Children With, Without Limb Loss Show Similar Stability Strategies When Carrying Heavy Loads

Children with limb loss maintain balance while carrying a backpack by developing similar strategies as able-bodied children to maintain stability, according to study results.

“There is a decent bit of data on able-bodied kids with heavy backpacks, but not so much on kids with limb loss,” Mark Geil, PhD, associate professor at Georgia State University, said. “This is one of those projects that started out of curiosity. Do [children with limb loss] shift all their weight to the contralateral limb [when carrying a heavy backpack]? Do they shift it more as the backpack gets heavier? We were interested in posture and weight shift in both standing and walking.”

Stability development

Geil, along with graduate students Kevin Wasco and Alison Brock, compared children with limb loss and age-matched controls in instances of quiet standing for 40 seconds while wearing a backpack of different weights. Weight levels were randomized between empty, 10%, 20% and 25% body weight. Researchers analyzed the middle 20 seconds of quiet standing sampled at 600 Hz, as well as two by four analyses of variance with a factor for group and backpack weight.

Mark Geil

Mark Geil

Study results showed significant differences for load, including in total distance of postural sway in the medial lateral direction. However, researchers found no differences between groups and no group load interaction. One reason for this result is children with limb loss can achieve similar stability as typically developing children.

“Through two studies — one on static standing and one on walking — we found that, at least in our small sample, kids with limb loss are quite symmetrical, and they tend to adopt the same postural changes in response to backpack weight as typically developing kids,” Geil told O&P Business News. “We did notice a change in strategy that is not readily observable in which the kids with limb loss sway a little bit more left-right in standing than the typical forward-backward sway.”

Researchers also found children with limb loss tended to overcompensate at 10% weight, even when starting at 20% or 25% weight.

Geil said they expected to see a certain load level that would be contraindicated in children with limb loss, but they did not.

“It is always encouraging for me to find out that kids with limb loss do something similar to their typically developing peers. We expect abnormalities and differences where there aren’t abnormalities and differences,” Geil said. “Understanding this can help us get beyond making prosthetic limbs for forward walking on a level surface in a straight line because we do a lot more shifting than we do walking.”

Future research

Overall, the researchers were surprised that the limb loss group did not have more deviations from the normal group.

“They have lost some important muscles that affect postural control, and they have altered sensation of the ground. But they managed to use their prostheses remarkably well,” Geil said.

Although the results showed that adequate prosthesis design, socket fit and therapy can enable children with limb loss to have common activity similar to their peers, Geil advised a larger sample study to be able to generalize the results. It would also be worth looking more into the overcompensation at 10% backpack weight for any underlying neuromuscular phenomenon, he said. — by Casey Tingle

For more information:
Geil M. Postural control strategies and balance in children with unilateral lower-limb with heavy backpack loads. Presented at: The American Orthotics and Prosthetic Association World Congress; Sept. 18-21, 2013; Orlando, Fla.

Disclosure: Geil has no relevant financial disclosures.

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