April 2020

Early Orthotic Intervention in Pediatric Patients, Part 3: Muscular Dystrophy

Image courtesy of Orthotic Care Services and LaunchPad O&P

Improving patient care includes questioning traditional treatment approaches; in this case, it’s also about developing ways to enhance and augment those techniques. 

By Cary Groner

The first two articles in this series looked, respectively, at early orthotic intervention in children with cerebral palsy (CP)1 and in those with Down syndrome and other neurological conditions.2 In those cases, although there were predictable differences of professional opinion, a rough consensus emerged around treatment strategies and decisions.

Not so with muscular dystrophy. Most experts don’t sanction the use of daytime ankle-foot orthoses (AFOs), and even nighttime wear is subject to debate. This article will explore these opinions, which are supported by evidence of varying strengths. It will also, however, examine an early orthotic intervention that has shown anecdotal promise in individual cases, and of which the clinical community may want to be aware.

Defining Terms

Muscular dystrophy comes in many forms, all of which are hereditary. The most common type is Duchenne muscular dystrophy (DMD), named for the French neurologist who first described it in the 1860s.3

DMD results from a genetic mutation that interferes with the production of a protein called dystrophin, which is necessary for maintaining healthy muscle tissue. Because the associated gene is found on the X chromosome, it is usually passed down by mothers to their sons; girls are protected by having two X chromosomes, only one of which needs to have a functioning gene for dystrophin production. Nevertheless, rare cases have been reported in girls (presumably if both X chromosomes contain the mutation), and roughly a quarter of cases arise spontaneously, with no known family history. The disease occurs in roughly 1 per 5,000 male children.4

Children with DMD have symptoms that typically appear between the ages of 2 and 5 years, and may include delayed sitting, standing, walking, and trouble learning to speak. Other common problems are fatigue, gait abnormalities, frequent falls, lordosis, scoliosis, and contractures (the attenuation of muscles or tendons around joints). Muscle weakness begins proximally, in the hips, pelvis, and upper legs—as well as in the shoulders and upper arms—and the associated degeneration progresses distally and relentlessly. Many patients need motorized wheelchairs by their mid-teens.

Exercise can help maintain strength, but one discouraging aspect of DMD is that too much exercise—especially weight training—in the absence of dystrophin can lead to muscle breakdown that ultimately weakens the child.

DMD has no cure, but treatment can ameliorate some symptoms and prolong ambulation. And although promising new approaches include gene therapy, and the administration of corticosteroids to preserve muscle strength, the atrophy of skeletal, cardiac, and pulmonary muscles typically leads to death in patients’ 20s or 30s.

As a result, pediatric neurologists, physical therapists, orthotists, and other specialists ideally work together to optimize patients’ quality of life.5 Exercise can help maintain strength, but one discouraging aspect of DMD is that too much exercise—especially weight training—in the absence of dystrophin can lead to muscle breakdown that ultimately weakens the child. As a result, exercise has to be carefully dosed, and the patient’s strength and resilience closely monitored. Pool exercises and other approaches that minimize eccentric contractions are a common choice.

Clinicians also emphasize the importance of range of motion (ROM), either by stretching or the use of orthotics such as AFOs. It’s in the latter realm that matters can become contentious.

The Argument Against

Eileen Fowler, PhD, PT, director of the Kameron Gait & Motion Analysis Laboratory in the UCLA Department of Orthopaedic Surgery, explained that most AFOs restrict ankle movement, which limits DMD patients’ ability to compensate for their proximal weakness. As LER has reported before, compensatory gait patterns often allow such children to sustain ambulation, and interfering with those patterns can do more harm than good.6

“Ankle plantar flexors contract during toe walking to place the line of gravity closer to the hip and knee joints, decreasing the moments required at those proximal joints and preserving muscle strength,” Fowler said. “When you restrict the ankle, it forces the knee into flexion so that the quadriceps are slowly controlling the lengthening of the muscles—an eccentric muscle contraction—and that’s how they damage their muscles. So I think it’s a bad idea to prescribe AFOs for young children with this condition. Sometimes the body is smarter than we are.”

“When I see these kids early enough in the course of the disease, I’ve been able to balance foot and ankle alignments and shank-to-vertical angles through stance phase, which enhances and assists during swing phase.”

