about age 30 years and may run a prolonged course with only moderate atrophy. When caused by an X-linked recessive gene, CMT usually has an onset in the patient’s 20s and leads to significant disability by age 30 years. The most severe subtype, transmitted by an autosomal recessive gene, appears around age 8 years and causes severe weakness by the second decade of life.
Practitioners understand that orthotic devices can’t actually correct ankle weakness and muscle imbalances, but they can still address them to some extent by maintaining ankle dorsiflexion and compensating for weakness and instability. As noted, it’s often difficult to decide how much to try to align the foot and how much to accommodate deformities.
“I seem to get the best results with my CMT patients when I seek the best functional correction of the foot,” McKale said. “I manage the coronal and transverse planes as well as I can, then try to maximize the ability of the foot to move in the sagittal plane.”
McKale noted that most CMT patients often adapt to their physical deterioration with strategies such as taking shorter and higher steps, and by restricting daily activities including running and walking.
“They may not be jogging the way they were, or walking the dog as frequently, or walking around the supermarket as much,” he said.
When the self-imposed restrictions become frustrating, however, patients may become more open to orthotic intervention. Researchers have shown that CMT patients tend to delay wearing ankle foot orthoses (AFOs) until their ability to walk is so impaired that the choice begins to seem inevitable. This transition imposes burdens of its own, of course, including a burden of responsibility on the practitioner.
“When they’re just getting ready to walk in that AFO for the first time, you need to be clear about how the devices will enable rather than disable them, how they’re really going to help,” McKale said. “We need to match the best tool we have to the individual patient, and that can vary considerably based on the patient’s needs, lifestyle, and ability to put the device on.”
The benefits are hard to deny, however. For example, in a 2012 study from the UK, researchers demonstrated that foot-drop splints improved proximal as well as distal leg control in CMT patients. The devices led to a decrease in hip flexion amplitude during swing phase, as well as increased ankle dorsiflexion and foot clearance.
Such effects on proximal biomechanics appear related to the fact that CMT patients typically compensate for foot drop by increasing hip flexion during swing phase, and may similarly employ hip abduction and pelvis elevation. But CMT also sometimes affects more proximal muscles, and in those patients, thigh muscle weakness can exacerbate knee instability and lead to sudden knee bending. The disease has also been associated with scoliosis, and occasionally even with weakness in the hands and arms.
|Align or accommodate?|
McKale believes that, depending on the patient, alignment is usually more of a priority than accommodation. This pertains particularly to the use of foot orthoses.
“Some orthotists build big holes [in foot orthoses] in places where the patient has calluses,” he said. “This feels good to the patients at first, but in time the foot deformity continues to progress and sink deeper into those holes. Rather than correcting the forces that are causing the calluses, they lead the foot in the direction of getting worse.”
Instead, McKale tries to functionally post a foot, placing the most pressure on the calluses.
“This helps distribute pressure in such a way that pain is relieved and the foot is better aligned,” he said. “I’ve found that important in getting an uncomfortable orthotic to be comfortable, and to make enough difference that the patient wants to wear it.”
Another Windy City denizen prioritizes somewhat differently. Bryan Malas, CO, MHPE, director of orthotics/prosthetics at the Ann & Robert H. Lurie Children’s Hospital of Chicago, believes accommodation has a primary place in the clinical toolkit, particularly in his pediatric patients.
“I think that it can be a problem when we provide an AFO that increases stiffness rather than attenuating shock,” Malas said. “The foot needs to be flexible in the early part of stance phase, then change in the later part and become rigid so we can push off. These patients already have a gait that isn’t absorbing much shock, and now you put something on them that is rigid and stiff; it’s no wonder they can’t tolerate it.”
Malas said a related problem with compliance is that clinicians sometimes try to force the foot into a position that isn’t attainable.
“Maybe the forefoot is plantar flexed, or there is a plantar flexed first ray, or they have a lack of range of motion across the ankle so they can’t really dorsiflex,” he said. “Then they’re given an AFO with a flat rigid plantar surface and no cushioning, and it’s set at ninety degrees, despite that the person doesn’t have the range of motion to get there. You’re trying to push this foot into an AFO that is not accommodating their alignment, so it becomes more and more difficult for the person to walk because it isn’t comfortable.”
Instead, Malas thinks it’s best in many cases to accommodate the patient’s existing alignment.
“Maybe they have an issue with clearing their foot during swing phase,” he said. “I can address that with an AFO, but I can also put in an insert that accommodates their malalignment issues so they’re more comfortable.”
For example, Malas’s patients tend to be between ages 5 and 9 years, and he’s found that many show limited heel contact during gait. In such patients, a padded heel insert helps redistribute pressure away from the metatarsal head.
