Summary

Biomechanical measures computed through 2D video-analysis and force platforms during pre-planned 90° change of direction tasks are associated to the occurrence of non-contact ACL injury in young competitive football players, based on a prospective epidemiology and biomechanical study on more than 1000 academy players

Abstract

Anterior Cruciate Ligament (ACL) injury has devastating consequences for the young football population. The 2D video-analysis of complex movements such as the 90° change of direction (COD) task are valuable solution to inspect the presence of poor biomechanics and neuromuscular control while resembling high-demanding movements in a clinical setting. In this scenario, the “CUTtheACL” project was designed as a prospective epidemiology and biomechanics investigation on risk factors for primary ACL injury mitigation on a large dataset (n>1000) of healthy football players. The present study presented the results of the first-year follow-up of the CUTtheACL study in terms of the association between ACL injury occurrence and 2D video analysis (kinematics, Ground Reaction Forces, and Movement Analysis Test score).
One-thousand-and-two healthy competitive football (soccer) players (age 16.3 ± 2.8, 738 males, 264 females) were prospectively enrolled. Each player performed a series of pre-planned 90° COD at the maximum speed. 2D kinematics at initial contact on the force platform (IC) and at maximum knee flexion angle (MKF) and GRFs were collected according to Della Villa et al. The MAT score was assigned to every trial ranging from 0 (worst) to 10 (best) according to 5 sub-criteria. The occurrence of ACL injuries was tracked during the first year after the test. Differences between ACL injured limb and non-injured limb were investigated within players through the paired t-test and the χ2 test; differences between ACL-injured players and the rest of the cohort were inspected through the unpaired t-test and χ2 test. Differences with at least a small effect size (p<0.05, Cohen’s d≥0.2) were considered.
At one-year follow-up, 29 players (2.9%) experienced an ACL injury. One partial ACL lesion and one direct contact injury were excluded from the final analysis. A higher percentage of female players was found among the ACL-injured population compared to the rest of the cohort (51.9% vs 25.6%, p=0.006). ACL-injured players landed with significantly more heel strike pattern (p=0.016), greater foot internal rotation (5.1°, p=0.030), and frontal plane knee projection angle (3.3°, p=0.041) at MKF with their injured limb compared to their non-injured limb. ACL-injured players obtained a lower total score (3.0/10 vs 3.5/10, p=0.006) compared to the rest of the cohort. Pelvic stability (PS, χ2=8.8, p=0.013) and Movement Strategy (MS, χ2=12.9, p=0.002) sub-scores were also lower in ACL injured players compared to the rest of the cohort. Lower hip-trunk flexion angle at IC and MKF (p<0.001) and greater trunk tilt angle at MKF (p=0.001) were also found.
Within-player asymmetries in landing pattern (heel/toe strike) and frontal plane kinematics (foot internal rotation and knee valgus) were found in ACL-injured players. Lower MAT total score, quadriceps dominance, and trunk imbalance characterized ACL-injured players compared to the rest of the cohort. The first-year follow-up assessment of the CUTtheACL study revealed key insights in the comprehension of ACL injury patterns through the 2D video-analysis of the COD task and could shape future recommendations to mitigate the ACL injury risk in young football players.