Anterior Cruciate Ligament Reconstruction Surgery Changes the Kinetic Jump Characteristics in Female Paediatric Patients

Characteristics of jumping kinetics have been extensively studied, serving as a performance metric in various sports and aiding in the assessment of rehabilitation progress following injury and clearance for return to sports. Deficits in jump propulsion have been observed in adults for up to 9 months post anterior cruciate ligament reconstruction (ACLR) surgery, suggesting its potential utility as an indicator of readiness to return to sport. However, it remains unclear whether this kinetic profile is replicated in adolescents. Given that adolescents face the highest risk of ACL injury, it is imperative to ascertain whether they exhibit a sustained deficit in kinetic performance following surgery. Therefore, this study aimed to determine if adolescents who have undergone ACLR present an altered kinetic profile during the countermovement jump (CMJ) compared to non-injured controls. Sixty-four female adolescents performed five CMJ on two force plates (FP4060-08, Bertec Corp., USA, 1000 Hz). Thirty-two participants underwent ACLR surgery between 5 and 20 months before the assessment and received the return-to-activity clearance. Thirty-two control participants were non-injured athletes (recreational or competitive level, Table 1). The phases of CMJ were defined as propulsion, the phase in which the center of mass starts moving upwards before the jump, and landing, the phase between initial contact after the jump and impact absorption. The kinetic outcomes measured were the ground reaction force peak (pGRF) and impulse during the propulsion phase; pGRF and absorption rate (pGRF/time to peak) during landing phase; and jump height. Data were normalized to the participant's body weight or height. Mann-Whitney U or Independent t tests were used to compare groups for demographic characteristics and jump height. A two-way ANOVA was used to identify the main effect of the group, leg, and group leg interaction on the kinetic outcomes, except for jump height. We identified a main effect of group (p = 0.003) and leg. Adolescents post-ACLR exhibit deficits in propulsion and landing during the CMJ, regardless of the jump height. Therefore, screening assessments of jump kinetics in adolescents following ACLR should incorporate both propulsion and landing phase outcomes rather than landing phase alone. It's important to note that using the contralateral leg as a comparator may not be advisable, as no interaction effect between leg and group was found, despite there being differences between the ACLR and control participants. For any figures or tables, please contact authors directly.