Despite the emergence in the 1990’s of snowboarding, skiboarding and on-piste telemark skiing, alpine skiing still remains the most popular snow sport by far, accounting for about two thirds of all those on ski slopes, depending on which country you focus on. The development of ‘carving’ or ‘shaped’ skis in the mid 1990’s certainly helped to reaffirm the sport’s appeal, allowing beginners to progress rapidly and more advanced skiers to perform tricks and manoeuvres that previously had been the domain of snowboarders. And manufacturers are not resting on their laurels. We now have so many off shoots of alpine skiing its hard to keep pace with developments. Manufacturers continue to push the boundaries further with advances in ski design, soft boot technology, mechatronic binding systems and more!
Whilst new developments are always to be welcomed, it can take quite a few years for sufficient data to emerge before one can judge their effect on snow sports safety – if its even possible at all – so I can’t offer an objective opinion on most of these pieces of kit. Interestingly though, some products that have definitely been shown to have a protective effect against injury (such as the Lange RRS boot system which was designed to protect against anterior cruciate ligament [ACL] injury) have been withdrawn as they weren’t a commercial success. Possibly a bit ahead of their time, I feel sure that rear release technology will appear again and hopefully save a few ACLs in the process. Protecting the ACL remains the number one priority for many ski safety developers. Rather controversially perhaps, some currently available ski bindings do claim to protect against ACL injury – time will tell if these bold claims are true or not!
Injury rate in Scotland (2009/10 season) – 2.38 injuries per 1000 skier days (419 MDBI)
Since ski injury studies were first reported in the 1970’s, the overall rate of alpine ski injuries has decreased by about 50%. It now stands at around 2 injuries per thousand skier days – lower than most people think. This rate has been stable (or even in some countries continuing to decrease slowly) for the last ten years or so. The decrease in the overall injury rate is most likely linked to advances in alpine equipment (carving skis being one example) as well as improvements in ski area management (grooming, slope design, signage, barriers etc). The biggest decrease has been in lower limb fractures, consequent on the introduction of release binding systems and plastic-shelled alpine boots.
There has also been a big reduction in the number of lacerations (cuts) that skiers sustain, thought to be due to ski leashes and ski brakes which now prevent a runaway ski shooting off and injuring someone else. The advent and widespread adoption of carving skis does seem to have had a positive influence on the incidence of alpine skiing injuries. A large part of this is that being easier to control than traditional skis, skiers tend to fall less on carving skis. Quite simply, falls equates to injuries so anything that reduces the fall rate will also reduce the injury rate. In addition to this, the shorter tail on a carving ski is thought to be linked to a reduction in the number of ACL injuries seen.
Another way of looking at injury risk is to calculate the mean days between injury (MDBI) – this is the total number of skier days in a season divided by the number of injuries seen. The higher the value, the less likely an injury is to occur. In Scotland currently, there are 419 MDBI for all alpine ski injuries. This means that on average an individual skier is only likely to injure some area of the body every 419 days they spend skiing. An upper limb injury occurs about once every 1478 days, compared to a lower limb injury once every 809 days – so you can see that the risk of an lower limb injury is about twice that of a upper limb injury on skis – the reverse of the pattern seen amongst snowboarders. The graph below compares the injury location by each of the three most popular snow sports in Scotland between 1999 and 2010.
Rates of shoulder, thumb and head injuries have remained static since the 1970’s. This is despite the growing number of skiers wearing helmets. Perhaps its too soon yet to see a major change. More on all these injuries later. The final graph below shows the type of injuries seen amongst alpine skiers.
The rate of serious knee sprains (in particular anterior cruciate ligament – ACL – sprains) initially jumped by some 240% (from the 1970’s to the early 1990’s), then remained static for about ten seasons with an ACL injury incidence rate in MDBI of about 2200. Since about the year 2000, the ACL injury rate has begun to decline. The next paragraph explains why this might be so.
It is the view of the American group that first videoed and described the common mechanisms behind injury to the ACL that the cause of almost 90% of these injuries is actually independent of the ski binding worn by the skier at the time. Certainly, despite some rather ambitious claims, no commercially available ski binding to date has yet been shown to conclusively reduce the risk of ACL injury. Furthermore, the interesting observation that ACL injuries are rarely seen in skiboarders (the vast majority of whom use an absolute non-release binding system) adds further credence to the belief that release of the binding is not related in isolation to ACL injury risk. The Vermont group have argued for some time now that the tail of the ski is the culprit – acting as a “Phantom Foot” (much more on this later) to exert a force across the ACL. Again, the fact that ACLs don’t seem to be a problem on skiboards goes along with this – because of the short length of a skiboard, there is not much of a ski tail there behind the boot to act as a lever on the ACL as there is on an alpine ski. It now seems that the wide-scale popularity of carving skis (which are shorter overall and hence have a shorter tail too) may be leading to a reduction in phantom foot forces across the ACL, hence the lower rates of ACL injury seen since about the year 2000.
