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A summary of the research findings presented at the 15th ISSS Congress on Ski Trauma and Skiing Safety held in St Moritz/Pontresina, Switzerland, April 2003.
The biannual ISSS symposia bring together researchers from ski areas worldwide to share knowledge and research findings in the area of alpine sports injuries. Specialist fields include epidemiology, orthopaedics, biomechanics, engineering, psychology and more! Hot topics in recent years have included the developments in alpine carving (shaped) skis, boot and binding developments, the growing popularity of skiboarding and the continuing issue of helmet and wrist guard use. The ongoing problem of anterior cruciate ligament (ACL) injuries continues to generate debate as researchers continue to try and find ways to reduce their incidence amongst alpine skiers.
The 2003 symposium was held in St Moritz - superbly organised by Georg Ahlbäumer and colleagues from Switzerland. This page attempts to present a summary of the main research presentations from this symposium. I am not commenting on every paper but concentrating on those that present new or interesting findings. I apologise if I offend any colleagues I don't mention who presented papers! In time, the other pages of this website will be updated in detail with more specific information. I have grouped the information together under the topic headings laid out below.
| Epidemiology/Injury Statistics | Equipment design |
| Safety on the slopes | Binding settings |
| Biomechanics |
Details from the 2001 symposium in New Zealand can be found here.
Epidemiology/Injury Statistics
As ever, Bob Johnson and colleagues from Vermont presented a detailed look at skier injury trends - this time using 30 years of data. The overall injury rate (expressed as mean days between injury- MDBI- statistically, the number of days you would have to ski before being injured) has improved from 231 days in 1972-1975 to 483 currently. In other words, the injury rate is now half what it used to be! In the first 17 years of their study, the incidence of lower leg injuries steadily fell as improvements in equipment (particularly) came about. In the last 12 years there has been no further improvement and, more recently, a tendency for the lower leg injury rate to start going up again. Several factors may be implicated in this including poorer boot and bindings care and the increased popularity of terrain parks and performing tricks amongst skiers. Interestingly, the ACL injury rate, having been static for some 10 years seems now to be showing a downward trend. This may be related to improved skier technique, shorter tails on modern carving skis (see the knee page for a more detailed description of why this might be so) and an ageing skier population. It will be interesting to see if this trend continues in the next couple of years.
This section
included (for the first time) information from ski resorts in Greece, presented
by Dr's Zacharopoulos, Tzanakakis and Mitsou. The 20 ski areas in Greece saw
140,000 skier visits last year. This presentation focussed on the 519 injuries
seen at the Parnassus ski area with a control population also included. The
patterns of injury seen are broadly similar to those of other countries although
the overall injury rate (6.38 per 1000 skier days) was higher than the average.
A presentation from Norway on injuries from 2000-2002 confirmed the established
injury patterns and noted that lower leg fractures were still a common injury
amongst children. They also found that the use of helmets did not increase the
risk of a neck injury, as some have believed might be the case. I then presented
our three year case-control data from Scotland on
skiboard injuries. We have now found that injuries on skiboards occur 1.6x
more frequently than on alpine skis (MDBI 192 and 315 respectively). 70.6% of
skiboard injuries affect the lower limb compared to 48.7% of alpine ski
injuries. The fracture rate amongst skiboarders (37.5%) was the highest of any
snow sport (compares to 15.9% for alpine skiing and 22% for snowboarding). It
would appear clear now that the non-release binding mechanism on skiboards is
implicated in these findings and that, although the absolute rate of injury is
still very low, when injuries do occur 4 out of 10 will be fractures - mainly to
the lower leg. Developments in skiboard release bindings are urgently
required.
An interesting study from Germany compared the injury frequencies and patterns
amongst alpine skiers using skis of different turn radii from 1999 to 2001. They
divided the skis into 4 groups (<14m, 14-20m, 20-26m & >26m) based on their turn
radius (basically, the lower the turn radius the quicker a ski will turn...hence
the more aggressive it's carving characteristics). In terms of total injury
numbers, they found no significant difference between carvers and non-carvers in
99/00 but a small increase in injuries with carvers in 00/01 although the odds
ratio was low (1.203). Regarding injury patterns, head and neck injuries were
more likely amongst those using carvers (O.R. 2.4) whereas those on non-carvers
had lower levels of shoulder and upper limb injuries (O.R. 0.469). It's a bit
early to read too much into these results - others have previously shown in the
US, New Zealand and Scotland that carvers no longer have an excess risk of
injury.
Marc Binet from Avoriaz presented the latest data from the Medicins de Montagne group in France. The overall injury rate in France has been stable now for the last 10 years, but they have noticed that snowboarding has become associated with a increased risk of injury (O.R. 1.52, MDBI 248). Amongst beginner snowboarders, 50% of injuries are wrist fractures! MdM have been strong proponents of wrist guards for snowboarders and this data shows why! I presented a paper shortly afterwards that illustrated that first day participants (FDP) in snow sports were 2.5x more likely to be injured than all others. 60% of FDP injuries amongst snowboarders affect the upper limb. One third of all injuries in this group are fractures. Taken together, this is more compelling evidence of the need for wrist guards amongst beginner snowboarders.
