Real-time assessment and neuromuscular training feedback techniques to prevent ACL injury in female athletes

Abstract

Some athletes may be more susceptible to at-risk knee positions during sports activities, but the underlying causes are not clearly defined. This manuscripts synthesizes in vivo, in vitro and in-silica (computer simulated) data to delineate likely risk factors to the mechanism(s) of non-contact ACL injuries. From these identified risk factors, we will discuss newly developed real-time screening techniques that can be used in training sessions to identify modifiable risk factors. Techniques provided will target and correct altered mechanics which may reduce or eliminate risk factors and aid in the prevention of non-contact ACL injuries in high risk athletes.

Figures

Figure 1

A. ACL injury mechanism with high knee abduction angle that is related to high LOAD. B. Videographic depiction of athlete with kinematic pattern that is likely to demonstrate high LOAD. C. Motion analysis depiction of athlete with kinematic and kinetic pattern indicative of high LOAD. D. Scatterplot of data comparing those who went onto ACL injury to uninjured control subject. Red-line indicates established cut-point which provided maximum sensitivity and specificity to predict ACL injured status. Athletes who demonstrate LOAD beyond (negative values indicate increased LOAD) red line may be at “high risk” for ACL injury during competition (figure 1A).

Figure 2

A. Representative subject whose combination of decreased tibia length and mass prior to her rapid growth spurt diminish risk to demonstrate high LOAD landing mechanics. Knee valgus motion during the drop vertical jump is calculated as the displacement measure between the two marked knee alignment in the X plane measured at the frame prior to initial contact and the frame with maximum knee flexion (X2− X1). B. Knee flexion range of ROM during the drop vertical jump is calculated as the difference in knee flexion angle between initial contact and maximum knee flexion positions (ϴ1−ϴ2). C. Completed nomogram for the representative subject (Tibia length: 32.5 cm; Knee valgus motion: 4.2 cm; Knee flexion ROM: 74.1°; mass: 30.7 kg; QuadHam: 1.64). Based on her demonstrated measurements this subject would have a 12% (62.5 points) percent chance to demonstrate high LOAD during the drop vertical jump. Her actual LOAD measure for the presented drop vertical jump that was quantified simultaneously with 3D motion analysis was 13.4 Nm of knee abduction load. D. Example of representative subject whose combination of increased tibia length and mass associated with her rapid growth contribute to her increased risk to demonstrate high LOAD landing mechanics when using the clinic-based ACL injury risk prediction algorithm. Knee valgus motion during the drop vertical jump is calculated (X2− X1). E. Knee flexion range of ROM during the drop vertical jump is calculated (ϴ1−ϴ2). F. Completed nomogram for the representative subject (Tibia length: 45 cm; Knee valgus motion: 3.0 cm; Knee flexion ROM: 60.0°; mass: 71 kg; QuadHam: 1.19). Based on her demonstrated measurements this subject would have a 91% (116.5 points) percent chance to demonstrate high LOAD during the drop vertical jump. Her actual LOAD measure for the presented drop vertical jump that was quantified simultaneously with 3D motion analysis was 48.5 Nm of knee abduction load.

Figure 3

TJA assessment tool can be utilized to score deficits during a jumping and landing sequence movement. To perform the tuck jump assessment the athlete is instructed to start in the athletic position with her feet shoulder-width apart (on line marked 35 cm apart). They are instructed to initiate the jump with a slight crouch downward while they extend their arms behind her. They then swing their arms forward as she simultaneously jumps straight up and pulls her knees up as high as possible. At the highest point of the jump the athlete is instructed to pull her thighs parallel to the ground. When landing, the athlete should immediately begin the next tuck jump. Encourage the athlete to land softly, using a toe to mid-foot rocker landing and land in the same footprint with each jump. The athlete is instructed to perform the tuck jump exercise for 10 seconds and should be instructed to not continue this jump if they demonstrate a sharp decline in technique during the allotted time frame. Figure reproduced from Myer, G. D., K. R. Ford, et al. (2008). “Tuck Jump Assessment for Reducing Anterior Cruciate Ligament Injury Risk.“ Athletic Therapy Today 13(5): 39–44 with permission from the editor.

Figure 4

Desired technical performance of the tuck jump exercise.

Figure 5

Tuck jump criteria grouped by modifiable risk factor categorizations.

Figure 6

Lower extremity valgus at landing. This is indicated by the athlete displaying a “knock-kneed” position while in contact with the ground.

Figure 7

Foot placement not shoulder width apart. This deficit can be manifested with feet either closer together or farther apart.

Figure 8

Excessive Landing contact noise. This is typically displayed by the athlete through landing with flat feet and is typically accompanied by a lack of knee and hip flexion during the stance phase.

Figure 9

Thighs not equal side to side during flight. Side dominance often is visible when an athlete has one thigh that does not achieve the same height as their contralateral thigh.

Figure 10

Foot placement not parallel (front-to-back). Often an athlete will “drop” one foot behind the other while on the ground to help minimize forces on an injured or weaker limb.

Figure 11

Foot contact timing not equal. Similar to not placing the feel parallel, the athlete will occasionally change the timing of the foot contacts to protect an injured or weaker limb.

Figure 12

Thighs do not reach parallel (peak of jump). This deficit is typically a product of the athlete's inability to create enough power to achieve a height at which the legs can become properly tucked.

Figure 13

Does not land in the same footprint. Many times an athlete will tend to float around the jumping area due to a lack of full body or “core” control. When this deficit is present, the coach should be careful in determining the cause so that training can be properly applied.