Evaluation Of Three-Dimensional Motion During Side-step Cutting After Anterior Cruciate Ligament Reconstruction in Pediatric Athletes

OBJECTIVES: This study assessed three-dimensional kinematic and kinetic data during side-step cutting in young athletes following anterior cruciate ligament (ACL) reconstruction. METHODS: The study included 28 pediatric athletes (mean age 15.6 ± 2.2 years) who underwent ACL reconstruction due to a non-contact injury. Lower extremity and trunk three-dimensional kinematic and kinetic data was collected during a side-step cut. Testing occurred within 12 months (mean time since surgery 5.3 ± 2.1 months) post-surgery. Outcomes were evaluated at initial foot contact and between initial foot contact and maximum knee flexion of the cutting limb. Differences between the operative limb and non-operative (contralateral) limb were investigated using paired t-tests. RESULTS: The operative limb had higher peak adduction (-0.14° ± 7.3 vs. -6.1° ± 5.0, p=0.001) and higher peak pelvic obliquity (14.0° ±6.2 vs. 10.5° ±5.7, p=0.01) compared to the non-operative limb. While there was no significant difference in peak ground reaction force (23.2 N/kg ± 4.7 vs. 24.5 N/kg ± 4.5, p=0.15), the operative limb had lower peak knee flexion (53.3° ± 13.5 vs. 59.6° ±10.0, p=0.004), ankle dorsiflexion (14.5° ± 7.5 vs. 18.6° ± 6.5, p=0.007), and external knee flexor moment (1.4 Nm/kg ± 0.61 vs. 1.9 Nm/kg ± 0.62, p=0.002) leading to the operative limb having less power absorption at the knee (0.38 Ws/kg ± 0.31 vs. 0.58 Ws/kg ± 0.28, p=0.005). At initial contact the operative limb was more adducted (-5.0° ± 7.6 vs. -8.6° ± 3.9; p=0.02) and flexed (56.3° ± 11.4 vs. 52.5° ± 12.7; 0.06) at the hip and more flexed at the knee (21.5° ± 17.1 vs. 17.2° ± 13.6; p=0.06). The operative limb also had more pelvic elevation (8.1° ± 7.0 vs. 5.5° ± 3.8; p=0.04) and had more trunk rotation (rotation relative to the lab; -11.4° ±7.2 vs. -5.3° ±8.6; p=0.004). Eight of the 28 operative limbs had an asymmetry greater than 10% of the non-operative limb on one of the kinematic or kinetic variables; though all eight limb asymmetries occurred on different movement variables. CONCLUSION: Following ACL reconstruction pediatric athletes exhibit asymmetry several months post-surgery. The operative limb displayed deficits and asymmetry in hip control and shock absorption strategies after initial contact until maximum knee flexion which could increase the risk of future re-injury based on prior biomechanical studies. The contralateral limb also demonstrated deficits and asymmetries at initial contact. These asymmetrical movement patterns and deficits potentially put the non-operative limbs at an increased risk for injury and potentially lend insight into why patients who tear one ACL are at increased risk of contralateral ACL injury. If asymmetry is indicative of future injury risk, this should be considered during treatment, rehabilitation and return to sport decision-making.