The Task Dependent Effect of Sex on Anterior Cruciate Ligament Reconstruction Recovery

Background: Following an anterior cruciate ligament reconstruction (ACLR), 32% of pediatric athletes have a secondary injury. Adolescent males and females experience different recovery trajectories and rates of reinjury. Lower extremity strength and landing kinetics have been linked to reinjury but there is a lack of research focused specifically on adolescents that includes data across the recovery timeline. Therefore, the purpose of this study was to assess the effect of biologic sex on strength and walking peak impact force (PIF) symmetry recovery following an ACLR. Hypothesis: We hypothesized that adolescent males would present with a greater increase in strength symmetry and walking gait PIF symmetry over time when compared to adolescent females. Methods: Longitudinal data were obtained from 64 patients (30 females, age = 17.1 ± 1.9 years) in an ongoing point of care study. All patients completed at least 2 and a maximum of 4 testing visits. The time frames for testing were identified as <5 months (TF1), 5-7 months (TF2), 8-10 months (TF3), and ≥ 11 months (TF4) post-surgery. Patients performed bilateral isokinetic concentric quadriceps and hamstrings strength assessments at 60 deg/s. Peak torque (PT) was recorded and normalized to body mass (Nm*kg-1). Additionally, patients completed a treadmill walking gait assessment at a self-selected pace while wearing force sensor insoles. Average PIF data (N) were collected during a one-minute trial and normalized to body weight. The PT and PIF data were used to calculate limb symmetry indexes (LSI) by dividing values from the injured limb by the values obtained from the contralateral limb. Linear and nonlinear regression models were assessed for analysis. The log models were a better fit for all variables. Results: The quadriceps LSI log model revealed a significant effect for time frame with values increasing over time (20.82 ± 2.73, p < 0.001) but not a significant interaction for time frame and sex (Figure 1). In contrast, there was not a significant effect for time frame, sex, or the interaction in the hamstrings LSI model. Finally, the results from the PIF LSI model revealed a significant effect for time frame with higher values at later time frames (4.98 ± 1.48, p < 0.001) but not for sex or the interaction. Conclusion: The results suggest sex may be an important consideration when interpreting LSI for different tasks in adolescents with ACLR. However, the trajectory of recovery may not differ by sex may not be different.