Strategies for Prevention of ACL Injuries in Sportive Females

In the last 40 years participation of women to sport has grown almost 10 times [1]. Currently, more than half of adolescent females are engaged in sports at school or clubs. In addition to an increased participation, young women have a higher incidence of knee injuries than male [2]. Furthermore, despite the ACL repair and correction of the instability, young women show an early onset of degenerative osteoarthritic changes [3].


Introduction
In the last 40 years participation of women to sport has grown almost 10 times [1]. Currently, more than half of adolescent females are engaged in sports at school or clubs. In addition to an increased participation, young women have a higher incidence of knee injuries than male [2]. Furthermore, despite the ACL repair and correction of the instability, young women show an early onset of degenerative osteoarthritic changes [3].
The importance of prevention of ACL injuries without trauma is based on the following elements: ACL Injuries are the most common, with longer disability times and a devastating influence on the levels of patient activity and quality of life. Additionally the ACL Injuries have the highest economic cost among sport traumas [4]. Finally, knees with ACL deficiency have increased risk for secondary injuries such as meniscal tears and early development of osteoarthritis [5].

Prevention of Risk-Factors and Reduction of Injury-Rate
Maybe the proper knowledge of mechanism how the ACL is loaded, how it fails and of all the risk factors for ACL tears is the first approach for a preventive intervention [6]. As we know, biomechanical features [6], joint geometry [7], lower extremity alignment [8], body composition [9], genetic assessment [10] and hormonal patterns [11] could be important variables for female gender that may lead to an increase risk for tears. Some of these feature have been well studied and can be challenged, other ones are still in discussion and can be changed partially or not at all.
In these fields of study, only the neuromuscular and biomechanical risk factors have received adequate attention as regards prevention programs. These protocols are used to change the sport technique and improve the conditioning through the neuromuscular control, strength, plyometrics and balance training. Among all the components of the prevention program, plyometric training has proven to be one of the most effective tools to reduce ACL injuries without contact.
The plyometric component of prevention programs train the muscles, connective tissue, and nervous system to effectively carry out the stretch-shortening cycle and focus on proper technique and body mechanics. They are able to optimize the muscular activation and performance of lower limbs during jumping exercises. Electromyography for the evaluation of the preparatory and reactive work of medialis and lateralis vastus, posterior muscles, medial and lateral thigh and hip abductors and adductors shows an increase of the preparatory adductor activity and cooperation adductor-abductor during jumpstop [12]. These data strongly support the role of strategies of activation of the hip muscles for control of dynamic alignment of the lower limbs in landing.
The neuromuscular training has been shown to be able to make a significant improvement in the total stability of the single limb and the anterior-posterior stability (sagittal plane), but not Juniper Online Journal of Case Studies 002 the medial-lateral stability (in the coronal plane). Furthermore, this improvement involves the total postural stability [13]. Among other beneficial effects of neuromuscular training in female athletes, an increased angle of knee flexion during landing from a vertical jump and a decreased torsion of valgus and varus knee should be improved; in fact these elements are well-known risk factors for ACL injuries in female gender [14]. Exercises "on the playground" are extremely important, requiring knee and hip flexion in landing and lateral movements, avoiding the excessive knee valgus in landing and squat exercise, increasing core strength, hamstrings, gluteus medius, hip abductors and techniques for addressing proper deceleration [15].
The kinematics of the hip and knee are considered important elements for the prevention of the risk of injury in women. In particular, training for proper kinematics of the hip and knee, during a landing exercise, seems to lead to a significantly lower internal rotation and greater angles of hip abduction during the landing gesture [16]. The "high risk" athletes that play a regular neuromuscular training have a lower knee-moment of abduction of 13% [17].
Training focused on hamstrings and on the relationship between power of quadriceps and hamstrings have shown an increase in the functional relationship (ratio: eccentric activity of hamstring and concentric activity of quadriceps) [18]. This object is specifically recommended for the prevention of ACL injuries [19].
In the jump, the angle moment of dynamic valgus knee, which is of high prevalence in the female gender, during the stop-jump support is decrease by neuromuscular training; the maximum knee flexion angles are increased during the stance phase of the jumps [20]. The anticipation of the external forces and the loads in order to stabilize the joint and protecting adjacent structures has revealed a decrease of the incidence of ACL injury up to 74% [21].
Finally, in prevention programs, the correct sport-specific movement is the most important element. The reduction of highrisk gestures can lead to a 41% reduction of LCA ruptures [22]. Programs that focus on correcting individualized techniques could be considered the best ones. [23]. For example, expert modeling that are combined with self-modeling are the most effective way to change risk mechanisms as landing biomechanics [24].
"The American Journal of Sports Medicine" in 2009, through an experimental study has drawn up a training program with the intention to emphasize the prevention of biomechanical risk factors. This protocol, whose name is "sport injury prevention training program" (SIPTP), still well-known and approved, has the target to improve muscle strength, flexibility and biomechanical properties (Table 1). Kinetic and kinematic outcomes such as the height of the jump, the maximum of the knee bending angle, the minimum distance between the two knees, the maximum angle of internal rotation of the knee, the maximum moment of knee extension and the moment of maximum valgus knee were evaluated. Results reported greater knee flexion angles, a greater distance between knees and optimization of the Hamstrings-Quadriceps (H-Q) ratio [25]. Table 1: sport injury prevention training program [25].

Exercise Specific Exercises
Warm-up An interesting thing is that training programs of force show no significant difference in the kinematics and kinetics of the knee and hip. The training of force alone does not improve the kinematics and kinetics of the knee and hip in amateur athletes. Therefore, only strength interventions may be not sufficient to reduce the risk of ACL injuries in female players. So it seems that the one-component prevention programs have no significant impact on the biomechanical risk factors in female athletes [26].

Conclusion
Preventing non-contact ACL injuries is a high relevance in sports traumatology. Although well-controlled ACL injuryprevention programs seem to be able to reduce the incidence of ACL injuries, to date there is no standardized intervention protocol. Currently, sex differences that lead to a higher rate of injury in female are object of several studies. Most of these