The Experimental Research Of Biomechanical Characteristics Of Amateur Athletes After Anterior Cruciate Ligament Reconstruction During Unanticipated Side Cutting

Purpose: The purpose of this study was to quantify the biomechanical characteristics of lower limbs during side cutting of athletes after Anterior Cruciate Ligament Reconstruction(ACLR)under anticipated and unanticipated conditions,and to investigate the potential risk of Anterior Cruciate Ligament(ACL)injury in unaffected and affected limbs of amateur athletes after ACLR.Methods: The Vicon motion capture system and 3D force platform were used to collect the kinematic and kinetic data of the affected and unaffected lower limbs of 42 subjects during side cutting under anticipated and unanticipated conditions.The infrared grating blocking system and red and green signal lights were used to set the unexpected conditions.The kinematic and kinetic data collected were processed by Visual3 D.The angle,range of motion,moment,ground reaction force(GRF),anterior tibial shear force and other test indexes were analyzed statistically by using two-way ANOVA with repeated measures.Results:(1)The kinematics results of this study showed that the knee flexion angle(P=0.016),the knee external rotation angle(P<0.001),and the hip internal/external rotation angle(P<0.001)initial contact showed significant limb main effect.Knee flexion angle(P=0.017)and hip internal/external rotation angle(P=0.030)showed significant conditional main effect.The peak knee flexion angle(P=0.008),hip flexion angle(P=0.027),hip abduction angle(P=0.005)and hip external rotation angle(P<0.001)of the unaffected and affected side of the limb during the side cutting under anticipated and unanticipated conditions had significant limb main effect.The peak knee flexion angle(P=0.007)and hip abduction angle(P=0.014)had significant conditional main effect.The peak knee internal/external rotation angle had significant interaction(P=0.036)and limb main effect(P<0.001).The post test results showed that the peak knee internal/external rotation angle on the unaffected side was significantly different under unanticipated conditions(P<0.001),and the peak knee internal/external rotation angle on the affected side was significantly different under anticipated and unanticipated conditions(P=0.043).(2)The kinetic results of this study showed that the results of the analysis of variance of repeated measurements of two factors showed that the knee valgus moment(P=0.004),hip adduction moment(P=0.003),knee internal rotation moment(P<0.001),hip internal rotation moment(P<0.001),lateral GRF(P<0.001)and tibial anterior shear force(P<0.001)of the unaffected and affected side limbs under the anticipated and unanticipated conditions showed significant limb main effect.The peak knee adduction moment(P<0.001),lateral GRF(P<0.001),anterior tibial shear force(P=0.002),and hip adduction moment(P=0.005)showed significant conditional main effect.The peak knee flexion moment(P<0.001),hip extension moment(P=0.001)and the peak value of anterior and posterior GRF(P=0.041)showed significant interaction main effect.The peak knee flexion moment(P<0.001)and hip extension moment(P<0.001)showed significant limb main effect.The peak value of anterior and posterior GRF(P=0.011)showed significant conditional main effect.Under unanticipated conditions,the peak knee joint flexion moment(P<0.001)and hip joint extension moment(P<0.001)of the affected limb were significantly lower than those of the unaffected limb.Compared with anticipated conditions,the peak knee joint flexion moment(P=0.013)and hip joint extension moment(P=0.010)of the affected limb significantly increased under unanticipated conditions,and the anterior and posterior GRF(P=0.002)of the unaffected limb significantly decreased.Conclusion:(1)Compared with the unaffected side,the affected side of ACLR athletes showed the biomechanical characteristics of smaller knee flexion angle and hip flexion angle,larger knee internal rotation moment and anterior tibial shear force during side cutting,which may suggest that the affected side have greater potential risk of ACL injury;(2)Under unanticipated conditions,both lower limbs of ACLR athletes showed the biomechanical characteristics of increased knee range of motion,hip abduction angle,knee internal rotation moment,hip extension moment,lateral GRF and anterior tibial shear force,which may suggest that different biomechanical strategies are used in the side cutting under unanticipated conditions,resulting in a greater risk of ACL injury.These results also suggest that the potential risk of ACL injury is not limited to the affected side,and ACL injury prevention should also be strengthened in the unaffected lower limb during side cutting.