Scott Hinshon, CO

Fowler acknowledged that AFOs are appropriate for children with other neuromuscular disorders such as cerebral palsy. She also supports stretching regimens and the use of night bracing to prevent contractures, and has found that corticosteroid treatment can help patients maintain their ability to walk until they’re older.7

“Some kids get foot deformities and walk on their toes with their foot in a terrible position,” she said. “I know orthotists have tried to come up with ways to accommodate that, but I’ve never seen it work very well.”

Bryan Malas, MHPE, CO, director of orthotics / prosthetics at the Ann and Robert Lurie Children’s Memorial Hospital in Chicago, told LER that he and his colleagues feel much the same way.

“It would be rare for us to use an AFO in this patient population,” he said. “We primarily use them for nocturnal wear in an attempt to maintain ankle range of motion and limit contractures.”

That said, Malas admitted that there isn’t enough data to arrive at decisions about dosing. “Is nighttime wear enough?” he asked. “Maybe it’s not—maybe these kids need to wear something that will help prevent the loss of range of motion for a longer period of time.”

Malas noted that because DMD patients have a progressive, terminal condition, they often have more on their plates than just concerns about ambulation.

“How critical is an AFO if they have to deal with all these other aspects of the disease?” he asked. “I don’t know that you’re going to have good compliance, or if you’ll even be able to measure it. Even with nocturnal bracing, until we’re able to quantify the amount of time these kids are actually wearing that orthosis, I think we’re going to have arguments on both sides of the fence.”

That said, Malas feels that ultimately ambulatory bracing isn’t helpful.

“In most cases, AFOs are going to disrupt balance,” he said. “That makes it harder for these kids to walk, which defeats the purpose. Ideally we want to keep them ambulating as long as possible.”

Poor Data

Perhaps not surprisingly, the literature about orthotic treatment of children with DMD is inconclusive. For example, a literature review from 2000 reported that the studies at the time were relatively weak, and suggested that AFOs could prolong assisted walking and standing (vs. wheelchair use), but probably didn’t prolong functional walking.8 Similarly, a 2015 study found that dynamic response AFOs didn’t significantly improve walking ability and might have increased falls—though the study included just 3 boys, lasted only 2 weeks (which raises questions about the time needed for the kids to adjust to the AFOs), and included a “placebo intervention” (it’s hard to imagine how either subjects or researchers would have been blind to the placebo).

On the other side, a 2017 study from India followed 126 children for 4 years and reported that they ultimately “required” AFOs as resting or walking splints.9 In the same vein, a Brazilian paper from 2016 studied 20 patients in 3 groups (“no orthosis,” “night orthosis,” or “day orthosis”) for 5 to 7 months, and concluded that early daytime and nighttime use of articulated AFOs minimized compensations and was thus recommended to prolong gait ability.10 This conclusion raises obvious questions, however, for as noted earlier, minimizing compensations may not be a sound strategy in these patients.

The quality of research, in other words, doesn’t appear to have improved significantly in the two decades since the 2000 literature review found it wanting.

The researchers noted that the typical DMD compensations—lumbar lordosis, increased anterior pelvic tilt, reduced hip extension, and increased ankle plantar flexion—tend to position the ground reaction force vector posterior to the hip and anterior to the knee, hence reducing the demand on weaker hip and knee extensors.

That said, a few papers have begun to shed light on the deeper biomechanics of the disease, and the strategies clinicians may use to address DMD. For example, in a study reported in Gait & Posture in 2016, researchers used 3D gait analysis to objectively quantify changes in lower extremity function due to muscle weakness.11 The researchers noted that the typical DMD compensations—lumbar lordosis, increased anterior pelvic tilt, reduced hip extension, and increased ankle plantar flexion—tend to position the ground reaction force vector posterior to the hip and anterior to the knee, hence reducing the demand on weaker hip and knee extensors. They concluded that gait analysis can detect deficits in hip joint kinetics in young boys with DMD, as well as improvements following a corticosteroid intervention, and may be useful in evaluating future therapeutic interventions.

Perhaps the most comprehensive assessment of DMD rehabilitation and management was published in 2018, in Pediatrics, by researchers at Duke and several other universities.12 Lead author Laura Case, PT, DPT, and her colleagues outlined a comprehensive approach to the disease that includes protecting muscles; maintaining strength; minimizing disease progression; supporting functional independence, social participation, and quality of life; and so forth. The paper includes a detailed pathokinesiology of DMD disease progression and concludes that resting or stretching AFOs—including nighttime bracing—are necessary to minimize plantarflexion contractures. The AFOs should be custom molded, fabricated for optimal foot–ankle alignment, and started when patients are young. If patients won’t tolerate night braces, the authors recommend daytime stretching AFOs for use during nonambulatory periods or by those in wheelchairs. They don’t recommend AFOs for ambulation, however, because they limit patients’ compensatory movements and add weight.

