Orthotic devices, tailored to each patient and adjusted for disease progression, can improve mobility by addressing gait impairments and maintaining stability.
By Cary Groner
Orthotic management of the muscle imbalances associated with Charcot-Marie-Tooth (CMT) disease is a critical part of preventing or delaying later complications, which may include foot deformities and severely impaired gait. Because CMT is caused by genetic mutations that affect the nerves, such interventions don’t affect the progression of the disease itself; they can, however, help ameliorate its worst manifestations.
Clinicians wrestle with balancing correction and accommodation when prescribing orthotic devices for patients with CMT, and such decisions depend partly on the patient’s condition and wishes, as well as on the progression of the disease.1
What’s most important to patients isn’t always at the top of the list for practitioners, however.
“I ask my patients to prioritize,” said Ken Cornell, CO, who practices with Cornell Orthotics & Prosthetics in the Boston area. “Usually they complain about lateral ankle instability, painful calluses, foot drop, or claw toes. Only rarely do they mention balance problems, but I’ve found that when you restore their balance they suddenly realize what a big problem it was.”
Cornell agreed that orthotic intervention doesn’t address the underlying pathologies associated with CMT—an ankle foot orthosis (AFO) doesn’t give patients back their lost muscle strength or proprioception—but it can do other things.
“What’s challenging and exciting is restoring both static and dynamic balance by derotating the foot and trying to restore its alignment,” he said. “That changes the path of the center of pressure as it tracks over the foot, and that improves patients’ functional balance.”
According to Cornell, skilled orthotists can also address the deterioration that may lead to a “slapping” foot during the stance phase of gait.
“Particularly with dynamic carbon bracing, we can restore those three stance-phase rockers to normalize someone’s gait pattern,” he explained. “They have a heel strike, then controlled plantar flexion as the foot comes down to the ground. They’re getting dynamic resistance from the carbon so it’s giving them a ground reaction that tells them where their center of gravity is over their base. Then the tibia advances over the foot until it gets resistance in dorsiflexion, and then it raises the heel, which is the normal third rocker.”
Research supports the efficacy of AFOs for treating gait issues in CMT patients. One 2012 study from the UK, for example, noted that CMT patients often compensated for foot drop by increasing hip flexion during swing. In 14 individuals, three types of AFOs designed to address foot drop improved both proximal and distal leg control, decreased hip flexion amplitude during swing, and increased both ankle dorsiflexion and foot clearance.2
In a study noted in LER last year,3,4 researchers fitted eight CMT patients with custom carbon-fiber braces and reported that participants walked faster with the braces, particularly if they were relatively weak to begin with. As velocity increased, moreover, maximum joint moments during loading response shifted from the hip to the ankle and knee joints; the hip joint dominated during propulsion.
Overall, however, the relative paucity of research on orthotic treatment of CMT means that clinicians often develop approaches based on their own experience and that of their colleagues. Collaboration is often a key element of success.
“The literature as to when to use orthotics or AFOs, or when to perform surgery, is very poor,” said Michael Shy, MD, a professor of neurology, pediatrics, and physiology at the University of Iowa’s Carver College of Medicine in Iowa City. “It’s almost always based on a person’s clinical judgment. I’ve been fortunate enough to work with many talented orthotists who’ve all seen a lot of patients with CMT. They understand the foot structures and disease progression, and they’ve seen people respond over time. They’re partners in providing care, and they know more about their field than I do.”
Although genetic screening has led to the identification of at least 80 subtypes of CMT, when making treatment decisions orthotists are more concerned with how the condition presents.
“It’s not really diagnosis-specific, because as an orthotist you have to deal with the biomechanics that are present,” said Sean McKale, CO, LO, practice manager at Midwest Orthotic and Technology Center in Chicago. “People with the same type of CMT may be at different stages of progression, or just affected very differently, so you have to evaluate them as individuals and assess their symptoms to address their needs.”
One of the first factors McKale evaluates is a patient’s strength—or, more precisely, how much of it they’ve lost.
“Muscle weakness plays a big role in terms of decisions about level of support and the dynamics of the orthotic device,” he said.
Other concerns are the position of the foot, loss of range of motion (ROM), triplanar deformity, and proprioception.
“You use these clinical findings to help guide you, to show you the path to take with that patient,” McKale said.
McKale believes functional alignment correction is more important than accommodation in most cases.
“I think that with accommodation you end up allowing the foot to become more deformed,” he said. “The exception is when there’s been surgical fixation or fusions, which limit range of motion so that you can’t gain functional corrections.” In such cases McKale prefers a stable nondynamic device to maintain an aligned position.
In more typical cases, however, his goal is to balance the foot as well as possible to prevent further deformity.
“Someone with better proprioception can deal with increased dynamics,” he said. “You have to vary the device you select, its stiffness and trim lines, based on the dynamic needs of the patient.”
According to Geza Kogler, PhD, CO, director of the Clinical Biomechanics Laboratory in the School of Applied Physiology at the Georgia Institute of Technology in Atlanta, addressing common gait issues with orthotic devices can make important contributions to patients’ quality of life.
