Abstract
Objectives:
This study assessed differences between pediatric athletes’ anterior cruciate ligament (ACL) reconstructed limb and non-reconstructed limb compared to limbs with no lower extremity surgical history during a side-step cut.
Methods:
28 limbs with an ACL reconstruction within the 12 months prior to testing (operative limbs), 28 contralateral limbs (non-operative limbs) and 56 limbs with no lower extremity surgical history (control limbs; 28 individuals) were included. Lower extremity kinematic and kinetic 3-dimensional data was recorded during the deceleration phase of a side-step cut. Outcomes were evaluated at initial foot contact and between initial foot contact and maximum knee flexion of the cutting limb. Differences between operative and non-operative limbs and control limbs were assessed using analysis of variance with Bonferroni post-hoc tests.
Results:
Operative limbs had higher peak hip adduction (-0.14° ± 7.3 vs. -6.1° ± 5.0, =0.01) and higher average external knee valgus moments (0.16 Nm/kg ± 0.50 vs. -0.21Nm/kg ± 0.58, p=0.02) compared to control limbs. In terms of shock absorption, operative limbs had lower peak ground reaction forces (23.2 N/kg ± 4.7 vs. 28.3 N/kg ± 5.8, p<0.0001) and peak ankle dorsiflexion (14.5° ± 7.5 vs. 20.0° ± 6.4, p=0.002) compared to control limbs with lower peak external knee flexor moments (1.4 Nm/kg ± 0.61 vs. 2.0 Nm/kg ± 0.63, p<0.0001) and less power absorption at the knee (0.38 Ws/kg ± 0.31 vs. 0.55Ws/kg ± 0.34, p=0.05) and ankle (0.43 Ws/kg ± 0.21 vs. 0.65 Ws/kg ± 0.41, p=0.01). Though non-operative limbs had less knee valgus (-1.0° ± 3.5 vs. 1.1° ± 3.3, p=0.04) at initial contact, they had higher peak knee valgus (3.6° ± 5.7 vs. 0.58° ± 4.1, p=0.04) and higher average external knee valgus moments (0.09 Nm/kg ±0.59 vs. -0.21Nm/kg ±0.58, p=0.06) compared to control limbs. Non-operative limbs also had less pelvic obliquity compared to control limbs (10.4° ± 5.8 vs. 14.6° ± 7.7, p=0.04). Lower peak ground reaction forces (24.5 N/kg ± 4.5 vs. 28.3 N/kg ± 5.8, p=0.005), increased power absorption at the hip (0.43 Ws/kg ± 0.48 vs. 0.15 Ws/kg ± 0.23, p=0.005), and decreased power absorption at the ankle (0.49 Ws/kg ± 0.23 vs. 0.65 Ws/kg ± 0.41, p=0.09) were seen in non-operative compared to control limbs.
Conclusion:
Limbs with ACL reconstruction exhibited poorer hip stability compared to control limbs. ACL reconstructed limbs also had less energy absorption at the knee and lower peak vertical ground reaction forces, likely reflecting an avoidance strategy when performing a cut using an ACL reconstructed limb. The uninjured, contralateral limbs of ACL reconstructed patients also demonstrated reduced ground reaction forces and altered neuromuscular control. These changes may reflect overall tentativeness in performing a cut but also suggest baseline suboptimal neuromuscular control that possibly lends insight into the increased risk of contralateral ACL tear seen in patients who have sustained an index ACL tear. It is also possible that the biomechanical strategies present on the operative side could be putting the non-operative limb at risk for injury. These findings support the need for ongoing research into rehabilitation protocols and return to sport timing and also support to existing injury prevention programs.