© Springer International Publishing Switzerland 2016
Piero Volpi (ed.)Arthroscopy and Sport Injuries10.1007/978-3-319-14815-1_66. Football: Epidemiology and Injury Mechanism
(1)
Knee Orthopedics and Sport Traumatology Unit, Humanitas Clinical Institute IRCCS, Milan, Italy
(2)
Head of Medical Staff FC Internazionale Milan, Milan, Italy
(3)
Aspetar Hospital, Sport City Doha, 29222, Qatar
(4)
Qatar Orthopaedic and Sport, Medicine Hospital, FIFA Center of Excellence, Doha, 29222, Qatar
(5)
Kinemove Centers, Pontremoli, La Spezia, Italy
Keywords
FootballInjuryEpidemiologyRisk factorPrevention6.1 Introduction
Football is the most popular sport in the world; according to data provided by the Federation of International Football Associations (FIFA), it counts 250 million members across the five continents. In this huge movement, the numerical contribution of young players is relevant, as well as the increasing number of women who are dedicated to this sport.
This massive participation has stimulated research and scientific activity on football injuries. Most of the players have to suspend periodically their activities in order to undergo medical treatment, surgery and rehabilitation following an injury, and this time out of the field may cause to the player a significant physical and psychological discomfort. Therefore, research on football injuries has significantly increased in the last decades. Initially, most of the efforts have focused on the study of injury treatment; however, despite a better comprehension of the physiopathology of sport injury, new scientific findings have a limited impact on the return-to-play time and the recurrence rate. Therefore, it has become clear that preventing injuries may be the main way to decrease the absence of the athlete from the competitions.
Many accidents are unpredictable; they are a natural part of the characteristics of a sport that requires speed, strength, explosiveness, but also physical contacts with the opponent. However, many injuries can be avoided; conducting injury surveillance studies is the fundamental first step in order to implement adequate programmes of prevention. A scientifically validated knowledge of the injury incidence and patterns will lead to a correct evaluation of their risk factors and therefore to the implementation of adequate prevention programmes.
It is necessary to underline how in football, even at professional level, while many efforts are focused on continuous improvement of the physical, technical and tactical performance, less is done in terms of injury prevention. This is at least curious, considering the impact of injuries on players’ health and performance and therefore on club finances. Recent researches have emphasised this, proving how injuries impact the team success: the higher the number of injuries in a team, the lower the results of that team during that season [1, 2].
6.2 Football Epidemiology
Epidemiology is the science studying the incidence and the patterns of injuries that occur during sport activities. Knowing injury incidence and patterns is the fundamental first step in order to implement an adequate programme of prevention. However, sometimes it is difficult to compare researches as they are based on a different methodology.
Epidemiological surveys on football injuries have been implemented in Europe since the end of the seventies, in particular in the Northern countries [3, 4]. These researches described football injuries showing for the first time the possibility of reducing their incidence [5, 6]. In the last three decades, professionalism in football has increased, and injury surveys have been performed at all levels of football: amateur [7], semiprofessional [8], professional [9] and elite [10]. Moreover, they have been performed also at youth level [11] and in women football [12] and implemented in many extra-European countries [13].
6.3 Methodological Considerations
Unfortunately, researches on football epidemiology have often employed different methods of data collection. These differences make difficult to interpret the findings, which can also be very different, in a comparable manner. In the last few years, experts have provided guidelines on injury definitions and collecting procedures [14] allowing comparisons of the results from more recent research, permitting a better definition of typical patterns of different settings.
Another important factor is the reliability of data. Football epidemiological studies often require the involvement of multiple clubs and therefore of different clinicians. This can be a source of bias. First, it has to be verified that all participants utilise the same medical approach in diagnosis and prognosis. In this view, it is better that all clinicians involved in the data collection are part of the same professional category, for example, sport medicine physicians, orthopaedic surgeons or physiotherapists. Sometimes, this is not enough because they may be part of different medical schools; some studies involve team from all over the world [15] with an undeniably different approach to sport medicine. Therefore, scientists have to keep in mind these considerations, in order to avoid bias. Another important issue is not only the quality of the data but also their completeness. Prospective studies may last an entire season or even more. Constant supervision of the people in charge of the data collection is fundamental in order to ensure complete collection. New technologies such as mobile phones, table PC and specific software have been implemented with this aim. In addition, recent literature shows the need for a revision of the best definition of injury to be utilised, in order to capture at the best kinds of injuries and complaints [16]. First reports utilised data from emergency departments or insurance companies; however, it is evident how minor injuries were overlooked in this way. The most utilised injury definitions are the medical attention and time-loss injuries. Medical attention injuries are all the injuries for which the footballers require the help of a member of the medical staff. In this way, a high number of injuries can be collected; however, it is more difficult to identify the categories of lesions that have an impact on players’ health and football performance. Time-loss injuries are those injuries for which the player has to stop football activity. This definition allows a good identification of the injuries impacting the footballer’s activity; however, sometimes players continue to play and train despite injuries that may decrease their performance or may lead to more severe or different injuries [17], and such injuries, for the above-mentioned consequences, must not be overlooked.