“If we bring the ground up to the heel and create more contact across the plantar surface, the kids have less fatigue and they’re more comfortable,” he said.
Malas may also use a multi-durometer foot orthosis to accommodate the plantar flexed first ray that is so common in CMT.
“We’ll use a tri-laminated top cover, then cork below that, which allows us to do posting and accommodation, then poron on the bottom to absorb shock,” he said. “If the first metatarsal head is plantar flexed, I’m not looking to push that back up into place, because it’s already rigid; I’d rather load the other metatarsal heads, then pad the first metatarsal so it’s not getting overloaded. Look at why AFOs fail all the time; it’s not because they accommodate, it’s because most of them are set to ninety degrees, and the patient doesn’t have the range of motion to wear it.”
|Range of motion|
Clinicians have had limited success addressing range of motion (ROM) deficits in CMT patients, as it turns out. Malas said practitioners’ attempts to elongate the Achilles tendon using AFOs are misguided.
“I don’t think you can stretch the Achilles that way, because the patient will just compensate somehow,” he said. “You have to create a low level of load over a prolonged period. You’re not going to gain ROM with what they’re using during the day; it has to be something they’d wear at night, where we try to incrementally gain that range. Once we’ve done that, then we may revisit the alignment of the AFO.”
The research into this is contradictory, as it turns out (and for some reason often takes place in Australia). For example, in a randomized crossover study researchers at the University of Sydney in New South Wales gave night splints to 14 CMT patients for use on each leg for six weeks. The primary outcome was dorsiflexion ROM; secondary outcomes were eversion ROM and several measures of strength. The authors concluded that night splinting didn’t increase ROM or strength significantly, though there were changes that didn’t reach statistical significance (e.g., a gain of 1° in both dorsiflexion and eversion ROM).
A similar study of 30 children and young adults at the Children’s Hospital at Westmead, also in New South Wales, reached similarly discouraging conclusions (the studies shared a couple of authors, but not all of them). Four weeks of serial night casting, followed by four weeks of gastroc and soleus stretching, did in fact improve ankle dorsiflexion by a mean of 3°. However, at eight weeks there was no significant difference between the intervention group and control groups, which received no intervention, in terms of other outcomes that included foot deformity, mobility, balance, falls, and self-reported activity limitations.
Finally, a Cochrane review—again, conducted by some of the same authors—evaluated four studies comprising 149 subjects and concluded that there was no evidence of significant benefit from any intervention for increasing ankle ROM in CMT patients.
One of the authors on those last two papers, Joshua Burns, PhD, who is associated with both the hospital and the university, emphasized several points about his team’s research in email correspondence with LER.
“Our results were similar to those seen in other serial casting studies of neurological patients such as those with post-traumatic brain injury and spinal cord injury,” he wrote.
Nevertheless, his team did achieve better gains in ankle ROM than others have, which he attributed to several aspects of the intervention.
“We cast the ankles at the end of maximal passive ankle dorsiflexion and changed the casts at two weeks, aiming for a greater range of passive ankle dorsiflexion than in the first cast,” he said. “In addition, our casts could not be adjusted [degree of ankle dorsiflexion could not be changed], so it is possible our participants received a stretch of greater intensity and duration than those in previous studies. It is thought that stretch intensity and duration are crucial for achieving long-term gains in joint ROM; we just haven’t determined what the ideal ‘dose’ is for our patients.”
As noted previously, studies do show that AFOs often work in these patients, regardless of the associated issues. For example, a 2001 French study found that, in 26 CMT patients, plastic AFOs improved both gait and posture, whereas elastic orthoses only partially affected dynamic gait control. Moreover, the AFOs were particularly effective when the model chosen compensated for specific muscle deficits.
A 2010 Italian case study spoke to the importance of individual design, as well. Clinicians crafted a custom device for a patient who wouldn’t wear his semirigid AFOs because they hampered his compensatory movements and caused pain. The device, which they called a “soft footdrop insert,” consisted of a sheet of a reticulated polyolephinic foam, heated and shaped, and placed in the back of a midcalf boot. The AFO kept the patient’s ankle as close as possible to 90° during swing phase, while its elasticity allowed full ROM in plantar flexion during stance, and its softness alleviated the patient’s previous Achilles pain.
“With any patient, the assessment is crucial,” Malas said. “You may need elements of a stiffer insert because you need to change alignment, but you may also need to give them a shock-attenuating property. I think it’s important to drill down with our questions: What is it you don’t like about the AFO? Is it disrupting your balance? Does it make it more uncomfortable for you to walk? I’ve seen papers that suggest there are cosmetic objections, but when I talk to patients, that’s not usually the first reason they’re discontinuing the AFO; it’s because they feel it’s cumbersome and it’s not helping.”
