Strength and Function Across Maturational Levels in Young Athletes at the Time of Return to Sport After ACL Reconstruction

Background: The impact of maturation on lower extremity strength and function after anterior cruciate ligament reconstruction (ACLR) may help guide future studies of age-specific rehabilitation. Hypothesis: Pediatric ACLR patients would demonstrate higher thigh strength symmetry and knee-related function at return to sport (RTS) compared with adolescent and young adult participants who underwent traditional ACLR. Study Design: Prospective cohort study. Level of Evidence: Level 2. Methods: A total of 144 young athletes at the time of RTS clearance post-ACLR were classified into 3 maturational groups (pediatric, n = 16 with physeal-sparing ACLR [mean age = 12.3 years; range = 9.2-14.6 years]; adolescent, n = 113 [mean age = 16.5 years; range = 14.1-19.8 years]; young adult, n = 15 [mean age = 22.0 years; range = 20.5-24.9 years]). Quadriceps and hamstring strength were measured using an electromechanical dynamometer. Knee-related function was measured using the International Knee Documentation Committee (IKDC) subjective form and single-leg hop tests. The Limb symmetry Index (LSI) was used in calculations for hop and strength tests. Group differences were compared with Kruskal-Wallis tests and Mann-Whitney U post hoc tests. Proportions of participants meeting literature-recommended RTS criterion cutoffs were compared among the groups using chi-square tests. Results: The pediatric group demonstrated higher quadriceps LSI (P = 0.01), IKDC scores (P < 0.01), single-hop LSI (P < 0.01), and crossover-hop LSI (P = 0.02) compared with the young adult group. In addition, the pediatric group demonstrated higher IKDC scores (P < 0.01) and single-hop LSI (P = 0.02) compared with the adolescent group. The adolescent group demonstrated higher IKDC scores (P < 0.01), single-hop LSI (P = 0.02), and crossover-hop LSI (P = 0.03) compared with the young adult group. The proportions of participants meeting all RTS criterion cutoffs were highest in the pediatric group and lowest in the young adult group (P = 0.03). Conclusion: Young athletes at RTS clearance after pediatric ACLR demonstrated higher quadriceps strength symmetry and knee-related function than adolescents and young adults after traditional ACLR. Clinical Relevance: These findings demonstrate the need for further study regarding the impact of these group differences on longitudinal outcomes after ACLR, including successful RTS and risk of second ACL injury.