Something New

It’s easy to conclude from such evidence that daytime, ambulatory AFOs simply aren’t appropriate for DMD patients. That’s a little like saying “cars are dangerous,” however; it depends on what kind of car you’re talking about and who’s driving it. If an ambulatory AFO could be designed that improved these patients’ gait mechanics without increasing the eccentric load on their muscles, it could theoretically prove beneficial.

One such AFO exists, as it happens. It has been used sparingly by its inventor and the reports of its efficacy are anecdotal. Nevertheless, it appears promising and warrants discussion here.

Marilyn Ash is a 43-year-old homemaker in suburban Minneapolis. DMD runs in her family; her brother died of it in 2015. When her son, Tyler, was three and a half, he too was diagnosed with the disease, and Ash began looking for people who could treat him.

One of those was Scott Hinshon, CO, who is CEO of both Orthotic Care Services and LaunchPad O&P, a maker of orthotic devices in Minneapolis.

“I think orthotics are being overlooked for DMD. It’s a tricky balance, because if these patients are too active they get muscle wasting, but if you don’t keep them mobile they’re going to get contractures and deformities. So you’re trying to prolong joint integrity…”

Carey Jinright, CO

“Scott said we could put these dynamic boots on him and then every time he takes a step it’s actually a stretch, and will increase his range of motion,” Ash said. “Tyler started wearing them a couple of hours a day, and we noticed that his ROM was increasing.”

That was 5 years ago, and Tyler still wears the AFOs about an hour a day. He sees Hinshon 2 or 3 times a year for an assessment and to have the AFOs adjusted, and Ash said that now, at age 8, his ROM remains normal. He tolerates the AFOs well, runs around a lot, and doesn’t fall. His neurologist, physiatrist, and pediatrician, she added, are skeptical.

“They’re apprehensive that the weight of the AFO might be harmful to Tyler’s muscles, but they’re pretty light, and he wears them with lightweight tennis shoes,” she said. “The funny thing is that they know how well he’s doing, but they’re reluctant to attribute it to that.” (None of the physicians Ash recommended returned LER’s calls requesting comment.)

Ash thinks that part of the reason she’s been able to keep Tyler up and running is that his relatively early diagnosis allowed the interventions to begin a year or two sooner than they typically would.

“When boys don’t get diagnosed until they’re 5 or older, by then they’re falling, they’ve lost range of motion, they have contractures, and there’s already been damage to their muscles,” she said.

Scott Hinshon agrees that early intervention can be key in cases like Tyler’s. He’s aware of the generalized professional dislike of ambulatory bracing, but feels it may change when better information becomes available.

“All bracing isn’t created equal,” he told LER. “If your goal is to prolong mobility, then you also have to maintain range of motion and prevent deformity, while at the same time avoiding the fatigue that contributes to muscle wasting. It’s a delicate balance.”

Hinshon and his colleagues evaluate DMD patients thoroughly at every appointment and make adjustments to their treatment plans accordingly.

“You see a domino effect in these kids,” he explained. “First weakness, then compensated gait, then contracture, then deformity. But if you have an opportunity to intervene early enough and normalize gait, you can sustain ROM and help prevent those irreversible physical consequences. Once deformity has progressed, ambulation becomes almost impossible and then there’s little you can do to treat them. The kids start to choose not to walk because it’s really difficult. There’s no benefit to daytime ambulatory bracing if it doesn’t provide a functional benefit.”

Hinshon believes the resistance to ambulatory bracing is based partly on a misunderstanding of what AFOs can do.

“If I put these kids in a sold-ankle AFO with a traditional heel, it creates a fulcrum effect that negatively pushes and pulls the knee during stance phase,” he said. “This creates a demand on proximal musculature, which is not what you want with DMD patients.”

Instead, he’s designed an AFO with a soft, flexible inner boot, combined with an articulated outer boot. The AFO includes an open cushioned heel that eliminates the fulcrum effect at heel strike. This approach, he said, helps control stance-phase rocker motion and eliminate push or pull on the knee. This is the AFO that Tyler Ash wears.

