Objective To establish the relationship between the history of hip and groin injuries in elite junior football players prior to elite club recruitment and the incidence of hip and groin injuries during their elite career.
Design Retrospective cohort study.
Setting Analysis of existing data.
Participants 500 Australian Football League (AFL) players drafted from 1999 to 2006 with complete draft medical assessment data.
Assessment of risk factors Previous history of hip/groin injury, anthropometric and demographic information.
Main outcome measurement The number of hip/groin injuries resulting in ≥1 missed AFL game.
Results Data for 500 players were available for analysis. 86 (17%) players reported a hip/groin injury in their junior football years. 159 (32%) players sustained a hip/groin injury in the AFL. Players who reported a previous hip or groin injury at the draft medical assessment demonstrated a rate of hip/groin injury in the AFL >6 times higher (IRR 6.24, 95% CI 4.43 to 8.77) than players without a pre-AFL hip or groin injury history.
Conclusions This study demonstrated that a hip or groin injury sustained during junior football years is a significant predictor of missed game time at the elite level due to hip/groin injury. The elite junior football period should be targeted for research to investigate and identify modifiable risk factors for the development of hip/groin injuries.
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Hip and groin injuries are common in athletes, particularly in sports requiring sudden direction changes, kicking and rapid acceleration and deceleration such as soccer, Rugby League, Australian football and ice hockey.1,–,5 Often, the pain is longstanding, and the pathology of hip and groin injuries is difficult to ascertain despite advanced imaging techniques.6 7 The complexity of both the diagnosis and the management of hip and groin injuries create a difficult rehabilitation prospect, and these injuries commonly recur,3 highlighting the importance of primary prevention.
Prevention of hip and groin injuries requires an understanding of the aetiology of these injuries. While numerous risk factors have been proposed, prospective studies investigating factors contributing to hip and groin injuries are few.8 9 The majority of the studies to date have investigated longstanding groin pain or groin strains, with little consideration of hip injuries. Previous studies have identified a relationship between hip joint range of movement, hip abductor and adductor strength, core muscle weakness, previous history and the onset of, or reporting of, groin injuries,1 2 9,–,13 but the evidence for a causal association is not strong.8
In the elite Australian football competition (Australian Football League (AFL)), it has been noted that hip and groin injuries are prevalent in younger football players,4 which contrasts with the greater injury risk associated with increased age noted in ice hockey.12 There is a perception that players recruited into the elite senior competition (AFL) already present with signs of groin injury, as a result of excessive training loads and poor management in the elite junior phase,14 suggesting that the injuries reported in the AFL are related to previous injuries. The aim of this project was to establish the relationship between the history of hip and groin injuries sustained in the elite junior Australian football years and the incidence of hip and groin injuries during their elite senior career.
Setting and study design
A retrospective cohort study was completed within the AFL, Australian football's elite competition.
Players recruited by an AFL club in the years 2000–2007, who played at least one AFL game and completed a draft medical assessment prior to recruitment, were eligible for inclusion in this study. Ethics approval for the project was granted by the Monash University Human Research Ethics Committee.
All players who nominate for the AFL draft each year are required to undergo medical screening, performed by a sports physician. The screening assessment captures identifiable data and includes medical and musculoskeletal questions, including questions about groin pain history and joint injuries. The questionnaire is completed by the player, or their next of kin, under the supervision of a sports physician. The questionnaire forms part of the routine data collection for the AFL draft process. The player and their next of kin (if they are <18 years of age) sign off on the document to indicate that the information provided is true, complete and accurate. Data for the years 1999–2006 were obtained in disc form. The medical questionnaire data were manually extracted from the discs provided with the presence or absence of a reported hip or groin injury (yes or no), and the self-reported diagnoses where available were recorded. The results of diagnostic investigations were not provided, and the detailed impact of the injury on participation and performance were not included in the questionnaire. Height, body mass and age at the time of drafting were also extracted from the assessment to enable analysis of these potential confounders.
