TORONTO - Children who fall off playground equipment and land on sand are far less likely to break an arm than those who take a tumble onto a wood-chip surface, a study has found.

In fact, the study by Toronto researchers concluded that the risk of arm fracture after such a spill is almost five times higher on engineered wood chips than on sand. Other injury types are also more likely with wood-chip surfaces.

"I think the difference between the performance of the sand and the performance of the wood-chip surfaces is actually pretty compelling," said lead author Dr. Andrew Howard, an orthopedic surgeon at the Hospital for Sick Children.

"So if the purpose of putting the surface there is to prevent fractures - which it is - then I would really strongly consider using the sand surfacing as the preferred choice."

The research, published online this week in the open-access journal PLoS Medicine, involved injury data collected from 28 Toronto schools following scheduled resurfacing of their playgrounds in 2003-2004. Nineteen schools chose wood chips, while nine went with granite sand.

The Sick Kids Hospital-York University study found there were 9.4 arm fractures per 100,000 student months with wood chips compared to 1.9 arm fractures per 100,000 student months with sand.

About half the arm fractures experienced by children involved the forearm bone near the wrist (distal radius), while more than a quarter were upper arm breaks above the elbow.

"These are the type of playground fractures we see in orthopedics day-in and day-out," said Howard, noting that they are not only common but can be severe, often requiring surgery under general anesthetic or sedation and bone manipulation in the emergency room.

"So this is the severe group of fractures that we're targeting and we're preventing, and those severe fractures do include things that children don't necessarily recover from completely."

Howard said there are fewer fractures on sand because the material is low-friction, allowing the hand to slide instead of becoming stuck.

"And when the hand is caught and the rest of the body is falling, piling up behind it, then the bone gets bent rapidly" and can fracture, he said. "And that's actually how children break their arms when they fall off playground equipment. It's not the vertical component of the fall only."

The Canadian Standards Association (CSA) sets the guidelines for materials to be used under playground equipment. Granite sand and engineered wood chips are two of the recommended products. Compared with hard surfaces like concrete and asphalt used decades ago, these materials have reduced the incidence of children's injuries, including broken arms.

"We found fewer injuries overall than we expected on playgrounds, which shows that the Canadian Standards Association requirement for playground surfaces is protecting children," said senior author Alison Macpherson, an associate professor of kinesiology and health science at York University.

"This study suggests schools could reduce the number of broken arms even further by choosing sand."

Safe Kids Canada, an organization that promotes measures to prevent injuries, says about 2,500 Canadian children under 15 are hospitalized each year because of playground accidents. About 80 per cent of those admissions are due to broken bones of all types, including arm fractures.

"When you look at playground injuries, while there are head injuries, the vast majority of them are fractures," said executive director Pamela Fuselli. "So any kind of information that can add to how to prevent that kind of injury, the better."

Fuselli said the study adds valuable evidence-based information about how to make playgrounds safer for children.

"Now I would think the CSA would have to go back and take a look at the findings of this research to see if those standards need to be tweaked."

One sticking point with sand - and the reason why wood chips are often chosen instead - is the worry that it will be tracked indoors or that animals such as cats, dogs and even raccoons could use the material as an outdoor litter box.

Cat and raccoon feces, in particular, can contain parasites. But cases of transmission to humans in North America are extremely rare.

"We studied broken arms, we didn't study toxicology," said Howard. "The broken arms are, from a public health perspective, a fairly big thing and the toxicology does not seem to be."

Still, Howard said the researchers addressed the concern during the study by monitoring the sites and found no animal feces in either sand or wood-chip surfaces.


On the Net:

PLoS Medicine: med.1000195

Safe Kids Canada: