Features of motor stereotype kinematics and kinetics in children with achondroplasia: a comparative cross-sectional study

Introduction The study of the kinematic and kinetic parameters of gait in children with achondroplasia would allow a more detailed understanding of the features of their locomotion and determine the strategy of planned treatment.Purpose To evaluate features of locomotor kinematics and kinetics in children with achondroplasia and compare with peers without orthopedic pathology.Materials and methods The locomotor profile was assessed by video gait analysis. Kinematic data were recorded by Qualisys7+ optical cameras (8 cameras) with passive marker video capture technology synchronized with six dynamic platforms KISTLER (Switzerland). The analysis of kinematics and kinetics was carried out in the QTM (Qualisys) and Visual3D (C-Motion) programs with automated calculation of the values of indicators of the total peak power in the joints. Three groups were formed for gait analysis: 1) children 6-7 years old, achondroplasia (6 subjectsle, n = 12 limbs); 2) their peers, children without orthopedic pathology, 6-7 years old (8 subjects, n = 16 limbs); 3) children without orthopedic pathology 3-4 years old similar in height (8 subjects, n = 16 limbs).Results In children with achondroplasia, statistically significant disorder in locomotor kinetics and kinematics were found. The former are associated with a longitudinal deficiency of limb segments and decreased walking speed. The latter are not associated with a longitudinal deficit, but manifested in all planes, namely: an increase in the maximum forward inclination of the pelvis, a flexion position in the hip and knee joints, and dorsal flexion of the ankle joint; increased maximum angle of hip abduction and varus deformity of the knee joint; increased rotational range of motion of the pelvis.Discussion Since the characteristic features of the main gait profile begin to appear in children by the age of 4-5 years, and is associated with the formation of the activity of central and spinal generators that induce the self-organization of motor stereotypes, we believe that the deviations detected in the locomotor kinematics are secondary pathogenetic manifestations of the kinetics due to the longitudinal deficit in limb segments.Conclusion Features of locomotor kinetics in children with achondroplasia are due to the longitudinal deficit of the limb length and are associated with low walking speed. Significant deviations of the locomotor kinematics were not associated with the longitudinal deficit of the segments, but were detected in all planes and are related to the entire biomechanical chain.