“When I see these kids early enough in the course of the disease, I’ve been able to balance foot and ankle alignments and shank-to-vertical angles through stance phase, which enhances and assists during swing phase,” he said. “Normalizing step length and foot projection angles is key to sustaining dorsiflexion range.”

Hinshon and his staff tune and finesse the design individually for each patient to optimize gait and prevent contracture and joint deformity.

Carey Jinright, CO, owner of Precision Medical Solutions in Montgomery and Auburn, AL, thinks the approach holds promise.

“I think orthotics are being overlooked for DMD,” he said. “It’s a tricky balance, because if these patients are too active they get muscle wasting, but if you don’t keep them mobile they’re going to get contractures and deformities. So you’re trying to prolong joint integrity any way you can.”

Jinright thinks that part of the problem is that pediatricians delay care decisions too long; as a result he often first sees patients when they’re 9 or 10 years old—far too late for the early interventions Hinshon describes. Jinright had one such patient who could walk about 100 feet without problems, but then would invariably fatigue and fall. He was able to treat him successfully with carbon fiber AFOs and delay use of a powered wheelchair. Part of this strategy involved using elongated orthoses to increase the lever arm in the feet.

“You give them an effective foot length that matches their height and weight, and that provides better proximal balance,” he said. “I’ve also found it can decrease their lordosis. If we could see them earlier, I think we could keep those proximal muscles more in the mix. And if we could see them often enough, we could work on keeping the fluidity of their gait cycle, and keep them ambulatory longer than they are now.”

Changing paradigms?

Hinshon admits that his approach remains controversial, but he figures that as more evidence becomes available, and further modifications are made, the design may gain acceptance.

“If nothing else comes of this than people start to consider it a viable alternative for early treatment, I’m fine with that,” he said. “We know that traditional AFOs don’t work in these kids, but if we can intervene early, and design AFOs with the right functional focus, I think we can treat them successfully.”

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

REFERENCES
  1. Groner C. Early orthotic intervention in pediatric patients, part 1: cerebral palsy. LER. 2019;11(August):23-30.
  2. Groner C. Early orthotic intervention in pediatric patients, part 2: down syndrome, other neurological conditions, and toe walking. LER. 2019;11(September):49-54.
  3. Muscular Dystrophy Association. Duchenne Muscular Dystrophy.  Available at https://www.mda.org/disease/duchenne-muscular-dystrophy. Accessed Feb. 5, 2020.
  4. Romitti PA, Zhu Y, Puzhankara S, et al. Prevalence of Duchenne and Becker muscular dystrophies in the United States. Pediatrics. 2015;135(3):513-521.
  5. Apkon SD, Alman B, Birnkrant DJ, et al. Orthopedic and surgical management of the patient with Duchenne muscular dystrophy. Pediatrics. 2018;142(Suppl 2):S82-s89.
  6. Groner C. AFO users must rethink concept of ‘normal’ gait. In. LER. 2011;2(August):25-33.
  7. Fowler EG, Staudt LA, Heberer KR, et al. Longitudinal community walking activity in Duchenne muscular dystrophy. Muscle Nerve. 2018;57(3):401-406.
  8. Bakker JP, de Groot IJ, Beckerman H, de Jong BA, Lankhorst GJ. The effects of knee-ankle-foot orthoses in the treatment of Duchenne muscular dystrophy: review of the literature. Clin Rehabil. 2000;14(4):343-359.
  9. Gupta A, Nalini A, Arya SP, et al. Ankle-Foot Orthosis in Duchenne muscular dystrophy: a 4 year experience in a multidisciplinary neuromuscular disorders clinic. Indian J Pediatr. 2017;84(3):211-215.
  10. de Souza MA, Figueiredo MM, de Baptista CR, Aldaves RD, Mattiello-Sverzut AC. Beneficial effects of ankle-foot orthosis daytime use on the gait of Duchenne muscular dystrophy patients. Clin Biomech (Bristol, Avon). 2016;35:102-110.
  11. Heberer K, Fowler E, Staudt L, et al. Hip kinetics during gait are clinically meaningful outcomes in young boys with Duchenne muscular dystrophy. Gait Posture. 2016;48:159-164.
  12. Case LE, Apkon SD, Eagle M, et al. Rehabilitation management of the patient with Duchenne muscular dystrophy. Pediatrics. 2018;142(Suppl 2):S17-s33.

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