Epidemiology and Risk Factor P

P

V

Introduction

Football is the world’s most popular sport. According to the International Football Federation (FIFA), there are more than 200 club members in its 203 affiliated nations. The Union of European Football Associations (UEFA) has 23 members in 51 countries while the Italian Football Association (FIGC) estimates that there are 1 million players in Italy, including more than 3,000 professionals. Many players are obviously young, and the number of women footballers is constantly growing.

The greater frequency of accidents in recent years in professional and amateur football [1–3], youth football [4–6], and women’s football [7, 8] has been the subject of several researches and publications. Many footballers have had to stop playing and undergo medical treatment and surgery followed by rehabilitation periods before being able to resume playing. Those who have been able and lucky enough to take part in professional soccer know that a second, or even a tenth of a second, is time enough for the occurrence of an accident that may require days, weeks, or months to put right and which results in considerable physical and mental distress. While it is true that markedly improved medical knowledge now ensures faster, more accurate, and more precise diagnosis, it is equally true that little is known about how to prevent injuries and little, indeed, is done to prevent them. Today’s profes- sionals must be on their guard against two great threats to their health and their career, namely, doping and accidents. In both cases, an understanding of preventive measures and the timely acquisition of clear, scientifically validat- ed information constitute the first line of defence.

Many accidents are unforeseeable, as they are the natural consequences of

a sport in which speed, strength, and explosive action are accompanied by

physical contact, tackling, and collisions with an opponent. Many others, how-

ever, could be avoided because they stem from mistakes, underestimation of

risk factors, or insufficient consideration of the ways in which they can be

prevented. The current opinion is that while improvements are continually

sought in a player’s physical, technical, and tactical performance, little is being done to prevent and contain the number of accidents.

Epidemiology

Epidemiological investigation of sport injuries assesses their incidence dur- ing the course of individual sports. Football gives rise to both sport-associat- ed injuries, namely, those that stem from the specific ways in which it is played, and sport-occasioned injuries, that is, those that occur incidentally during training or the course of a match. The incidence of injuries can be expressed in several ways, including number per season, per match and/or training, per hours of activity, per exposure to a type of injury.

Epidemiological data are used to formulate appropriate preventive meas- ures. In one of our recent studies [2], we collected the 5-year data for a top- level Italian professional team comprising 22–26 players per year. Account was taken of all match or training accidents that obliged a player to remain inactive for 3 or more days. An average of 245 training sessions were held per season (Table 1), and an average of 66 official matches were played (Italian League, Italy Cup, European Cups, same-level friendlies) (Table 2), giving a training-to-match ratio of 3.6:1. This ratio itself shows how little time is devoted to preparation as opposed to playing, especially since sessions prior to a match are devoted to the tactics to be adopted rather than to training while those conducted after it are mainly concerned with unwinding. It is also defective insofar as it takes into no account the matches in which many play- ers, both Italian and foreign, take part as members of their national teams. We were the first to introduce this indicator, and it has since been adopted by other workers [9]. This index also helps trainers and coaches to prevent injuries: The greater the ratio of training to matches, the lower the risk of injury.

Table 1.Training sessions per season

Season Number of sessions

1995/1996 235

1996/1997 248

1997/1998 231

1998/1999 256

1999/2000 243

As can be seen in Table 3, we recorded 335 injuries requiring inactivity for 3 or more days in 5 seasons, with an average of 67 per season. There was no significant difference between the number of accidents in matches and those during training. Compared to the past, this reflects an increase in the number of accidents that occur during training due to the greater intensity during the sessions. With respect to previous studies, there was no difference between the roles of players in accordance with their present characteristics, namely, defence, construction, and attack. There was no difference between the first and the second half of a match. There was a higher incidence of injuries when a team was attacking as opposed to defending. Elite footballers seemed more prone to injury. A study published in 2004 by the FIFAs Medical Assessment Table 2. Matches and competitions per season. Numbers in brackets under Italian League indicate additional matches played to reach final league positions

Season Italian Italy European Friendly Total

League Cup Cup matches

1995/1996 34 6 2 22 64

1996/1997 34 7 12 14 67

1997/1998 34 6 11 18 69

1998/1999 34 (2) 8 10 16 70

1999/2000 34 (1) 8 0 18 61

Table 3. Types of injuries: 5 seasons – 1995/2000 (inactive for 3 or more days).

