Vertical Video-based Gait Analysis for Assessment of Transverse Plane Motion: Reliability and Validity in a Neuromuscular Population

Background: In the absence of 3-dimensional gait analysis (3DGA), assessment of transverse plane motion of the lower extremity from sagittal and coronal video has a high degree of error. We propose a standardized method through vertical video-based gait analysis (VVGA) to assess the position of the pelvis and lower extremity in the transversal plane. This study aims to evaluate the reliability and accuracy of VVGA compared with 3DGA for transverse plane kinematics. Methods: VVGA and 3DGA were obtained simultaneously on subjects between the ages of 6 and 35 referred to a motion analysis center. Gait Deviation Index (GDI) and Gait Profile Score (GPS) were used to estimate overall gait deviation of the subjects. Three raters at different levels of experience performed VVGA on all patients utilizing a standardized technique. Inter-rater and intrarater reliability was calculated using interclass correlation coefficients (ICC). Mean absolute difference (MAD) between VVGA measurements and 3DGA data was calculated for each body-segment. Results: Twenty-six patients (median age: 12 y, 61.53% male) with neuromuscular disorders participated in the study, with the majority (65%) having cerebral palsy. The mean GDI of the subject group was 80.7 and the mean GPS was 1082, indicating a neuromuscular cohort with significant gait deviations. Inter-rater and intrarater reliabilities were excellent, with ICC ranging from 0.94 to 0.99. The overall MAD between VVGA analysis and 3DGA was 4.90 degrees, indicating a clinically acceptable overall error. Segment-specific errors were 4.63 degrees for pelvis rotation, 5.35 degrees for hip rotation, and 4.70 degrees for foot progression. Conclusions: VVGA is an accurate and reliable method for assessing the transverse plane position of the pelvis, hip, and foot when utilizing a standardized method of collection and data analysis. Further study is required to assess whether this technique can be used for surgical decision-making or outcome assessment.