Researchers work to make skiing easier on the knees
BOISE, Idaho ” Downhill skiers often lug something more than their skis, boots and poles up to mountains. They bring along a nagging fear of a knee injury, a trauma that has prompted many an alpine aficionado to switch to snowboarding or give up the slopes entirely.
But a handful of researchers across the country are trying to make skiing safer, analyzing ski-related knee injuries and working to build bindings that can sense ligament-ripping forces and release milliseconds before an injury occurs.
“There are four major ligaments of the knee and you can injure all of them in a bad ski crash,” said Dr. Kevin Shea, an orthopedic surgeon with Intermountain Orthopaedics in Boise.
“Right now, ski bindings protect the tibia (shin bone) at the expense of the knee. So we want to create a smarter binding that doesn’t forget about the tibia but stops ignoring the knee.”
Both Shea and Carl Ettlinger, a ski injury expert and president of Vermont Safety Research, are running separate research projects on the subject.
If the work done by Shea or Ettlinger is successful, it could have a big impact.
Overall, skiing injuries have declined by about 55 percent since 1972, and injuries to the lower limbs have dropped by about 58 percent, according to numbers gathered by Ettlinger and his co-researchers.
But in the two decades since 1972 serious knee sprains increased by about 268 percent, Ettlinger said.
Since the mid-1990s, serious knee sprain rates have dropped somewhat, but not nearly as much as injuries to other parts of the leg.
“If you look 30 or 50 years ago most of the injuries we saw were called boot-top fractures,” Shea said. “Because of the way the boots and bindings were designed, most of the force in a crash was transferred right to the top of the boot, breaking the tibia.”
Tibia fractures were greatly reduced thanks to research on the problem in the 1970s and 1980s, much of it by Ettlinger, that led to improvements in release bindings and anti-friction devices that allowed the boot to pull free of the ski in a crash.
The research also led to new standards for binding release settings based on the weight, height, age and type of skiing done by the user.
The trade-off was a new problem: the ratchet effect. When a skier attempts an overly aggressive turn, the bindings may sometimes release, causing a crash, Ettlinger said.
“If they release and the skier thinks it wasn’t a necessary release ” and they may be right but it may be ego ” they’ll adjust the bindings to be tighter,” he said.
Over time, the binding settings get ratcheted up to unsafe levels, rendering them ineffective in a crash.
That’s when many skiers find themselves visiting the likes of Shea for a knee repair.
But Shea, himself an avid skier, would rather not get his patients that way. Current ski bindings are based on simple spring mechanisms, he said, and the design is overdue for some refining.
“Technology has allowed the creation of sensors that are relatively small ” about the size of a couple of postage stamps ” that you could integrate into a ski boot and binding design.
These sensors can recognize acceleration and angular velocity using small gyroscopes embedded into chips,” Shea said. “They’re getting small enough and most importantly cheap enough that they could be used as a ski binding and boot interface.”
First, however, researchers have to figure out a way to differentiate between the forces used in an aggressive skiing maneuver and the forces that will destroy a knee.
Shea and Dr. Ron Pfeiffer, co-director of the Center for Orthopedic and Biomechanics Research at Boise State University, are sending out in-depth surveys to ski resorts, ski patrollers and hospitals that treat injured skiers.
Once a skier is stabilized after a crash, the first responder shows them a series of pictures of ski crashes, asking them to select the one that was closest to what they experienced.
The skier also has the option of describing his own crash, if none of the pictures apply, and may agree to share his crash-related medical information with the study.
Shea hopes that in five years he’ll have enough data to identify exactly how most skiers injure their knees.
Money for the work is coming from Shea’s pocket and Intermountain Orthopaedics’ research foundation.
“If we find one mechanism that contributes to 75 or 80 percent of the knee injuries, then we want to go back to the lab and redesign those bindings so it doesn’t occur,” Shea said.
But it could be a race to the lab.
This winter Ettlinger and his partner David Dodge plan to begin skiing on a small prototype interface that fits between the bindings.
The interface will measure not only the twisting loads that a skier feels on the leg, but where that load is coming from ” be it the inside edge, outside edge, front or back of the ski.
Ettlinger’s background research is funded by Fletcher Allen Health Care, a hospital affiliated with the University of Vermont Medical School. His company, Vermont Safety Research, is paying for development work on the knee-friendly binding invention.
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