Total number of injuries: 335

Kind of injuries Number of cases Percentage

Muscle injuries 103 30.7

Bruises 97 28.9

Sprains 58 17.3

Tendinopathies 33 9.8

Backaches 19 5.6

Cuts 11 3.2

Chondropathies 8 2.3

Fractures 6 1.7

and Research Centre (F-MARC) reported the incidence of injuries during the 2002 Korea-Japan World Cup: 171 injuries in 64 matches, corresponding to 2.7 injuries per match and 81 injuries per 1,000 h of playing time. The latter were calculated as 11 players x 90 min x number of returned injury report forms [10]. The incidence of injury in men’s international matches ranged from 51 to 144 per 1,000 match hours, that is, 2 to 3 injuries per match [10].

We made a similar survey of the final stages of the 1990 World Cup in Italy in conjunction with the Coverciano Technical Sector [11]. There were 106 injuries, an average of 3 per match.

Risk Factors

Football is usually regarded as a sport in which injuries are the result of con- tact though in some respects it is similar to collision sports. Its risks have been the subject of several studies [12–18] that cannot be readily compared owing to the differences in their methods, parameters, and aims. A distinction must naturally be drawn between injuries occurring in young players, women, amateurs, and professionals. Consideration of the incidence due to multiple factors is also of importance [19–21].

Professionals, especially those at a high level, are exposed to the risks posed by many official matches, engagements within the course of the week, and overintense and overhasty inaugural seasons that shorten the period of physiological preparation (Table 4). Today, the business of a match in profes- sional football is certainly higher than it was in the past. The cost of the foot- ball product and the corresponding interest of media, as demonstrated by the

Table 4. Risk factors

Direct Collateral

- Play/technical and tactical aspects - Age

(Rapid actions/faster play/intensity) - Previous traumatic events

- Physical/athletic aspects - Physical and biological characteristics (Increased muscle strength)

- Life style Smoking/alcohol/diet - Psycho-physical stress - Severity of referees

(Number of matches/fatigue/ - Fair play recovery/travels/business)

- Pitches and shoes

relevant presence of television at every match, increase the interest and rele- vance of sports events. Such a type of involvement causes increased pressure and agonistic stress in players, trainers, and managers in order to reach the best possible outcome, even going as far as using unfair play.

Faster play, quicker movements and more intensive action, training meth- ods differing both in quality and the amount of exercise and number of ses- sions per week, and changes in technique and tactics are other factors.

Pressing in several parts of the pitch and offside and double marking are tac- tics practised with great intensity both in training and during a match and constitute other risk factors. Creation of a very compact or short team results in more contact between the players. It is common to see several players engaged in intense and rapid action on small portions of the pitch and hence increasing the likelihood of impacts and collisions.

Both in football and other sports, the essentially physical nature of the actions required and the great strength acquired by the muscles combine to form one of the main causes of both acute injuries (damaged knee ligaments, especially the anterior cruciate, and torn tendons) and chronic injuries (tendinopathies, enthesitis, cartilage disorders) since the joints and their sur- roundings, the tendons and the nervous control systems, are not always able to resist such an exaggerated concentration of muscular force. Stress and fatigue, too, may upset the workings of the proprioceptors. One of the most complicated questions to which an answer must be found, in fact, is how far stress and fatigue can be responsible for causing an injury.

Football pitches are also a potential source of injuries. Those used for both training and matches should be grassy with level surfaces and free from dan- gerous structures beside their edges. Matches should be played on similar surfaces. Both the FIFA and UEFA have recently looked into the possibility of using synthetic grass. Its characteristics, in fact, are technologically advanced and very similar to those of natural grass.

A footballer’s footwear has always consisted of specially designed boots

fitted with studs, bars, and the like to get a firmer grip on the ground. The

constraints to the pitch imposed by this type of footwear during running alter

both the correct mobility of the hindfoot when the heel strikes the ground

and the function of the subtalar joint. The physiological movements of the

forefoot during take off are also modified. Soles that assign priority to the

maximum grip, as required by today’s faster play, promote greater blocking of

the ankle and foot coupled with greater vulnerability of the knee. New mod-

els fitted with such soles ensure higher grip coefficients with respect to slip-

page coefficients. Uneven pitches combined with ever more powerful leg mus-

cles and rapid movements increase the risk of injury to muscles, tendons, and

joints.

