Kinematic changes in gait in boys with Duchenne Muscular Dystrophy: Utility of the Gait Deviation Index, the Gait Profile Score and the Gait Variable Scores

Background: Duchenne Muscular Dystrophy (DMD) is an X-linked muscle disorder caused by a mutation or deletion in the dystrophin gene. In boys with DMD, muscle weakness progresses in a proximal to distal pattern, leading to gait abnormalities at all joints, in all planes of motion. Longitudinal studies are imperative to quantify changes in gait function due to DMD and are of particular importance when examining the efficacy of treatment interventions. Research question: The purpose of this study was to examine the sensitivity of the Gait Deviation Index (GDI) and Movement Analysis Profile (Gait Profile Score (GPS) and Gait Variable Score (GVS)) to quantify the longitudinal ambulatory decline in boys with DMD. A secondary aim was to quantify the effect of corticosteroid (CS) treatment. Methods: The gait patterns of 75 boys were assessed longitudinally, 11 were steroid naive (SN), and 64 received CS treatment. Joint kinematics were collected using either a VICON 612 or a Motion Analysis Corporation 3-D system. Representative trials were used to compute the GDI, GPS and the nine GVS for each boy for each visit. Results: At baseline, GVS for the boys with DMD revealed abnormalities in all lower extremity joints and in all planes of movement compared to TD peers. GDI and GPS indices verified that the overall quality of gait in boys with DMD decreases at a significant rate with age. Boys who were steroid naive changed at a rate 3 times greater than boys on CS in coronal plane hip motion. Significance: The gait indices of GDI and GPS are able to identify changes in the quality of gait patterns in boys with DMD. Although boys on steroids had greater gait deviations than boys who were SN at baseline, the rate of decline in gait quality was slower in boys on CS.