I mentioned earlier that for the last few years a new ski binding has been developed that offers a potential hope of ACL protection. It works in a different way to all other bindings and works by providing a lateral release mechanism at the ski boot heel. By so doing it may reduce the risk of damage to the ACL by the so-called “Phantom Foot” mechanism of injury – thought by some to be responsible for the majority of ACL injuries.
Alpine ski bindings
Now, a little bit about alpine ski bindings – equipment that is generally both taken for granted and completely misunderstood by most skiers. If you think about it, a ski binding has a pretty difficult job to do – not only does it have to hold you in the ski when you want it to but it also has to recognise the exact moment when things go wrong and you need it to release from your ski. This job is made harder by the fact that the forces applied to a binding in the course of an average ski run (during which you may alternatively ski hard for a time and then ski more sedately) vary enormously – and yet we expect our bindings to instantly recognise the moment when the forces become too strong and release. Not only that, but the direction of the force applied varies considerably too as the ski moves and tilts through the turns. Traditionally, bindings have released either laterally (to the side) or vertically (heel and toe) – i.e. they have three modes of release.
Currently available alpine ski bindings are designed to protect against lower leg fractures, NOT knee injuries. They can only sense forces applied at the boot/binding interface – they do not sense or react to the forces felt at the knee joint itself. In other words, “what the legs feels and what the binding feels are not the same thing” (Carl Ettlinger, 2nd World Congress on Sports Injury Prevention, Tromso, Norway May 2008). Ski bindings have been successful at doing what they were primarily designed to do – we don’t see anything like as many lower leg fractures as occurred in the 1960s before their introduction. As modern bindings can’t sense the same forces applied at the knee joint though, this at least in part explains why despite all the advances in bindings so far, we still see a high number of knee injuries amongst skiers.
Many ski injury experts believe despite this that the international settings standard for ski bindings (the charts used to set the tightness of ski bindings by technicians, such as ISO) could be safely reduced in order to protect the knee joint. This might be advantageous, especially in some important sub groups such as women. The hypothesis is that reducing binding settings might reduce the incidence of knee injuries like MCL sprains. Based on this hypothesis, in the year 2000 France, largely driven by the Medicins des Montagne (MDM) – an association of French ski doctors – introduced a new system for setting bindings called the AFNOR standard. This is based on gender, boot size and skier weight as well as a subjective description of skier ability made by the skier themselves. On average, French settings are 15% lower for the following groups – males <55kg, all females and all beginners. The initial results were encouraging – in 2005 they reported that there had been a 26% reduction in ACL injury rates, and a 38% reduction in other knee sprain rates – both for men and women. The immediate question was whether these improvements had occurred because of the lower binding settings or not – you can’t directly say that it has. It may, for example, relate to other factors such as the increasing use of shorter carving skis – or indeed may purely be down to chance. At the ISSS meeting in 2011, MDM subsequently reported less convincing data. They put this down to a reduction in the number of skiers whose bindings had been set to the AFNOR standard.
The obvious concern with reducing binding settings is that this might lead to an increase in injuries from ‘inadvertent release’ (the binding releasing when you don’t want or need it to). Fortunately, work presented at the 2005 ISSS Congress shows that there has been no increase in injuries from these inadvertent releases. Time will tell whether other countries will follow the bold lead of the French. Previous work from Denmark has also shown that encouraging skiers to “self test” their ski bindings each day before skiing may reduce the risk of knee injury. The theory is that by self testing, you ensure that on that day your bindings are set so that they should release for you. It works by getting the skier to try and pop out of their own bindings and, if they can’t, to reduce the binding settings until they were able to release their foot from the binding at both the heel and the toe in separate manoeuvres. The mean reduction in binding setting from the ISO recommended level was 1.5. Reductions in the rate of knee injuries of 7% (in 1998), 11% (in 1999) and 10% (in 2000) were observed. Again, no excess of inadvertent release was found.
Designing a binding that can protect the anterior cruciate ligament against injury has been the goal of binding engineers for many years now. To help you to understand the concept, I need to get a bit technical so bear with me. When a traditional ski binding releases laterally at the toe, the boot pivots around an axis located near the heel of the boot. The position of this pivot as well as the binding release characteristics determine the combination and direction of forces required to release the boot from the binding. With the pivot point so far back, traditional bindings are better at sensing the loads applied at the front of the ski compared to those at the back of the ski. Hence they release in a typical forward twisting fall (which to a degree protects the medial collateral ligament from injury) but they do not release in a backwards fall (which is what happens in the so called Phantom Foot mechanism).