Many injuries are followed by reestablishment of function and hence full resumption of sport but not by total anatomical restitutio in integrum, and other disorders may ensue. Tendinopathy is a case in point. This can be cured, but the healed tissue, while functionally effective, has lost part of its elastici- ty. In the same way, surgical repair of an anterior cruciate lesion reestablish- es the functional efficiency of the knee but not its original anatomy.

Many different constitutional factors may play a part even though several footballers have reached very high levels of performance without serious injury despite muscle and bone abnormalities that more readily lead, how- ever, to overuse injuries. The most frequent pictures are lower extremity dis- symetries, foot dysmorphisms, and femoral-tibial (varus-valgus) and femoral-patellar misalignments. Age is another factor because bones, mus- cles, and tendons lose their best features (strength, elasticity, resistance, absorption of knocks and traumas) over the course of time while a long career usually results in knee- and ankle-joint degeneration typical of sport- induced attrition.

Mention can also be made of the importance of fair play on the part of footballers, trainers, and managers, as well as the strictness of referees in defending and safeguarding the physical integrity of the players.

Injurious Mechanisms

Injuries are classed as acute due to overuse or chronic according to their char- acteristics, the moment when they occur, their type and location, and the mechanisms responsible. Acute lesions are the outcome of a single, usually macrotraumatic, low- or high-energy episode occurring either without con- tact with an opponent or during a tackle. They are typically fractures, sprains, and muscle or tendon injuries. Pain, generally acute and immediate, is the ini- tial sign, followed by oedema, which may appear in the subsequent hours.

Further training or play is often impossible. Immediate examination prior to the onset of oedema and reflex contractures is the best way of securing an already indicative diagnosis.

Overuse injuries, as their name suggests, are the result of repeated micro-

traumas and often attributable to the stresses associated with a particular

sport. They primarily manifest as tendon and cartilage disorders, low back

pain, fasciitis, and the like. All tissues may be involved when repeatedly sub-

jected to maximum loads that eventually lead to inflammation, pain, and

functional impotence and compel the suspension of sport. Their overture is

insidious. After a warm up, indeed, they may be less intense or disappear, only

to return as the training session or the match continues and thus become

chronic. In about 2 out of 3, they appear without contact, during a swerve, for

example, or slowing down or landing after a jump, and take the form of a knee or ankle sprain or muscle injury. In contact injuries, tackles with the ball at the feet or sliding tackles and elbowing or butting during mid-air collisions predominate. The lower extremities are primarily involved. The knee and ankle are most frequently injured because the stresses and direct and indirect insults imposed by fast, explosive movements expose them to greater risks.

The most recurrent knee lesions are sprains, especially of the tibial collateral and anterior cruciate, together with meniscus and cartilage lesions. Anterior cruciate injuries are nearly always indirect, without contact, whereas tibial collateral injuries are usually the result of collision with an opponent. The former are serious and often require surgical reconstruction followed in most cases by 5–6 months of inactivity [22–24].

More than 90% of ankle injuries are sprains, often underestimated in both diagnosis and treatment. All professional footballers have probably had an ankle sprain during their careers [25, 26]. Direct and indirect muscle lesions are numerically substantial [27–29], especially in the thigh, often underesti- mated, and the cause of troublesome recurrences. Overuse injuries are increasingly common, and bones, cartilages, ligaments, muscles, and tendons may be involved. Typical forms, such as pubalgia, patellar tendinitis, and chronic footballer’s ankle, are determined by the subject’s biological and physical characteristics, the use and choice of materials, and the stresses inherent to training.

Upper limb injuries, too, are increasing. Here, the goalkeeper is obviously involved because of the use of hands and arms. Clavicle, forearm, and finger fractures, along with dislocations of the shoulder, are suffered also by other players as the result of collisions or heavy falls. Craniofacial lesions are also much more frequent, particularly as the outcome of butting and elbowing in aerial tackles.