The AFL has been collecting prospective data about injuries sustained by AFL players since 1992. A reportable injury is defined as “any injury or other medical condition that prevents a player from participating in a regular season (home and away) or finals match,” and complete capture of injuries meeting this definition has occurred since 1997.3 4 Each club has an injury survey coordinator responsible for ensuring player monitoring, and data recording for each reportable injury is collected. Data are collected by the medical team at the club, and the full season of data are provided, in identifiable format, to the centralised database (or register) at the completion of the season. Data for all hip and groin injuries recorded by the AFL Injury Survey, identified through the Orchard Sports Injury Classification System (OSICS) diagnosis code during the years 2000–2007, were provided for analysis.15
A unique identifier was allocated to each eligible player to enable linkage of the draft medical assessment and AFL Injury Survey data. Data were analysed using SAS (Version 9.1; SAS Institute Inc, Cary, North Carolina, USA) or STATA (Version 10; StataCorp, College Station, Texas, USA). The predictor variable of interest was whether the player had reported or sustained a hip or groin injury in the pre-AFL setting. The outcome of interest was the number of hip or groin injuries sustained resulting in at least one missed AFL game. Age at the time of drafting, body mass and height were assessed as potential confounders of the relationship between previous injury and sustaining an AFL injury. Age at the time of drafting was categorised for analysis (17, 18, >18 years) due to the narrow range of ages and the highly skewed distribution.
The association between the pre-AFL injury history, other predictor variables and the number of AFL hip or groin injuries sustained was assessed using negative binomial regression due to the count nature of the outcome variable and the overdispersion of the data. As the draft data related to the period 1999–2006 and the AFL Injury Survey data were for the years 2000–2007, not all players were followed up through the AFL Injury Survey data for the same period. The exposure time was defined as the weeks between AFL drafting and the end of the final AFL Injury Survey year (2007). Games (weeks) missed due to hip/groin injury were subtracted from the exposure time for injured players. Incidence rate ratios (IRR) and 95% CI around the IRR were calculated. For all statistical tests, a p value <0.05 was considered significant.
There were 500 players with draft medical assessment data who were drafted by an AFL club and played at least one AFL game. The mean (SD) height and body mass of the cohort were 186.9 (6.7) cm and 79.9 (7.4) kg, respectively. The majority (55%) of players were aged 18 years at the time of drafting, followed by 34% aged 17 years. The remainder of drafted players were aged 19–23 years (11%). Of the player cohort, 86 (17%) reported a past history of hip or groin injury on their draft medical assessment questionnaire. The diagnosis of the previous hip or groin injury was not documented for 26% of the 86 cases, while the most commonly reported diagnosis was osteitis pubis (n=36, 43%).
From the AFL Injury Survey, there were 267 separate hip or groin injuries that were sustained by 159 players. Most (83%) were single episode injuries, with 10% recurring once, 5% recurring twice and the remainder (2%) recurring more than twice. The 10 most common diagnoses of hip and groin injuries resulting in at least one missed game in the AFL among the cohort are shown in table 1 and account for 88% of all hip and groin injuries recorded by the AFL Injury Survey. Half of the recurrences were osteitis pubis cases followed by adductor tendinopathy/tear cases and hip labral tears/chondral lesions.
There was no association between age at the time of drafting (p=0.21), height (p=0.59) and body mass (p=0.86) and the number of hip or groin injuries sustained in the AFL. Players who reported a previous hip or groin injury at the draft medical assessment demonstrated a rate of hip/groin injury in the AFL >6 times higher (IRR 6.24, 95% CI 4.43 to 8.77) than players without a pre-AFL hip or groin injury history.
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.
The prevalence of hip and groin injuries in many sports remains a concern. This study has demonstrated the prevalence of these injuries in the junior football years and the strong association with missed game time in the AFL due to hip or groin injuries, particularly due to osteitis pubis or hip chondral/labral lesions. The findings suggest that the elite junior participation period should be targeted for research to investigate and identify modifiable risk factors for the development of hip and groin injuries.
What is already known on this topic
▶. Hip and groin injuries are prevalent in younger football players in the professional Australian Football League (AFL).
▶. There is a perception that players recruited into the AFL already present with signs of groin injury, as a result of excessive training loads, and poor management in the elite junior phase.
What this study adds
▶. This study used empirical data to confirm that hip/groin injuries sustained during junior football participation are a predictor of missed game time in the AFL due to hip/groin injury.
▶. The elite junior participation period should be targeted for research to identify modifiable risk factors for the development of these injuries.
James Westmore is sincerely thanked for his assistance with the extraction of the draft medical data and compilation of the list of drafted AFL players. Shane McCurry and Alan McConnell are thanked for providing the data for this project. Dr. Hugh Seward is thanked for his support of the project.
Funding This project was funded by the Australian Football League Research Board. Dr. Belinda Gabbe was supported by a Career Development Award (465103) from the National Health and Medical Research Council of Australia during the preparation of this manuscript.
Competing interests None.
Ethics approval This study was conducted with the approval of the Monash University Standing Committee on Ethics in Research involving humans.
Provenance and peer review Not commissioned; externally peer reviewed.
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