Orthotic solutions for children with hypotonia

New research underscores years of positive clinical results.

When it comes to orthotic management of pediatric patients with hypotonia, the medical literature is only beginning to document the effectiveness that clinicians have been reporting anecdotally for years.

By Cary Groner, Lower Extremity Review September 2013

“The efficacy of treating low tone with orthoses is very poorly studied, but it is the standard of care because I feel intuitively that we can help these kids, and because we’ve seen good clinical results,” said Kathy Martin PT DHS, a professor and director of the Doctor of Physical Therapy program at the University of Indianapolis.

Important considerations related to orthotic management of children with hypotonia include which children need what type of device (whether an ankle-foot orthosis, a supramalleolar orthosis [SMO], or an in-shoe foot orthosis) and how early to intervene.

The evidence

There is, at least, some research that examines the case for bracing. Lisa Selby-Silverstein PT PhD, c-oauthored a 2001 paper reporting that foot orthoses affected the gait of children with Down syndrome; effects included reduced heel eversion and transverse plane foot angle during gait, but also a decrease in walking speed.^[1] And, in a small (two-subject) 2012 study, researchers found that a flexible SMO improved functional motor performance, whereas a less flexible one impeded it.^[2]

SureStep SMO

Martin published the results of a more robust and compelling study in 2004. Seventeen children with Down syndrome (mean age 5 years, 10 months) were given flexible SMOs and tested three times over 10 weeks on a number of measures that included standing, walking, and running. She found that the devices were associated with significant improvements in postural stability both at the time of fitting (week 3) and after seven weeks of wear (week 10). Martin noted that, the more challenging the task, the more time was needed to see significant improvement, but also that degree of joint laxity did not affect results.^[3]

Martin and a couple of colleagues—Julia Looper PT PhD, assistant professor of physical therapy at the University of Puget Sound, in Tacoma, WA; and Shelby-Silverstein, who is associate professor of physical therapy at Neumann University in Aston, PA—have put together a proposal for a multisite clinical trial to assess treatment variables, but, even if funding becomes available, results are likely years away.

Individual practice

As noted, clinicians have seen results in their own practices.

“When a normal child is learning to walk, their arms come out, their knees are straight, they’re moving from side to side, trying to balance,” said Curt Bertram CO, National Orthotic Specialist for Hanger Orthopedic Group who works at Children’s Hospital of Wisconsin, in Milwaukee. “That’s normal in the pre-walking child; but a child with Down syndrome may be in that phase at twenty-eight months, and the condition of their foot isn’t going to improve. So in those cases I think it’s important to realign the foot in an SMO, to provide a more stable base of support so they can get the proprioceptive feedback they need for balance.”

Bertram said that, if the orthosis is flexible enough, it will allow the child to explore movement range but still return them to a more normal biomechanical alignment in the gait cycle.

“I’m in favor of treating as soon as possible because they’re already delayed,” he continued. “These kids don’t have normal biomechanics or muscle tone. We sometimes see older children with Down syndrome who haven’t been treated with orthotics, and they typically end up with very deformed, rigid, stiff foot deformities.”

The needs of individual patients with hypotonia can be complex and challenging, however.

“We work very closely with the physical therapist in making these decisions,” said Jason Henry MSPT LO, the practice manager at Hope Orthotics in Spring, TX. “You’re looking at age, anatomy, range of motion, strength, coordination, and functional status. I start with an SMO, then work my way up the chain. Are they able to stand independently? If not, they may need a little more support than you get with an SMO. Do they go into a great deal of recurvatum? If so, how are we going to address that?”

Henry prefers flexible SMOs because they allow all the important motions in the sagittal plane—plantar flexion and dorsiflexion at the ankle, forefoot extension, and the like.

“The child can pronate and supinate out of subtalar neutral, which is what you want,” he said.

He too believes in bracing earlier rather than later.

“Some people say you shouldn’t put braces on kids until they’re twenty-four to thirty months old, and I don’t agree with that,” he said. “They’re getting further behind on developmental milestones, and the body is maturing. The limbs are elongating and they’re motor learning things in improper alignment, so they’ll walk, but what’s the quality of the gait?”

Changes

Faye McNerney PT DPT, a pediatric physical therapist in Troy, OH, has seen the field evolve over the course of her 36 years of practice.