6.4 Epidemiological Researches in Professional Football
The highest expression of club level football in the world is arguably represented by the UEFA Champions League. Since 2001, UEFA has implemented an injury analysis among some clubs participating to this competition, with the aim of reducing injuries which, at this level, has a high economical impact. Actually, this study involves more than 20 European top level football clubs from different countries. Each day, injury data, together with information on the football activity exposure of each player, are collected by the medical staff of these clubs [18]. The results of this survey have been extensively published in the scientific literature [10, 19] and helped to identify the most common injuries at that level of football and their characteristics. Moreover, feedback on the club’s injury profile is sent periodically by the study group to the clubs, in order to help them to implement specific prevention programmes.
Similarly, FIFA is also conducting surveys in all its main competitions, in male, female and young players [15, 20, 21]. Many national associations, such as in Norway [22], Qatar [13], Sweden [23, 24] and Denmark [23, 25], have implemented prospective epidemiological studies in football, and numerous clubs have developed independent injury registries for their teams [26].
Some of these data are available in the scientific literature and allowed a better delineation of the football injury incidence and patterns in professional footballers. However, due to the many intrinsic and extrinsic risk factors related to football, further research is warranted.
6.5 Injury Incidence in Football
Professional football is an extremely high–injury risk profession. It has been estimated that its overall risk of injury is about 1,000 times higher than for typical industrial occupations generally regarded as high risk [27].
Fortunately, while in the last three decades the training and match volume has remarkably increased due to the improvement in professionalism, the risk of injury has not augmented. This is perhaps due to the development of athlete healthcare and to the implementation of prevention programmes. According to the UEFA Champions League injury study, a professional football team can expect about 50 injuries that cause time loss from play each season, which equates to two injuries per player per season and, on average, 12 % of the squad unavailable due to injury at any point during the season [28]. Most injuries occur during matches, where there is five times higher risk of injury compared with training. This is possibly due to the high intensity of the match play and also to the higher number and energy of duels and impacts. It has to be also considered how there is no possibility, during matches, of seeking medical care if not for few minutes, while during training injuries may be evaluated more carefully by the medical staff and preventive measures can be taken. In particular, the last 15 min of each half are the periods in which players are most vulnerable to injuries, and fatigue plays a major role in this.
In accordance with their aetiology, injuries are classified into overuse and traumatic. For overuse injuries a specific moment in which the injury occurred cannot be identified [29]. While there is evidence that overuse football injuries have a higher incidence during the preseason, different trends of seasonality are linked to different regions and their specific environmental conditions.
In epidemiological studies taking into consideration time-loss injuries, the most common injury location is the thigh, followed by the knee, groin and ankle, while the most common type of injury is strain, followed by contusion and sprain. When considering medical attention injuries, contusions are the most common type of injuries. However, a contusion seldom obliges a player to stop his sport activity; therefore, they are less recorded in studies utilising a time-loss definition. This example highlights the importance of choosing an appropriate injury definition and the implication of a correct interpretation of the results in accordance with the chosen definition.
Hamstring strains are the most common subtype of injuries, and a typical 25-player team can expect about seven hamstring strains per season [19, 28]. It is therefore evident how, like in many other sports, many efforts are focused on the prevention and treatment of this injury.
Despite their relative low incidence (<1 % of all injuries), anterior cruciate ligament (ACL) ruptures are the most attention-drawing pathology in football. Nowadays, in football, ACL lesions are generally treated surgically, and the average time to return to play is between 6 and 7 months. While some decades ago it was a career-ending injury, progress in athletes’ healthcare has led to a return-to-football outcome at the same level as before the injury in 90 % of the patients. However, on return to play there is an increased risk of new knee pathologies, especially overuse in aetiology [30]. This may indicate knee abuse due to the absolute necessity of professional footballers of returning to play [31].
The hip and groin are normally the third and fourth most common injury location in prospective epidemiological studies based on a time-loss injury definition [13, 28]. It seems that the real magnitude of the problem has been underestimated so far, due to the relatively difficult of diagnosis of the pathologies located in that region, not always allowing their clear identification and classification. Moreover, groin injuries are often overuse in aetiology and may be underestimated in researches based on a time-loss injury definition [16]. In the champions league, an average of seven groin injuries per team per season has been estimated [32], but, for the above-mentioned reasons, this may be only the tip of the iceberg. In fact, it is well known among clinicians working with footballers that the groin pain syndrome often requires long treatments, with periods of exacerbation of symptoms and recurrences, and an appropriate management of training and match loading by the medical staff.