A five year American study of abdominal trauma secondary to skiing and snowboarding showed that these injuries were more likely amongst male teenagers - most of whom struck the ground. Interestingly, more than half continued to ski or snowboard after their injury before realising something wasn't right! This has important implications for those of us dealing with these folk - even if they can ski, board or walk afterwards they may still have a severe injury. The spleen was the most commonly injured organ - another previous paper describes how the left elbow often jabs into the upper left part of the abdomen in a fall and may lead to splenic damage.
This section of the conference kicked off with a very interesting talk by Dr Jacomet, lead physician with the Swiss Rega air ambulance service. Out of 5100 primary missions flown by Rega in 2002, 28% were to attend winter sports accidents (compared to 13% for mountaineering incidents). About one third of all injuries were head injuries - back injuries also accounted for another third of missions flown. Rega helicopters can reach most incidents within 15 minutes and obviously play a vital role in immediate care in the Swiss mountains.
Jake Shealy presented more of his data on the average speeds of skiers and snowboarders on the piste. Using an accurate radar gun at a mixture of different ski resorts, the mean speeds were 18.6 mph (easiest slopes), 34.5 mph (more difficult slopes) and 28.8 mph (most difficult slopes). The highest single speed measured was 52mph (83.7 km/h). On the whole, skiers tended to go faster than snowboarders, those with helmets on went faster than those without and speeds were higher on days with good visibility. The mean speed of a helmeted skier travelling on a day with good visibility was 50.7 km/h. This compares to the mean speed of a snowboarder without a helmet on a misty day of 34.5 km/h. The interesting point of all this is that skiers and boarders typically travel at speeds well in excess of the impact criterion speeds used for helmet standards (for ASTM 2040 this is 13.9mph). An impact at 34.5 mph would have 6.2x more kinetic energy than this!
Two presentations from Switzerland described in detail the ongoing research in this field. One point I found very interesting was the typical characteristics of an avalanche involving a recreational skier or snowboarder:
| Length | 200m |
| Width | 60m |
| Fracture depth | 50cm |
| Slope angle | 35-40o |
| Slope aspect | Northern facing |
You have been warned!!
Sulheim and colleagues performed a study in Norway designed to test the ability of skiers and snowboarders to rank their level of skill - this was then compared to an objective assessment of skill level by an expert observer. They found that telemark skiers were the most accurate at defining their skill levels. Estimation based on turning techniques and simple description (expert, advanced, intermediate, beginner) were the most discriminating factors allied to actual ability. The frequency of falling over had no correlation with skill level!
One of the most interesting studies for me was work presented by Uffe Jφrgensen on the ability of self-testing of alpine ski bindings to reduce knee injury rates. This work has been previously published (Knee Surg Sports Traumatol, Arthrosc 1998; 6: 198-200) and demonstrated that showing a video on how to self-test ski bindings lead to a reduction in knee injuries compared to a control group who did not see the video. This current work reported on the results of a national educational campaign that followed in Denmark - it showed a good uptake of the technique with 64% of skiers reporting that they performed the test before skiing. The mean reduction in binding setting from the ISO recommended level was 1.5. Reductions in the rate of knee injuries of 7% ('98), 11% ('99) and 10% ('00) were observed. Unfortunately, the funding for this project has now been pulled - typical!
Finally, Swiss workers again reported on the development of safe bump skiing for less skilled skiers in Zermatt. An area of a blue slope was left ungroomed so that in time small bumps developed on the slope. These stayed smooth and round and did not become hard, icy and steep like many moguls tend to do. Observations indicated that skiers liked the bumps and - importantly, their ease of skiing meant that families could stay together on the slope. It was relatively easy for those who did not like the bumps to return to the groomed blue piste alongside. It was postulated that such gentle bump skiing would deliver a more effective cardiovascular workout and also help with the development of better proprioception and coordination. From a psychological standpoint, it was also hypothesised that it provided a good balance of challenge to skiers without significantly increasing the risks they face.
Many of the presentations in this section focussed on mechanisms of ACL injury and, in particular, the so-called "phantom foot" scenario described in detail on my knee injuries page. Several researchers demonstrated impressive 3D computer modelling programs designed to replicate the exact movements of the knee whilst skiing and in certain injury-prone situations. The level of sophistication shown was simply superb, but I guess it merely serves to reinforce how amazing the human body is in the first place!