“The ability for someone to lift their toe during swing phase has a dramatic impact on their ability to walk efficiently,” Kogler said. “That’s the primary benefit of the orthosis; a secondary benefit is that it slows down the foot during heel strike and stance phase, to help minimize foot slap. It also helps with stability during standing, and these things together have a profound impact on patients.”
Kogler agrees with McKale that alignment should be maximized. In some cases, however, it isn’t possible.
“Over time, with the loss of muscle, there can be contractures of the calf musculature, and that can lead to permanent deformity,” Kogler said. “That can change the alignment so that you can’t get the foot into a neutral position during standing, and in those cases you have to accommodate that alignment. You might have to put a lift under the heel to reach neutral, for example.”
Allowing the muscles to work
According to David Misener, CPO, who practices with Clinical Prosthetics and Orthotics in Albany, NY, orthotists typically strive to find the best balance between correction and accommodation. Misener has a deeper experience of CMT than most clinicians because the disease runs in his family and he has it himself.
“You have to be careful not to overbrace someone,” he said. “The muscles need to work. Orthoses do need to support and align the body, though, and that can be as simple as an in-shoe orthosis. You can start with a very low profile device, inside the shoe, and then as the disease progresses, start working your way up the chain.”
In his practice, however, Misener frequently sees patients who haven’t been diagnosed early enough to allow for more minimal interventions.
“Ideally you want preventive orthotic management to maintain range of motion around specific joints,” he said. “To balance correction and accommodation, I think we have to be more proactive in getting functional corrections of alignment around joints, because bracing becomes exponentially more difficult when more range of motion is lost.”
According to Misener, patients should never be made physically uncomfortable by their devices, but other factors can also affect compliance. His experience is that CMT patients resist wearing corrective devices because they want to feel as “normal” as possible. This tends to backfire, however, as they start to lose range of motion.
“Ideally, you’ll get a diagnosis early and start with simple corrective orthoses,” Misener said. “Then, if you’re starting to get muscle weakness around the ankle, or foot drop, a carbon brace will still allow range of motion and allow the muscles to work without over-supporting them. I think having some fatigue throughout the day is good, because it means you’re exercising and strengthening your muscles.”
Maintaining range of motion is paramount as CMT progresses, Misener said.
“The key is to get the foot in subtalar neutral so you’re really stretching what you need to be stretching,” he said. “Night splinting [for Achilles tightness] can help, particularly with kids. They don’t want to wear braces, but if they do they’ll often gain range of motion.”
As Misener evaluates disease progression in his patients, he tries to address problems with the least drastic intervention possible.
“I think dynamic braces are a solid way to go,” he said. “Carbon systems are great because they’re lightweight and reduce fatigue, but you have to get the alignment correct. I like to be a minimalist whenever possible, but if I have to build something to overpower a muscle imbalance, then I have to go stronger. But I try to go stronger in a more dynamic way; you’d like to have the individual control their body as much as they can.”
Geza Kogler agreed that it’s crucial for the clinician to adapt to disease progression. In his experience, orthotic treatment and stretching should work together.
“A patient may go for years wearing an AFO that sets an alignment, but if they don’t keep up their stretching routine, they can end up with significant foot and ankle deformities that can complicate the fit of that AFO,” he said.
Kogler sees patterns in adjusting orthotic devices to disease progression.
“Early on, if someone has drop foot, a dorsiflexion-assist AFO might be enough, so the ankle can still move. But with time, if they develop more of a contracture, that assist will be overcome by the patient’s calf muscles, and they’ll have to switch to a solid-ankle AFO. But if they’ve stuck to a good stretching regimen, they may be able to avoid that step. It can’t always be avoided, but it can be delayed,” he said.
Ken Cornell agreed that a primary goal of orthotic intervention is to prevent deformity as CMT progresses, but that strategies depend on the individual patient.
“There is no one CMT brace, because everyone has a different level of gadget tolerance,” Cornell said. “You really have to make the patient part of the plan. If I apply too much pressure, to the point that the brace is uncomfortable and breaking down skin, no one is going to wear that. You have to understand the patient’s priorities.”
The role of physical therapy
As noted, physicians and orthotists play a big part in determining how patients respond to orthotic interventions. But physical therapists often play an important role, too, particularly because they often work with patients who have just received an orthotic device.
“Walking is an automatic task for most of us, but when people develop weakness or sensory changes, it requires much more cognitive attention,” said Katy Eichinger, DPT, CS, who practices in the neuromuscular division of the Department of Neurology at the University of Rochester in New York. “In slowly progressive conditions such as CMT, the body adapts and gait changes over time. We can be instrumental in helping patients relearn walking, by using different strategies and gait-training techniques to accommodate assistive or orthotic devices.”
For example, as part of these overall goals, physical therapists can help patients compensate for sensory loss, according to Eichinger. As clinicians have noted above, however, the success of such strategies has partly to do with getting the patient on board.
“Some people don’t like to use a cane, but they’ll use a hiking pole,” Eichinger said. “That may be all they need; you can see their gait improve because the pole provides increased sensory input about their position in space. It’s just a matter of teaching them to accommodate assistive and orthotic devices to maximize their functional abilities and gait techniques so they’re as energy efficient as possible.”
Cary Groner is a freelance writer in the San Francisco Bay Area.
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