In the phantom foot scenario, the weight of the skier is applied to the inside edge of the downhill ski tail. Computer modelling performed in Canada has predicted that a binding with two pivot points, one in front as well as one at the back, may indeed be able to sense twist loads applied to both the front and the back of the ski and potentially may offer protection to the ACL. [Reference: St-Onge N et al. Effect of ski binding parameters on knee biomechanics: A 3D computational study. Med. Sci. Sports Exerc. 2004: 36(7). p1218-1225]. This work relates to a relatively new binding which became commercially available in the 2008/9 season.
Types of injuries in alpine skiing
Most ski injuries are ligament sprains. Soft tissue bruising and joint injuries are the next most common injuries. Skiers have half the rate of fractures (broken bones) that skiboarders do – about 17% compared to 34%. Joint injuries can be subdivided into dislocations (when the joint surfaces are completely torn apart) and subluxations (when the joint surfaces are moved out of position, but not completely). Very simplistic, but the easiest way to visualise the difference between them is that a dislocation means the joint structures are pulled apart completely whereas in a subluxation things get stretched.
The graph below illustrates the type of injury seen from alpine skiing in Scotland.
Dislocations occur when the forces applied across the joint are so great that all the supporting muscles and other soft tissue structures are torn and the bones of the joint are no longer in alignment. This usually affects the shoulder joint or thumb/fingers. A joint subluxation (which usually involves the AC joint between the collar bone and shoulder blade) occurs when the forces are less but the supporting tissues are stretched nevertheless and the joint is pulled out of shape but to a lesser degree.
Injuries to the knee are the bread and butter of ski patrollers and ski physicians. Injuries tend to follow identifiable patterns and an experienced doctor or patroller will often know the diagnosis after a few questions and a quick look. Damage to the medial collateral ligament (MCL) is the commonest single ski injury of all. This occurs when the lower leg twists outwards relative to the thigh and the MCL takes the strain. Thankfully, most MCL injuries have a good chance of full recovery, as many occur at low speed on beginner slopes. Injury to the anterior cruciate ligament (ACL) is a far more serious situation, and can lead to the end of a skier’s career if not diagnosed and treated adequately. Injuries to the lateral collateral ligament, tibial plateau and meniscus (cartilage) are all possible. The important thing is first to differentiate a serious injury from a more minor one, but in all cases appropriate therapy must be started as soon as possible to increase the chances of a successful recovery.
Many things have been developed and trialled over the years to try and reduce the incidence of ACL injuries in particular. One such product was the concept of a rear release boot system. Introduced by Lange, the RRS V9 boot was based on the Vermont studies of the Phantom Foot mechanism of ACL injury. The idea being that the stiff high back on modern plastic ski boots might be implicated in a % of ACL injuries, pushing the tibia (shin bone) forwards relative to the femur (thigh bone) breaking the ACL in the process. So this boot had a mechanism that released the rear of the boot when excess force was applied here (such as when a skier falls off balance to the rear). Despite this promising development having received positive reports at the 2001, 2003 and 2005 ISSS Congresses it did not attract the commercial sales that its innovative design deserved and for now has been removed from sale.
Attention has for now focused back on the potential role for ski bindings in reducing the risk of ACL injury. The 2008/09 winter season will see the commercial release of a new binding that may offer a degree of protection to the ACL.
There are four main shoulder injuries seen in alpine skiers:- dislocated shoulders, fractured clavicles, AC (Acromio-clavicular) joint subluxations and a fractured humerus.
1. Shoulder dislocations
These usually occur as the result of a fall onto an outstretched hand with a twist of the shoulder into external rotation. The diagnosis is largely clinical – once you’ve seen a few they’re pretty easy to spot. The patient is usually supporting the affected arm and is in great pain. On examination, the normal rounded contour of the shoulder is lost and palpation reveals that the humeral head is not sitting where it should be. Reduction to put the joint back in place should be attempted as soon as possible (but always in a controlled environment, not out on the hill by a “have a go” hero!!) and gives instant relief – both to patient and doctor; its a really satisfying manoeuvre to relieve someone’s distress. At our clinic in Aviemore, we are able to reduce about 90% of all shoulder dislocations and, although other methods exist, we use Kocher’s technique as it seems to work for us and our patients. After successful reduction, the shoulder is immobilised in a sling, analgesia given and mobilisation under the care of a physio can begin fairly rapidly. The risk of a re-occurrence of the condition is about 85%, as the supporting tissues will never be as strong as they were. Its much easier to relocate a joint that keeps dislocating – some patients learn to do it themselves (but not quite in the Mel Gibson style!) In cases where the shoulder does keep popping out, stabilising surgery can be performed. There is now good evidence that primary surgery at or near the time of dislocation leads to better outcomes – especially amongst younger sporty patients.
