Theoretical studies by Dr. Dan Mote of Berkeley, Calif., predicted that in a twisting fall, torque on the ACL rises sharply if the foot is twisted along its axis, as by an edge-locked ski. A study of 2300 Utah ski injuries by Rick Greenwald, MS, of the Orthopaedic Surgical Hospital in Salt Lake City confirmed that about 42 percent of ACL ruptures occur just this way, typically when a recreational skier falls forward between skis held in a wedge position (most ACL ruptures to professional skiers and racers occur in backward falls, as in landing after a jump).
Greenwald’s results are backed up by similar data collected on 323 knee injuries in France by Dr. Pierre Chambal, the French ski team surgeon based in Lyons. Salomon’s Spheric binding—available to the public next fall in versions for aggressive skiers (based on the existing 997-type toe unit) and for intermediate skiers (based on the current Quadra-type toe)—uses a redesigned AFD to sense rolling motions of the boot. In effect, the new AFD is a Salomon Equalizer turned sideways. When the foot is torqued sharply, the AFD activates a lever system to preload the release-tension spring, reducing twist-out torque.
According to Dave Bertoni, international marketing manager for Salomon bindings: “Our job as a manufacturer is to take what the doctors give us and see if we can engineer an answer. When they told us that in 80 percent of serious knee injuries there was no binding release, we felt an obligation to look into the problem. Now that we have a product, it will take a long time—several years, perhaps—to see whether it actually reduces the rate of knee injuries in the skier population.”
Although Salomon has contributed funds for research done by Vermont Safety Research, Carl Ettlinger, who heads the company says he is skeptical of Salomon’s new theory. Ettlinger and his associates developed a training program, which is based on a rear-weighted fall principle, to help prevent ACL injuries. “We collected videos of 22 ACL-injury falls,” he said, “and none of them show a scenario like that described by the Salomon binding people.
“If they [Salomon’s researchers] are correct, how do you explain the 60 percent improvement in the accident rate among people who have taken the ACL course?” he asked.
