Motion analysis to track navicular displacements in the pediatric foot: relationship with foot posture, body mass index, and flexibility.
Kothari A., Dixon PC., Stebbins J., Zavatsky AB., Theologis T.
BACKGROUND: Increased navicular drop (NDro) and navicular drift (NDri) are associated with musculoskeletal pathology in adults. The aim of this study was to investigate navicular motion in children, with respect to foot posture, and identify altered patterns of motion that demonstrate midfoot dysfunction. Navicular motion in different activities was evaluated as well as the role of flexibility and body mass index (BMI). METHODS: Twenty-five children with flatfeet and 26 with neutral feet (age range, 8-15) underwent gait analysis using a 12-camera Vicon MX system (Vicon, UK). Navicular motion indices were calculated from marker coordinates. Student t tests and Pearson's correlation coefficient (R) were used to investigate navicular motion differences between groups. The relationship between NDRo, NDRi, and their dynamic counterparts was also assessed. RESULTS: Normalized NDri (NNDri) and normalized NDro (NNDro) correlated strongly in neutral feet (R = 0.56, P = .003) but not in flatfeet (R = 0.18, P > .05). Flatfeet demonstrated reduced NNDri compared to neutral footed children (0.7 vs 1.6, P = .007). No difference was observed in NNDro between groups. Standard and dynamic measures of NDri and NDRo were highly correlated. Navicular motion correlated poorly with BMI and flexibility. CONCLUSION: Motion of the navicular in the transverse and the sagittal plane is important when investigating foot function. Uncoupling of this motion in flatfeet may indicate impaired midfoot function. Reduced navicular medial translation in flatfeet may indicate altered alignment of the talonavicular joint. CLINICAL RELEVANCE: The measurement of dynamic navicular motion indices did not add information about dynamic foot function compared to measurement of static indices.