Foot Mobility Magnitude and Stiffness in Children With and Without Calcaneal Apophysitis

Abstract

Background: This study evaluated quasi-static measures of foot mobility magnitude (FMM) and foot stiffness (FS) in children, aged 8 to 14 years, with and without calcaneal apophysitis. Methods: Between 2016 and 2017, FMM and FS measurements were captured on 41 children (22 cases and 19 controls) using a custom-built foot assessment platform. The platform incorporated a portable force plate that allowed quantification of vertical force during double-limb stance (DLS). Results: There was no significant difference in FS in children with and without calcaneal apophysitis ( P = .459). FMM was significantly greater (+19%) in children with calcaneal apophysitis than in those without ( P = .045). The mean difference in FMM between groups (1.4 mm), however, did not exceed the minimum detectable change at the 95% confidence level (MDC95%) for the measurement (±2.5 mm). Conclusion: Differences in FMM in children with calcaneal apophysitis were small and within the observed error of measurement. Clinical measures of FS did not differ in children with and without calcaneal apophysitis during quasistatic loading. Further research evaluating the level of uncertainty of the measurement techniques in children and under dynamic loading conditions is recommended. These findings question the rationale behind interventions which aim to modify quasistatic foot mobility and stiffness in children with calcaneal apophysitis. Level of Evidence: Level III, comparative series.