The quarter-ellipsoid foot: A clinically applicable 3-dimensional composite measure of foot deformation during weight bearing

Abstract

Study DesignDescriptive Laboratory ObjectivesTo assess change in foot morphology across loading using innovative, clinically accessible 3-dimesional composite measurements of surface area (SA), volume (V), and SA:V ratio in recreationally-active young adults. MethodsThe feet of 53 female [mean age:20.7 ± 3.8 years, BMI:23.9 ± 4.2 kg m−2, foot posture index (FPI):3.8 ± 3.7] and 31 male participants (mean age:20.8 ± 2.4 years, BMI:23.7 ± 2.5 kg m−2, FPI:3.8 ± 4.1) were evaluated. FPI was assessed and foot length, width, and dorsal arch height were measured in sitting and bipedal standing and used to calculate the SA and V of a quarter-ellipsoid. ΔSA characterized foot widening and lengthening and ΔV characterized arch deformation during loading. The SA:V represented changes in both foot size and shape. Linear regression was performed to assess the effects of component foot change measures during loading on the composite measurements. The composite measures were compared to the established measures of ΔArch Height Index (ΔAHI), Arch Flexibility, Foot Mobility Magnitude (FMM), and FPI. ResultsFoot width and dorsal arch height change measures were significant predictors (p < 0.001) for the ΔV and SA:V composite measures, explaining 90–91% of the variance. Significant fair to good associations (p < .05) were found between the novel and established composite measures: ΔSA: Arch flexibility (r=-0.27); SA:V: ΔAHI (r=-0.57), Arch Flexibility (r=-0.75), FMM (r=-0.30), FPI (r = 0.42). ConclusionQuarter-ellipsoid measures calculated from morphologic measurements may have clinical utility in quantifying 3-dimensional foot changes during loading and may be useful when assessing need and response to clinical interventions.