Mechanisms of snowboarding-related severe head injury: shear strain induced by the opposite-edge phenomenon.

OBJECT To date, there has been no published study in which the focus was on the mechanisms of head injuries associated with snowboarding. The purpose of this study was to identify these mechanisms. METHODS The patient population consisted of 38 consecutive patients with snowboarding-related major head injuries who were treated at two hospitals in Japan, where for years many winter sports injuries have been treated. The skill level of the snowboarder, the cause of the accident, the direction of the fall, the site of impact to the head, and the condition of the ski slope were examined. The injuries were classified as coup, contrecoup, or shear injuries. The predominant features of snowboarding-related major head injuries included: falling backward (68% of cases), occipital impact (66% of cases), a gentle or moderate ski slope (76% of cases), and inertial injury (76% of cases [shear injury in 68% and contrecoup injury in 8% of the patients]). Acute subdural hematoma frequently occurred after a patient fell on the slope (p = 0.025), fell backward (p = 0.0014), or received an occipital impact (p = 0.0064). Subcortical hemorrhagic contusions frequently occurred after the patient fell during a jump (p = 0.0488), received a temporal impact (p = 0.0404), or fell on the jump platform (p = 0.0075). Shear injury frequently occurred after a fall that occurred during a jump or after simple falls on the ski slope, and contact injury was frequently seen after a collision (p = 0.0441). CONCLUSIONS The majority of severe head injuries associated with snowboarding that occur after a simple fall on the slope are believed to involve the opposite-edge phenomenon, which results from a fall backward on a gentle or moderate slope causing occipital impact. The use of a device to protect the occiput is proposed to reduce head injuries associated with snowboarding.