Categorising sports injuries in epidemiological studies: the subsequent injury categorisation (SIC) model to address multiple, recurrent and exacerbation of injuries

OBJECTIVE: Sports injuries are often recurrent and there is wide recognition that a subsequent injury (of either the same or a different type) can be strongly influenced by a previous injury. Correctly categorising subsequent injuries (multiple, recurrent, exacerbation or new) requires substantial clinical expertise, but there is also considerable value in combining this expertise with more objective statistical criteria. This paper presents a new model, the subsequent injury categorisation (SIC) model, for categorising subsequent sports injuries that takes into account the need to include both acute and overuse injuries and ten different dependency structures between injury types. METHODS: The suitability of the SIC model was demonstrated with date ordered sports injury data from a large injury database from community Australian football players over one playing season. A subsequent injury was defined to have occurred in the subset of players with two or more reported injuries. RESULTS: 282 players sustained 469 subsequent injuries of which 15.6% were coded to categories representing injuries that were directly related to previous index injuries. This demonstrates that players can sustain a number of injuries over one playing season. Many of these will be unrelated to previous injuries but subsequent injuries that are related to previous injury occurrences are not uncommon. CONCLUSION: The handling of subsequent sports injuries is a substantial challenge for the sports medicine field—both in terms of injury treatment and in epidemiological research to quantify them. Application of the SIC model allows for multiple different injury types and relationships within players, as well as different index injuries.