Better braces for kids with cerebral palsy

Working as a clinical orthotist in Tehran, Sara Chami designed and fitted ankle-foot support braces for children with cerebral palsy. It was rewarding work, but she kept hearing the same frustrating story from parents.

“Families would come in holding their brace and say, ‘This is a rigid plastic boot. When my kid wants to run or play with friends he won’t wear it. It gives him blisters and we can’t find shoes that fit’.

"It was overwhelming, because as a clinician you want to help, and I felt we could do better."

Cerebral palsy is the most common physical disability in children, affecting one in 500 kids. Approximately 10,000 New Zealanders live with CP.

Caused by brain damage before or during birth, it affects children in different ways, but the main symptoms are related to movement and posture.

About half of children with cerebral palsy need ankle-foot braces to help them walk and prevent muscle tightening, but they can be bulky and uncomfortable.

They are also tricky and slow to make; they are crafted by clinicians from a plaster mould and heavily reliant on that clinician's level of skill and experience, rather than on patient-specific data.

“When an uncomfortable brace restricts someone’s walking to the extent they prefer not to wear the brace, their condition can get worse,” Chami says. “This can result in them doing less, and potentially lead to an increased reliance on a wheelchair, more intensive interventions such as surgery, and other consequences such as social isolation.

“This is especially so in kids, because they are super-active.”

Chami’s practical experience in the Iranian capital made her wonder if there wasn’t a way to make braces that was quicker and easier, and also took the child’s movement into account, not just the shape of their foot.

During her masters degree in Tehran, Chami was introduced to biomechanics and the scientific analysis of how people move. This eventually led to a PhD at the Auckland Bioengineering Institute at Waipapa Taumata Rau, University of Auckland.

Now Chami is using her skills to create a different kind of brace. She starts with a weight-bearing 3D scan of the child’s foot and ankle, creating a digital model. From there, the orthotic brace can be 3D printed in just a few days – a big improvement on the eight weeks New Zealand families currently wait for fabrication and shipment from overseas.

The brace is modular and comes in three parts. The first is an insole, which fits neatly into an existing shoe, Chami says. ("That's important, because children get to wear the shoes they want instead of specialised shoes.")

The second part attaches below the knee, and the third component consists of two small carbon fibre rods that connect the other parts together.

Using rods of different stiffness changes the flexibility of the entire brace, Chami says.

"We have to answer two questions: What is the optimal stiffness for that child, and how does that change with different activities?

"Personalising the stiffness of the brace is not a trivial task."

Chami uses an experimental approach called ‘human-in-the-loop optimisation' to personalise the stiffness to a particular walking pattern. The child tests the brace on a force-instrumented treadmill at different speeds and slopes, while Chami analyses their movement and measures the influence of the brace on ankle power production with every step. She then fine-tunes the brace with different rods to find the optimal stiffness for each child and movement pattern.

The result is a brace, comfortably shaped to the child’s foot and tailored to the way they move. At home, a simple swap of the rods adjusts the brace’s flexibility to match the activity – whether that’s walking, biking or kicking a ball.

And if the child is sitting or doesn't need the full support of the brace, the rods and top part can be removed.

Being able to tweak and improve the brace to find the best fit is what makes the research so satisfying, Chami says.

“It’s nice because I’m doing something to help the children, and I can go back and fix my work”. 

Every child has their own challenges and personality, she says.

"It’s like doing a different research project with each child.”

In the future, Chami’s work could benefit a far wider group, including people who have had a stroke, she says.

"Orthotics like these are used for a range of disabilities and injuries."

But for now, she is focused on helping the ten children in her cerebral palsy study have a more normal childhood.

“My big vision is that parents say, ‘We've finally found a good brace that our kid can wear. They are happy. They went for a hike last week’."

Article written by Sally Gallaugher