To take one example, Tom Andriacchi from Stanford University (USA) examined the movements of the knee joint in deep flexion and its relation to potential ACL damage. He found that in deep flexion (especially beyond 130o) that the tibia rotates internally and translates anteriorly which is an integral component of the phantom foot mechanism. Anterior displacement of the tibia increased dramatically beyond 130o and would place severe strain upon the ACL. If the quads muscles contract at this point, this would pull the tibia backwards and thus relieve some of the pressure on the ACL by resisting anterior tibial shift. With the knee held in valgus (lower leg pointing outwards relative to the thigh...as in the snowplough position), squatting with the knee in deep flexion increases the force on the inside edge of the downhill ski tail and increases the internal rotatory torque on the ACL.....without the need for the skier to be travelling at great speed. The greater the degree of valgus, the greater the force. On the contrary, if the leg is held in the varus position, this loads the outer edge of the downhill ski and applies an opposite external rotation torque which helps to release pressure across the ACL. Could it be possible to design a boot that not only releases to the rear (see below) but which also to the side to avoid excessive valgus movements? Bottom line in the meantime? Avoid squatting in deep flexion on your skis especially in the snowplough position!!
The first research presentation in this section concerned the characteristics of new 'soft' alpine ski boots. Manufacturers of such boots have advertised various positive aspects of these boots - among them easier access, better handling, increased dorsiflexion, better cold and water resistance, lighter weight and better fit. The presentation focussed on the functional aspects of these boots - did they improve performance, skier safety & protection and ergonomics? To do this, a group of 17 schoolchildren aged 13-14 yrs were tested during a one week ski trip. The subjects were assigned soft boots without their knowledge to use and each student was tested at the beginning and end of the week by experts from the German Ski Instructors Federation. A 2D video was also taken of the subjects as they passed over a combination of moguls to study the ankle angles involved. At the end of the week, the students were also given a questionnaire to fill in to describe their own experiences. 88% of the subjects ranked the soft boot's overall performance as "excellent" or "good". The increased flexibility afforded by the boots was judged as "very good", even when riding on moguls. Almost 100% rated riding on prepared slopes as "good" or "excellent". The video analysis showed that the degree of ankle movement was greater in the soft boots at the end of the week. A controlled study in March 2003 comparing a group in hard boots to a group in soft boots showed that whilst the hard boot group were judged to have improved significantly in 2 manoeuvres, the soft boot group improved across all manoeuvres. Thus, initial indications are that soft boot may have a positive influence on a skier's overall experience. However, more research is still needed to look at safety aspects of the boots, especially regarding ankle protection.
In one of the few presentations on snowboarding, Greg Woolman from NZ continued his work on 3D ankle movements during snowboard landings. In particular, Greg wanted to relate the ankle movements to the possible forces involved in fractures of the lateral process of the talus (FLPT - "snowboarder's ankle"). He found that the maximum forces applied to the ankle occur at roughly the same time regardless of the type of boot worn but that inversion occurs first. It would appear that the foot is placed in an unnatural position during a snowboarding landing and that this may create an external rotation force that causes the LPT to shear up on the calcaneus and fracture. Snowboard boot manufacturers maybe need to think again to provide the ankle with more protection?
There were two presentations relating to Lange's rear release boot (already featured elsewhere on ski-injury.com). The work carried out confirms the initial work that this boot may protect the ACL in dangerous rearward situations. Like all new developments, it would appear to need refining - in particular a gradual (not sudden) release mechanism is suggested and the mechanism for relocking also needs a bit of fine tuning. But in a nutshell, the idea works!
Another new equipment development evaluated independently by ISSS researchers and presented at the Congress is the "Skibo-Edge". This involves machining the edges of the skis only in the binding area to leave the ski with a saw-tooth like edge. To do this, a 0.3-0.5mm cut is made every 1cm. It is claimed that this will lead to increased edge grip and durability of the edge. Furthermore, this increased grip quality could improve safety, especially on icy slopes. Veit Senner and colleagues tested this edge out using 114 students and varying edge combinations as below:
A. Both skis with skibo-edges
B. One ski conventional edge (right or left) and one ski skibo-edge
C. Both skis conventional edges
Skiers did not report any significant subjective differences on the different ski edge combinations. However, the test was not performed on ice. It was observed though that the Skibo-Edge seemed to retain its quality longer than a conventional edge and (although not studied) this could be of importance in that many skiers never bother to get their edges retuned after they have bought them with consequential deterioration in their ability to grip.
Finally, two presentations carried on earlier work on binding settings. Marc Binet had previously presented work in New Zealand on a new set of binding settings that were introduced in France in 2000. This was first reported at the ISSS meeting in 2001 and more details are here. The idea had been that the current ISO settings were too high leading to an excess of knee injuries from non-release. On average, French settings are 15% lower for the following groups - males <55kg, all females and all beginners. Whilst there has been no overall reduction in MDBI, there has been a 26% reduction in ACL injury rates, and a 38% reduction in other knee sprain rates - both for men and women. It seems likely that the improvement in ACL rates is independent of the binding settings (as it appears ACL injuries are not a function of binding release) - it may relate to the use of shorter carving skis as mentioned earlier. Of most importance, there was no increase in injuries from inadvertent releases - the binding releasing too soon - as had been feared by some.
The next ISSS Congress will be in St Moritz from 27th April to 2nd May 2003 – for details, click on the logo below
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