Relationship Between Dynamic Limb Symmetry And Subjective Limb Confidence Post ACL Reconstruction In Youth Athletes

Abstract

Limb symmetry index (LSI) of dynamic movement is used as return to sport criteria for athletes who have undergone an anterior cruciate ligament reconstruction (ACLR). However the relationship between an individual’s perception of confidence and dynamic performance is poorly understood. PURPOSE: To discern a relationship between dynamic limb symmetry during a drop landing (DL) and single leg hop (SLHOP) task with subjective limb confidence in athletes who have had an ACLR. METHODS: 23 subjects (13 female, 10 male; 16±1.4 years) underwent a biomechanical assessment, including a DL and SLHOP task, at around 7±1 months post op ACLR. Subjects were outfitted with a custom marker set and recorded with a 3D camera system while performing tasks on 2 force platforms. To examine dynamic limb symmetry, kinematic variables of peak hip flexion, knee flexion, and ankle dorsiflexion, with kinetic variables of peak hip extension moment, knee extension moment, ankle plantar flexion moment, and vertical ground reaction force (GRFz) were collected and analyzed as an index between the involved and non-involved limb. Subjects completed questionnaires for limb confidence; International Knee Documentation Committee (IKDC)/Pedi-IKDC and Tampa Scale of Kinesiophobia (TSK). The relationship between LSI during DL and SLHOP with the IKDC and TSK scores were tested using a multilinear regression analysis. RESULTS: A significant strong relationship was found between LSI of DL mechanics and IKDC (86±12, r= 0.84, p<0.05). Among predictor variables, peak GRFz (LSI 79±21, p<0.05) was significant in its explanation of IKDC scores. Independent regressions showed significant moderate correlations between IKDC and LSI for peak hip extension moments (LSI 107±24, r= 0.56, p<0.01), knee extension moments (LSI 80±23, r=0.51, p<0.05), and GRFz (r= 0.62, p<0.01). No significant relationships were found for SLHOP and IKDC scores, or with TSK for either dynamic test. CONCLUSIONS: Subjective limb confidence demonstrated a strong relationship with limb symmetry of sagittal plane mechanics with a 1% difference in LSI of GRFz corresponding to a 0.4% difference in IKDC scores during a DL and not SLHOP task. Symmetry in mechanics during a bilateral task may be more reflective of patient confidence in utilizing the affected limb prior to return to sport after ACLR.