A dynamic analysis of knee ligament injuries in alpine skiing

The aim of this study is to understand better the dynamic mechanisms of anterior cruciate ligament (ACL) rupture in alpine skiing. As a result of these findings, improvements in the boot-binding release systems are proposed. Six patients who sustained ACL rupture, aged 19 to 43 years, were studied. A step by step reconstruction of the accident was made using a questionnaire followed by an interview. The skiing equipment was tested in a specialized laboratory and the release levels of the boot-binding systems were measured in twist and in forward lean. ACL injury was confirmed by arthroscopy or surgery. Most patients had recent skiing equipment; their binding systems were correctly mounted and in perfect working order. Release levels of the bindings were equal to or slightly above those suggested by the ISO standards. The mechanisms of injury were valgus-external rotation in knee flexion of more than 90 degrees, internal rotation in knee flexion of more than 120 degrees with anterior drawer loads, internal rotation-valgus in knee flexion of less than 30 degrees with anterior drawer loads, external rotation-valgus in knee flexion of more than 120 degrees with anterior drawer loads, external rotation in knee flexion of about 100 degrees with anterior drawer loads and internal rotation-valgus. Even with a modern boot-binding system, properly adjusted, ACL injury remains possible. The improvements in the current equipment should be concerned with the behavior when confronted with combined loads producing friction in the system. We concluded that for lateral release at the toe, there should be a better compensation of the vertical parasite forces and an improvement of the antifriction devices. In order to prevent excessive anterior drawer loads on the ACL an additional release direction of the binding system, especially backwards, could, if properly adjusted, enhance the opportunities of early release in a dangerous backward lean "out of control" position.