Background: Gait indices were developed to represent the magnitude of impairment extracted from a gait analysis with a single value. The Gillette Gait Index (GGI), and the Gait Deviation Index (GDI) are 2 widely used indices that represent gait impairment differently based on their statistical properties. Our purpose was to (1) report on the results of gait analysis for a broad spectrum of pediatric conditions using the GGI and GDI, and (2) identify the parameters that dominate impairment.
Methods: A total of 1439 children with 13 different diagnoses with a complete, baseline gait analysis were identified. The GGI and its 16 parameters were calculated in all cases, and the GDI was calculated from a smaller subset. T tests, and z-scores were used to compare each of these values to typically developing children for each diagnosis. A separate linear regression controlling for age, sex, and use of an orthosis, or assistive device was performed for the GGI.
Results: In our series, there were 71 typically developing children with a GGI of 31. We qualify relative gait impairment as severe, mild, or moderate as based on the GGI, and propose that values <100 represent mild, 100 to 200 represent moderate, and >200 represents severe impairment. On the basis of strong correlation between the GGI and GDI, we suggest that GDI values >80 represent mild, and values <70 represent severe impairment. T tests and z-scores demonstrated that both the number and magnitude of abnormal parameters increase the GGI. These tests also identified the most clinically relevant parameters contributing to functional impairment for each diagnosis. Multivariate linear regression showed that all diagnoses except flatfoot and scoliosis demonstrated statistically significant differences in GGI scores.
Conclusions: This is the first study to apply these gait indices to a large population of diverse pediatric conditions. We propose GGI and GDI values to qualify gait impairment among these conditions as severe, moderate, or mild. Furthermore, impairment in gait reflects both the number and magnitude of abnormal parameters within each condition.
Level of evidence: Level III-retrospective comparative study.