There is growing interest, at all levels of football, in new generation ASPAs that use synthetic infill materials. Therefore, for the first time a reference to the field surface was included in the Laws of the Game of football on 1 July 2004 with the phrase; Matches may be played on natural or artificial surfaces, according to the rules of the competition 8
. Turkey Football Federation issued a circular in 2009 for the first time and has set the standards for the supervision and control of ASPAs 9
First generation ASPAs were introduced to the professional sporting activity in 1960s 10. These fields are produced from stiff nylon fibers including no filling materials like sand or rubber 1. Risk of skin injuries were high on these surfaces 11. Second generation ASPAs improved in the 1970s that fibers were made from soft polyethylene with sand as a filling material 1. In 1990s third generation ASPAs were introduced that made of polyethylene monofilaments that textured and coated with rubber particles or sand as filling materials 1. In our study while 69 ASPAs were third generation turf, 18 were second generation. ACL injury can occur on both type of ASPA's. For this reason structure of the playing surface is not the most important factor on ACL tears in Turkish office workers population who have irregular sport activity.
Shoe and playing surface interaction contains many different factors. These are body weight, velocity, acceleration, deceleration and surface type 12. The sole, cleat or stud material and number, size of cleats and their configuration in shoe are the important factors that affect the shoe and ground interaction 1. Generally the conventional soccer and football shoes have different cleat lengths and types of sole and the ASPA shoes have dense pattern of short elastomeric studs over the all surface of sole 1. New generation ASPA shoes modified to include midsole weight absorbing to distribute the force during ground contact. In our study, only 7 individuals were wearing the special designed shoes for football playing on ASPAs. The remaining were other types of shoes for designed other types of sporting activities, as walking, jogging, tennis playing or running. In our opinion, improper shoes on ASPAs may one of the most important factor predisposing for ACL tears that pointing to insufficient equipment.
The strength, balance and flexibility of the surrounding musculature of the knee are the important factors for preventing knee from injuries. Consequently, warm-up exercise before any type of sporting activity is an important procedure. The football is a contact sport and the rate of ACL injuries are relatively high whether ASPA or natural grass players. The warm-up exercises before playing was found effective at preventing common injuries as well as ACL injuries in football (13-15). Several studies reported that warm-up exercises showed 57-77% reduction in the knee injury incidence 16-17. According to the results of Mandelbaum et al. during the year of 2000 football season, there was an 88% decrease in anterior cruciate ligament injury. During the year of 2001 football season, there was a 74% reduction in anterior cruciate ligament tears with 20 minutes warm-up exercises performed before matches and training 18. Therefore the warm-up exercises must be the essential part of the football before playing in order to prevent injuries. In our study, sparing time for warm-up exercise before football in individuals who had ACL injury on ASPAs were mean 6.42 minutes with a range between 0-15 minutes.
Typically, ACL tears happen as a result of trauma. During sudden deceleration, turning and pivoting movement, ACL tears may occur. The most common mechanism of ACL injury is knee hyperextension with tibial varus and internal rotation. While both medial collateral ligament and medial meniscus tears can occur with severe valgus and external rotation force before the ACL tears, severe varus force can cause lateral collateral ligament tear and ACL tear and not withstanding, ACL tears with hyperextension and hyperflexion are rarely seen 19. In our study 65 individuals had ACL tear with non-contact injury, while the remaining 22 of the patients had ACL tear with a direct contact due to any type of trauma.
Sparing less time for warm-up exercise is producing seriously trauma like ACL and also the other injuries. The number of non-contact injured ACL individuals is significantly higher than contact injured ACL individuals in our series. It is clearly provides that most ACL tears occur with non-contact injuries in individuals who perform less, insufficient, ineffective knee and corresponding muscularity warm-up exercise on ASPAs while sporting.
Playing surface had a significant effect on injury rates with an incidence rate of 1.73 ACL injuries per 10,000 on ASPAs compared with a rate of 1.24 per 10,000 on natural grass and the rate of ACL injury on ASPAs is 1.39 times higher than the injury rate on natural grass surfaces 13. Significantly higher rates of all types of injury in football have been reported on ASPAs compared with natural grass 3-6. However, some reports documented that no difference in ACL injury rates on ASPAs and natural grass surfaces 20-21, while a different study found increased rates of noncontact ACL injuries on natural grass compared with ASPAs 22. Interestingly, most of the patients in our study are considering this activity as a social activity that having time with friends rather than a regular sport activity.
Among 4307 patients from Turkey population with mean age 47.1±14.7 years (20-83) the average body mass index was determined as 28.3±5.2kg/m² 23. According to Turkey nutrition and health study, 62.8% of the population between the ages 19 to 30 the body mass index was below 25 kg/m² and 38.9% of the population between the ages 31 to 50 body mass index was 25-30 kg/m² and 38.9% of the population between the ages 31 to 50 body mass index was over 30 kg/m² 24. In our study, the mean BMI is 24.9 kg/m² (range 19.2-32.8 kg/m²). The mean age of patients was 34.02 (21-51). The mean BMIs of patients in our study are almost at the normal levels of Turkish population.
Patients with ACL tear whose profession was sports return to sportive activity most commonly occurs at least 6 months postoperatively 25. The mean period for return to work was 17.41 weeks (range 12-24) according to our study. But patients were not professional athletes in our study.