The ankle is the most common injury location in many sports [33]. While first football epidemiological researches performed in the 1980s were reporting that the ankle was the most common location of injury (around 30 % of total number of injuries), more recent researches show a much inferior incidence rate [34]. This decreasing trend can be the result of prevention strategies (e.g. neuromuscular training, bracing, taping) which have proved to be effective in reducing the incidence of ankle sprain, or this may be due to changes of the rules of the game which have been applied, such as a red card for a tackle from behind. In any case, this finding has to be taken into account as this may be an example of the possibility of reducing injuries in football.
Women’s football has gained more and more prominence in the last years and with the number of participants quickly increasing together with the discipline’s professionalism. While males have a general higher risk of injury compared with female players, the risk of sustaining a moderate to severe injury (>1 week absence) does not vary between men and women. Injury patterns are also basically comparable, but women have relatively more knee injuries, while men more groin pathologies [35]. Female players are particularly more vulnerable to ACL injuries than men. It has been estimated that the risk is two to three time higher than their male counterparts. Females also tend to sustain their ACL injury at a younger age and have a higher risk of injury especially during match play, although no significant gender-related dissimilarity has been described during training sessions [35]. These data have provided the basis for an extensive scientific research on the prevention for ACL injury in female footballers.
Young footballers’ injuries are more overuse in aetiology compared with adults. Of vital importance seems to be a strict training load monitoring. The huge differences in growth between subjects and the unpreparedness to too intense training loads may be a serious risk factor [36–38].
In general, a reinjury is defined as an injury at the same side and location of a previous lesion. When it occurs within 2 months from the return to play, it is usually defined as early reinjury and is often seen as a failure of the treatment.
Therefore, reinjury rate is sometimes considered as an instrument to measure the skills of medical staff. In fact, while injury frequency may be mostly affected by technical and performance activities, reinjuries, as determined by an early return to play and incomplete rehabilitation, are often associated with medical staff performance. In more recent football studies, a reinjury rate between 12 and 30 % has been reported [10, 24, 39]. Also, reinjuries are generally associated with higher severity (return-to-play time) compared with first injuries. This relatively high incidence and severity underline the importance of correct guidelines in the return-to-play decision. There is a need for new football-specific medical and physical tests to assess athletes before they return to play. Objective data could help the clinician avoid an attitude that is too aggressive (which could increase the risk of reinjury) or too conservative (which would have a negative impact on the layoff time of the athletes).
These data highlight the importance of the medical staff, whose role in many clubs and federations is still undervalued. Often, investments on medical personnel and equipment are still overlooked in professional clubs. There is debate on the methods of medical staff recruitment and its effective impact on the economy of the clubs [40]. Undeniably, however, epidemiological data suggest that, due to the impact of injuries, professional football managers should at least carefully evaluate the possibility of providing their athletes with the best medical care, with the aim to preserve their health but also to increase their availability and performance.
6.6 Risk Factors
In football, injury risk is multifactorial [27]. Several intrinsic and extrinsic risk factors have to be taken into consideration.
Among the intrinsic risk factors, age, career duration and previous injury have been shown having a negative effect on the athlete injury risk. Players with positive injury history have been shown to be two to three times more likely to suffer an identical injury in the subsequent season [24]. Mechanical instability in ankles or knees, joint laxity or functional instability also seems to predispose players to injuries, in particular of the hamstrings, groin and knee [41–45]. Other potential intrinsic risk factors, like ethnicity and mental characteristics, may play a role, but the scientific literature is still inconclusive and further research is warranted.
The analysis of intrinsic risk factor may allow clinicians to prepare individual programmes of prevention at the beginning of the season.
The influence of extrinsic risk factors needs to be analysed as well.
Physical and psychosocial stress appears to increase the injury risk. However, the role of testing the level of stress of the footballers is still generally underestimated. In order to prevent injuries, a close training load monitoring seems at least necessary.
As stated initially by Ekstrand et al. [4] and confirmed by successive researchers [46–49], a high training/match ratio is a protective factor in football. This is probably due to the fact that physically well-trained and mentally prepared players can bear the physical stress during the game with a reduced risk of injury.
Also, the relative shortness of the period of physiological pre-season preparation can be considered a potential contributing factor to the occurrence of accidents [49].
The “economic value” of the game is today definitely higher than previously. Also, the constant pressure of the media is contributing to increase the stress on footballers and therefore may put them at further risk. In addition to this, also the increased performance during the game, the different training methodology and technical and tactical innovations are aspects to consider in modern football. Indeed, the widespread use of tactical solutions, such as the pressing, the offside trap and the double marking, made at maximum intensity, is a potential risk factor for injury.
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