Discussion

This study used existing data related to the elite junior years of drafted athletes to investigate the relationship between hip or groin injury prior to drafting and the risk of missing elite senior game/s because of hip or groin injury. The study used empirical data to confirm that hip or groin injuries sustained during junior football participation are a significant predictor of missed game time at the elite senior level due to hip or groin injuries, particularly due to osteitis pubis or hip chondral/labral lesions. While the finding that a previous groin injury predisposes an athlete to a subsequent groin injury has been reported previously for ice hockey and soccer,1 10 12 our study suggests that these injuries occur prior to elite senior competition. The study findings provide valuable information about the onset of these injuries and add weight to the perceptions that management and preparation of elite junior football players for elite senior competition could be highly important in the reducing the risk of these injuries and their long-term implications.

Almost a fifth of drafted AFL players had sustained a hip or groin injury during their elite junior career, although very limited information about the injury severity were provided. Nevertheless, the findings give weight to the concerns expressed among AFL medical personnel and sports medicine professionals about the preparation and management of elite junior Australian football players.14 In particular, Pizzari and colleagues identified concern among those interviewed about the training and playing workloads of elite junior football players and groin injury risk, particularly the impact on a skeletally maturing athlete.14 Of note, recurrences of osteitis pubis were common. Osteitis pubis was also the most commonly reported diagnosis of hip or groin injury for players reporting a pre-AFL injury. While osteitis pubis is described as a self-limiting condition in the literature,16 the condition is painful, debilitating and costly for the athlete due to the prolonged course, lost participation time and potential financial losses due to unavailability for match selection. The diagnosis is likely an umbrella term for a variety of underlying pathologies including pubic bone stress injury,17 potentially including injuries which would now be classified as femoro-acetabular impingement, a diagnosis not specifically classified by the OSICS system.

Similarly, recurrences of hip chondral lesion or labral tears were also common. Six per cent of hip and groin injuries reported in the AFL Injury Survey were for hip chondral or labral injuries; this is substantially higher than the 0.9% reported for National Football League players in the United States.6 While a relatively uncommon injury, the long-term implications of these injuries are not well known, but the potential for an increased risk of osteoarthritis, associated long-term disability and a prematurely shortened player career have been proposed.6 16

Importantly, a previous injury history is a non-modifiable risk factor. Elite junior Australian football players are at significantly elevated risk of groin injury than elite senior players.4 This group of athletes arrives at AFL clubs already predisposed to hip or groin injury, creating a treatment and management challenge for the medical personnel in an area where evidence-based rehabilitation programs are lacking. To understand the aetiology of hip and groin injuries in elite football players would require studies undertaken prior to the index injury. Therefore, these athletes should be targeted during their elite junior careers with respect to studies to identify modifiable risk factors and the development of prevention programs. This has implications for the direction of injury prevention research for hip and groin injuries in Australian football and potentially for other sports, highlighting the elite junior phase as a clear priority for future studies.

Although our study cohort was relatively large, limitations exist and must be acknowledged. The draft medical assessment of injury history was reliant on player recall which is potentially biased as players may not remember injuries sustained, particularly if considerable time has passed since the injury, or they may choose not to report injuries for a variety of reasons, leading to under-reporting of injuries of interest. The questions related to injury history do not provide a timeframe for recall but instead ask for the recollection of injuries with an open-ended time period. A prior study undertaken within a cohort of amateur Australian football players found evidence of significant recall bias over a 12-month period18 and questions the validity of the methods used to collect injury history data in the draft medical questionnaire. Ideally, prospectively collected data similar to the AFL Injury Survey could potentially have provided a more valid source of pre-AFL injury history. However, routine injury surveillance at this level of participation does not exist, and only limited data from individual injury studies were available and were insufficient for the study purposes. Only limited exposure (time at risk) information was available for analysis. Only AFL hip or groin injuries were provided for analysis; therefore, the exposure time could not be adjusted to account for time missed due to other injuries, training time of the athletes and games missed for other reasons. As a result, the exposure measured used in the model was an estimate only. Nevertheless, whether the data were modelled using logistic regression with the outcome categorised as sustaining a hip or groin injury or not, or using survival analysis (time to first injury) or the included negative binomial model accounting for multiple injuries sustained, the findings were consistent. The findings of the analyses were highly significant and plausible, suggesting that the relationship between previous injury and AFL injury is strong.