“I used to lock up the foot using a rigid SMO or AFO, because I was afraid of what would happen to their foot if they kept rolling inward,” she said.

A 2008 study helped quantify the deleterious effects of such approaches, she noted, though it didn’t include children with hypotonia. In a British case study of a woman who had her lower leg immobilized following a foot fracture, researchers measured substantial and rapid loss in leg muscle volumes both proximal and distal to the immobilization site. Recovery remained incomplete up to two months after the cast was removed.^[4] And, in another study by the same lead author, children immobilized due to hip osteochondritis showed increased ankle stiffness throughout the immobilization period.^[5]

McNerney has seen the positive effects of SMOs as her own practice patterns have changed over the years.

“With the flexible braces we immediately see their feet come closer together,” she said. “Over time, we don’t see the flat-footed gait pattern; a heel-toe pattern develops. In my adult patients with Down syndrome who don’t have these flexible SMOs available, I see a much more flat-footed gait pattern.”

When to start

One controversy that has arisen in recent years has to do with the point in the child’s development when orthotic intervention is most appropriate. In her studies of Down syndrome patients, for example, Julia Looper has argued that intervening prior to the acquisition of independent walking may interfere with the child’s motor-learning skills.^[6-8] Kathy Martin acknowledges that this may be the case but points out that it is also important to consider the larger context of cognitive and emotional development.

“We agree that once these kids have learned to walk, orthoses help them,” Martin said. “Where we disagree is that Julia’s research suggests we should not intervene prior to the acquisition of independent walking. My clinical experience has shown that if you put kids in an orthosis when they are interested in pulling to stand, they start walking sooner. And once they gain independent mobility, their cognitive and social-emotional development explodes. So when I look at a child with Down syndrome who already has cognitive delay, I think the earlier we get them exploring their environment independently, the better their ultimate cognitive function will be.”

In her conversation with LER, Looper addressed this collegial disagreement by conceding the point.

“She’s right,” she said of Martin. “My take is that, in kids who are going to be wearing orthoses forever, it doesn’t matter that much if they develop control of their ankle. They will be in the orthoses anyway, so exploring their environment and getting the cognitive development is more important.”

Looper’s position now is that children with milder conditions, who may need to wear orthoses for a shorter period of time, might benefit from watchful waiting.

“I think there is a gradation, and it depends on how much calcaneal eversion we’re seeing, and what’s going on generally with the child,” she said.

Martin emphasized, however, that orthotic interventions have to be carefully selected and matched to the child. Too little is a problem, but so is too much.

“When you and I walk, we pronate and supinate around midline; that’s what normal gait is,” she said. “Being stuck in pronation throughout the gait cycle isn’t normal, but putting a child in a rigid orthosis that holds them in midline constantly isn’t normal either. That’s where some of the newer SMOs come in; they are more lightweight plastic, thin and flexible and dynamic, so they can bring a child back to midline but not rigidly hold them there. They can pronate and supinate around midline as they walk, and that should be the goal.”

Early intervention

If there’s a practitioner who has redefined the meaning of early intervention, it’s Debbie Strobach MA PT, a pediatric physical therapist and splinting specialist at Mercy Children’s Hospital in St. Louis, MO.

“We splint children with AFOs before they leave our neonatal intensive care unit,” Strobach said.

According to Strobach, preemies born earlier than 30 weeks have a higher risk of hypotonia and muscle imbalance, and may present with significant ankle and hindfoot eversion. This, in turn, causes problems with adjoining muscles.

“We see the fibularis become more powerful than the anterior and posterior tibialis, stretching the medial structures of the foot and putting children at risk for pronation when they’re getting ready to stand,” she said. “I want them in good alignment so that, as they grow, their tendons and ligaments can support the ankle and foot correctly. That helps the adjoining muscles contract and work as they should, as well.”

Strobach and her colleagues use customized solid ankle-foot splints similar to AFOs, in order to counteract such forces. She has been able to assess the effects of her interventions simply by comparing them to children who didn’t receive them.

