Background Severe cervical spine injury in rugby union (rugby) exerts a major impact on the individual who sustains the injury and on the broader society. Since the late 1970s, authors of rugby case report studies have postulated that the underlying mechanism of cervical spine injury is hyperfl exion of the neck. However, this is in confl ict with fi ndings from more recent experimental studies. These have shown that it is more likely that the majority of cervical spine injuries occur due to buckling of the cervical spinal column. Objective To investigate the primary mechanism of cervical spine injury in rugby. Methods A comprehensive and systematic review of the literature was undertaken. Six key factors were identifi ed and subsequently used to investigate the two principally postulated mechanisms of cervical spine injury: hyperfl exion and buckling. Results Facet dislocations, in particular bilateral facet dislocations, were identifi ed as the most common types of cervical spine injury in rugby. Trauma occurred most often at lower cervical spinal levels, notably the C4/5 and C5/6 motion segments. Experimental studies demonstrate that bilateral facet dislocations occurring at the lower cervical spinal levels are primarily produced via buckling. Conclusion Our analysis of key factors for cervical spine injury in rugby shows that it is unlikely that the majority of injuries occur after hyperfl exion of the neck. It appears more likely that they are the result of buckling of the cervical spinal column. INTRODUCTIONRugby union (rugby) is a full contact team sport that has gained worldwide popularity. Unfortunately, participation in rugby carries with it a high risk of injury to the cervical spine that in severe cases results in quadriplegia, or even death.To quantify risk, the Health and Safety Executive of the United Kingdom has defi ned norms for participation in certain activities. A standardised level of risk for any given activity is expressed as number of events per 100 000 of an exposed population per year. 1 Under this framework, the risk for sustaining cervical spine injury in rugby may be as high as 13/100 000 per year within certain countries. Although this fi gure falls within the 'tolerable risk' category (2-100/100 000 per year), mortality and morbidity associated with cervical spine injury exert a major impact on the individual who sustains the injury and on the broader society. 2 For example, in New Zealand, a country where rugby is arguably the premier sport, the lifetime cost for a 20-year-old individual who became quadriplegic was reported to be between $2 and 3 million in the late 1990s. 3 Multiple factors contribute to cervical spine injury in rugby and anatomical and biomechanical (structural) features are relevant. Data from case reports suggest that certain distinctive anatomical features of the cervical spine such as hypermobility of the facet joints, a proportionately small vertebral body size, as well as relatively weak muscle protection constitute an increased risk for injury. [...