2. Clavicle (collar bone) fractures
Fractures of the clavicle are frequently the result of the impact radiating up the arm to the collar bone. Most can be diagnosed clinically by finding a tender bump along the line of the bone and x-rays are often unnecessary. Treatment involves resting the arm in a sling or collar and cuff and adequate analgesia, followed by shoulder exercises to keep the elbow and shoulder joint mobile within the limits of one’s pain. The support can usually be discarded after 2 weeks or so, depending on the level of pain. If the broken bone is putting pressure on the skin, then surgery may be contemplated but as a general rule, these injuries heal up well without functional loss.
3. AC joint injuries
The acromioclavicular joint sits between the outside end of the clavicle and the bit of the shoulder blade known as the acromion. A ligament connects the two and holds the joint together. A fall with direct impact on the outside of the upper arm may lead to this ligament being damaged and tearing, allowing the joint to distort (a so-called subluxation, also known in the game as a “sprung” AC joint). As with all ligament sprains it can be graded 1 to 3 depending on the degree of damage. Sometimes it can be difficult to distinguish an ACJ sprain from a fracture of the very end of the clavicle. Careful (and gentle!) palpation though will usually reveal that the tenderness of an ACJ sprain is very localised to the joint whereas with a broken collar bone it is more spread out. See the photo above left for a classic case of a third degree ACJ sprain – note the prominent deformity at the joint.
4. Fractured humerus
Finally, a fractured humerus (upper arm bone) can also result from (usually) a direct blow but sometimes a fall onto the outstretched hand. Palpation will reveal tenderness along the line of the bone (best done gently on the inside aspect of the arm where there is less fat and muscle to get in the way). These breaks can be across the shaft of the bone or off the head of the bone at the actual shoulder joint. X-rays are needed here although treatment usually is conservative with a sling and analgesia. Surgery is very rarely needed. The worst case scenario here is someone thinking the arm is dislocated when it is not and pulling on an arm that is actually broken!
Skier’s thumb is a term coined for an injury affecting the ulnar collateral ligament (UCL) at the metacarpophalangeal joint of the thumb. Its an important injury that is often mis-diagnosed, under-treated and its functional importance not appreciated by both doctors and patients – at least initially. Talk to someone who now has to suffer the long term consequences of a poorly treated injury and they’ll tell you how debilitating it can be. You wouldn’t believe how important your thumb is for grip strength until you injure it!
The mechanism of injury is fairly simple. When a skier falls with a pole in their hand, there is a danger that the handle of the pole will act as a fulcrum applying force across the joint and thereby putting the ligament under strain. Depending on the force applied, the ligament may tear completely (grade 3) or partially (grades 1 & 2). Tenderness is localised to the joint area, especially when stress is applied across it by the examining doctor in order to assess the stability of the ligament. Paradoxically, if the ligament has completely torn, its often not very painful (as there’s no injured ligament remnant left to stretch) but the joint can be opened up markedly – compare with the other thumb if need be. If you injure your thumb in this manner skiing, my advice is don’t be fobbed off with a bland “oh, its just a sprain”. The thumb joint is the most important joint in the hand!
X-rays should be taken in most cases to excluded an associated fracture. Grade 3 injuries should be surgically repaired within 2 weeks. Grade 1 & 2 injuries may need support with a splint or a plaster for 6-8 weeks, analgesia and subsequent physiotherapy.
Injury prevention involves not skiing with the pole straps on so that in the event of a fall the pole will fall from the hand and not injure the thumb joint. OK, so the pole may slide down the hill a wee bit but at least you’ll be left with a hand that can still pick it up! This advice doesn’t hold when skiing off piste or in deep powder on piste when the loss of a pole could be very important.
Various devices have been designed to try and help involving the pole clipping directly into the glove. Others involved “grip poles” (strapless poles with a device that wraps around the hand and retains the pole). However, studies showed no difference in the rate of thumb injuries with these devices and one study even showed that these devices were associated with a higher rate of thumb injuries (Primiano GA. Skiers’s thumb injuries associated with flared ski pole handles. Am. J. Sports Med. 1985; 13: 425-427). Thumb injuries seem to have become somewhat forgotten in recent times as attention is firmly directed at reducing knee injuries amongst alpine skiers. No question though that a grade 2-3 UCL injury is more disabling than a grade 1-2 MCL injury of the knee.