A 2008 study from Italy surveyed 25 CMT patients (17 women, mean age about 42) and found that only five of them (20%) reported satisfactory functional results with their AFOs. Many felt that the devices highlighted their disability, were uncomfortable, and weren’t essential for their limited daily walking. A UK study published in 2011 surveyed 15 CMT patients, as well as their orthotists, and reported several trends. The patients felt that their AFOs improved their walking, but that they sometimes interfered with work, were uncomfortable, or were cosmetically unacceptable. Practitioners’ opinions were more variable.
“The orthotists we talked to seemed split between those who took a primarily biomechanical view—very much about preventing future deformity—and those who had more understanding of the patients with regard to comfort and cosmesis,” said the paper’s lead author, Margaret Phillips, MD.
Phillips, a clinical associate professor in rehabilitative medicine at the University of Nottingham, noted that patients’ concerns sometimes broke out along gender lines.
“Quite a few of the men were working in physical jobs, on building sites and so on, and that’s just the place you would want to use AFOs if they worked well,” she said. “But often the devices didn’t fit properly into their work boots, and it made it very difficult for them to bend down properly, so they weren’t practical.”
The women, by contrast, were more concerned about having a choice of devices and about cosmesis.
“Many people felt that they could not do with just having one type of orthosis,” Phillips said. “They wanted different ones for different activities. The polypropylene orthoses worked very well, but a lot of that depends on the skill of the orthotist. It’s important to have someone skilled, who has seen a lot of people with CMT and is really an expert.”
David Misener CPO, who practices in Albany, NY, is in a unique position to understand the needs of CMT patients because he has the disease himself. Misener, who is 44, was an active child and didn’t start wearing AFOs until his early 40s.
“I don’t think I’m in this career because I have CMT,” he said. “But as a child I wore foot orthoses, and they were very helpful to stabilize my foot. As I aged, I was interested in a career where you build things, but I didn’t think I could just build foot orthoses my whole life. That’s when I learned about orthotics for bracing the whole body. I came from a medical family; my degree is in human kinetics, and for me it just seemed a natural progression.”
Perhaps not surprisingly, he does his best to strike a balance between compensation and accommodation.
“I think most practitioners need some education in how to treat a CMT foot,” he said.
Misener explained that the foot’s inversion and related pathomechanics are often driven by a plantar flexed first ray, but there are usually coexisting neuropathic issues that demand protective and corrective padding.
“There is a real balance between appropriate padding and appropriate alignment,” he said. “You never want to overbrace; you want to maintain that range of motion. But I think most practitioners are not getting the foot in the proper position—you have to do that so the range of motion is effective.”
Because CMT is a progressive disease, patients may need different things at different times.
“If someone just has ankle instability, but still enough muscle strength for ‘normal’ gait, then a short hinged AFO allows you to maintain and potentially strengthen muscular use,” Misener said. “But again, you’ll want a soft interface along with corrective posting, a foot orthosis, to neutralize the foot and allow range of motion in the proper orientation.”
As patients weaken over time, practitioners should respond to the disease’s progression with a progression of their own, he added—starting with custom foot orthoses, then a lightweight AFO that primarily addresses foot drop, then onto stronger systems that store and release energy during gait.
“There are definitely cases where bracing cannot win the battle,” he acknowledged. “Eventually, if you’re not able to get to that neutral alignment, contractures will develop, and you’ll have more of a fixed deformity. Then you have to make accommodations while correcting what you can.”
For Misener, the first step is to establish the patient’s objectives.
“You have to talk to them, find out what their goals are, what they do, what they want to achieve,” he said. “Part of that assessment is to find out their muscle weaknesses, what needs to be supported by bracing. Alignment is a huge issue; that cavus foot is going to invert, and we need to try to control that.”
Psychological issues play a part, too.
“I think patients aren’t voicing their concerns, or practitioners aren’t addressing their concerns correctly,” Misener said. “Many CMT people are so close to normal, but they need a little help, and crossing that bridge to wearing an AFO may seem like a big leap.”
Other clinicians agreed.
“We need to figure out why the patient is coming to see us,” said Bryan Malas. “If it’s because of discomfort or pain, then I probably can’t go with something rigid—or if I do, I’d better incorporate a softer insert.”
“It requires a lot of patience,” said Sean McKale. “You have to listen to the patient and translate what they’re saying is bothering them, then see what you can do, mechanically, to help.”
|Cary Groner is a freelance writer in the San Francisco Bay Area.|
Source Lower Extremity Review
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☞ Disease severity, walking needs may guide patients’ orthosis choice
☞ Use of Orthotics Linked to Improved Gait, Balance in CMT Patients
Balance with benefits Charcot-Marie-Tooth Association
Important Foot Care for People with CMT Charcot-Marie-Tooth Association