Abstract: BACKGROUND: Children and adolescents are in the growth and development stage, so the use of the same reconstruction methods as adults is easy to induce complications including limb length differences, high graft failure rate and re-surgical intervention. Simultaneously, the occurrence of osteoarthritis will also be advanced.  
OBJECTIVE: To explore the anatomical characteristics of the anterior cruciate ligament between children, adolescents and adults on MRI, and to provide an anatomical basis for the reconstruction of the anterior cruciate ligament in children and adolescents.
METHODS:  A retrospective analysis of patients undergoing knee MRI examination in Qingdao Municipal Hospital from October 2016 to October 2018 was conducted. These patients were divided into child and adolescent group and adult group (n=48 per group). The angle between the anterior cruciate ligament and the tibia and femur on the sagittal plane and the position of the anterior cruciate ligament tibial insertion, the angle between the anterior cruciate ligament and the tibia on the coronal plane, the tibial insertion of the anterior cruciate ligament and femur, and the position of the femur stop point on the axial position were measured in both groups. The data obtained from the measurement of the anterior cruciate ligament of children and adolescents were processed. The growth curves of the shape and position of the anterior cruciate ligament of children and adolescents were drawn, and the law of its growth changes was analyzed.  
RESULTS AND CONCLUSION: (1) The angle between the sagittal plane of the anterior cruciate ligament and the femur (t=-2.906, P < 0.05), the angle between the sagittal plane of the anterior cruciate ligament and the tibia (t=-10.280, P < 0.05), the anterior cruciate ligament angle between the coronal plane and the tibia (t=-5.714, P < 0.05) were smaller in the child and adolescent group than those of the adult group, and the difference was significant. (2) The ratio of the tibia coronal plane of the anterior cruciate ligament (t=-7.263, P < 0.05) and the ratio of the anterior cruciate ligament and femur axial plane (t=-7.378, P < 0.05) were lower in the child and adolescent group than those of the adult group, and the difference was significant. (3) There was no significant difference in the anterior cruciate ligament and tibia sagittal plane ratio (t=-1.588, P > 0.05) and anterior cruciate ligament and femoral coronal surface ratio (t=-1.647, P > 0.05) between the child and adolescent group and the adult group. (4) The growth curve results showed that during the growth and development, the angle between the anterior cruciate ligament and the femur and tibia on the sagittal plane and the angle with the tibia on the coronal plane changed from small to large (P < 0.05). The relative position of the tibial insertion in the coronal position changed from small to large, which indicates that during the growth and development, the tibial insertion moved from inside to outside relative to the inside of the tibial plateau on the coronal plane (P < 0.05). (5) The relative position of femoral insertion in the axial position changed from small to large, suggesting that during the growth and development, the femoral insertion moved from the outside to the inside relative to the lateral femoral condyle (P < 0.05). (6) There was no significant difference in the tibial insertion and the femoral insertion between the child and adolescent group and adult group (P > 0.05).

Key words: children, adolescents, adults, anterior cruciate ligament, MRI, anatomy