“Kids from other hospitals who weren’t splinted in the NICU come to us at nine, twelve, eighteen months of age, and they may even have contractures in the fibularis muscles. We find that the babies can wear splints for maybe a month in the NICU, and then we’ll follow them up as outpatients for another month or two. In the NICU, they wear the splints three hours on and three hours off, coordinated with their feeding and handling times. We find that if we splint them early, very few need splints later when they start to stand and walk independently.” Strobach and her colleagues also deal with older children with benign hypotonia, who typically get SMOs or UCBL (University of California Biomechanics Laboratory)-style splints.

“Some of those kids are still not walking by sixteen or eighteen months, so we start them as soon as we get a referral,” she said. “Most of them graduate into a plantar orthosis by the time they are four to six years old, and then they’re done. The key is having splints that don’t inhibit the muscles so you can strengthen them and align the foot correctly throughout the day, for good muscle balance.”

Bringing research home

Such approaches, however convincing, remain more a matter of personal clinical experience than evidence-based medicine. Given the paucity of controlled trials, then, clinicians are increasingly documenting their results.

Megan Smith CO, director of clinical research for SureStep, a maker of flexible SMOs, will present the findings of four recent case studies at the O&P World Congress in Orlando this September.

“The four kids were fifteen or sixteen months old, and presented with diagnoses of developmental delay, benign hypotonia, and significant pronation,” she said. “We put them in flexible SMOs and followed them for sixteen weeks, with film every other week.”

When the subjects had mastered a skill on the Peabody developmental motor skills scale (e.g., pulling to stand, cruising, taking steps, walking fast), Smith noted the child’s age and compared those numbers with the Peabody norms.^[9] Although the participants began their evaluations at a baseline of about five months’ developmental delay, by the end of the sixteen weeks of study, that disparity had been cut to only a month (see “Orthotic success stories: Four cases in a series,” pages 16-23).

“We found that the kids who wore the SMOs had a rate of change 1.8 times greater than normal,” she said. “In other words, they were acquiring gross motor skills nearly twice as fast as normal kids and catching up to their peers.”

The future

As clinicians continue to define and refine the effectiveness of their interventions, and if better funding becomes available to conduct randomized trials, ideally the kind of protocols described here will become better documented, adjusted, and, where appropriate, standardized. It will make life easier for practitioners, of course, but the ultimate beneficiaries will be children whose development has been hindered by hypotonia.

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

Source Lower Extremity Review
In step with hypotonia, LER Special Education Series and SureStep

References

The effect of foot orthoses on standing foot posture and gait of young children with Down syndrome, Selby-Silverstein L, Hillstrom HJ, Palisano RJ. NeuroRehabilitation. 2001;16(3):183-93.
Single-subject design study of 2 types of supramalleolar orthoses for young children with down syndrome, Tamminga JS, Martin KS, Miller EW. Pediatr Phys Ther. 2012 Fall;24(3):278-84. doi: 10.1097/PEP.0b013e31825c8257.
Effects of supramalleolar orthoses on postural stability in children with Down syndrome, Kathy Martin PT DHS. Dev Med Child Neurol. 2004 Jun;46(6):406-11
Effect of foot and ankle immobilization on leg and thigh muscles’ volume and morphology: a case study using magnetic resonance imaging, Grosset JF, Onambele-Pearson G. Anat Rec (Hoboken). 2008 Dec;291(12):1673-83. doi: 10.1002/ar.20759.
Follow-up of ankle stiffness and electromechanical delay in immobilized children: three cases studies, Grosset JF, Lapole T, Mora I, Verhaeghe M, Doutrellot PL, Pérot C. J Electromyogr Kinesiol. 2010 Aug;20(4):642-7. doi: 10.1016/j.jelekin.2010.02.003. Epub 2010 Mar 1.
Orthosis use in children with Down syndrome, Looper J. LER 2013;5(4): 31-37.
Effect of treadmill training and supramalleolar orthosis use on motor skill development in infants with Down syndrome: a randomized clinical trial, Looper J, Ulrich DA. Phys Ther. 2010 Mar;90(3):382-90. doi: 10.2522/ptj.20090021. Epub 2010 Jan 14.
What to measure when determining orthotic needs in children with Down syndrome: a pilot study, Looper J, Benjamin D, Nolan M, Schumm L. Pediatr Phys Ther. 2012 Winter;24(4):313-9. doi: 10.1097/PEP.0b013e31826896eb.
Peabody developmental motor scales and activity cards, Folio MK, Fewell R. Chicago: Riverside Publishing; 1983. PDF