Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

Featured on Channel NewsAsia

Etiology of Skiing Injuries

Skiing

Since the 1960s participation in downhill skiing has increased at least 40-fold in the USA. The number of skiers is estimated to be around 8 million on an annual basis. The number of ski injuries annually is probably more than 1 million per year worldwide.

Skier-related factors

Relative to the population at risk, men tend to have a higher incidence of collision injuries than women. Avoidance of reckless skiing habits and using care when skiing near fixed objects are probably important factors in preventing injuries.

Equipment

From the standpoint of skiing safety there can be no doubt that the ski bindings are the most important factor. The number of injuries caused by the ski acting as a lever to bend or twist the leg has diminished significantly, especially during the 1980s. However, the perfect ski binding has yet to be invented. Boots should be comfortable and fit correctly; they should distribute the load widely on the leg in both forward and backward lean. At the binding interface the boot should conform to internationally accepted standards.

Type of injury

The most common injuries in alpine skiing are knee sprains, representing around 23% of all injuries. Other common injuries are: ligament injuries to the thumb, 10%; lacerations, 8%; shoulder contusion, 5%; and boot-top contusion, 4%. Tibia fractures constitute around 3.4% of all injuries, which is a dramatic decrease compared with the 1970s.

Since 1980 there has been an enormous increase in the number of anterior cruciate ligament (ACL) injuries, which in the early 1970s accounted for less than 1% of all skiing injuries. There are significant differences between skiers with predominantly severe medial collateral ligament (MCL) injuries and those with isolated ACL injuries. More ACL injuries result from backward falls. Individuals sustaining ACL injuries were more skilled and were more likely to be male than those who sustained MCL injuries. Those sustaining ACL tears wore higher and stiffer boots than a control group of skiers in one study.

Injury mechanism

During the 1970s excessive external rotation loading of the lower extremity was the most important factor in production of ski injuries. Other mechanisms have been described including internal rotation of the tibia relative to the femur. In the 1990s new mechanisms of injury have been responsible for severe injuries, especially ACL injuries.

In one common mechanism the skier falls backwards while the upper shell of the boot produces anterior drawer loading to the proximate tibia. The mechanism involved in complete tears of the ACL has been the boot-induced ACL injury. After a jump the skier lands on one ski while slightly off-balance, with the upper body leaning backwards. The tail of the ski hits the snow first, the ski is driven into the snow and the boot top drives the tibia shaft forward. At the moment of landing the skier’s knee is in full extension and the opposite arm is thrown back in an attempt to regain balance. The actual injury to the ACL occurs at about the time the foot is driven flat on the snow. The fixed forward lean built into modern ski boots is instrumental in the production of this type of injury.

A second mechanism of injury of the ACL is when the skier is falling out of control. The only way this injury could be prevented would be for the toe of the boot to release or to allow the ankle to plantar flex. The injury mechanism here is unique to skiing accidents and is called the ‘phantom foot’ mechanism. In this injury the skier falls backwards, and the ski leaves the surface of the snow so that only the inside edge of the portion of the ski behind the skier’s foot is in contact with the snow. As soon as this set of circumstances occurs the ski carves a turn and produces an internal rotation of the tibia in relation to the femur. This occurs when the knee is flexed past 90°. This mechanism can produce isolated injuries to the ACL or injury resulting in some damage to the lateral and posterior lateral aspects of the knee. This mechanism is probably more common than the boot-induced anterior drawer mechanism.

The combination of high, stiff boots and bindings that are incapable of releasing upwards at the toe is at least partly responsible for the unfortunate increase in ACL sprains. It is now apparent that modern ski equipment is not very effective at protecting the ACL.

In skiing the high velocities to which the unprotected human body is exposed by the unnatural lengthening of the foot by the ski-binding-boot system generate a large number of devastating injuries. As many as 30% of all ski injuries are probably the result of failure of the ski binding to function properly.

Comments are closed.