References

1. Arnason A, Sigurdsson SB, Gudmundsson A et al (2004) Risk factors for injuries in football. Am J Sports Med 32[Suppl. 1]:5–16

2. Volpi P (2000) Soccer injury epidemiology. J Sports Traumatol 22:123–131 3. Ekstrand J, Gillquist J, Moller M et al (1983) Incidence of soccer injuries and their

relation to training and team success. Am J Sports Med 11:63–67

4. Peterson L, Junge A, Chomiak J (2000) Incidence of football injuries and complaints in different age groups and skill level groups. Am J Sports Med 28[Suppl]:51–57 5. Junge A, Chomiak J, Dvorak J (2000) Incidence of football injuries in youth players.

Comparison of players from two European regions. Am J Sports Med 28[Suppl.

5]:16–21

6. Volpi P, Pozzoni R, Galli M (2003) The major traumas in youth football. Knee Surg

Sports Traumatol Arthrosc 11:399–402

7. Engstrom B, Johansson C, Tornqvist H (1991) Soccer injuries among elite female players. Am J Sports Med 19:372–375

8. Giza E, Mithofer K, Farrell L et al (2005) Injuries in women’s professional soccer. Br J Sports Med 39:212–216

9. Ekstrand J (2003) Preventing injury. Football Medicine. Martin Dunitz, London, pp 39–119

10. Junge A, Dvorak J, Graf-Baumann T (2004) Football injuries during the World Cup 2002. Am J Sports Med 32[Suppl. 1]:23–27

11. Volpi P (1990) I traumi nel mondiale di calcio 1990. Settore Tecnico FIGC, Firenze 12. Boden BP, Kirkendall DT, Garrett WE (1998) Concussion incidence in elite college

soccer players. Am J Sports Med 26:238–241

13. Chomiak J, Junge A, Peterson L et al (2000) Severe injuries in football players.

Influencing factors. Am J Sports Med 28[Suppl. 5]:58–68

14. Hawkins RD, Fuller CW (1999) A prospective epidemiological study of injuries in four English professional football clubs. Br J Sports Med 33:196–203

15. Nielsen AB, Yde G (1989) Epidemiology and traumatology of injuries in soccer. Am J Sports Med 17:803–807

16. Luthje P, Nurmi I, Kataja M et al (1996) Epidemiology and traumatology of injuries in elite soccer; a prospective study in Finland. Scand J Med Sci Sports 6:180–185 17. Murphy DF, Connolly DA, Beynnon BD (2004) Risk factors for lower extremity

injury: a review of the literature. Br J Sports Med 37:13–29

18. Drawer S, Fuller CW (2002) Evaluating the level of injury in English professional football using a risk-based assessment process. Br J Sports Med 36:446–451 19. Inklaar H (1994) Soccer injuries. I: Incidence and severity. Sports Med 18:55–73 20. Morgan BE, Oberlander MA (2001) An examination of injuries in major league soc-

cer. The inaugural season. Am J Sports Med 29:426–430

21. Lindenfeld TN, Schmit DJ, Hendy MP et al (1994) Incidence of injury in indoor soc- cer. Am J Sports Med 22:364–371

22. Caraffa A, Cerulli G, Projetti M et al (1996) Prevention of anterior cruciate ligament injuries in soccer. A prospective controlled study of proprioceptive training. Knee Surg Sports Traumatol Arthrosc 4:19–21

23. Agel J, Arendt EA, Bershadsky B (2005) Anterior cruciate ligament injury in natio- nal collegiate athletic association basketball and soccer. Am J Sports Med 33:524–530

24 Bjordal JM, Arnly F, Hannestad B et al (1997) Epidemiology of anterior cruciate liga- ment injuries in soccer. Am J Sports Med 25:341–345

25. Ekstrand J, Tropp H (1990) The incidence of ankle sprains in soccer. Foot ankle 11:41–44

26. Andersen TE, Floerenes TW, Arnason A et al (2004) Video analysis of the mecha- nism for ankle injuries in football. Am J Sports Med 32[Suppl. 9]:69–79

27. Volpi P, Melegati G, Tornese D et al (2004) Muscle strains in soccer: a five-year sur- vey of an Italian major league team. Knee Surg Sports Traumatol Arthrosc 12:482–485

28. Askling C, Karlsson J, Thorstensson A (2003) Hamstring injury occurrence in elite soccer players after preseason strength training with eccentric overload. Scand J Med Sci Sports 13:244–250

29. Orchard J, Marsden J, Stephen L (1997) Preseason hamstring muscle weakness asso-

ciated with hamstring muscle injury in Australian footballers. Am J Sports Med

25:81–85